nasa-gesdisc/es-publications-researchareas huggingface dataset:
Case study of a convective cluster over the rain shadow region of Western Ghats using multi-platform observations and WRF model (2020)

Unique observational features of a convective cluster, occurred on 12-Sept-2015, over the rain shadow region in the leeward side of Western Ghats have been presented in this study. The synoptic environment had preconditioned the formation of a convergence zone over the study area. Moisture transport from the Arabian Sea was responsible for the moistening in the lower layers. Boundary layer convective thermals contributed to middle level moistening and subsequent onset of the cloud cluster was accompanied by a sudden surge of moist and warm air into the middle troposphere, and subsequent lifting of freezing level (FL) and wet bulb temperature zero (WBT0) levels. Sudden changes in the FL and WBT0 levels in association with the gust front prior to the initiation of the cloud system has been documented with high-resolution measurements using microwave radiometer and wind profiler. Thermodynamical parameters from radiometer illustrate the percussive conditions for formation of the cloud system. The cloud cluster had resulted in 25.50 mm rainfall, attributing to ~ 91% of convective rain. Intense fall velocity (1012 ms1) was noted up to ~ 7 km during the convective rain and the fall velocity was reduced to ~ 7 ms1 (below the melting layer) during the stratiform counterpart. The cloud system was forecasted using WRF model (version 3.6.1), which was reproduced reasonably well as in the observations and the model output has been analyzed to understand the morphology of the system. The features such as formation of a cold pool, initiation of convective rainfall from the system were well forecasted by the model. Microphysical characteristics of the cloud cluster have also been examined. Riming was the dominant microphysical process within the convective regime. A major contribution to precipitation was from melting of ice hydrometeors especially graupel and snow was noted. Deep warm layer and associated production of supercooled liquid by the lifting of liquid water above the freezing level in updrafts exceeding 15 ms1 was important for the production of a mixed-phase cloud system. Vapor deposition and aggregation process was noted in the stratiform/anvil counterpart, which also contained mixed phase hydrometeors, primarily of snow.

Research areas: Atmospheric/Ocean Indicators
Spatial Distribution of Land Surface Temperatures in Kuwait: Urban Heat (2020)

The global rise of urbanization has led to the formation of surface urban heat islands and surface urban cool islands. Urban heat islands have been shown to increase thermal discomfort, which increases heat stress and heat-related diseases. In Kuwait, a hyper-arid desert climate, most of the population lives in urban and suburban areas. In this study, we characterized the spatial distribution of land surface temperatures and investigated the presence of urban heat and cool effects in Kuwait. We used historical Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra satellite 8-day composite land surface temperature (LST) from 2001 to 2017. We calculated the average LSTs of the urban/suburban governorates and compared them to the average LSTs of the rural and barren lands. We repeated the analysis for daytime and nighttime LST. During the day, the temperature difference (urban/suburban minus versus governorates) was 1.1 C (95% CI; 1.2, 1.00, p < 0.001) indicating a daytime urban cool island. At night, the temperature difference (urban/suburban versus rural governorates) became 3.6 C (95% CI; 3.5, 3.7, p < 0.001) indicating a nighttime urban heat island. In light of rising temperatures in Kuwait, this work can inform climate change adaptation efforts in the country including urban planning policies, but also has the potential to improve temperature exposure assessment for future population health studies.

Research areas: Heat
Barrier layers in a high‐resolution model in the eastern tropical Pacific (2020)

This study examines salinity barrier layers (BLs) in the eastern tropical North Pacific in the region of the Salinity Processes in the Upper ocean Regional Studies-2 field campaign. We utilize a high-resolution numerical model to study BLs and their relationship to frontal features and small-scale ocean variability, focusing on two specific events. One is associated with a large outbreak of BL presence near 7°N along 125°W. The other is a relatively isolated but persistent BL that forms near 13°N, again along 125°W. In both cases we find that the BL is proximate to a salinity frontal feature in which isohalines tilt toward the fresh side of the front at its base. The BLs studied are associated with divergent flow at the surface on the fresh side of the front and convergent flow on the salty side. Tilting of the front is invoked to explain this, with an additional mechanism involving a vertical circulation which causes the base of the front to tilt preferentially.

