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Two lines of thinking concerning fluid rotation—using either vorticity or circulation—emerged from the nineteenth-century work of Helmholtz and Thomson (Lord Kelvin), respectively. Vilhelm Bjerknes introduced an extension of Kelvin's ideas on circulation into geophysics. In this essay a historical perspective will be given on what has become known as the “Bjerknes circulation theorem.” Bjerknes wrote several papers on this topic, the first being in 1898. As Bjerknes noted, a Polish physicist, Ludwik Silberstein, had previously published an equivalent result concerning vorticity generation in 1896. Silberstein's work had built on an earlier paper by J. R. Schütz in 1895. In his 1898 paper Bjerknes describes many possible applications of the theorem to meteorology and oceanography including to extratropical cyclones, a subject that made his “Bergen School” famous. [ABSTRACT FROM AUTHOR]

Meteorological extremes on the seasonal time scale have received increased attention due to their relevance for society and economy. A recently developed approach to identify seasonal extremes is applied here to ERA5 reanalyses from 1950 to 2020 to identify hot and cold, wet and dry, and stormy and calm extreme seasons globally. The approach consists of (i) fitting a statistical model to seasonal mean values (of temperature, precipitation, and wind speed) at each grid point, (ii) selecting a local return period threshold above which seasonal mean values are deemed extreme, and (iii) forming spatially coherent extreme season objects. The paper introduces the ERA5 extreme season explorer, an open-access web portal enabling researchers to visualize and download extreme season objects of any of the six types in their region of interest, for further investigating their underlying dynamics, statistical properties, and impacts. To illustrate the potential of our extreme season objects, we first discuss the top 10 cold winters in ERA5 globally and then focus on an unusual triple-compound extreme season in winter 1953/54 in Europe, which was simultaneously extremely cold, dry, and calm. We show that detailed analysis of weather system dynamics, including cyclones, blocks, jets, and Rossby waves, provides important insight into the processes leading to extreme seasons. In summary, this study presents for the first time a catalogue of objectively identified extreme seasons in the last decades, shows exemplarily how large-scale dynamics can lead to such seasons, and with the help of the explorer supports the community in accelerating research in this important area at the interface of weather and climate dynamics. [ABSTRACT FROM AUTHOR]

This paper makes a case for why Hawaii is the rainbow capital of the world. It begins by briefly touching on the cultural and historical significance of rainbows in Hawaii. Next it provides an overview of the science behind the rainbow phenomenon, which provides context for exploring the meteorology that helps explain the prevalence of Hawaiian rainbows. Last, the paper discusses the art and science of chasing rainbows. [ABSTRACT FROM AUTHOR]

The Arctic is a vital component of the global climate, and its rapid environmental evolution is an important element of climate change around the world. To detect and diagnose the changes occurring to the coupled Arctic climate system, a state-of-the-art synthesis for assessment and monitoring is imperative. This paper presents the Arctic System Reanalysis, version 2 (ASRv2), a multiagency, university-led retrospective analysis (reanalysis) of the greater Arctic region using blends of the polar-optimized version of the Weather Research and Forecasting (Polar WRF) Model and WRF three-dimensional variational data assimilated observations for a comprehensive integration of the regional climate of the Arctic for 2000-12. New features in ASRv2 compared to version 1 (ASRv1) include 1) higher-resolution depiction in space (15-km horizontal resolution), 2) updated model physics including subgrid-scale cloud fraction interaction with radiation, and 3) a dual outer-loop routine for more accurate data assimilation. ASRv2 surface and pressure-level products are available at 3-hourly and monthly mean time scales at the National Center for Atmospheric Research (NCAR). Analysis of ASRv2 reveals superior reproduction of near-surface and tropospheric variables. Broadscale analysis of forecast precipitation and site-specific comparisons of downward radiative fluxes demonstrate significant improvement over ASRv1. The high-resolution topography and land surface, including weekly updated vegetation and realistic sea ice fraction, sea ice thickness, and snow-cover depth on sea ice, resolve finescale processes such as topographically forced winds. Thus, ASRv2 permits a reconstruction of the rapid change in the Arctic since the beginning of the twenty-first century-complementing global reanalyses. ASRv2 products will be useful for environmental models, verification of regional processes, or siting of future observation networks. [ABSTRACT FROM AUTHOR]

This paper presents the background, scientific objectives, experimental design, and preliminary achievements of the Third Tibetan Plateau (TP) Atmospheric Scientific Experiment (TIPEX-III) for 8-10 years. It began in 2013 and has expanded plateau-scale observation networks by adding observation stations in data-scarce areas; executed integrated observation missions for the land surface, planetary boundary layer, cloud-precipitation, and troposphere-stratosphere exchange processes by coordinating ground-based, air-based, and satellite facilities; and achieved noticeable progress in data applications. A new estimation gives a smaller bulk transfer coefficient of surface sensible heat over the TP, which results in a reduction of the possibly overestimated heat intensity found in previous studies. Summer cloud-precipitation microphysical characteristics and cloud radiative effects over the TP are distinguished from those over the downstream plains. Warm rain processes play important roles in the development of cloud and precipitation over the TP. The lower-tropospheric ozone maximum over the northeastern TP is attributed to the regional photochemistry and long-range ozone transports, and the heterogeneous chemical processes of depleting ozone near the tropopause might not be a dominant mechanism for the summer upper-tropospheric-lower-stratospheric ozone valley over the southeastern TP. The TP thermodynamic function not only affects the local atmospheric water maintenance and the downstream precipitation and haze events but also modifies extratropical atmospheric teleconnections like the Asia-Pacific Oscillation, subtropical anticyclones over the North Pacific and Atlantic, and temperature and precipitation over Africa, Asia, and North America. These findings provide new insights into understanding land-atmosphere coupled processes over the TP and their effects, improving model parameterization schemes, and enhancing weather and climate forecast skills. [ABSTRACT FROM AUTHOR]

