nasa-gesdisc/es-publications-researchareas huggingface dataset:
Drought dynamics of Northwestern Teesta Floodplain of Bangladesh: a remote sensing approach to ascertain the cause and effect (2021)

Drought is an affliction for a region that primarily depends on agriculture as economic activity. Commonly monitoring and characterizing of drought is performed by only analyzing the meteorological aspect, assuming precipitation as the primary source of water. However, in riverine Bangladesh, this can lead to an erroneous conclusion, as there is a multitude of available water sources. Consequently, in this study, vegetation condition (Standard Vegetation Index), soil moisture (Soil Moisture Index), and precipitation (Standard Precipitation Index) are separately investigated from 2003 to 2019, in the Northwestern Teesta floodplain. Subsequently, statistical regression analysis is performed to determine the relationships between different aspects of drought. In addition, information obtained from field visits and expert opinions has also been assimilated. Analysis of vegetation and soil moisture condition presents a progressively improving scenario. However, SPI shows an incessant decline in meteorological drought conditions, especially after 2007. Evidently, regression analysis does not provide any indication of an interrelationship between the studied agricultural and meteorological parameters. Presumably, this absence is instigated because the study area is highly irrigated as the groundwater table is suitably near the surface and the existence of nearby Teesta river allows for the utilization of surface water. Moreover, the cropping pattern is shifting toward crops that require much less water and to places where soil moisture is scarce. Thus, this study addresses the gap in knowledge regarding the nature of agricultural drought and the dynamics of different aspects of drought which will be invaluable for the water management and agricultural policy in the study area as well as other regions with a similar backdrop.

Research areas: Droughts
Simulation of an extreme dust episode using WRF-CHEM based on optimal ensemble approach (2021)

Extreme dust episodes have been noticeably increasing in recent years. Dust burden during such events imparts several threats to the environment and human health. Therefore, forecast of such extreme events becomes of utmost importance to minimise the adverse impact on various socio-economy sectors. In the present study model experiments have been carried out for the simulation of an extreme dust episode that emanated over the western Indian region that coupled with previously transported dust from the West Asia region and resulted in the highly degraded air quality over the Indian region. For this purpose four ensemble members, using Weather Research and Forecasting model fully coupled with chemistry (WRF-CHEM), have been generated for identical model configuration but for the perturbed initial conditions. Model performance has been evaluated with respect to the available ground based measurements from Central Pollution Control Board (CPCB) and the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA2) data sets using standard statistical measures. Ensemble spread is noted amongst the four ensemble members generated based on 4 varying initial conditions, therefore it is suggested to use ensemble mean forecast for the dust storm monitoring and analysis. It is revealed from the analysis based on the categorical validation scheme that the WRF-CHEM simulated dust load is able to capture the locational accuracy with respect to the reanalysis/observational data sets over Indian subcontinent fairly well with 0% false alarm ratio, 7892% probability of detection and 7990% accuracy. It is noted that thick blanket of dust load enveloped Northern part of India subsequent to the dust storm which resulted in substantially dropped ground reaching solar radiation (~100150 W/m2) and a consequential reduction in the surface temperature (~2 C). Further to this enhanced temperature in association with reduced relative humidity from 800 to 600 hPa has also been noted in response to the enhanced dust loading in the model simulations. Results obtained in the present study suggests that WRF-CHEM is able to simulate both the direct and semi-direct effects of dust aerosols reasonably well. Present work has implications for improved prediction skills of WRF-CHEM in simulating extreme dust episodes and investigating the impact of dust aerosols on weather and climate.

Research areas: Air Quality
Exploring Meteorological Conditions and Human Health Impacts during Two Dust Storm Events in Northern Cape Province, South Africa: Findings and Lessons Learnt (2022)

Dust storms are meteorological hazards associated with several adverse health impacts including eye irritations, respiratory and cardiovascular disorders, and vehicular road accidents due to poor visibility. This study investigated relations between admissions from a large, public hospital that serves people living in Northern Cape and Free State provinces, South Africa during 2011 to 2017, and meteorological variables (temperature and air quality) during two dust storms, one in October 2014 (spring) and the second in January 2016 (summer), identified from the media as no repository of such events exists for South Africa. Distributed nonlinear lag analysis and wavelet transform analysis were applied to explore the relationships between hospital admissions for respiratory and cardiovascular diseases, eye irritation, and motor vehicle accidents; maximum temperature, and two air quality proxy measures, aerosol optical depth and Angstrom exponent, were used as ground-based air quality data were unavailable. Eye irritation was the most common dust-related hospital admission after both dust storm events. No statistically significant changes in admissions of interest occurred at the time of the two dust storm events, using either of the statistical methods. Several lessons were learnt. For this type of study, ground-based air quality and local wind data are required; alternative statistical methods of analysis should be considered; and a central dust storm repository would help analyze more than two events. Future studies in South Africa are needed to develop a baseline for comparison of future dust storm events and their impacts on human health.