Research areas: Atmospheric/Ocean Indicators
An Overview of Aerosol Properties in Clear and Cloudy Sky Based on (2022)

A full understanding of the climatological properties of aerosols is an important step towards characterizing their effects on climate. Utilizing the observations from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, we study cloud-free and cloudy aerosol properties with attention on aerosol and cloud layer relative vertical positions. On a global scale, the cloud-free aerosols account for about 56% of all detected aerosols with a mean optical depth (τ¯<SUB>a</SUB>) and mean uncertainty of 0.135 ± 0.047. The cloudy aerosols, accounting for 44%, have a larger τ¯<SUB>a</SUB> and larger mean uncertainty of 0.143 ± 0.074 compared to the cloud-free aerosols. The above-cloud aerosols (∼4%), primarily composed of elevated smoke, dust/volcanic ash and polluted dust, have a much smaller τ¯<SUB>a</SUB> of (0.056 ± 0.038). The below-cloud aerosols (∼21%) have τ¯<SUB>a</SUB> ∼ 0.165 ± 0.087. The below-cloud and cloud-free aerosols show close τ<SUB>a</SUB> probability density distributions and similar aerosol types, indicating that cloud-free aerosol climatologies from passive sensors are likely representative of all-sky conditions. In addition, about 27% of the detected aerosol profiles are found to have cloud layers vertically connected to the detected aerosol layers. The lidar backscatter profiles of these aerosols have larger median values than the cloud-free, above-cloud and below-cloud aerosols. The seasonal variations of the cloud-free and the cloudy aerosols significantly vary with regions. Our results imply that quantifying the impact of clouds, particularly cirrus due to the wide coverage of cirrus-aerosol overlap, on aerosol direct radiative effect is crucial to assess aerosols' roles in the Earth-climate system.

Research areas: Atmospheric/Ocean Indicators
Fine‐Scale Geothermal Heat Flow in Antarctica Can Increase Simulated Subglacial Melt Estimates (2022)

Antarctic geothermal heat flow (GHF) affects the thermal regime of ice sheets and simulations of ice and subglacial meltwater discharge to the ocean, but remains poorly constrained. We use an ice sheet model to investigate the impact of GHF anomalies on subglacial meltwater production in the Aurora Subglacial Basin, East Antarctica. We find that spatially-variable GHF fields produce more meltwater than a constant GHF with the same background mean, and meltwater production increases as the resolution of GHF anomalies increases. Our results suggest that model simulations of this region systematically underestimate meltwater production using current GHF models. We determine the minimum basal heating required to bring the basal ice temperature to the pressure melting point, which should be taken together with the scale-length of likely local variability in targeting in-situ GHF field campaigns.

Research areas: Atmospheric/Ocean Indicators, Cryospheric Indicators
Heat coupling of the pan-European vs. regional electrical grid with excess renewable energy (2017)

The feasibility of heating sector integration into future highly renewable electrical grid is examined for a regional and pan-European network. A novel geographical weather dependent model for calculating the heat demand using a temporal resolution of an hour with a spatial resolution of 40  40 km2 and an optimized solution for the utilization of excess renewable generation with least energy needs is presented. Heating sector is modeled and coupled separately with two different heat coupling models, heat-pump coupling and electric-resistance coupling, both having heat-storage and gas-boiler. Results show coupling with the regional network requires least heat-storage capacity and coupling with an individual country network requires the least gas-boiler capacity. However, coupling with the pan-European network results in least balancing energy needs. It is found that heat-pump coupling provides more benefit than the electric-resistance coupling, with 4 times more heat-storage energy and 38% less requirement for the gas-boiler energy. Optimum energy mix between the heat-storage energy and gas-boiler energy suggests that the present amount of excess generation is not enough to fully support the heating sector, but if the renewable energy generation is increased by 50% then heat-storage will play an important role.