It is challenging to accurately characterize the three-dimensional distribution of horizontal wind vectors (known as 3D winds). Feature-matching satellite cloud top or water vapor fields have been used for decades to retrieve atmospheric motion vectors, but this approach is mostly limited to a single and uncertain pressure level at a given time. Satellite wind lidar measurements are expected to provide more accurate data and capture the line-of-sight wind for clear skies, within cirrus clouds, and above thick clouds, but only along a curtain parallel to the satellite track. Here we propose Vientos—a new satellite mission concept that combines two or more passive water vapor sounders with Doppler wind lidar to measure 3D winds. The need for 3D wind observations is highlighted by inconsistencies in reanalysis estimates, particularly under precipitating conditions. Recent studies have shown that 3D winds can be retrieved using water vapor observations from two polar-orbiting satellites separated by 50 min, with the help of advanced optical flow algorithms. These winds can be improved through the incorporation of a small number of collocated higher-accuracy measurements via machine learning. The Vientos concept would enable simultaneous measurements of 3D winds, temperature, and humidity, and is expected to have a significant impact on scientific research, weather prediction, and other applications. For example, it can help better understand and predict the preconditions for organized convection. This article summarizes recent results, presents the Vientos mission architecture, and discusses implementation scenarios for a 3D wind mission under current budget constraints. [ABSTRACT FROM AUTHOR]

The search for an explanation of correlations of weather and climate with solar activity has uncovered some subtle effects of the varying solar inputs, which include irradiance, energetic particles, electric fields induced by the solar wind, and the modulation of the galactic cosmic ray flux. Relevant phenomena have been identified in stratospheric chemistry and dynamics and in aerosols, atmospheric electricity, and clouds. The effects are small and appear intermittently in statistical analyses of observations. Correlations and theory permit responses to several solar inputs effective on the decadal time scales, making it difficult to distinguish them observationally. No mechanism for tropospheric decadal change can be considered to be definitely established, but for the day-to-day time scale there is clear observational evidence for clouds responding to solar wind-induced current flow (JZ) in the global electric circuit, due to changes in ionospheric potential, and independently from Forbush decreases of the cosmic ray flux. The responses to JZ also correlate separately with ionospheric potential changes due to changes in day-to-day thunderstorm activity. The identified mechanism is for electric charge effects on in-cloud scavenging, and this implies a decadal response, in view of decadal changes in JZ. However, a complete and quantitative model of the inferred electrically induced changes in cloud microphysics is not yet available. The failures, successes, and controversies of the search illustrate the somewhat chaotic process of scientific discovery. [ABSTRACT FROM AUTHOR]

The steeply rising coastal terrain of southeast Alaska can produce a wide variety of terrain-induced flows such as barrier jets, gap flows, and downslope wind storms. This study uses a combination of satellite remote sensing, field observations, and modeling to improve our understanding of the dynamics of these flows. After examining several thousand synthetic aperture radar (SAR) high-resolution wind speed images over the Gulf of Alaska, several subclasses of barrier jets were identified that do not fit the current conceptual model of barrier jet development. This conceptual model consists of an acceleration and turning of the ambient cross-barrier flow into the along-barrier direction when the ambient low-level flow is blocked by terrain; however, the SAR imagery showed many barrier jet cases with significant flow variability in the along-coast direction as well as evidence for the influence of cold, dry continental air exiting the gaps in coastal terrain. A subclass of jets has been observed where the transition from the coastal to the offshore flow is abrupt. The results from these climatological studies have motivated modeling studies of selected events as well as field observations from the Southeast Alaska Regional Jets (SARJET) experiment field campaign in the Gulf of Alaska during fall of 2004. This paper will highlight preliminary results obtained during SARJET, which collected in situ measurements of barrier jets and gap flows using the University of Wyoming's King Air research aircraft. [ABSTRACT FROM AUTHOR]

The 2021 northwest Pacific marine heatwave was favored by the atmospheric and oceanic conditions; changes in the mean climate due to anthropogenic warming made the event 43 times more likely. [ABSTRACT FROM AUTHOR]

