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This paper describes 2007/2008 inter-annual changes in runoff from the Zhadang Glacier located on the northern slope of Nyainqêntanglha Range, Tibet, and analyzes their causes. Precipitation increased by 17.9% in summer months of 2008 compared with the same period in 2007, drainage basin runoff decreased by 33.3%, and glacial meltwater decreased by 53.8%. Change in positive accumulated air temperature explained approximately half of the inter-annual difference in glacial meltwater using a degree-day model. This suggests that the glacier is extremely sensitive to changes in air temperature. Energy balance analysis showed that change in glacier surface albedo, considered to be caused by difference in precipitation form, resulted in the large inter-annual difference in glacial meltwater. It was shown statistically that precipitation form in the summer months of 2007 was mainly rainfall which comprised 71.5% of total precipitation, while during the same period in 2008 rainfall accounted for 30.7%, with the majority of precipitation falling as snow. Precipitation form should be considered an independent factor when analyzing glacier sensitivity to climate change or forecasting the runoff from certain glaciers. [ABSTRACT FROM AUTHOR]

Sensible heat flux greatly influences the Indian monsoon. In this study, we calculated sensible heat flux time-series for 12 sites over the western Tibetan Plateau using Price and Dunne's formula and adjusting the stability function. The time-series were derived from the field observations from the GEWEX Asian Monsoon Experiment (GAME)/Tibet programme under the Global Energy and Water Cycle Experiment (GEWEX). This paper demonstrates that monthly sensible heat fluxes show strong correlations with corresponding precipitation, and that the correlation coefficients increase with precipitation amount. The preceding winter and spring solid precipitation (snowfall and resulting snowpack) can also influence sensible heat flux in May, but the situation is complex. The correlations between heat flux and snowfall at Amdo, Naqu, and Lhasa are negative, but they are positive at Gaize (also known as Gerze) and Dingri. There is a significant relationship between how the variations from the mean calculated heat fluxes at Amdo differ from those at Rikaze, or Dingri, Cuona and Longzi, and their respective June-September precipitation amounts. This phenomenon may result from changes in circulation. When the sensible heat fluxes are above average north of the influence of the Indian monsoon and below average to the south, the summer monsoon circulation develops early and with greater intensity and precipitation, and vice versa. [ABSTRACT FROM AUTHOR]

Extreme precipitation events, which have intensified with global warming over the past several decades, will become more intense in the future according to model projections. Although many studies have been performed, the occurrence patterns for extreme precipitation events in past and future periods in China remain unresolved. Additionally, few studies have explained how extreme precipitation events developed over the past 58 years and how they will evolve in the next 90 years as global warming becomes much more serious. In this paper, we evaluated the spatiotemporal characteristics of extreme precipitation events using indices for the frequency, quantity, intensity, and proportion of extreme precipitation, which were proposed by the World Meteorological Organization. We simultaneously analyzed the spatiotemporal characteristics of extreme precipitation in China from 2011 to 2100 using data obtained from the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Despite the fixed threshold, 95th percentile precipitation values were also used as the extreme precipitation threshold to reduce the influence of various rainfall events caused by different geographic locations; then, eight extreme precipitation indices (EPIs) were calculated to evaluate extreme precipitation in China. We found that the spatial characteristics of the eight EPIs exhibited downward trends from south to north. In the periods 1960–2017 and 2011–2100, trends in the EPIs were positive, but there were differences between different regions. In the past 58 years, the extreme precipitation increased in the northwest, southeast, and the Tibet Plateau of China, while decreased in northern China. Almost all the trends of EPIs are positive in the next two periods (2011–2055 and 2056–2100) except for some EPIs, such as intensity of extreme precipitation, which decrease in southeastern China in the second period (2056–2100). This study suggests that the frequency of extreme precipitation events in China will progressively increase, which implies that a substantial burden will be placed on social economies and terrestrial ecological processes. [ABSTRACT FROM AUTHOR]