Research areas: Energy Production/Use
Impact of smoke and non-smoke aerosols on radiation and low-level clouds over the southeast Atlantic from co-located satellite observations (2021)

Abstract. Data derived from instruments on board the CloudAerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat satellites as well as meteorological parameters from reanalysis are used to explore situations when moist aerosol layers overlie stratocumulus clouds over the southeast Atlantic during the biomass burning season (June to October). To separate and quantify the impacts of aerosol loading, aerosol type, and humidity on the radiative fluxes (including cloud top cooling), the data are split into different levels of aerosol and moisture loadings. The aerosol classification available from the CALIPSO products is used to compare and contrast situations with pristine air, with smoke, and with other (non-smoke) types of aerosols. A substantial number of cases with non-smoke aerosols above clouds are found to occur under similar meteorological conditions to the smoke cases. In contrast, the meteorology is substantially different for the pristine situations, making a direct comparison with the aerosol cases ambiguous. The moisture content is enhanced within the aerosol layers, but the relative humidity does not always increase monotonously with increasing optical depth. Shortwave (SW) heating rates within the moist aerosol plumes increase with increasing aerosol loading and are higher in the smoke cases compared to the non-smoke cases. However, there is no clear correlation between moisture changes and SW absorption. Cloud top cooling rates do not show a clear correlation with moisture within the overlying aerosol layers due to the strong variability of the cooling rates caused by other meteorological factors (most notably cloud top temperature). No clear influence of aerosol type or loading on cloud top cooling rates is detected. Further, there is no correlation between aerosol loading and the thermodynamic structure of the atmosphere nor the cloud top height.

Research areas: Atmospheric/Ocean Indicators
Thunderstorm induced changes in near-surface O3, NOx and CH4 and associated boundary layer meteorology over a tropical coastal station (2018)

The paper presents four cases of the response of near-surface O3, NOx and CH4 to thunderstorm activity at a tropical coastal site in India, occurred during pre-monsoon and post-monsoon seasons. The associated changes in boundary layer meteorology in terms of temperature, relative humidity (RH), wind and boundary layer height (BLH) are also examined. The meteorological parameters like temperature and RH respond very fast depicting changes during the initial phase of the thunderstorm activity, whereas a delayed response is observed in the wind direction (changing from the sea breeze to land breeze) and collapse of the BLH (11:30 h delay) at the mature phase of the activity. Associated with the thunderstorm activity, significant changes were observed in the mixing ratios of the near-surface O3, NOx and CH4. An increase in NOx (5.28.7 ppbv) and CH4 (36.7134.6 ppbv) and reduction in O3 (9.918.8 ppbv) were recorded at the mature phase of the thunderstorm. The rise in NOx is attributed to the combined effect of thunderstorm activity and wind reversal whereas that in CH4 is attributed to the wind reversal and associated change in air mass. A post activity increase is observed in mixing ratio of O3 in all the four cases. This is attributed to the downdrafts characteristic of the dissipation phase of thunderstorm activity which brings in O3 rich upper air down.

Research areas: Atmospheric/Ocean Indicators
Lightning geolocation and flash rates from LF radio observations during the RELAMPAGO field campaign (2021)

The lightning data products generated by the low-frequency (LF) radio lightning locating system (LLS) deployed during the Remote sensing of Electrification, Lightning, and Mesoscale/Microscale Processes with Adaptive Ground Observation (RELAMPAGO) field campaign in Argentina provide a valuable data set to research the lightning evolution and characteristics of convective storms that produce high-impact weather. LF LLS data sets offer a practical range for mesoscale studies, allowing for the observation of lightning characteristics of storms such as mesoscale convective systems or large convective lines that travel longer distances which are not necessarily staying in range of regional VHF-based lightning detection systems throughout their lifetime. LF LLSs also provide different information than optical space-borne lightning detectors. Lightning measurements exclusive to LF systems include discharge peak current, lightning polarity, and lightning type classification based on the lightning-emitted radio waveform. Furthermore, these measurements can provide additional information on flash rates (e.g., positive cloud-to-ground flash rate) or narrow bipolar events which may often be associated with dynamically intense convection. In this article, the geolocation and data processing of the LF data set collected during RELAMPAGO is fully described and its performance characterized, with location accuracy better than 10 km. The detection efficiency (DE) of the data set is compared to that of the Geostationary Lightning Mapper, and spatiotemporal DE losses in the LF data set are discussed. Storm case studies on November 10, 2018, highlight the strengths of the data set, which include robust flash clustering and insightful flash rate and peak current measures, while illustrating how its limitations, including DE losses, can be managed.