To better understand variability in weather and climate, it is vital to address past atmospheric circulation. This need requires meteorological information not just from the surface but also at upper levels. Current global upper-level datasets only reach back to the 1940s or 1950s and do not cover some important periods in the first half of the twentieth century. Extending the observational record is therefore considered important in order to analyze climate variability in the past and verify global climate models used to predict future climate change. Although earlier upper-air data from platforms such as radio-sondes, aircraft, pilot balloons, registering balloons, and kites are available from various sources, no systematic compilation and quality assessment of upper-level data prior to the International Geophysical Year (1957/58) has ever been performed. Here we present the Comprehensive Historical Upper-Air Network (CHUAN). It is a consistent global historical upper-air dataset that has been derived from heterogeneous data available from various sources as well as from newly digitized data. This paper describes the CHUAN dataset, the metadata, the quality control procedures, and the relationship to existing datasets. Some examples are given of its usefulness for analyzing weather and climate during the first half of the twentieth century. The CHUAN dataset comprises 3987 station records worldwide or about 16.4 million profiles (of which 12.6 million are before 1958 and 5.3 million, primarily from pilot balloons, are before 1948). A monthly mean version can be downloaded from the World Wide Web (). A supplement to this article is available online: DOI: [ABSTRACT FROM AUTHOR]

The article presents research into the application of regional dynamical downscaling for the evaluation of air quality. Meteorologists' ability to answer questions regarding the impact of climate change on air quality and vice versa depends on the ability of climatology models to simulate meteorological conditions. One atmospheric simulation is driven by a global circulation model (GCM) control simulation while a second atmospheric simulation is driven by a global reanalysis. A comparison is made of selected meteorological variables, namely diurnal wind patterns, unvented hours, precipitation, and 500-hPa heights.

Teleconnections are sources of predictability for regional weather and climate, but the relative contributions of different teleconnections to regional anomalies are usually not understood. While physical knowledge about the involved mechanisms is often available, how to quantify a particular causal pathway from data are usually unclear. Here, we argue for adopting a causal inference-based framework in the statistical analysis of teleconnections to overcome this challenge. A causal approach requires explicitly including expert knowledge in the statistical analysis, which allows one to draw quantitative conclusions. We illustrate some of the key concepts of this theory with concrete examples of well-known atmospheric teleconnections. We further discuss the particular challenges and advantages these imply for climate science and argue that a systematic causal approach to statistical inference should become standard practice in the study of teleconnections. [ABSTRACT FROM AUTHOR]

Focuses on the evolution of cloud tracking via satellite imagery. Early work on detection of atmospheric motion by remote sensing; Operational satellite detection of winds; Example applications; Research areas.

Reports on the symposium on atmospheric general circulation modeling held at the University of California, Los Angeles. Guest of honor; Participants; Papers presented.

High concentrations of dust can affect climate and human health, yet our understanding of extreme dust events is still limited. A record-breaking trans-Atlantic African dust plume occurred during 14–28 June 2020, greatly degrading air quality over large areas of the Caribbean Basin and the United States. Daily PM2.5 concentrations exceeded 50 µg m−3 in several Gulf States, while the air quality index reached unhealthy levels for sensitive groups in more than 11 states. The magnitude and duration of aerosol optical depth over the tropical North Atlantic Ocean were the greatest ever observed during summer over the past 18 years based on satellite retrievals. This extreme trans-Atlantic dust event is associated with both enhanced dust emissions over western North Africa and atmospheric circulation extremes that favor long-range dust transport. An exceptionally strong African easterly jet and associated wave activities export African dust across the Atlantic toward the Caribbean in the middle to lower troposphere, while a westward extension of the North Atlantic subtropical high and a greatly intensified Caribbean low-level jet further transport the descended, shallower dust plume from the Caribbean Basin into the United States. Over western North Africa, increased dust emissions are associated with strongly enhanced surface winds over dust source regions and reduced vegetation coverage in the western Sahel. While there are large uncertainties associated with assessing future trends in African dust emissions, model-projected atmospheric circulation changes in a warmer future generally favor increased long-range transport of African dust to the Caribbean Basin and the United States. [ABSTRACT FROM AUTHOR]

Earth's climate is strongly influenced by energy deficits at the poles that emit more thermal energy than they receive from the sun. Energy exchanges between the surface and atmosphere influence the local environment while heat transport from lower latitudes drives midlatitude atmospheric and oceanic circulations. In the Arctic, in particular, local energy imbalances induce strong seasonality in surface–atmosphere heat exchanges and an acute sensitivity to forced climate variations. Despite these important local and global influences, the largest contributions to the polar atmospheric and surface energy budgets have not been fully characterized. The spectral variation of far-infrared radiation that makes up 60% of polar thermal emission has never been systematically measured impeding progress toward consensus in predicted rates of Arctic warming, sea ice decline, and ice sheet melt. Enabled by recent advances in sensor miniaturization and CubeSat technology, the Polar Radiant Energy in the Far Infrared Experiment (PREFIRE) mission will document, for the first time, the spectral, spatial, and temporal variations of polar far-infrared emission. Selected under NASA's Earth Ventures Instrument (EVI) program, PREFIRE will utilize new lightweight, low-power, ambient temperature detectors capable of measuring at wavelengths up to 50 μm to quantify Earth's far-infrared spectrum. Estimates of spectral surface emissivity, water vapor, cloud properties, and the atmospheric greenhouse effect derived from these measurements offer the potential to advance our understanding of the factors that modulate thermal fluxes in the cold, dry conditions characteristic of the polar regions. [ABSTRACT FROM AUTHOR]

