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To mitigate uncertainties in wind resource assessments and to improve the estimation of energy production of a wind project, this work uses a decision tree machine learning model to assess the effectiveness of hub-height wind speed, rotor-equivalent wind speed, and lapse rate as variables in power prediction. Atmospheric data is used to train regression trees and correlate the power outputs to wind profiles and meteorological characteristics to be able to predict power responses according to physical patterns. The decision tree model was trained for four vertical wind profile classifications to showcase the need for multiple calculations of wind speed at various levels of the rotor layer. Results indicate that when compared to traditional power curve methods, the decision tree combining rotor-equivalent wind speed and lapse rate improves prediction accuracy by 22% for the given data-set, while also proving to be the most effective method in power prediction for all classified vertical wind profile types. Models incorporating lapse rate into predictions performed better than those without it, showing the importance of considering atmospheric criteria in wind power prediction analyses.

Din-Gad basin, located in central Himalaya is occupied by the Dokriani glacier in upper reaches. Landsat TM, OLI and Sentinel MSI data sets of seven years from 2009 to 2011 and 2013 to 2016 are utilized to map the areal extent of snow-cover, its seasonal variability and topographical controls (elevation, aspect, and slope). Coefficient of Variation (CV) in Snow Cover Area (SCA) below the elevation of ~5000 m asl is high (~2.0), and is low at higher elevations. CV is also higher for southern as compared to northern aspects. Meteorological data (temperature, relative humidity, and solar radiation) from Automatic Weather Stations (AWSs) is utilized to compute isotherms (~0, 1, and 2 °C) by extrapolation method using Near-surface Temperature Lapse Rate (NSTLR). These data sets are integrated and presented by graphical as well as on Geographical Information System (GIS). Month-wise isotherms closely correspond with snow-cover extent during ablation season, suggesting that the extrapolated temperatures represent a significant proxy for depletion pattern, while month-wise and hourly isotherms deviate largely from the SCA during winter months due to snow events. Elevation zones above 5200 m asl retain snow throughout the year, indicating proximity with Equilibrium Line Altitude (ELA). The effects of Relative Humidity (RH) and solar radiation on melting history during different seasons have also emerged. The proposed methodology is efficient and reliable in terms of estimating the depletion patterns, and deriving the isotherms that can be applied to other comparable snow-covered areas.

The Nepal Himalaya is a transition zone for pollutants transport from the South Asia onto the Tibetan Plateau, with the moist convection identified as dominating the chemical composition that would be transported onto the Plateau. Yet little is known regarding the atmospheric water vapor transport over this region, and how the summer monsoon flows would interact with local topography, with traces detectable from ground sample and observations. The stable oxygen and hydrogen isotopes in precipitation (δ18Op and δDp) are important tracers for understanding various hydrological processes. This study reports, for the first time, stable isotope data in daily precipitation at five stations along a north-south transect on the southern slope of Himalaya, with altitudes ranging from 102 m to 5050 m above sea level (a.s.l). The altitude effect of δ18Op across the region of interest is apparent with an altitudinal lapse rate as 0.17‰/100 m. Seasonal trends in δ18Op and δDp show low values during June–September and higher values during October–May at all of the study sites, with the noticeable decrease of δ18Op during summer indicative of the presence of the Indian monsoon over the eastern Nepal Himalaya. The average d-excess values in the summer precipitation increase with altitudes til 3800 m a.s.l before decreasing afterward to 5050 m a.s.l. This corroborates with previous meteorological discovery in the region, and probably confirms the replacement of prevailing westerly by the southerly monsoon flows during summer monsoon season.

The near-surface lapse rate reflects the atmospheric stability above the surface. Lapse rates calculated from land surface temperature ( γ Ts ) and near-surface air temperature ( γ Ta ) have been widely used. However, γ Ts and γ Ta have different sensitivity to local surface energy balance and large-scale energy transport and therefore they may have diverse spatial and temporal variability, which has not been clearly illustrated in existing studies. In this study, we calculated and compared γ Ta and γ Ts at ~ 2200 stations over China from 1961 to 2014. This study finds that γ Ta and γ Ts have a similar multiyear national average (0.53 °C/100 m) and seasonal cycle. Nevertheless, γ Ts shows steeper multiyear average than γ Ta at high latitudes, and γ Ts in summer is steeper than γ Ta , especially in Northwest China. The North China shows the shallowest γ Ta and γ Ts , then inhibiting the vertical diffusion of air pollutants and further reducing the lapse rates due to accumulation of pollutants. Moreover, the long-term trend signs for γ Ta and γ Ts are opposite in northern China. However, the trends in γ Ta and γ Ts are both negative in Southwest China and positive in Southeast China. Surface incident solar radiation, surface downward longwave radiation and precipitant frequency jointly can account for 80% and 75% of the long-term trends in γ Ta and γ Ts in China, respectively, which provides an explanation of trends of γ Ta and γ Ts from perspective of surface energy balance.

Characterization of the dispersion behaviors of spilled liquid hydrogen is necessary from the safety prospective. In this study, the two-phase flow of liquid hydrogen spill is predicted with the mixture multiphase model, Lee model and Realizable k-e model, and the dispersion of hydrogen vapor cloud with the atmospheric inversion layer is numerically analyzed. The inversion layer restrains the upward movement of the cloud and the mixing of the cloud with air, increasing its ground-level hydrogen concentration. The heights of the flammable cloud can be reduced by 5.71%, 10.49% and 12.86%, respectively, with the temperature lapse rates of 0.03, 0.06 and 0.10 K/m in our investigated scenarios. Besides, the restraining effect is strengthened by increasing the ground air temperature if the temperature lapse rate remains unchanged.

Although the parcel method and the convective available potential energy (CAPE) are widely used to predict the strength and height of convection, they ignore the pressure perturbation and fail to explain strong updrafts observed in tropical cyclones and hurricanes without CAPE, or deep, strong warm downdrafts in hurricane eye-walls, tropopause folds, or downslope winds leeward of mountains. Those phenomena can be explained by the Bernoulli equation that conserves the sum of kinetic energy, potential energy and enthalpy in an inviscid fluid. Our analytic and numerical results also show how, in a moist stable environment without CAPE, updrafts and clouds can develop against negative buoyancy. Deep warm downdrafts can also form in cloud-free regions or areas without significant evaporative cooling from precipitation.

The Tian Shan in Central Asia are a unique mountain range in that they are in the world's most continental location. Seasonal precipitation in the northern Tian Shan is segregated into distinct elevation bands where high elevations receive precipitation primarily during summer and low elevations to the north receive precipitation primarily during the late winter and spring. In this study, we sampled stream water along multiple altitudinal transects to determine the effect unique seasonal patterns of precipitation have on the isotopic composition of surface water. Our results suggest that the northern Tian Shan exhibits an isotopic lapse rate for waters sampled in late spring, but not for those sampled in late summer, when stream water budgets are dominated by high elevation precipitation and snow melt. Deuterium excess results suggest that subcloud evaporation significantly affects the isotopic composition of precipitation at low elevations in spring and that sublimation of snow has a minor impact on δ18O values of summer melt water. Because high and low elevation δ18O values are similar, conventional paleoaltimetry based on Rayleigh distillation of an air mass is not applicable to the Kyrgyz Tian Shan. Stream water proxies from the rock record are likely to reflect changes in the seasonal distribution of precipitation which occur on the same spatial scale as altitudinal changes. These results highlight the need to understand modern controls on local stable isotopes of meteoric water in reconstructions of past climate or topography using geologic proxy materials.

The thermal regime of permafrost in the rugged topography on parts of the Qinghai-Tibet Plateau (QTP) remains ambiguous, due to general inaccessibility and inconvenient investigations with geophysical prospecting. While the relatively easy implementations of monitoring ground surface temperature (GST) may facilitate the investigations of permafrost thermal state. Here, surface freezing and thawing and the relationship between GST and permafrost temperature are investigated in the Bayan Har Mountains, NE QTP on the basis of 22 monitoring sites. Results demonstrate that, unlike the air temperature (Ta) mainly controlled by elevation, the GST is complicately influenced by elevation and the surface characteristics, such as vegetation, local soil textures, as well as the exposure to solar radiation. Mean annual GST (MAGST) ranges from 1.1 °C to −3.1 °C and is averaged at −0.8 °C. MAGST generally decreases at a lapse rate of 1.1 °C/100 m in relation to elevation. Surface freezing and thawing processes depend on topography and local surface characteristics. The onset of unstable thawing, stable thawing, unstable freezing, and stable freezing are averaged at 6 April 2015, 15 May 2015, 14 October 2015, and 21 October 2015. Based on the relationship between MAGST and the ground temperature at the depth of zero annual amplitude, GST likely serves as a reliable indicator of the thermal state of permafrost. For the 22 sites, it is estimated that the lowest TZAA of permafrost is −3.4 °C and the thickest permafrost is 106.2 m. However, detailed investigations of subsurface characteristics are indispensable for the accurate inference of permafrost.