Research areas: Public Health, Air Quality
Effects of the COVID-19 lockdown and recovery on People's mobility and air quality in the United Arab Emirates using satellite and ground observations (2022)

The stringent COVID-19 lockdown measures in 2020 significantly impacted people's mobility and air quality worldwide. This study presents an assessment of the impacts of the lockdown and the subsequent reopening on air quality and people's mobility in the United Arab Emirates (UAE). Google's community mobility reports and UAE's government lockdown measures were used to assess the changes in the mobility patterns. Time-series and statistical analyses of various air pollutants levels (NO2, O3, SO2, PM10, and aerosol optical depth-AOD) obtained from satellite images and ground monitoring stations were used to assess air quality. The levels of pollutants during the initial lockdown (March to June 2020) and the subsequent gradual reopening in 2020 and 2021 were compared with their average levels during 20152019. During the lockdown, people's mobility in the workplace, parks, shops and pharmacies, transit stations, and retail and recreation sectors decreased by about 34%79%. However, the mobility in the residential sector increased by up to 29%. The satellite-based data indicated significant reductions in NO2 (up to 22%), SO2 (up to 17%), and AOD (up to 40%) with small changes in O3 (up to 5%) during the lockdown. Similarly, data from the ground monitoring stations showed significant reductions in NO2 (49%  57%) and PM10 (19%  64%); however, the SO2 and O3 levels showed inconsistent trends. The ground and satellite-based air quality levels were positively correlated for NO2, PM10, and AOD. The data also demonstrated significant correlations between the mobility and NO2 and AOD levels during the lockdown and recovery periods. The study documents the impacts of the lockdown on people's mobility and air quality and provides useful data and analyses for researchers, planners, and policymakers relevant to managing risk, mobility, and air quality.

Research areas: Air Quality, Energy Production/Use
Understanding the Trend of NO2, SO2 and CO over East Africa from 2005 to 2020 (2021)

The atmospheric chemistry constituents of nitrogen dioxide (NO2), sulphur dioxide (SO2) and carbon monoxide (CO) are associated with air pollution and climate change. In sub-Saharan Africa, a lack of sufficient ground-based and aircraft observations has, for a long time, limited the study of these species. This study thus utilized satellite observations as an alternative source of data to study the abundance of these species over the East African region. The instruments used included the Ozone Monitoring Instrument (OMI), the Atmospheric InfraRed Sounder (AIRS), and the TROPOspheric Monitoring Instrument (TROPOMI). An investigation of trends in the data series from 2005 to 2020 was carried out using the sequential Mann-Kendall test while the Pearson correlation coefficient was used to compare the data records of the instruments. The analysis revealed no trend in NO2 (p > 0.05), a decreasing trend in SO2 (p < 0.05), a decreasing trend (p < 0.05) in CO closer to the surface (850 hPa to 500 hPa) and an increasing trend (p < 0.05) in CO higher up in the atmosphere (400 hPa to 1 hPa). There is likely a vertical ascent of CO. The correlation between the instrument records was 0.54 and 0.77 for NO2 and CO, respectively. Furthermore, seasonal fires in the savanna woodlands were identified as the major source of NO2 and CO over the region, while cities such as Kampala, Nairobi, and Bujumbura and towns such as Dar es Salaam and Mombasa were identified as important NO2 hotspots. Similarly, the active volcano at Mt. Nyiragongo near Goma was identified as the most important SO2 hotspot.