Atmospheric dynamics can represent a significant hurdle for students; the need to successfully apply concepts from calculus and physics, as well as the sometimes counterintuitive nature of fluid flow, combine to produce frustration and suboptimal learning. Additionally, there is often an emphasis on equation derivations and theory, rather than real-world applications. A new approach for teaching atmospheric dynamics, known as worked examples, is discussed herein. This pedagogy resolves identified challenges in a few ways: 1) reducing the cognitive load of students by explicitly demonstrating (via an expert-constructed guide) how mathematics and physics are applied to the atmosphere; 2) utilizing (as much as appropriate) real-world scenarios to demonstrate how equations explain what we observe; and 3) providing opportunities for students to critically examine the scenario, the relevant math and physics, and the underlying theory via a series of self-explanation prompts throughout the example. This study provides detailed information on the creation and implementation of worked examples in the two-semester atmospheric dynamics course sequence at the University of North Carolina at Charlotte. Comparisons in performance between students who took the course as a traditional lecture and derivation-based course and those who were subject to the worked examples pedagogy identify significant improvements with the new approach, especially for first-semester dynamics. Students also express deep satisfaction with the hands-on, application-based pedagogy. [ABSTRACT FROM AUTHOR]

Droughts are complex and may be triggered by different mechanisms, such as atmospheric circulation, moisture transport, and thermodynamic processes. Significant research has been completed to characterize precipitation in the Intergovernmental Panel on Climate Change (IPCC) reference regions (RRs), but a systematic analysis of atmospheric transport linked to drought episodes is still missing. This article describes a catalog in which the drought episodes over the RRs are identified during 1980–2015, and the role of the moisture transport anomalies from the respective major climatological moisture sources during the most severe meteorological drought episode registered for each RR is analyzed. For each of the 27 RRs defined in the IPCC Fifth Assessment Report, drought episodes were identified at 1-, 6-, and 12-month time scales through the standardized precipitation evapotranspiration index (SPEI). SPEI values were computed using time series of the monthly precipitation and atmospheric evaporative demand (AED) averaged over each RR. The approach, which was applied to both identify the major climatological moisture sources and sinks for each RR and to investigate anomalies in moisture transport during the episode, is based on the Lagrangian flexible particle dispersion model (FLEXPART), integrated with the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data. For each RR, the following components were analyzed: a) moisture uptake over sources, b) moisture supply from the sources into the RR, and c) moisture supply from the RR into its sink. Although performed for just one case, this analysis illustrates how the moisture transport may impact the RR during extreme conditions. The results are organized in a web page available to the scientific community and stakeholders. [ABSTRACT FROM AUTHOR]

The Aerosol, Radiation and Clouds in southern Africa (AEROCLO-sA) project investigates the role of aerosols on the regional climate of southern Africa. This is a unique environment where natural and anthropogenic aerosols and a semipermanent and widespread stratocumulus (Sc) cloud deck are found. The project aims to understand the dynamical, chemical, and radiative processes involved in aerosol–cloud–radiation interactions over land and ocean and under various meteorological conditions. The AEROCLO-sA field campaign was conducted in August and September of 2017 over Namibia. An aircraft equipped with active and passive remote sensors and aerosol in situ probes performed a total of 30 research flight hours. In parallel, a ground-based mobile station with state-of-the-art in situ aerosol probes and remote sensing instrumentation was implemented over coastal Namibia, and complemented by ground-based and balloonborne observations of the dynamical, thermodynamical, and physical properties of the lower troposphere. The focus laid on mineral dust emitted from salty pans and ephemeral riverbeds in northern Namibia, the advection of biomass-burning aerosol plumes from Angola subsequently transported over the Atlantic Ocean, and aerosols in the marine boundary layer at the ocean–atmosphere interface. This article presents an overview of the AEROCLO-sA field campaign with results from the airborne and surface measurements. These observations provide new knowledge of the interactions of aerosols and radiation in cloudy and clear skies in connection with the atmospheric dynamics over southern Africa. They will foster new advanced climate simulations and enhance the capability of spaceborne sensors, ultimately allowing a better prediction of future climate and weather in southern Africa. [ABSTRACT FROM AUTHOR]

The ChocoJet Experiment (CHOCO-JEX) is an interinstitutional research program developed by the Universidad Nacional de Colombia, the General Maritime Directorate of the Ministry of National Defense of Colombia, the Colombian Air Force, and the Desert Research Institute. The main goal of CHOCO-JEX is to characterize the vertical structure of the low-level Chocó jet (ChocoJet) through observations and modeling. Thus, four 7-day intensive observation periods (IOPs) took place during different seasons in 2016, two over land and two over the far eastern Pacific off the coast of Colombia, including the deployment of upper-air soundings four times per day to monitor the predominant diurnal cycle and the synoptic and seasonal variability. Preliminary results show deeper westerly moisture flow and a stronger diurnal cycle over land than over ocean. IOP4 provides the first observational evidence of the southwesterly ChocoJet with mean winds of 5 m s–1. Diurnal cycles of zonal wind are coherent with mountain–valley and sea–land breezes at low levels and the easterly flow is predominant at midlevels. Potential temperature anomalies appear to be related to gravity waves that modulate the diurnal cycle of precipitation in the region. [ABSTRACT FROM AUTHOR]