The selection of general circulation models (GCMs) with high capability to represent the past and likely future climate for a specific geographical location is a crucial step to assess impacts of climate change on different sectors. This study included pool of 105 and 78 GCMs for representative concentration pathways (RCPs) 4.5 and 8.5, respectively, from Coupled Model Intercomparison Project—Phase 5, applied an advanced envelope‐based selection approach to select representative GCMs for the Koshi river basin in China and Nepal at short‐term (2016–2045), mid‐century (2036–2065) and end‐of‐century (2071–2100) periods, and developed range of possible future precipitation and temperature scenarios with high resolution downscaled data (10 × 10 km2), which is the novelty contribution of the study. Considering RCP4.5, average annual precipitation is expected to increase by 0–16%, 4–23% and 4–24% in the short‐term, mid‐century and end‐of‐century periods, respectively. Using RCP8.5, equivalent predictions are 6–20%, 6–36% and 13–49% in the short‐term, mid‐century and end‐of‐century periods, respectively. Average annual temperature is expected to increase, but with higher increases during winter than in the monsoon period. Considering RCP4.5, average annual temperature is expected to increase by 1–1.4°C, 1.3–1.9°C and 1.6–2.8°C in the short‐term, mid‐century and end‐of‐century periods, respectively. Similarly, using RCP8.5, equivalent predictions are 1–1.6°C, 1.8–2.9°C and 3.1–5.6°C in the short‐term, mid‐century and end‐of‐century periods, respectively. The ensemble mean of absolute change in average precipitation and temperature projects that High Himalaya and Tibet regions are more sensitive to climate change considering precipitation and temperature, respectively. The results also suggest that GCMs selection for a catchment varies with climate scenarios and specific future time periods. [ABSTRACT FROM AUTHOR]

Measurements of precipitation isotopic composition have been conducted on a daily basis for 1 yr at Bomi, in the southeast Tibetan Plateau, an area affected by the interaction of the southwest monsoon, the westerlies, and Tibetan high pressure systems, as well as at Lhasa, situated west of Bomi. The measured isotope signals are analyzed both on an event basis and on a seasonal scale using available meteorological information and airmass trajectories. The processes driving daily and seasonal isotopic variability are investigated using multidecadal climate simulations forced by twentieth-century boundary conditions and conducted with two different isotopic atmospheric general circulation models [the isotopic version of the Laboratoire de Méétééorologie Dynamique GCM (LMDZiso) and the ECHAM4iso model]. Both models use specific nudging techniques to mimic observed atmospheric circulation fields. The models simulate a wet and cold bias on the Tibetan Plateau together with a dry bias in its southern part. A zoomed LMDZ simulation conducted with ~50-km local spatial resolution dramatically improves the simulation of isotopic compositions of precipitation on the Tibetan Plateau. Simulated water isotope fields are compared with new data and with previous observations, and regional differences in moisture origins are analyzed using back-trajectories. Here, the focus is on relationships between the water isotopes and climate variables on an event and seasonal scale and in terms of spatial and altitudinal isotopic gradients. Enhancing the spatial resolution is crucial for improving the simulation of the precipitation isotopic composition. [ABSTRACT FROM AUTHOR]

Variations of precipitation over the eastern edge of the Tibetan Plateau are analyzed by using data over station Yaan including daytime, nighttime, and daily-mean precipitation and satellite-derived information. A comparison of some features over Yaan and other stations is also carried out. Over Yaan, light-moderate precipitation contributes significantly to both the number of rainy days (96.9%) and the amount (66.9%) of total precipitation. The light-moderate precipitation occurs more frequently at nighttime than at daytime (by 44.5 days, or 33.4%, and by 520.6 mm, or 134.4%, each year), and the nighttime precipitation is mainly in the form of light-moderate precipitation. The number of rainy days and the amount of total precipitation have decreased from the 1950s to the 1970s and during the recent 20 years, associated with negative trends of light-moderate precipitation. Similar features are also found in the Tropical Rainfall Measuring Mission satellite data. Local convective precipitation is the main form of the light-moderate precipitation over Yaan. The absorption of latent heat at the lower troposphere and the release of latent heat at the upper troposphere are larger at nighttime than at daytime by 1–2 times and 2–3 times, respectively. Both the peak value and the total release of latent heat over Yaan are significantly larger than those over the Tibetan Plateau, eastern China, and the western Pacific warm pool. These distinct local characteristics of the “rain city” Yaan are closely related to the interaction between the atmospheric circulation and the steep topography on the eastern edge of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Based on the snow cover fraction (SCF) data acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra spacecraft from 2000–2006, statistical analyses are performed to explore the spatial and temporal distribution and variation of the snow cover over the Tibetan Plateau (TP). It is found that the snow persistence over the TP varies in different elevation ranges generally becomes longer with increases in the terrain elevation. In addition, the spatial distribution of the snow cover not only depends on the elevation but also varies with terrain features, such as aspect, slope, and curvature in the local areas. With 7-year observational data, seasonal and interannual variability of snow cover has been detected. There are slight decreasing trends in SFCs from 2000–2006. With MODIS satellite snow-cover fraction data and the National Centers for Environmental Predictions and U.S. Department of Energy NCEP/DOE reanalysis II dataset, the relationship between snow cover anomalies over the TP and the East Asian Summer Monsoon (EASM) is examined. Results indicate that the onset of the EASM is closely associated with snow cover anomalies in the spring. Specifically, a positive (negative) snow cover anomaly is followed by a later (earlier) onset of the EASM. [ABSTRACT FROM AUTHOR]