Information about the pressure field of tropical cyclones (TCs) is of crucial importance for determining a TC's wind structure. However, despite the fact that TC pressure deficit (ΔP) decreases with increasing height below a TC's outflow layer, most existing models focus only on the radial distribution of TC pressure. Quantitative studies on the spatial pressure field of TCs are considerably limited. This study presents a field study on the vertical pressure profiles of Typhoon Hato which is one of the few strongest sampled TCs in Hong Kong. Meteorological observations from eight radiosonde balloons released at different storm-relative positions during Hato's passage are investigated. Results show that the vertical profiles of ΔP below the outflow layer are distributed linearly with respect to altitude, with the slope increasing almost linearly with the increase of surface pressure deficit. Based on the above observation, an empirical model of the typhoon's spatial pressure field is established. Budget analysis of ΔP is then conducted. Both the dry-air component and water-vapor component are found to be evident. This study further presents an analytical model of TC pressure deficit. Comparison of results with various values of key input model parameters show that the model prediction is highly sensitive to the lapse rate of atmospheric temperature and surface air temperature. It is believed that both the empirical model and the analytical model have the potential to facilitate the development of TC spatial wind-field models.

Weighted mean temperature (Tm) is a crucial parameter for retrieving precipitable water vapor (PWV) in Global Navigation Satellite System (GNSS) meteorology. The difference between the height of the GNSS receiver and the height of the derived Tm may cause large uncertainty in the value of the retrieved PWV. In this study, we analyze the vertical variation of Tm on a global scale and build a new vertical correction model using the operational reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF). Another dataset from ECMWF and the radiosonde data derived from 678 globally distributed stations are used to independently validate the performance of the newly built model and demonstrate its superiority compared with the existing vertical correction method. The results show that the lapse rate of Tm has geographic and seasonal variations, and the Tm has large nonlinear variation along the vertical direction in the high-latitude regions, especially in the polar regions. A performance improvement of 15%–35% compared with the existing vertical correction method is achievable for the newly built model when tested with the ECMWF data, and the improvement is 10%–25% when tested with the radiosonde data.

Smith fir (Abies georgei var. smithii), which is the timberline constructive tree species in the cool slope of Mt. Sygera in the southeast of Tibet, plays a very important role in maintaining the timberline completeness and indicating global climate change. This study uses the instrumental recorded meteorological data along the altitude from 3600 to 4400 m at every 200 m in the growing season, investigates the smith fir growth biomass from 2006 to 2010 in the same timberline ecotone, and makes a non-linear regression analysis to determine the relationship between the alpine tree growth biomass and its in-situ environment condition. The results showed that the cool and warm slope share different air temperature lapse rates, which were −0.48 °C (100 m)−1 in the warm slope and −0.54 °C (100 m)−1 in the cool slope, respectively. However, the dominant timberline tree species in the warm slope was Sabina saltuaria, and it can reach as high as 4570 m, which is approximately 170 m higher than that in the cool slope. Moreover, the smith fir in the cool slope was only distributed in the range of elevation from approximately 3600 to 4400 m. The altitude of approximately 3800 m was the appropriate altitude for the growing smith fir, where the mean air temperature in the growing season was about 9.0 °C, and the young smith fir tree can form more biomass. The results suggested that alpine forest chose a suitable environment where trees can grow more in the prolonged succession, but not in the warmer or cooler condition, it could be seen as a biological evidence for climate change. Keywords: Abies georgei var. smithii, Growth biomass, Sabina saltuaria, In-situ environment condition, Non-linear regression analysis

Mountainous terrain creates variability in microclimate, including nocturnal cold air drainage and resultant temperature inversions. Driven by the elevational temperature gradient, vapor pressure deficit (VPD) also varies with elevation. Soil depth and moisture availability often increase from ridgetop to valley bottom. These variations complicate predictions of forest productivity and other biological responses. We analyzed spatiotemporal air temperature (T) and VPD variations in a forested, 27-km2 catchment that varied from 1000 to 1650 m in elevation. Temperature inversions occurred on 76% of mornings in the growing season. The inversion had a clear upper boundary at midslope (∼1370 m a.s.l.). Vapor pressure was relatively constant across elevations, therefore VPD was mainly controlled by T in the watershed. We assessed the impact of microclimate and soil moisture on tree height, forest productivity, and carbon stable isotopes (δ13C) using a physiological forest growth model (3-PG). Simulated productivity and tree height were tested against observations derived from lidar data. The effects on photosynthetic gas-exchange of dramatic elevational variations in T and VPD largely cancelled as higher temperature (increasing productivity) accompanies higher VPD (reducing productivity). Although it was not measured, the simulations suggested that realistic elevational variations in soil moisture predicted the observed decline in productivity with elevation. Therefore, in this watershed, the model parameterization should have emphasized soil moisture rather than precise descriptions of temperature inversions.

Stable isotope-based paleoaltimetry is the most widely used approach for paleoelevation reconstruction. Interpretations of stable isotope data in continental interiors, however, are undermined by surface water isotope compositions that are influenced by multiple factors. Here we present a stable isotope dataset of modern river water samples collected over two summers and one spring from the central Rocky Mountains (Rockies) and the adjacent Great Plains. By examining the spatial and temporal variations of river water δ 18 O, δD and d-excess values, and their relationships with climatic and geographic parameters, as well as through back trajectory analysis of moisture sources, we elucidate the influences of elevation and climatic parameters on the spatiotemporal variation of river water isotopic values. In the Bighorn River drainage, a typical intermontane drainage in the central Rockies, the isotopic difference between highland and lowland rivers is small, which we attribute to highland precipitation that dominates lowland river discharge. In the North Platte River drainage across the central Rockies and Great Plains, the river water δ 18 O values show poor correlation with elevation west of 105°W (central Rockies), but increase as elevation decrease east of 105°W (in the western Great Plains). This eastward increase across the western Great Plains leads to an average oxygen isotope lapse rate of −2.3‰/km, which we interpret as being caused primarily by condensation temperature-controlled isotopic fractionation at various elevations, and secondarily by evaporation in the upper reaches of streams that contribute to the North Platte River plus direct contribution of moisture from the Gulf of Mexico in the Great Plains. In this continental interior setting, multiple moisture sources, including recycled continental moisture, contribute to surface water, and evaporation influences river water isotope values to various degrees depending on the relative humidity within an individual river catchment. These results suggest that paleoclimate and atmospheric circulation pattern must be carefully evaluated when applying stable isotope-based paleoaltimetry in continental interiors. Our findings have implications for paleoelevation reconstruction in the study area, including that 1) within the central Rockies, the isotopic difference of river water and unevaporated basinal precipitation can be used to infer paleorelief of the Laramide ranges with respect to the basin floors; 2) along a regional transect crossing the central Rockies and Great Plains, the modern isotope lapse rate of the North Platte River drainage can be used to constrain the paleorelief between the two regions in semi-arid climate.

The Pasquill system was designed to describe dispersion conditions and was never intended to be a “stand-alone” measure of stability, but it has nevertheless been used to characterize stability in a wide range of applications unrelated to atmospheric dispersion. In this study we evaluate whether the method's underlying assumptions are sufficiently robust for characterizing stability, and whether the method provides acceptable characterizations when used as a stability classification tool outside the context of atmospheric dispersion. Observed temperature lapse rates at six locations across Eurasia largely fail to support the Pasquill method's “exclusivity” assumptions prohibiting the identification of stable classes during daytime, unstable classes at night, and all non-neutral classes during day/night transition and overcast periods. While observed nighttime stability is mostly stable or neutral and thus largely consistent with the Pasquill method, daytime lapse rates frequently indicate stable conditions. Moreover, the majority of lapse rates during day/night transition periods are non-neutral. Substantial seasonal variability is observed in diurnal stability variations and is unaccounted for in the Pasquill system. When compared with observed stability based on lapse rates, the Pasquill classification scheme exhibits a strong neutral bias at most sites. The method performs particularly poorly during daytime, correctly identifying instability in only 1%–29% of cases at the sites analyzed. Nighttime stability is correctly identified more frequently, but the strength of nocturnal stability is overestimated at all sites analyzed.