For the next generation of the World Area Forecast System (WAFS), the global Graphical Turbulence Guidance (G-GTG) has been developed using global numerical weather prediction (NWP) model outputs as an input to compute a set of turbulence diagnostics, identifying strong spatial gradients of meteorological variables associated with clear-air turbulence (CAT) and mountain-wave turbulence (MWT). The G-GTG provides an atmospheric turbulence intensity metric of energy dissipation rate (EDR) to the 1/3 power (m2/3 s–1), which is the International Civil Aviation Organization (ICAO) standard for aircraft reporting. Deterministic CAT and MWT EDR forecasts are derived from ensembles of calibrated multiple CAT and MWT diagnostics, respectively, with the final forecast provided by the gridpoint-by-gridpoint maximum of the CAT and MWT ensemble means. In addition, a probabilistic EDR forecast is produced by the percentage agreement of the individual CAT and MWT diagnostics that exceed a certain EDR threshold for turbulence (i.e., multidiagnostic ensemble). Objective evaluations of the G-GTG against global in situ EDR measurement data show that both deterministic and probabilistic G-GTG significantly improve the current WAFS CAT product, mainly because the G-GTG takes into account turbulence from various sources related to CAT and MWT. The probabilistic G-GTG forecast is more reliable at predicting light-or-greater (EDR > 0.15)- than moderate-or-greater (EDR > 0.22)-level turbulence, although it suffers from overforecasting. This will be improved in the future when we use this methodology with NWP ensembles and more observation data will be available for calibration. We expect that the new G-GTG forecasts will be beneficial to aviation users globally. [ABSTRACT FROM AUTHOR]

Recent studies have indicated the importance of fall climate forcings and teleconnections in influencing the climate of the northern mid- to high latitudes. Here, we present some exploratory analyses using observational data and seasonal hindcasts, with the aim of highlighting the potential of the El Niño–Southern Oscillation (ENSO) as a driver of climate variability during boreal late fall and early winter (November and December) in the North Atlantic–European sector, and motivating further research on this relatively unexplored topic. The atmospheric ENSO teleconnection in November and December is reminiscent of the east Atlantic pattern and distinct from the well-known arching extratropical Rossby wave train found from January to March. Temperature and precipitation over Europe in November are positively correlated with the Niño-3.4 index, which suggests a potentially important ENSO climate impact during late fall. In particular, the ENSO-related temperature anomaly extends over a much larger area than during the subsequent winter months. We discuss the implications of these results and pose some research questions. [ABSTRACT FROM AUTHOR]

The article offers information on the importance of laboratory experiments in understanding the atmospheric fluid dynamics in the U.S. The topics discussed include the collaboration between universities and the Massachusetts Institute of Technology (MIT) in exploring approaches in teaching meteorlogy to students and the effectiveness of laboratory experiments and real-world events in teaching students about the subject.

The article presents an overview of the Global Aerosol Synthesis and Science Project (GASSP), an initiative that aims to measure and reduce aerosol models from ships, aircrafts and ground stations. The topics discussed include the diverse kinds of aerosol instruments utilized in the GASSP, the effects of aerosol changes on atmospheric circulation, precipitation and regional climate, and the dramatic rise of sophistication in aerosol measurements.

The lexical evolution of "pulse thunderstorm" within meteorological texts is chronicled, revealing two common, yet incompatible, present-day uses. A standard definition is proposed. [ABSTRACT FROM AUTHOR]

The main field activities of the Coordinated Airborne Studies in the Tropics (CAST) campaign took place in the west Pacific during January-February 2014. The field campaign was based in Guam (13.5°N, 144.8°E), using the U.K. Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 atmospheric research aircraft, and was coordinated with the Airborne Tropical Tropopause Experiment (ATTREX) project with an unmanned Global Hawk and the Convective Transport of Active Species in the Tropics (CONTRAST) campaign with a Gulfstream V aircraft. Together, the three aircraft were able to make detailed measurements of atmospheric structure and composition from the ocean surface to 20 km. These measurements are providing new information about the processes influencing halogen and ozone levels in the tropical west Pacific, as well as the importance of trace-gas transport in convection for the upper troposphere and stratosphere. The FAAM aircraft made a total of 25 flights in the region between 1°S and 14°N and 130° and 155°E. It was used to sample at altitudes below 8 km, with much of the time spent in the marine boundary layer. It measured a range of chemical species and sampled extensively within the region of main inflow into the strong west Pacific convection. The CAST team also made ground-based measurements of a number of species (including daily ozonesondes) at the Atmospheric Radiation Measurement Program site on Manus Island, Papua New Guinea (2.1°S, 147.4°E). This article presents an overview of the CAST project, focusing on the design and operation of the west Pacific experiment. It additionally discusses some new developments in CAST, including flights of new instruments on board the Global Hawk in February-March 2015. [ABSTRACT FROM AUTHOR]

The article discusses the influence of North American monsoon and its contribution to the total annual precipitation for agriculture and water resources in the region. It highlights the expanded all-weather, high-time-resolution GPS networks with surface meteorology throughout the southwestern United States and Mexico. The GPS networks offer opportunities for improved understanding of the North American monsoon convection and weather forecasting of hazards from organized convective events.