We illustrate the vast expanse and the connection of anticyclonic flows of the Tibetan high (at the 200 hPa level) to the pole centred hemispheric North Polar anticyclone at the 10 hPa level during 1988. This feature of clockwise flows appears in the form of a tilted cone that appears to connect the Asian summer monsoon to the 10 hPa high. The anticyclonic flow tapers down to the vortex of the cone near the 400 hPa level. The tropical easterly jet of the Asian summer season is found near 10°N, at the 200 hPa level. Summer monsoon rainfall resides on the poleward side of this jet where the circulation carries a large negative relative vorticity. Over these precipitating regions, large-scale upward motion contributes to a transport of negative vorticity into the lower stratosphere. We show that this region of the stratosphere carries the kinematics for a large conversion of anticyclonic shear vorticity into anticyclonic curvature vorticity. Four-dimensional parcel trajectories emanating and rising from this region slowly carve out the hemispheric anticyclonic gyre at the 10 hPa level (i.e.) the North Polar anticyclone. This kinematics plays an important role in establishing this tilted system and a connection with the 10 hPa circulation. [ABSTRACT FROM AUTHOR]

A 107-cm-long lake core was drilled in South Hongshan Lake (35°10′N, 80°04′E, 5060 m a.s.l.) shows 150 yr of environmental change as inferred from ostracoda assemblages. Four species of ostracoda, which belong to four genera, have been identified. The ostracoda distribution in the core can be divided into six ostracoda assemblages as follows: OA1--Ilyocypris biplicata-- Limnocythere inopinata assemblage; OA2--Limnocythere inopinata--Leucocythere mirabilis assemblage; OA3--Leucocythere mirabilis--Limnocythere inopinata assemblage, in which dominant species is Limnocythere inopinata; OA4--Nearly ostracoda free; OA5--Eucypris inflata--Limnocythere inopinata assemblage; and OA6-- Limnocythere inopinata changes from dominant to sole species. These ostracoda assemblages, together with other proxies, imply the following environmental sequence for the past 150 yr in the study area. Shallow moving water appears in A.D. 1850--1884, followed by a warm-humid climate in 1884--1922. Lake level decreased and water temperature supported maximum ostracoda growth in 1922--1946, followed by cooling conditions in 1946--1960. From 1960 to 1980, declining lake level is closely linked with local precipitation. The period since 1982 is characterized by less precipitation and continuous aridity under warming climatic conditions. [ABSTRACT FROM AUTHOR]

The quantitative estimation of paleoaltitude has become an increasing focus of Earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts, as well as the influence of mountain belt growth on regional and global climate. The general observation of decreasing δ18O and δ²H values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation. These studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming. In this review we provide a theory behind the application of stable isotope-based approaches to paleoaltimetry. We apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations. Examples of the application of paleoaltimetry techniques to Himalaya-Tibet and the Andes are discussed with implications for processes that cause surface uplift. [ABSTRACT FROM AUTHOR]

Time series analysis of Normalized Difference Vegetation Index (NDVI) imagery is a powerful tool in studying land use and precipitation interaction in data-scarce and inaccessible areas. The Fast Fourier Transform (FFT) was applied to the annual time series of 36 average dekadal NDVI images. The dekadal annual average pattern was calculated from 189 NDVI images from April 1998 to June 2003 acquired with the VEGFTATION instruments of the SPOT-4 and SPOT-5 satellites in Tibet. It is shown that the first two harmonic terms of a Fourier series suffice to distinguish between land use classes. The results indicate that the highest biomass production occurs before the monsoon peak. Regression analysis with 15 meteorological stations has shown that the total amount of precipitation during the growing season shows the strongest relation with the sum of the amplitudes of the first two harmonic terms (R² = 0.72). Inter-annual NDVI variation based on Fourier-transformed time series was studied and it was shown that, early in the season, the expected NDVI behaviour of the up-coming season could be forecast; if linked to food production this might provide a robust early warning system. The most important conclusion from this work is that harmonic time series analysis yields more reliable results than ordinary time series analysis. [ABSTRACT FROM AUTHOR]