The properties of temperature at the level of lapse rate minimum (LRM) in the tropical tropopause layer between 20°S and 20°N are investigated using 3-year radio occultation observations based on the FORMOSAT-3/COSMIC mission from November of 2006 to October of 2009. The correlations between this LRM temperature and Outgoing Longwave Radiation (OLR) are analyzed by 5° × 5° grids in longitude and latitude. Two primary regions, one from 60°E to 180°E and the other from 90°W to 30°E, are found to have higher correlations and can be associated with regions of lower OLR values. The patterns of this spatial distributions of regions with higher correlations begin to change more obviously when the altitude ascends to the level of Cold Point Tropopause (CPT). This correlation at the LRM altitude in annual and seasonal scales also shows spatial distributions associated with OLR intensities. The altitudinal dependence of the correlations between temperature and OLR is further analyzed based on grids of high correlations with significance at LRM altitude, for the two primary regions. The results show that for the different time scales in this analysis (3-year, annual, and seasonal), the correlations all gradually decrease above the LRM levels but maintain a significant level to as high as 2.5–3.5 km. Below the LRM level, the correlation decreases with a slower rate as the altitude descends and still keeps significant at the deep 5 km level. These suggest that the vertical temperature profiles could be affected by the convection mechanism for a wide range of altitudes in the troposphere even above LRM altitude. Applying the same analysis on one complete La Nina event during the survey period also reveals similar features.

This study aims to characterize the wind and thermodynamic structure of the Planetary Boundary Layer (PBL) on the northern coast of Brazil (NCB) via the CHUVA datasets. Three synoptic conditions were present in the NCB region between March 1 and 25, 2010: a dry period, the Upper Tropospheric Cyclonic Vortex (UTCV) and the Intertropical Convergence Zone (ITCZ). Nighttime precipitation accounted for 78% of the total precipitation observed in the month, mainly during the ITCZ. In general, the surface meteorological fields were few changed by intense weather events due to proximity to the ocean and the predominant contribution of the northeasterly trade winds. There was also a weak sea breeze signal that maintained the horizontal moisture flow in the studied area. On dry days, the PBL depth was higher, drier, and warmer, resulting in stronger winds below 500 m. Moreover, trends throughout the period suggest that PBLs are near-neutral below 500 m. However, the wind variability was intensified by up to 20% due to downdrafts and higher wind shears during the deep convection mechanisms derived by UTCV. Furthermore, ITCZ mixed rainfall cooled the PBL at approximately 2 K, making it very stable according to the Richardson number classification adopted. The observed temporal and spatial scale represent challenges to the physical parameterizations used to improve numerical weather prediction models over tropical coastal areas.

Profiles of periodic GPS Radiosonde ascends collected from a station at the west coast of India (Goa) during summer monsoon months (June to September) of 2009 and 2013 have been used to analyze the thermal inversion statistics at various heights and their repercussions on the regional weather is studied. The interaction of contrasting air masses over the northern Arabian Sea often produces a two layer structure in the lower 5000 m close to the coastal station with warm and dusty air (Summer Shamal) occupying the space above the cool and moist Low Level Jet (LLJ) by virtue of their density differences. The warm air intrusion creates low lapse rate pockets above LLJ and modifies the gravitational stability strong enough to inhibit convection. It is observed that the inversion occurring in the lower 3000 m layer with an optimum layer thickness of 100–200 m has profound influence on the weather beneath it. We demonstrated the validity of the proposed hypothesis by analyzing the collocated data from radiosonde, lidar and the rain gauge during 16th July 2013 as a case study. The lidar depolarization ratio provides evidence to support the two layer structure in the lidar backscatter image. The presence of dust noticed in the two layer interface hints the intrusion of warm air that makes the atmosphere stable enough to suppress convection. The daily rainfall record of 2013 surprisingly coincides with the patterns of a regional break like situation centered at 16th July 2013 in Goa.

The Global Positioning System (GPS) has been applied in meteorology to monitor the change of Precipitable Water Vapor (PWV) in atmosphere, transformed from Zenith Wet Delay (ZWD). A key factor in converting the ZWD into the PWV is the weighted mean temperature ( T m ), which has a direct impact on the accuracy of the transformation. A number of Bevis-type models, like T m - T s and T m - T s , P s type models, have been developed by statistics approaches, and are not able to clearly depict the relationship between T m and the surface temperature, T s . A new model for T m , called weighted mean temperature norm model (abbreviated as norm model), is derived as a function of T s , the lapse rate of temperature, δ, the tropopause height, h trop , and the radiosonde station height, h s . It is found that T m is better related to T s through an intermediate temperature. The small effects of lapse rate can be ignored and the tropopause height be obtained from an empirical model. Then the norm model is reduced to a simplified form, which causes fewer loss of accuracy and needs two inputs, T s and h s . In site-specific fittings, the norm model performs much better, with RMS values reduced averagely by 0.45 K and the Mean of Absolute Differences (MAD) values by 0.2 K. The norm model is also found more appropriate than the linear models to fit T m in a large area, not only with the RMS value reduced from 4.3 K to 3.80 K, correlation coefficient R 2 increased from 0.84 to 0.88, and MAD decreased from 3.24 K to 2.90 K, but also with the distribution of simplified model values to be more reasonable. The RMS and MAD values of the differences between reference and computed PWVs are reduced by on average 16.3% and 14.27%, respectively, when using the new norm models instead of the linear model.

This is the first comprehensive evaluation of the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived near-surface air temperature, which has been used widely in a series of large-scale models varying in various disciplines ranging from climatology, hydrology to ecology. Four retrieval methods: the highest available pressure in the atmospheric profile product, interpolation by the adiabatic lapse rate, interpolation by the hypsometric equation and the combination with land surface temperature, were developed in the past, but only with validation in regional scale. All of these are evaluated in this paper against 2168 hourly meteorological recordings with an elevation span of over 5000 m in China. Results show that the method of the highest available pressure exhibits a serious underestimation, especially in areas of high elevation, such as the Tibetan Plateau. Interpolation by the hypsometric equation can only fix the underestimation to a very small extent, while interpolation by the adiabatic lapse rate can achieve a relatively good performance. In addition to the elevation influence, substantially variable estimates occur with the parabola-like distribution in low elevation areas, which implies the influence of cloud in Southern China. The combination of the underestimation from interpolation by the adiabatic lapse rate and overestimation in land surface temperature can eliminate the disturbance of both elevation and cloud, resulting in the best performance with r = 0.94, bias = −0.83°C and root-mean-square-error = 4.18°C.

As the largest intracontinental basin in the Tibetan Plateau hinterland, the Hoh Xil Basin is an ideal area for exploring the coupled history of climate-tectonic relationships in the plateau's interior. However, the detailed paleoenvironmental research on the Hoh Xil Basin is quite insufficient. In this study, we collected palynological and ostracod samples from well-exposed Cenozoic lacustrine strata in the Hoh Xil Basin to reconstruct the paleoenvironment and paleoelevation of the Hoh Xil Basin. Based on the discovery of two key index fossils (Austrocypris cf. posticaudata and Lychnothamnus vectensis), we propose the latest Eocene-early Oligocene (latest Priabonian-earliest Rupelian) age for the strata of the Yaxicuo Formation in the Tongtianhe section. The palynological assemblage suggests that the Hoh Xil Basin was dominated by temperate broadleaved forest and that a warm climate prevailed in this region during the latest Eocene-early Oligocene. Roughly consistent with the overall warm climate confirmed by palynological evidence, the ostracod record indicates that a large freshwater lake existed within the warm environment of the Hoh Xil Basin during the latest Eocene-early Oligocene. By using the coexistence approach (CoA) to evaluate the fossil palynological assemblage, combined with the calibration of the effects of temperature differences and lapse rates, a paleoelevation of 2700 ± 200 m a.s.l. was estimated for the Hoh Xil Basin during the latest Eocene-early Oligocene, representing the height between the basin lake and the crests of the surrounding mountains.

Little is known about the effects of glacier-air interactions on the Himalayan glacier mass balance. Until this knowledge gap is filled, a reliable projection of the future changes in the Himalayan glaciers is hardly possible. Here, we describe the drying effect of the katabatic winds on the up-valley summer monsoon flows by creating favorable conditions for local convergence-induced precipitation to occur near the glacier fronts. We postulate that this retarding effect on the up-valley monsoon flows results in a negative feedback mechanism mediated by glacier-air interactions, in which glacial retreat pushes precipitation upwards as the down-valley katabatic winds weaken, resulting in greater local precipitation and enhanced snow accumulation across the upper parts of the Himalayan glaciers. Our analyses are based on the exclusive data recorded in the Khumbu valley and the Langtang valley in the Nepalese Himalayas. These data revealed higher afternoon precipitation in summer associated with surface wind convergence near the glacier fronts and a sharp decrease in the temperature lapse rate over the glacier surfaces. The principle of the observed phenomena was proven by our high-resolution modeling sensitive experiment, which involved two simulations, one with the present glaciers and the other without. This numerical experiment also supports the proposed negative feedback. Furthermore, we report a low deuterium excess near the glacier fronts, indicating below-cloud re-evaporation facilitated by the local convergence induced by the dry katabatic winds. Our study suggests that current models may overestimate the retreat of Himalayan glaciers because they have completely ignored the glacier-air interactions.