The article presents the authors' response concerning the comment to their article "Tropical cyclone destructive potential by integrated kinetic energy." According to the authors, the commentators are right in their idea of incorporating an alternative central pressure ranges to maximum winds in the Saffir-Simpson (SS) scale. However, they assert that the current operational use of the SS scale is used to determine the maximum wind speed only. They claim that the proposed integrated kinetic energy (IKE)-based scales could lead to a more consistent warnings of potential damage of wind and surge.

The article discusses the hybrid paradigm for predicting the occurrence probability of continental-scale cold air outbreaks one month in advance. Topics discussed include the premises of the proposed hybrid paradigm such as the existence of robust diagnostic relationships between indices and operational models, rationales for the choice of circulation indices and data, methods and definitions used in the study.

The article offers information on the global climatic conditions in 2014. Various topics discussed include global surface temperature, hydrological cycle, atmospheric circulation, temperature in the North Atlantic region, air temperature in Arctic region, history of floods in Balkan Peninsula and upper ocean stratification.

The article discusses the impact of atmospheric circulation over the wet winter in southern Europe in 2013. Topics discussed include the state of precipitation during the season, including locations that recorded the anomalously high precipitation amounts, the significant impact brought by the atmospheric circulation on precipitation during winter 2013 and the trends of seasonal average precipitation between 1971 and 2013.

The 2011 Spring Forecasting Experiment in the NOAA Hazardous Weather Testbed (HWT) featured a significant component on convection initiation (CI). As in previous HWT experiments, the CI study was a collaborative effort between forecasters and researchers, with equal emphasis on experimental forecasting strategies and evaluation of prototype model guidance products. The overarching goal of the CI effort was to identify the primary challenges of the CI forecasting problem and to establish a framework for additional studies and possible routine forecasting of CI. This study confirms that convection-allowing models with grid spacing ~4 km represent many aspects of the formation and development of deep convection clouds explicitly and with predictive utility. Further, it shows that automated algorithms can skillfully identify the CI process during model integration. However, it also reveals that automated detection of individual convection cells, by itself, provides inadequate guidance for the disruptive potential of deep convection activity. Thus, future work on the CI forecasting problem should be couched in terms of convection-event prediction rather than detection and prediction of individual convection cells. [ABSTRACT FROM AUTHOR]

The Dominica Experiment (DOMEX) took place in the eastern Caribbean from 4 April to 10 May 2011 with 21 research flights of the Wyoming King Air and several other observing systems. The goal was an improved understanding of the physics of convective orographic precipitation in the tropics. Two types of convection were found. During a period of weak trade winds, diurnal thermal convection was seen over Dominica. This convection caused little precipitation but carried aloft air with island-derived aerosol and depleted CO[sub 2]. During periods of strong trades, mechanically forced convection over the windward slopes brought heavy rain to the high terrain. This convection was "seeded" by trade-wind cumuli or neutrally buoyant cool wet patches of air. In this mechanically forced convection, air parcels did not touch the island surface to gain buoyancy so no island-derived tracers were lofted. With fewer aerosols, the mean cloud droplet diameter increased from 15 to 25 µm. Plunging airflow and a wake were found in the lee of Dominica. The DOMEX dataset will advance our understanding and test our theories of cumulus triggering and aerosol influence on precipitation. [ABSTRACT FROM AUTHOR]

The observing and forecasting conditions of coastal oceans in Alaska is technically challenging because of the mountainous terrain, the notoriously stormy seas, and a complex hydrological system of freshwater from rivers and glaciers. The Alaska Ocean Observing System and their partners developed a demonstration project over a 5-yr period in Prince William Sound. This location was chosen because of historical efforts to monitor ocean circulation following the Exxon Valdez oil spill of 1989. The primary goal is to develop a quasi-operational system that delivers weather and ocean information in near-real time to diverse user communities. This observing system now consists of a spatial array of atmospheric and oceanic sensors and a new generation of computer models to numerically simulate and forecast weather, waves, and ocean circulation. The project culminated in a 2009 field experiment that evaluated the performance of the model forecasts. Three ships, 44 surface drifters, an underwater glider, and an autonomous underwater vehicle, as well as two shore-based surface current radar systems, augmented the routine atmospheric and oceanographic measurements from weather stations and oceanographic buoys. Observations from terrestrial and moored weather stations were compared with atmospheric circulation forecasts, and wave gauges provided data that were used to evaluate the forecasts of significant wave heights and periods. The radar current mappers and drifter buoys validated the surface ocean circulation forecasts. Improved observations and forecasts of coastal oceans will benefit oil spill responders, commercial shippers that convey large amounts of freight to and from Alaska, and U.S. Coast Guard search-and-rescue operations. [ABSTRACT FROM AUTHOR]

The article discusses the meteorological conditions in Antarctica. It notes that in 2008, a strong warming along the Antarctica Peninsula and West Antarctica was observed. A reduction in sea-ice concentration in Amundsen/Bellingshausen Seas and in the region's surface pressure was also observed. It adds that extent of snowmelt on the Antarctica ice sheet in 2008 has also decreased. Observations on the atmospheric circulation and ozone layer depletion in Antarctica are also offered.