Research areas: Atmospheric/Ocean Indicators
Air-sea exchange of carbon dioxide in the Southern Ocean and Antarctic (2016)

Direct carbon dioxide flux measurements using eddy covariance from an icebreaker in the high-latitude Southern Ocean and Antarctic marginal ice zone are reported. Fluxes were combined with the measured water-air carbon dioxide partial pressure difference (ΔpCO<SUB>2</SUB>) to compute the air-sea gas transfer velocity (k, normalized to Schmidt number 660). The open water data showed a quadratic relationship between k (cm h<SUP>-1</SUP>) and the neutral 10 m wind speed (U<SUB>10n</SUB>, m s<SUP>-1</SUP>), k<SUB>open</SUB> = 0.245 U<SUB>10n</SUB><SUP>2</SUP> + 1.3, in close agreement with decades old tracer-based results and much lower than cubic relationships inferred from previous open ocean eddy covariance studies. In the marginal ice zone, the effective gas transfer velocity decreased in proportion to sea ice cover, in contrast with predictions of enhanced gas exchange in the presence of sea ice. The combined open water and marginal ice zone results affect the calculated magnitude and spatial distribution of Southern Ocean carbon flux.

Research areas: Atmospheric/Ocean Indicators
Changes in winter stationary wave activity during weak mid-latitude and Arctic thermal contrast period (2020)

Using reanalysis data set, this study investigates the changes in winter mean stationary wave activity, when the thermal contrast between mid‑latitude and Arctic is weak. The mid‑latitude and Arctic thermal contrast was stronger during 1986–2003 and weaker during 1966–1985 and 2004–2017. The changes in stationary wave characteristics are studied based on the stationary wave activity flux (SWAF). Compare to the period when the contrast was stronger (1986–2003), both the convergence of SWAF and stationary wave amplitude have been enhanced in the Northern part of Eurasia during the periods 1966–1985 and 2004–2017. We further proposed that a weak mid‑latitude/Arctic thermal contrast provides a good condition for the enhancement of the stationary wave activity. The weak mid‑latitude‑Arctic thermal contrast is conducive to the enhancement of blocking frequency around Ural Mountains, which may contribute partly to the increase in stationary wave amplitude and associated changes in the SWAF. Furthermore, the weak thermal contrast is associated with the decrease in baroclinicity and synoptic‑scale eddy activity, which in turn contributes to the generation of stationary waves via eddy feedback processes.

Research areas: Atmospheric/Ocean Indicators
Water vapor variability in the Atacama Desert during the 20th century (2020)

This study focuses on integrated water vapor (IWV) which is the main source for precipitation, fog and dew formation in the Atacama Desert in northern Chile. In order to study its long-term variability, a consistent meteorological record is needed. Here, we utilize the European Centre for Medium-Range Weather Forecasts' reanalysis ERA-20C which provides IWV among other atmospheric variables over the course of the entire 20th century (19002010). In this two fold study, we first present a validation of ERA-20C IWV for the Atacama and the bordering southeast Pacific region. Comparisons to satellite observations, i.e. the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data record and the Moderate Resolution Imaging Spectroradiometer measurements, for overlapping time periods prove the suitability of ERA-20C to study IWV variability. Assessment of the observation feedback in ERA-20C reveals a higher uncertainty for the beginning of the 20th century when fewer observations are assimilated. Nevertheless, departures of the assimilated observations do not show a systematic bias in space or time supporting suitability of ERA-20C for long-term investigations. In the second part of the study, we describe the IWV variability over the course of the 20th century. Deviations from the long-term mean greater than 30% are found on an inter-annual time scale over the continental Atacama. Furthermore, we investigate potential drivers of the IWV variability such as the Pacific Decadal Oscillation (PDO) and the El Nino Southern Oscillation (ENSO) phenomenon. The relationship between the local IWV and these large scale indices depends on region and season. For instance, during austral summer, La Nina conditions yield overall greater IWV variability in the Atacama allowing both drier and even more pronounced wetter extremes than El Nino conditions.