Urban breathability is fundamentally important for improving urban air environment. Nowadays, air pollution and extreme heat waves heavily threaten modern cities and residents. In this paper, a methodology combined with an idealized High-Reynolds-Number Porous-Media city model and a multi-scale Computational Fluid Dynamics (CFD) method will be firstly proposed to quantify the urban ventilation breathability under no geostrophic winds. Breathability of city was then evaluated in terms of air change rate per hour (ACH) and age of air. The contribution of five factors to urban heat island and air quality is analyzed qualitatively and quantitatively. Numerical results further demonstrate that, 1) For heat island intensity, the dominant importance of influencing factors is: heat flux > temperature lap rate > urban scale > building height > urban density. Urban heat flux and temperature lapse rate have great influences on the urban heat island intensity and air quality. Comparing with neutral atmosphere, ACH in urban canopy decreased by more than a half under inversion condition, whereas ACH in pedestrian layer decreased by nearly 100%. 2) For air quality, the importance of the influencing factors could be listed as, building height > heat flux > temperature lapse rate > urban scale > urban density. Building height has the greatest impact on air quality. With the increase of urban scale, average age of air for a city decreases first and then increases. There exists an optimal city size to minimize the age of urban air. Urban building density (regardless of heat emission) on the buoyancy driven flow was very weak. Present model and research results could have theoretical significance for the council and urban planners to alleviate urban heat island and urban air pollution through reasonable planning of urban building layouts.

The role of temperature as a key driver for plant phenology is well established. However, an increasing lack of winter chilling may strongly slow down spring phenological advances in the course of warming. Along elevational gradients in the mountains, differential changes in winter chilling as well as more homogeneous leaf unfolding due to warming have been observed. In this study, we analyzed the elevation-linked lapse rates of phenological ground observations and remote sensing data in the pre-alpine and alpine regions of the Bavarian Alps, Germany. Seasonal start (SOS) and end of season (EOS) dates were extracted from time series data of 4-day maximum value composite Moderate Resolution Imaging Spectrometer (MODIS) sensor's Normalized Difference Vegetation Index (NDVI) for the years 2001-2016. Longer snow duration in the alpine region could be a possible reason of higher SOS elevational lapse rates as compared to the pre-alpine region. Significant and maximum differences in SOS rates between alpine and pre-alpine areas were observed in years with preceding warm winters with insufficient chilling. Minimum differences in SOS elevational lapse rates along the elevational gradients were found for cold spring and cold winter years. The MODIS-based SOS showed the highest correspondence when validated against the gridded German Meteorological Service (DWD) leaf unfolding data. However, EOS dates were in comparatively lower agreement with DWD data, and their lapse rates in the pre-alpine and alpine regions were difficult to validate. Contrary to the SOS, lower positive lapse rates of EOS were revealed in the alpine but not in the pre-alpine areas.

Quantifying how land surface height, such as that of the Tibetan region, has changed with time is crucial for understanding a range of Earth processes, including atmospheric dynamics, biotic evolution and tectonics. Elevation reconstructions are highly uncertain and controversial, in part because of assumptions used in their calculation. The largest uncertainties are in the choice of unconstrained thermal lapse rates. Thermal lapse rates are defined as a change in surface temperature with altitude and have long been used to estimate paleoelevation. If we know both the lapse rate and the temperature at two sites at different elevations, then in theory we can calculate their height difference. There are different types of lapse rates (Dry, Saturated, Environmental and Terrestrial), yet which is the most useful for paleoaltimetry is unknown. Previous paleoelevation studies have often used observed modern-day global annual mean free air or terrestrial thermal lapse rates to measure elevation change, with the assumption that observed modern-day lapse rates are similar to those of the past. Here, using the HadCM3L paleoclimate model we demonstrate that Eocene global mean free air and terrestrial thermal lapse rates are not only different from the modern, but also show little predictive skill in reproducing prescribed model topography. Free-air lapse rates are largely insensitive to increased pCO2 (showing only a decrease of ∼0.1-0.5 °C/km), whereas lapse rates at Earth's surface, the most applicable for fossil-based paleoaltimetry, differed significantly locally and globally in the past compared to the Pre-industrial. This suggests that modern terrestrial lapse rate expressions are inappropriate for tracking altitude changes through geologic time. Moist processes and resultant moisture content of airmasses play a critical role in much of this uncertainty. The use of a wet-bulb temperature-derived lapse rate reduces this uncertainty significantly improving the predictive skill. Local terrestrial thermal lapse rates can be useful in paleoaltimetry, but only through climate model mediation where uncertainties can be reduced and quantified. Critically, paleoclimate models offer the opportunity to provide mean sea-level surface temperature to derive an elevation estimate where proxy-based values may not be available.

Mountains contain steep but constricted climate gradients that can provide climate warming refugia often overlooked in coarse-scale models of species migrations. With continued climate warming, the potentially important role of mountains in maintaining suitable climate for migrating species is still not clear. To determine if mountains in the northeastern U.S. can continue to serve as refugia for species in high-elevation spruce-fir forests under warming climate, we studied climate and climate-vegetation relations along elevational gradients across 76 sites on 11 mountains in four states of this region. We calculated (a) fine-scale temperature lapse rates using in situ climate loggers on each mountain, and (b) regional long-term temperature trends using 36 meteorological stations, in order to determine (c) recent and expected future shifts in species temperature envelopes along elevational gradients by linking lapse rates with regional temperature trends and climate warming scenarios for 2100 (+1, 3, and 5 °C). Since 1960, temperature regimes have shifted upslope on average by 377 m and 133 m for the monthly mean of daily minimum (T min ) and maximum (T max ) temperatures, respectively, although climate did not warm equally for all months. By 2100, mid-range warming of 3 °C may shift monthly temperature regimes upslope relative to their 1960s locations on average by 986 m for T min (580 m for 1 °C, and 1393 m for 5 °C scenario) and 588 m for T max (285 m for 1 °C, and 891 m for 5 °C scenario). We confirmed that spruce-fir forest distribution in the northeastern U.S. is strongly related to temperature, particularly October T max that has surprisingly differed from the overall warming trend as it cooled slightly since the 1960s and thus possibly contributed to the recent downslope shifts in some species ranges documented across the region in other studies. However, the vast majority of monthly temperature variables suggest considerable climate warming since the 1960s, and, given the expected future warming, the temperature regimes characteristic of the lower range margin of spruce-fir forests are unlikely to be present on many mountains in the region by 2100. Consequently, mountains in the northeastern U.S. may not provide long-term climate refugia for species dependent on the climate currently found in spruce-fir forests unless they can adapt to warmer temperatures.

GPS Radio Occultation (RO) cloudy profiles during a seven-year period from 2007 to 2013 over the globe are firstly selected and grouped into four types of ice clouds (e.g., nimbostratus, deep convective, cirrus, altostratus) based on collocated CloudSat data. Vertical temperature profiles within ice clouds below − 20 °C are then retrieved from GPS RO refractivity observations, in which the vertical profiles of ice water content required by the forward model of refractivity are obtained from CloudSat retrievals of ice water content. Vertical distributions of relative humidity and lapse rate within clouds are finally examined in terms of their occurrences, mean values and standard deviations. It is found that ice clouds have preferred values of relative humidity and lapse rate depending on cloud types and altitudes. Most altostratus ice clouds are located between 4 and 8 km with relative humidity between 55 and 75%. The cirrus clouds have a relative humidity around 60% and are located mostly above 6 km to as high as 13 km. Difference from cirrus and altostratus ice clouds, nimbostratus ice clouds that occur mostly in polar regions are found at all altitudes below 10 km with a relative humidity decreasing linearly from about 90% near the surface to about 60% around 6 km. Within deep convective ice clouds, the relative humidity also decreases linearly from about 100% around 2.5 km to about 60% around 9 km. The lapse rate slightly increases with altitude and its value ranges between 5 and 8 °C km − 1 within nimbostratus, deep convective and altostratus ice clouds. The lapse rate within cirrus clouds varies from 6 °C km − 1 to 9 °C km − 1 . Vertical variations of the lapse rate derived from GPS RO cloudy retrievals compared favorably to those derived from radiosonde profiles. Both showed that the mean lapse rate increases with altitude from about 5 °C km − 1 around 3 km to about 7 °C km − 1 around 7 km, and the standard deviations are much smaller than the mean lapse rate.