The exchange, or flux, of heat between the oceans and atmosphere is an important driver of the global oceanic and atmospheric circulations but remains poorly quantified. Direct measurement of heat flux remains a research activity and so global heat flux datasets are generated using observations of winds, air and sea temperatures, and humidity as input to heat flux parameterizations known as "bulk formulas." We remain dependent on the observations from merchant ships in the Voluntary Observing Ships (VOS) program, which are archived in the International Comprehensive Ocean-Atmosphere Dataset (ICOADS); measurements from buoys are sparse and satellites cannot accurately recover all the variables required for heat flux calculation. Careful analysis of VOS data is necessary to produce gridded datasets of meteorological variables and fluxes with the accuracy required for climate research. Past in situ flux datasets have averaged observations on monthly timescales to reduce random uncertainty. It has therefore been hard to understand the contributions to observed variability from measurement errors, poor sampling, or natural variability. The new dataset, which covers the period 1973 to 2006, avoids this problem by first constructing daily mean fields using optimal interpolation. This allows each component of variability to be handled correctly and, for the first time, uncertainty estimates to be produced. New bias adjustments have also been developed and applied. The new dataset is described and a preliminary comparison with flux estimates from moored buoys, satellites, and atmospheric reanalysis models is presented. [ABSTRACT FROM AUTHOR]

The article discusses the Tibetan observation and research platform (TORP) in Tibet, China. The study focuses on the land-surface processes and environment over the plateau, with an emphasis on atmosphere-land interaction. It says that the data collected in TORP could be helpful in the analysis of land and atmospheric processes, model or scheme development, model calibration, validation, and other tasks. Furthermore, the TORP can help on the study of impacts of the Tibetan Plateau on the Asian Monsoon system and climatic changes in the world.

The article offers information on the data set of derived parameters which aims at simplifying the tasks of monitoring variations in atmospheric stability and analyzing the characteristics of the planetary boundary layer (PBL) on a global scale. The dataset, which consists of a set of temperature, humidity, and wind parameters that have been derived from radiosonde observations contained in the Integrated Global Radiosonde Archive (IGRA), is intended to facilitate studies of the vertical structure of the atmosphere. A description of the methods used in computing the parameters ("Dataset Construction") as well as of the temporal and spatial coverage of the resulting dataset ("Temporal and Spatial Coverage") is also presented.

The article examines the atmospheric predictability of synoptic numerical weather prediction (NWP) versus cloud-resolving scales. It is stated that small-scale uncertainties amplify with time, leading to a divergence of initially nearby phase-space trajectories, and disrupt the skill of the forecast. In result, the predictability limitations set an upper bound on potential forecast capabilities and amenable lead times, constituting a fundamental aspect of NWP. On the other hand, the chaotic nature of the atmospheric dynamics has been addressed by the development of ensemble prediction systems (EPS) on synoptic scales.

The article discusses a study which utilized an existing conventional primitive-equation atmospheric general circulation models (AGCMs) and an ocean general circulation models (OGCMs), wherein subgrid-scale convection and mixed-layer turbulence are parameterized. The particular AGCM used for the simulation is called the AGCM for the Earth Simulator. The original code was adopted from an earlier version of a Japanese community AGCM that had been jointly developed by the Center for Climate System Research, the University of Tokyo and the Japanese National Institute for Environmental Studies.

The 2004 Atlantic basin hurricane season was one of the most active on record with nine hurricanes and six major hurricanes (maximum sustained winds > 49 m s 1) forming during the season. All six major hurricanes formed during August and September, causing this two-month period to be the most active on record. The primary reason the 2004 hurricane season will be remembered, however, is because of the four hurricanes that devastated the Caribbean and the southeastern United States (Hurricanes Charley, Frances, Ivan, and Jeanne). Estimated total U.S. hurricane damage was between $40 and $50 billion, and much additional damage was sustained in the Caribbean. It is shown that a very strong central Atlantic equatorial trough, associated with anomalously warm tropical Atlantic sea surface temperatures and anomalously weak tropospheric vertical wind shear, combined with extremely favorable midlatitude steering conditions to allow many of the Africa-spawned easterly waves to develop into major hurricanes in the central Atlantic. These major hurricanes then moved on long west-northwest tracks that brought them through the Caribbean and across the southeastern U.S. coastline. The very active and destructive 2004 Atlantic basin hurricane season is attributed to two primary features: a strong Atlantic equatorial trough and steering currents that caused hurricanes to track westward across the U.S. coastline. [ABSTRACT FROM AUTHOR]