Research areas: Atmospheric/Ocean Indicators
Argo Observations of the Deep Mixing Band in the Southern Ocean: A (2018)

The Southern Ocean plays an important role in mediating oceanic uptake of CO<SUB>2</SUB> and heat due to a strong meridional overturning circulation. Gridded Argo float data for 2004-2017 were used to evaluate subsurface processes at the mixed layer depth (MLD) that occur in a narrow deep mixing band. Shifts in the value of the Turner Angle at the MLD indicate that early in the season the MLD deepens slowly as it encounters and is stabilized by a subsurface salt maximum. By September mixing has penetrated this salinity feature and the rate of deepening is faster once the MLD is deeper than the depth where the maximum salinity occurs ( 150-200 m). This distinctive salinity layer is the result of surface Ekman transport of fresh water from the south and subsurface advection of high-salinity water from the north. Two configurations of the Community Earth System Model (CESM) ocean-ice forced hindcast experiments—one with 1° and the other with 0.1° horizontal resolution (Parallel Ocean Program low and high resolutions [POP-LR and POP-HR], respectively)—are compared with the Argo data for 2005-2009. POP-LR has a shallow MLD bias common to many Fifth Coupled Models Intercomparison Project (CMIP5) models, while POP-HR has a mix of deep and shallow MLD biases. While both models were able to replicate the large-scale processes leading to formation of a high-salinity layer, the salinity feature in POP-HR is too strong and deep. Neither model was able to replicate the vertical mixing processes leading to penetration of the subsurface salt maximum.

Research areas: Atmospheric/Ocean Indicators
Strong Precipitation Suppression by Aerosols in Marine Low Clouds (2020)

The adjustment of cloud amount to aerosol effects occurs to a large extent in response to the aerosol effect on precipitation. Here the marine boundary layer clouds were studied by analyzing the dependence of rain intensity measured by Global Precipitation Measurement on cloud properties. We showed that detectable rain initiates when the drop effective radius at the cloud top (r<SUB>e</SUB>) exceeds 14 μm, and precipitation is strongly suppressed with increasing cloud drop concentration (N<SUB>d</SUB>), which contributes to the strong dependence of cloud amount on aerosols. The rain rate increases sharply with cloud thickness (CGT) and r<SUB>e</SUB> when r<SUB>e</SUB> &gt; 14 μm. The dependence of rain rate on r<SUB>e</SUB> and CGT presents a simple framework for precipitation susceptibility to aerosols, which explains other previously observed relationships. We showed that sorting data by CGT and using alternative cloud condensation nuclei proxy rather than aerosol optical depth are critical for studying aerosol-cloud-precipitation interactions.

Research areas: Atmospheric/Ocean Indicators
Enhanced eddy activity in the Beaufort Gyre in response to sea ice loss (2020)

The Beaufort Gyre freshwater content has increased since the 1990s, potentially stabilizing in recent years. The mechanisms proposed to explain the stabilization involve either mesoscale eddy activity that opposes Ekman pumping or the reduction of Ekman pumping due to reduced sea iceocean surface stress. However, the relative importance of these mechanisms is unclear. Here, we present observational estimates of the Beaufort Gyre mechanical energy budget and show that energy dissipation and freshwater content stabilization by eddies increased in the late-2000s. The loss of sea ice and acceleration of ocean currents after 2007 resulted in enhanced mechanical energy input but without corresponding increases in potential energy storage. To balance the energy surplus, eddy dissipation and its role in gyre stabilization must have increased after 2007. Our results imply that declining Arctic sea ice will lead to an increasingly energetic Beaufort Gyre with eddies playing a greater role in its stabilization.

Research areas: Cryospheric Indicators, Atmospheric/Ocean Indicators