The Tibetan Plateau (TP) is a vast elevated plateau in central Asia, and profoundly impacts regional weather and climate, and even global atmospheric circulation. Here, two frequently used ERA-Interim reanalyses with a spatial resolution of 1.5° × 1.5° (EIN15) and 0.75° × 0.75° (EIN75) are evaluated using a gridded observation dataset at 0.25° spatial resolution from the National Climate Center in China across the TP that covers the period 1979–2012. Climatological characteristics, mean monthly changes, and spatial–temporal trends are examined, with a focus on air temperature and precipitation. Topographic corrections for temperature in ERA-Interim are first conducted based on a vertical temperature lapse rate. The results show that EIN15 and EIN75 with topographic correction closely reproduce the spatial distribution and mean monthly change of temperature on the TP, notwithstanding some cold biases not seen in the observations. The two reanalysis datasets exhibit significant temperature increases over most of the TP, which is similar to the observations. However, the trends exhibit different spatial patterns for all seasons aside from summer, and have lower magnitudes than the observations. EIN15 and EIN75 also reproduce the broad spatial distribution of precipitation, but overestimate precipitation amounts, especially on the southern TP. They also capture some of the observed spatial patterns in the precipitation trend for the period 1979–2012, particularly in winter. Overall, the mean monthly change, mean annual, winter, and summer climatology, and their temporal trends of temperature reproduced by the ERA-Interim data are much better than those of precipitation. As a result of its higher resolution and more accurate topography, EIN75 generates a closer fit to the observed temperatures on the TP than EIN15, but there are no significant differences in precipitation between the two reanalysis datasets. Evaluation of these datasets would be very informative for further climate research and simulations on the TP.

Radiometric observations of relative humidity profile at Kolkata show a significant fall at around 1 to 2 km height during convective rain events. An extensive investigation shows that the fall of relative humidity is not seen during calm conditions but is strongly related to the characteristics of temperature lapse rate profiles. Moreover, the phenomenon may have strong association with boundary layer structure. The reason for such anomalies in the planetary boundary layer humidity profile might be due to the release of latent heat at the mentioned altitude. The abundance of pollutant aerosols in urban regions has also been found to contribute to this relative humidity anomaly. It has also been reported that this boundary layer relative humidity is accompanied by high latent heat release and condensation of vapour to liquid which is not much prominent in other rain types as observed in stratiform rain. Hence, convective rain produces some unique boundary layer characteristics which have also been partially supported with allied satellite and multi-station observations.

The main objective of this study is to examine the influence of atmospheric circulation patterns and sounding-derived parameters on thunderstorm occurrence in Central Europe. Thunderstorm activity tends to increase as one moves from the north to the south of the research area. Maximal thunderstorm occurrence is observed in the summer months, while between October and March such activity is much lower. Thunderstorms are also more frequent in spring than in autumn. In the warm season, the occurrence of thunderstorm is associated with the presence of a trough associated with a low located over the North Sea and Scandinavia. In the cold season, the synoptic pattern indicates a strong zonal flow from the west with significantly higher horizontal pressure gradient compared to the warm season. Thunderstorms are more likely to form when the boundary layer's mixing ratios are higher than 8 g kg − 1 . Deep convection is also more likely to occur when the vertical temperature lapse rates (between 800 and 500 hPa pressure layers) exceed 6 °C km − 1 . During the cold season, considerably higher lapse rates are needed to produce thunderstorms. The values obtained for the convective available potential energy indicate that at least 50 J kg − 1 is needed to produce a thunderstorm during wintertime and 125 J kg − 1 during summertime. Cold season thunderstorms are formed with a lower instability but with a more dynamic wind field having an average value of deep layer shear that exceeds 20 ms − 1 . The best parameter to distinguish thunderstorm from non-thunderstorm days for both winter and summer months is a combination of the square root of the convective available potential energy multiplied by the deep layer shear.

Densely populated cities experience adverse effects of Urban Heat Island (UHI) including higher numbers of emergency hospital admissions and heat related illnesses. Studying UHI effects and temperature variations has become even more important as global temperatures continue to rise. To better understand UHIs within New York City, an exploratory study was done using a field campaign to measure high resolution spatial and temporal temperature variations within Manhattan's urban setting. These time correlated temperature measurements along with weather model data of temperature and relative humidity were used to predict temperature variability using weather forecasts. The amplitude of spatial variations was most dependent on temperature (r = 0.400) and low level lapse rate (r = − 0.258) while temporal variations were most dependent on temperature (r = 0.398), low level lapse rates (r = − 0.361), and mid-level lapse rate (r = − 0.320). Regression of weather variables can be used to predict the amplitude of spatial and temporal variation in temperature within a city for each day. This study directs attention towards high resolution near-surface air temperature analysis and offers a new look at surface thermal properties. The application of the resulting data and modeling is most suitable for forecasting microscale variability in urban settings.

Organic molecular proxies provide a record of the hydrogen isotopic composition of ambient precipitation and paleoenvironmental temperature. In terrestrial settings, two classes of organic biomarkers are commonly utilized to reconstruct these past environmental conditions: straight-chained normal alkanes (n-alkanes) and branched glycerol dialkyl glycerol tetraethers (brGDGTs). We measured the δDn-alkane and the ratio of cyclisation and methylation indexes of branched tetraethers (CBT/MBT) from surface soils along a ∼1000 km transect along the southeast margin of the Tibetan Plateau to assess how these proxies record changes in climate parameters that are related to elevation, despite variations in ecosystem. Abundance-weighted δDnC27-31 data record the δD of precipitation across the orogen and indicate minimal change in apparent fractionation (en-alkane/water = −133‰) with elevation. n-Alkane δD mirrors the pattern of Rayleigh distillation of an air mass undergoing rainout as moisture moves from the Bay of Bengal into the SE margin of the Tibetan plateau. Soil tetraether temperatures provide a reliable measure of modern temperature with an MBT/CBT calculated temperature lapse rate (5.8 °C/km) close to the moist adiabat. These data reflect “ground-level” conditions that are independent of the shape of the orogen or the source of moisture. In combination with a Rayleigh distillation model that incorporates temperature and precipitation isotope data, paired tetraether temperature and leaf wax isotope data produce a reliable record of changes in environmental conditions associated with modern elevation change across the largest orogen. However, some tetraether calibrations may impart systematic temperature bias, most notably in cold or dry climates. These calibration uncertainties can result in underestimates of paleoelevations by up to 1.5–2 km. Paired isotopic and temperature paleoelevation reconstructions can minimize errors associated with an individual proxy method, however we recommend that application of tetraether temperature paleoelevation reconstruction take potential calibration biases into account in paleoelevation estimates.

A hail observation dataset for 1972–2013 is analyzed to examine the temporal and spatial distributions of hail occurrence in South Korea. Furthermore, using radiosonde data, three thermodynamic factors which are 700–500 hPa temperature lapse rate, water vapor mixing ratio in the lowest 100 hPa, and convective available potential energy (CAPE) and one dynamic factor which is 0–6 km bulk wind shear are calculated and their correlations with hail occurrence in South Korea are examined. Hail days per year in South Korea show a decreasing trend. The monthly variation of hail days exhibits double peaks in April and November. The minimum value of hail days appears in August, which is related to the high freezing-level height, the small midlevel temperature lapse rate, and the weak bulk wind shear. During a day, 44% of the whole hail events occur between 1200 and 1800 local standard time. Spatially, hail primarily occurs in the west coastal area and the east mountainous area of South Korea. Both the regions exhibit double peaks in the monthly variation of hail days, but the east mountainous area exhibits the later spring peak (May) and the lower hail frequency in late autumn compared to the west coastal area. The midlevel temperature lapse rate is strongly correlated with the monthly variation of hail occurrence. Hail is likely to occur when the low-level water vapor mixing ratio is in the range of ~ 3–6 g kg − 1 . CAPE is not strongly correlated with hail occurrence. The strong bulk wind shear is correlated with hail occurrence. The bulk wind shear is decreasing and the freezing-level height is increasing annually, which contributes to the annual decrease of hail occurrence.

The main objective of this study was to investigate whether dynamically downscaled high resolution (4-km) climate data from the Weather Research and Forecasting (WRF) model provide physically meaningful additional information for reference evapotranspiration (E) calculation compared to the recently published GridET framework that uses interpolation from coarser-scale simulations run at 32-km resolution. The analysis focuses on complex terrain of Utah in the western United States for years 1985–2010, and comparisons were made statewide with supplemental analyses specifically for regions with irrigated agriculture. E was calculated using the standardized equation and procedures proposed by the American Society of Civil Engineers from hourly data, and climate inputs from WRF and GridET were debiased relative to the same set of observations. For annual mean values, E from WRF (EW) and E from GridET (EG) both agreed well with E derived from observations (r2 = 0.95, bias < 2 mm). Domain-wide, EW and EG were well correlated spatially (r2 = 0.89), however local differences ΔE=EW-EG were as large as +439 mm year−1 (+26%) in some locations, and ΔE averaged +36 mm year−1. After linearly removing the effects of contrasts in solar radiation and wind speed, which are characteristically less reliable under downscaling in complex terrain, approximately half the residual variance was accounted for by contrasts in temperature and humidity between GridET and WRF. These contrasts stemmed from GridET interpolating using an assumed lapse rate of Γ = 6.5K km−1, whereas WRF produced a thermodynamically-driven lapse rate closer to 5K km−1 as observed in mountainous terrain. The primary conclusions are that observed lapse rates in complex terrain differ markedly from the commonly assumed Γ = 6.5K km−1, these lapse rates can be realistically resolved via dynamical downscaling, and use of constant Γ produces differences in E of order as large as 102 mm year−1.