The Second Global Soil Wetness Project (GSWP-2) is an initiative to compare and evaluate 10-year simulations by a broad range of land surface models under controlled conditions. A major product of GSWP-2 is the first global gridded multimodel analysis of land surface state variables and fluxes for use by meteorologists, hydrologists, engineers, biogeochemists, agronomists, botanists, ecologists, geographers, climatologists, and educators. Simulations by 13 land models from five nations have gone into production of the analysis. The models are driven by forcing data derived from a combination of gridded atmospheric reanalyses and observations. The resulting analysis consists of multimodel means and standard deviations on the monthly time scale, including profiles of soil moisture and temperature at six levels, as well as daily and climatological (mean annual cycle) fields for over 50 land surface variables. The monthly standard deviations provide a measure of model agreement that may be used as a quality metric. An overview of key characteristics of the analysis is presented here, along with information on obtaining the data. [ABSTRACT FROM AUTHOR]

The article discusses the implications in using the Atmospheric InfraRed Sounder (AIRS). AIRS hyperspectral data, used within the present stringent operational constraints, signifies positive impact forecast skill over both the Northern and Southern Hemisphere for January 2004. The results suggest that a considerable chance to improve operational analyses forecasts with hyperspectral data. Furthermore, AIRS data are now being used in the operation of National Centers for Environmental Prediction, with impending system upgrades predicted to increase the impact of the AIRS data.

The North American Monsoon Experiment (NAME) is an internationally coordinated process study aimed at determining the sources and limits of predictability of warm-season precipitation over North America. The scientific objectives of NAME are to promote a better understanding and more realistic simulation of warm-season convective processes in complex terrain, intraseasonal variability of the monsoon, and the response of the warm-season atmospheric circulation and precipitation patterns to slowly varying, potentially predictable surface boundary conditions. During the summer of 2004, the NAME community implemented an international (United States, Mexico, Central America), multiagency (NOAA, NASA, NSF, USDA) field experiment called NAME 2004. This article presents early results from the NAME 2004 campaign and describes how the NAME modeling community will leverage the NAME 2004 data to accelerate improvements in warm-season precipitation forecasts for North America. [ABSTRACT FROM AUTHOR]

Presents an extract on the investigation of noctilucent clouds and atmospheric movements by astronomer Otto Jesse in Berlin, Germany. Establishment of the Berlin Atmospheric Program for the monitoring of noctilucent clouds; Problems of dynamic processes in noctilucent clouds and the corresponding upper-atmospheric layers.

This article highlights the North American Monsoon Experiment's (NAME) monsoon model assessment project. NAME will need to improve numerical simulations of the monsoon circulation and its large-scale effects to achieve its goals. The project's activities over the next few years are aimed at delivering models capable of forecasting the evolution of warm-season climate anomalies months to seasons in advance. NAME employs a tiered approach of monitoring, diagnostics and modeling in the heart of the monsoon region, on the regional scale, and on the continental scale, defined as Tiers I, II, and III, respectively. The project was designed to provide benchmark simulations of warm-season precipitation, and the physical processes that control precipitation, in Tiers I and II.

Coupled global ocean–atmosphere models currently do a poor job of predicting conditions in the tropical east Pacific, and have a particularly hard time reproducing the annual cycle in this region. This poor performance is probably due to the sensitivity of the east Pacific to the inadequate representation of certain physical processes in the modeled ocean and atmosphere. The representations of deep cumulus convection, ocean mixing, and stratus region energetics are known to be problematic in such models. The U.S. Climate Variability and Predictability (CLIVAR) program sponsored the field experiment East Pacific Investigation of Climate Processes in the Coupled Ocean–Atmosphere System 2001 (EPIC2001), which has the goal of providing the observational basis needed to improve the representation of certain key physical processes in models. In addition to physical processes, EPIC2001 research is directed toward a better understanding and simulation of the effects of short-term variability in the east Pacific on climate. This variability is particularly important in the region because conditions in the intertropical convergence zone are highly variable on daily to intraseasonal time scales. The effects of such variability rectify strongly onto climate time scales in this region. [ABSTRACT FROM AUTHOR]

Reports on the results of the Atmospheric Model Intercomparison Project (AMIP), which was undertaken to study atmospheric general circulation models. Simulation of the evolution of climate; Validation of the AMIP models; Simulation of the seasonal cycle; Subsets of the AMIP models; Diagnostic and experimental structure of the project.

The article discusses the contribution of large-scale atmospheric circulations to the precipitation anomalies of summer 2012 in Northern Europe. It describes the use of a flow-analogue approach similar to the analysis of 2011 temperatures by meteorologists J. Cattiaux and P. Yiou. It is suggested that high precipitation rates were the result of cyclonic conditions that prevailed over Scandinavia during the early summer.

The article evaluates atmospheric circulation's contribution to the heat wave of spring-summer 2012 in the contiguous U.S. It describes the use of a flow-analogue method, similar to the analysis of 2011 European temperatures, to assess daily temperature observations from the Global Historical Climatology Network. It was found that large-scale circulations played a significant role in the hot record of spring 2012 but not in the spatial pattern of the warm 2012 summer.