Thermal tropopause represents the region of the atmosphere where the environmental lapse rate changes from tropospheric positive to stratospheric negative. It also defines the altitude of the atmosphere beneath which significant weather perturbations occur except occasional overshooting thunderstorms in the tropical regions. Accordingly, how the temporal and spatial variability of thermal tropopause behaves is of great concern in atmospheric research and, hence, investigated in this study by using radio occultation (RO) observations obtained from seven space missions during the period from May 2001 to April 2013 (with a total of 6,075,359 occultations). While RO observations have been demonstrated to provide precise measurements of temperature profiles of the atmosphere, their results are inter-compared before further use in our analysis, showing expected high-precision observations with mean differences

Constraining temporal and spatial variability in water stable isotopes (δ18O and δD) is requested for interpreting proxy records of paleoclimate/paleoaltimetry. The southeastern Tibetan Plateau (TP) receives large amounts of precipitation in both summer (JJAS) and spring (MAM) and this makes it different from most other parts of the TP where annual precipitation concentrates only in summer. However, our knowledge of controls on precipitation and surface runoff generation in this region is still far from sufficient. In this study, the δ18O and δD of precipitation and stream waters across the southeastern TP were analyzed to investigate moisture sources and empirical isotope-elevation relationships. Herein, seasonal precipitation patterns, moisture trajectories and precipitation isotopes suggest this region is seasonally dominated by the monsoon in summer and the southerlies (from the Bay of Bengal) or a mix of southerlies and westerlies in spring. Spatially, vertical variations in precipitation seasonality exert profound influences on isotopic variability for stream waters. Larger contributions of spring precipitation (with higher δ18O and d-excess (d-excess = δD-8δ18O) compared to summer precipitation) vs. summer precipitation in the surface runoff generation at lower elevations account for the uncommon altitudinal decrease in streamwater d-excess. Such a cause also contributes to the slightly greater vertical lapse rates of streamwater δ18O (−0.28 to −0.48‰/100 m) relative to the Himalayan front. In addition, although a robust δ18O-elevation relationship is demonstrated based upon our measured and other published data on a broad spatial scale (over a 5200 m elevation range), this relationship is found to deviate from the empirical/theoretical pattern in the Himalayan front, which is also caused by the substantial spring precipitation in the southeastern TP. It is suggested that long-term changes in δ18O or δD of paleowater in this region actually represent both changes in past regional elevations and contributions of summer vs. spring atmospheric circulations.

It is well known that remote sensing techniques hold the potential to explore the spatial estimation of air temperature (Ta) with fine spatial and temporal resolution across the world. However, because of the complex interaction of land-atmosphere system and the contamination of cloud cover, the retrieval of daytime Ta exclusively from remote sensing data is still far from straight forward, especially under cloudy sky conditions. In this paper, we presented a simple parameterization scheme of daytime Ta under all-weather conditions entirely based on Moderate Resolution Imaging Spectroradiometer (MODIS) products. To evaluate its applicability, the scheme was demonstrated in two regions with totally different geomorphological and climatic conditions, the east part of the Qaidam Basin (EQB) in China and the Southern Great Plains (SGP) in the United States of America. The instantaneous Ta under clear sky conditions (Ta , clear) was determined as the average of near surface air temperature (TaS) retrieved from MOD07_L2 product and land surface temperature (Ts) retrieved from MOD06_L2 product. Then a regression model between Ta , clear and Ts was established, and the instantaneous Ta under cloudy sky conditions (Ta , cloudy) was estimated by applying the regression model to Ts retrieved under cloudy sky conditions. The results showed that the averaging parameterization scheme has significantly improved the accuracy of Ta , clear retrievals with MAE = 1.95 °C, RMSE = 2.50 °C, and B = 0.02 in the EQB, and MAE = 2.02 °C, RMSE = 2.56 °C, and B = 0.01 in the SGP. The Ta , cloudy estimates also showed good agreement with Ta observations in both regions with a correlation coefficient (r) higher than 0.91. The values of RMSE calculated for the EQB and SGP were 3.42 °C and 2.91 °C, respectively. The accuracy of both Ta , clear and Ta , cloudy estimates has reached a level comparable with other traditional statistical approaches that adopt ancillary Ta measurements as training dataset. Therefore, it is feasible to estimate daytime Ta under all-weather conditions entirely based on MODIS products.

This study examines the spatial and temporal patterns of tropical tropopause layer (TTL) cirrus clouds (i.e., clouds with bases higher than 14.5 km) and their relationship to tropical tropopause including both cold point tropopause (CPT) and lapse rate tropopause (LRT). We use eight years (2006–2014) data from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements. In addition to the CALIPSO cloud layer product, the clouds included in the current CALIPSO dataset as stratospheric features have been considered by separating clouds from aerosols, which are important in the TTL cloud analysis. It is also shown that the temporal variation of the stratospheric aerosols matches well with the volcanic eruption events. The TTL cloud fraction and the tropical tropopause temperature both have pronounced annual cycles and are strongly negatively correlated both temporally and spatially. The examination of the TTL cloud height relative to tropopause from collocated CALIPSO and COSMIC observations indicates that the tropopause plays a critical role in constraining the TTL cloud top height. We show that the probability density function of TTL cloud top height peaks just below the CPT while the occurrence of TTL clouds with cloud tops above the CPT could be largely explained by observed tropopause height uncertainty associated with the COSMIC vertical resolution.

To investigate the variability of in situ profile shapes under a variety of meteorological and pollution conditions, results are presented of an agglomerative hierarchical cluster analysis of the in situ O3 and NO2 profiles for each of the four campaigns of the NASA DISCOVER-AQ mission. Understanding the observed profile variability for these trace gases is useful for understanding the accuracy of the assumed profile shapes used in satellite retrieval algorithms as well as for understanding the correlation between satellite column observations and surface concentrations. The four campaigns of the DISCOVER-AQ mission took place in Maryland during July 2011, the San Joaquin Valley of California during January–February 2013, the Houston, Texas, metropolitan region during September 2013, and the Denver-Front Range region of Colorado during July–August 2014. Several distinct profile clusters emerged for the California, Texas, and Colorado campaigns for O3, indicating significant variability of O3 profile shapes, while the Maryland campaign presented only one distinct O3 cluster. In contrast, very few distinct profile clusters emerged for NO2 during any campaign for this particular clustering technique, indicating the NO2 profile behavior was relatively uniform throughout each campaign. However, changes in NO2 profile shape were evident as the boundary layer evolved through the day, but they were apparently not significant enough to yield more clusters. The degree of vertical mixing (as indicated by temperature lapse rate) associated with each cluster exerted an important influence on the shapes of the median cluster profiles for O3, as well as impacted the correlations between the associated column and surface data for each cluster for O3. The correlation analyses suggest satellites may have the best chance to relate to surface O3 under the conditions encountered during the Maryland campaign Clusters 1 and 2, which include deep, convective boundary layers and few interruptions to this connection from complex meteorology, chemical environments, or orography. The regional CMAQ model captured the shape factors for O3, and moderately well captured the NO2 shape factors, for the conditions associated with the Maryland campaign, suggesting that a regional air quality model may adequately specify a priori profile shapes for remote sensing retrievals. CMAQ shape factor profiles were not as well represented for the other regions.

The uplift history of the Tibetan Plateau is poorly constrained. A key problem is the discrepancy between reconstructions based on different paleoaltimeters. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) produced by soil-dwelling bacteria offer a potential tool for paleoaltimetry reconstruction. However, because in-situ soil temperature–the direct link between brGDGTs and altitude–is generally not well-constrained, the reliability and uncertainty of this approach remain uncertain. Here, we investigated brGDGT distributions and in-situ soil temperature along an altitudinal gradient at 2300–4000 m on Mt. Laji, northeastern Tibetan Plateau, to test the relationships among altitude, temperature, and brGDGTs. The results show that: 1. the measured mean annual soil temperature (MAST) is strongly correlated with altitude (R2 = 0.73), but compared with those for mean annual air temperature (MAAT) derived from weather stations, the absolute values are substantially higher particularly at higher altitudes, while the lapse rate (−0.39 °C/100 m) is much lower; 2. brGDGT-reconstructed MAST using published soil temperature calibrations is generally consistent with in-situ soil temperature measurements, displaying similar lapse rates (−0.48 °C/100 m for MASTsr and − 0.41 °C/100 m for MASTsrs at the sunny slope) to that for measured MAST; 3. the slope aspect may affect both measured and brGDGT-reconstructed MAST by up to >3 °C. Overall, our results demonstrate that soil brGDGTs can quantitatively capture elevation-dependent soil temperature variation on the Tibetan Plateau. However, the use of ex-situ air temperature instead of in-situ soil temperature, and the effect of slope aspect on temperature, may introduce uncertainties in evaluating the brGDGT paleoaltimeter in this region. In paleo-applications, suitable calibrations are required and soil temperature lapse rates should be constrained before applying brGDGTs to quantitatively reconstruct past uplift histories.

Analytical solution for two-dimensional thermal plume updraft velocity is obtained under the assumption of a uniform temperature excess inside the plume. In this way, the thermal plume motion is modeled in both mixed layer and entrainment zone. Also, a semi-analytical solution is obtained using an empirical model for the plume temperature excess in the mixed layer. In addition, an analytical model for entrainment zone thickness is obtained by computing the overshoot distance of the modeled plumes, and a semi-analytical model by using the empirical model for plume temperature. By using a nonlinear profile for the lapse rate in the surface layer based on the Monin–Obukhov similarity theory, our model predicts that the characteristics of the surface layer plays an important role in the structure of the entrainment zone. Finally, our solutions for plume velocity allow us to consider the effect of the lateral entrainment on the plume excess temperature and velocity in the convective boundary layer. It is shown that the lateral entrainment has an important role on the plume dynamics and the solutions in the zero entrainment limit offer large overestimated values for the plume velocity, which also result in overestimated values of the entrainment zone thickness.

To understand the characteristics of atmospheric pollution in Xi'an, China, the vertical structure of aerosols and meteorological data (temperature and relative humidity) during atmospheric pollution processes were obtained and studied. Lidar and radiosonde data were used for analyses of atmospheric pollution. Polarization lidar was used to study the vertical distribution and optical properties of aerosols during haze and dust processes that occurred in 2015–2016. The planetary boundary layer height (PBLH) and types of aerosol particles were retrieved from polarization lidar. A case study shows that a low PBLH and complex vertical distributions of aerosols, temperature and relative humidity (RH) were the main structural characteristics of haze days. The backscatter coefficient exceeded 0.015 km−1·Sr−1, while the linear particle depolarization ratio was relatively small. A large depolarization ratio above the haze layer, which induces the existence of floating dust, was observed by polarization lidar. Compared with those of haze processes, the vertical aerosol and temperature distributions of dust processes were different. Statistical analyses of the PBLH, temperature inversion, RH and near-surface aerosol concentration were also presented. A lower PBLH, lower average lapse rate of temperature within the PBL, and higher RH were found when haze pollution occurred. An inversion at the top of the boundary layer aggravates ground pollution, while there is not always a temperature inversion when haze occurs in Xi'an. Together, a lower PBLH and lower average lapse rate of temperature weaken the vertical diffusion of pollutants. Decreased vertical diffusion should be the main reason for the formation and persistence of pollution in Xi'an. Increased RH was the catalyst for haze pollution. The aggravation of haze was usually accompanied by an increase in RH, and the decline of haze processes was also accompanied by a decrease or increase (>90%) in RH.

Snow cover and seasonally frozen ground (SFG) are the key cryospheric elements on the southern edge of Altai Mountains (SEAM). Quantifying the thermal effect of snow cover on the frozen ground remains challenging. Utilizing the datasets observed at Altai Kuwei Snow Station (AKSS) and by National Meteorological Stations of China Meteorological Administration (CMA), we evaluated the thermal effect of snow cover on SFG regime. The results observed by AKSS indicated that the energy exchange between the ground and atmosphere was significantly insulated by snow cover, resulting in a considerable temperature offset between the snow surface and the ground below. This offset reached a maximum of 12.8°C for a snow depth of 50 cm, but decreased for snowpack depths of >70 cm, whereas the snow temperature lapse rate was systematically steeper in the upper snowpack than at depth. Snow cover was the dominating driver of inter-annual differences in the SFG regime, as represented by the annual maximum freezing depth and soil heat flux. The observed average soil heat loss rate increased from 2.68 to 5.86 W/m2 on two occasions when the average snow depth decreased from 61.2 cm to 13.7 cm, resulting in an increase in maximum freezing depth of SFG from 69 cm to >250 cm soil depth. The results observed by CMA also demonstrate how snow cover controlled the SFG regime by warming the ground and inhibiting freezing of the soil column. Snow cover caused a 44.5-cm decline of annual maximum freezing depth during 1961-2015 period. SFG degradation between 1961 and 2015 was accompanied by increases in both air temperature and snow cover, with the former playing the dominant role. The correlation between snow cover and the ground–atmosphere temperature offset provides a new empirical method of evaluating the effective thermal effect of snow cover on SFG.

The detailed evolution of different tropical tropopause layer (TTL) parameters, such as tropopause height (cold point (CPH)/lapse rate (LRH)/convective (COH)), its corresponding temperature (CPT/LRT/COT) and TTL thickness in response to recent 2015–16 El Nino event are delineated using high-resolution Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Radio Occultation (RO) measurements. Distinct TTL anomalies are noticed between June-July-August (JJA), September-October-November (SON), and December -January-February (DJF) seasons during 2015–16 El Nino event. A pronounced positive anomaly in the CPH and LRH (~0.8 km) is noticed in JJA over most of the tropical equatorial region, whereas, in DJF, positive anomalies mostly concentrate over off equatorial central Pacific (CP) and eastern Pacific (EP) regions. Interestingly, prominent higher positive anomalies are evident in the convective outflow level altitude (~1 km) particularly over the tropical CP and EP regions in JJA and DJF. The CPT and LRT exhibit strong negative anomalies (>4 K) over CP and EP regions and positive anomalies over the western Pacific region in all the seasons. However, significant positive CPT and LRT anomalies are evident over the Atlantic region in DJF. In contrast, the COH (COT) and TTL thickness anomalies are well-matched with the outgoing long wave radiation anomalies compared to the CPH and LRH (CPT and LRT) anomalies. Overall, the observed TTL parameters exhibit similar El Nino signatures as observed for the other events. However, the 2015–16 El Nino event was one of strongest summer ENSO events in the 21st century compared to the previous events. As a result, prominent warm tropopause temperatures are evident over the WP region during JJA and these anomalies reaches maximum in DJF. The observed changes in the TTL parameters are explained in the context of circulation and convection changes over the tropics.

In this paper, we use molecular paleothermometry, based on the TEX86 proxy derived from fossilized archaeal lipids, to reconstruct absolute sea surface temperatures (SSTs) for the northwest Tethys Shelf during the late Pliensbachian to early Toarcian (Early Jurassic, ~183 Ma) stages. Our composite record from outcrops in Spain and Italy reveals that tropical SSTs varied between 22 and 32 °C over a ~ 3 Myr time period, including transient temperature excursions of 5–10 °C magnitude with lapse rates of ~0.1 °C/kyr. Changes in reconstructed SSTs covaried with sea level fluctuations and δ18O isotope signatures of marine biocalcifiers, recording recurrent shifts between icehouse and greenhouse states. Parallel trends of reconstructed SST and δ13C isotopes of atmospheric CO2 may reflect storage of isotopically light carbon in cryosphere reservoirs during icehouse phases and release during greenhouse phases. The existence of a labile cryosphere is considered a prerequisite to explain the inferred rapid climate fluctuations and as a reservoir to facilitate pronounced carbon isotope excursions.

On 14 July 2012 a shortwave trough with a cold front passed through Poland. A few tornadoes were reported in the north central part of the country within an isolated cyclic supercell. The cell moved along the thermal and moisture horizontal gradients and the support of a synoptic scale lift. An analysis allowed for setting up four tornado damage tracks in a distance of 100 km and with a total length of 60 km. Tornadoes damaged 105 buildings with predominant intensity of F1-F2/T3-T4 (maximum F3/T6) in Fujita/TORRO scale, caused 1 fatality, 10 injures and felled 500 hectares of Bory Tucholskie forest. The main aim of this article was to analyze this event and assess the possibilities of its short-term prediction. In order to achieve this, a model forecast data derived from WRF-ARW simulation with a spatial resolution of 15 km and initial conditions extracted from 0000 UTC GFS was used. An analysis yielded that the cell moved in the environment of a low lifting condensation level, rich boundary layer's moisture content and a steepening vertical lapse rates that provided the presence of a thermodynamic instability. A wind vectors tilting with height and an increased vertical wind shear occurred as well. A forecasting method that combined a Universal Tornadic Index composite parameter with a convective precipitation filter showed that convective cells at 1500 UTC in the north central Poland had a potential to become tornadic. Within the use of a proposed methodology, it was possible to issue a tornado forecast for the areas where an index pointed the risk.

The temperature trend estimated from the distribution of bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soil (i.e. the MBT–CBT or MBT′–CBT index) was studied along an altitude transect from 1850 m to 5139 m in the southeast Tibetan Plateau. Measured temperature values from weather stations in the area showed increasing seasonality with increasing elevation. The measured lapse rate of mean annual air temperature (MAAT) in the region was −7.2 °C/km, whereas that estimated from the MBT- or MBT′–CBT index was lower, with only −3.2 °C/km for the MBT′–CBT estimate. At elevation > 4 km, MBT′–CBT temperature values were increasingly higher than measured MAAT values. We hypothesized that the systematic changes in the length of the warm season, as well as the seasonal period of brGDGT production, with elevation are likely the cause of overestimation of the MBT′–CBT temperature at high elevation sites, and hence the underestimation of lapse rate. The hypothesis was supported by a similar lapse rate of −3.1 °C/km calculated from the measured mean warm season temperature (MWST) that only included monthly temperature values > 0 °C. This suggests that care should be taken in interpreting brGDGT derived temperature values in environments with large seasonal contrasts.

Estimates of continental paleoelevation using proxy methods are essential for understanding the geodynamic, climatic, and geomorphoric evolution of ancient orogens. Fossil-leaf paleoaltimetry, one of the few quantitative proxy approaches, uses fossil-leaf traits to quantify differences in temperature or moist enthalpy between coeval coastal and inland sites along latitudes. These environmental differences are converted to elevation differences using their rates of change with elevation (lapse rate). Here, we evaluate the uncertainty associated with this method using the Eocene North American Cordillera as a case study. To do so, we develop a series of paleoclimate simulations for the Early (∼55–49 Ma) and Middle Eocene (49–40 Ma) period using a range of elevation scenarios for the western North American Cordillera. Simulated Eocene lapse rates over western North America are ∼5 °C/km and 9.8 kJ/km, close to moist adiabatic rates but significantly different from modern rates. Further, using linear lapse rates underestimates high-altitude (>3 km) temperature variability and loss of moist enthalpy induced by non-linear circulation changes in response to increasing surface elevation. Ignoring these changes leads to kilometer-scale biases in elevation estimates. In addition to these biases, we demonstrate that previous elevation estimates of the western Cordillera are affected by local climate variability at coastal fossil-leaf sites of up to ∼8 °C in temperature and ∼20 kJ in moist enthalpy, a factor which further contributes to elevation overestimates of ∼1 km for Early Eocene floras located in the Laramide foreland basins and underestimates of ∼1 km for late Middle Eocene floras in the southern Cordillera. We suggest a new approach for estimating past elevations by comparing proxy reconstructions directly with simulated distributions of temperature and moist enthalpy under a range of elevation scenarios. Using this method, we estimate mean elevations for the North American Cordillera of ∼2 km using proxy temperatures and ∼3 km using proxy moist enthalpy. This discrepancy is likely related to an inconsistency between the proxy data for temperature and moist enthalpy. The combination of temperature and moist enthalpy estimates implies a warm and dry environment, which is inconsistent with geological evidence for humid conditions. Our study emphasizes that lapse rates in warm climate were likely much different than today's, and highlights the advantages of using climate models to understand past climate states and regional circulation patterns to derive more accurate paleoelevation estimates using proxy temperature and moist enthalpy.

This paper draws attention to highlight the spatial and temporal variability in precipitation lapse rate (PLR) and precipitation extreme indices (PEIs) through the mesoscale characterization of Teesta river catchment, which corresponds to north Sikkim eastern Himalayas. A PLR rate is an important variable for the snowmelt runoff models. In a mountainous region, the PLR could be varied from lower elevation parts to high elevation parts. In this study, a PLR was computed by accounting elevation differences, which varies from around 1500 m to 7000 m. A precipitation variability and extremity were analysed using multiple mathematical functions viz. quantile regression, spatial mean, spatial standard deviation, Mann–Kendall test and Sen's estimation. For this reason, a daily precipitation, in the historical (years 1980–2005) as measured/observed gridded points and projected experiments for the 21st century (years 2006–2100) simulated by CMIP5 ESM-2 M model (Coupled Model Intercomparison Project Phase 5 Earth System Model 2) employing three different radiative forcing scenarios (Representative Concentration Pathways), utilized for the research work. The outcomes of this study suggest that a PLR is significantly varied from lower elevation to high elevation parts. The PEI based analysis showed that the extreme high intensity events have been increased significantly, especially after 2040s. The PEI based observations also showed that the numbers of wet days are increased for all the RCPs. The quantile regression plots showed significant increments in the upper and lower quantiles of the various extreme indices. The Mann–Kendall test and Sen's estimation tests clearly indicated significant changing patterns in the frequency and intensity of the precipitation indices across all the sub-basins and RCP scenario in an intra-decadal time series domain. The RCP8.5 showed extremity of the projected outcomes.

Reconstructing topography of our planet not only advances our knowledge of the geodynamic processes that shape the Earth's surface; equally important it adds a key element towards understanding long-term continental moisture transport, atmospheric circulation and the distribution of biomes and biodiversity. Stable isotope paleoaltimetry exploits systematic decreases in the oxygen (δ18O) or hydrogen (δD) isotopic composition of precipitation along a mountain front when the interaction of topography and advected moist air masses induces orographic precipitation. These changes in δ18O or δ D can be recovered from the geologic record and recent geochemical and modeling advances allow a broad range of proxy materials to be evaluated. Over the last 10 yr stable isotope paleoaltimetry has witnessed rapidly expanding research activities and has produced a broad array of fascinating tectonic and geomorphologic studies many of which have concentrated on determining the elevation history of continental plateau regions. These single-site studies have greatly expanded what used to be very sparse global paleoaltimetric data. The challenge now lies in disentangling the surface uplift component from the impact of climate change on δ18O and δ D in precipitation. The robustness of stable isotope paleoaltimetry can be enhanced when high-elevation δ18O or δ D data are referenced against low-elevation sites that track climate-modulated sea level δ18O or δ D of precipitation through time (‘ δ – δ approach’). Analysis of central Andean paleosols documents that differences in δ18O of soil carbonate between the Subandean foreland and the Bolivian Altiplano are small between 11 and 7 Ma but rise rapidly to ca. 2.9‰ after 7 Ma, corroborating the magnitude of late Miocene change in δ18O on the Altiplano. Future advances in stable isotope paleoaltimetry will greatly benefit from addressing four key challenges: (1) Identifying topographically-induced changes in atmospheric circulation and associated teleconnections in the global climate system that affect δ18O or δ D of precipitation; (2) Evaluating on a case-by-case basis if temporal and spatial changes in isotope lapse rates influence interpretations of paleoelevation; (3) Interfacing with phylogenetic techniques to evaluate competing hypotheses with respect to the timing of surface uplift and the diversification of lineages; (4) Characterizing feedbacks between changes in surface elevation and atmospheric circulation as these are likely to be equally important to the diversification of lineages than changes in surface elevation alone. Tackling these challenges will benefit from the accelerating pace of improved data-model comparisons and rapidly evolving geochemical techniques for reconstructing precipitation patterns. Most importantly, stable isotope paleoaltimetry has the potential to develop into a truly interdisciplinary field if innovative tectonic/paleoclimatic and evolutionary biology/phylogenetic approaches are integrated into a common research framework. It therefore, opens new avenues to study the long-term evolution of landscapes and life.

The interpretation of speleothem paleoenvironmental records requires understanding of spatial–temporal variations in vadose drip water chemistry and isotopic composition. This study reports on intra- and inter-cave differences in δD, δ18O and electrical conductivity, using 18 monthly water samples from three adjacent drips ( All drips showed isotopic seasonal signals, despite varied patterns of drip hydrology. There was overlap in isotopic ranges (at 1 SD) between all three caves, in contrast with the expected δ18O depletion of −0.15 to −0.5‰/100 m of ascent observed in standard precipitation. The isotopic seasonality was approximated with sine curves, and compared to a GNIP data set from Victoria ∼300 km to the south. The δD and δ18O drip isotopes lagged the Victoria record by 155 ± 26 days and 165 ± 50 days respectively. The longest lag was at the slowest drip (sea level), while the shortest lag (87 days for δ18O, 550 m ASL) implies a short residence time, paradoxically from the drip with the highest mean electrical conductivity. Vadose residence time was less than one climatic year, reflecting a combination of negligible matrix porosity in the host rock and super-humid climatic conditions. Beneath the epikarst, drip hydrology was evidently by simple piston flow. Phase-shifted drip isotope records showed excellent agreement with sea level mean monthly air temperatures at the Tahsis meteorological station over the study period. The δD and δ18O drip amplitudes were damped on average 74% and 73% respectively compared to the Victoria data. The drips at 740 m ASL are tightly aligned to the global mean meteoric water line (GMWL) and 18O-depleted; the drips at 550 m ASL and at sea level plot along the GMWL, or between it and the Victoria LMWL, with the exception of the slowest drip (sea level) which displays some seasonal evaporitic enrichment. The findings quantify substantial intra- and inter-cave variation of δD and δ18O in drips having a wide range of drip type and volume of flow, sufficient to mute the altitudinal isotopic lapse rate in this local coastal rainforest environment.