Research areas: Air Quality, Wildfires, Volcanic Eruptions
A Complete Study on the Costliest Super Cyclone Amphan (May 2020) with Its Devastating Impact on West Bengal, India (2022)

Amphan (1621 May 2020) is the most intense tropical storm in the history of West Bengal during recent decades (20112020). After the 1999 Odisha Super Cyclone (OSuC), it is also the most intense super cyclonic storm (SuCS) that has originated over the Bay of Bengal (BoB) and caused irreparable damages during the storm event. The intensification time of Amphan was slow initially, but it grew from category 1 to 5 in record time, just within 18 h. This paper highlights mainly the pre-disaster state-level preparedness and also the severity of cyclonic storm Amphan on West Bengal. To map the flooded areas of southern West Bengal, the Sentinel-1 SAR dataset have been analyzed in the Google Earth Engine (GEE) environment. The results derived from the pixel-based analysis show that nearly 1075 km2 of land has been inundated due to intense rainfall and storm surges during Amphan. The powerful high storm surge is also responsible for the embankment breaching, which is 160 km long along the coastal belt of West Bengal.

Research areas: Severe Storms, Floods
Assessment of Landslides Along NH 29 in the Kevuza Area, Kohima, Nagaland (2021)

National Highway (NH) 29 is a strategic highway of India that runs from Assam to Manipur, through Nagaland. This highway, also known as the Asian Highway 1 (AH 1), connects India to the Southeast Asian countries via Myanmar. A section of the highway, located near the capital city of Kohima, was damaged by major landslides on 1st August 2018. Another landslide occurred in the same area on 4th August 2019, which totally blocked vehicular movement for nearly a month. In both instances, the area received heavy rainfall intermittently for some days preceding slope failure. Geologically, the area is made up of highly jointed and fractured Disang rocks that are composed predominantly of shales intercalated with minor beds of siltstone, and some clay pockets indicating weathering of these rocks. The slide material comprises a mixture of loose debris of shales and saturated clays. A multi-parameter study involving geotechnical, kinematic and joint analyses, slope mass rating, resistivity surveys, and remote sensing using an Unmanned Aerial Vehicle (UAV) was carried out to determine the factors responsible for the two landslide events in this area. The study finds that the soils, with low values of unconfined compressive strength, are one of the major contributors to slope failure in the area. Slope stability analyses demarcate the slopes of the study area as partially stable to highly unstable. Kinematic and joint analyses indicate that the rocks are structurally weak due to the presence of joints, which make them susceptible to wedge failure. Analyses of joints and slickensides confirm complex deformation taking place in the area. The study of satellite imagery of the study area, coupled with field evidences, indicate that the area is crossed with faults. The presence of one such fault and two confined aquifers was validated by resistivity surveys, which explains the shearing of the rocks and high degree of weathering of the country rocks. The low shear strength of the soils and saturation of other slope materials due to heavy rainfall led to the two landslides events.

Research areas: Land Surface/Agriculture Indicators
Multidisciplinary study with quantitative analysis of isotopic data for the assessment of recharge and functioning of volcanic aquifers: Case of Bromo-Tengger volcano, Indonesia (2019)

Study region
The Bromo-Tengger volcanic aquifer system, (East Java, Indonesia).
Study focus
Andesitic volcanic aquifers in Indonesia are an important source of groundwater supply for the population. The artesian flow from high discharge springs facilitates the access for irrigation and drinking water but continuously flowing artesian wells exert an increasing pressure on the groundwater resource. Given the complexity of the volcanic edifice, a multidisciplinary approach including geological, hydrometeorological, hydrochemical and isotopic measurements was performed to characterise the hydrogeological functioning of the volcanos northern flank.
New hydrogeological insights for the region
Two main hydrogeological systems are identified: a system with perched aquifers in the lava flows and pyroclastic complex, supplying low discharge springs or infiltrating to a deep flow system. The latter system is unconfined and provides groundwater to the downstream plain that hosts a confined multi-layer volcano-sedimentary aquifer. The joint implementation of a quantitative isotopic approach and a groundwater budget allows characterising aquifer recharge along the whole volcano flank. It is mainly controlled by the rainfall distribution that peaks around 1200 m elevation. The caldera basin on the top of the volcano has a very limited contribution to recharge. A conceptual hydrogeological model is proposed and compared to the main concepts of volcanic islands. This study is a first step for further scientific and management discussions to implement protection policies on the Bromo-Tengger aquifer system.

Research areas: Volcanic Eruptions
Non-deforestation drivers of fires are increasingly important sources of aerosol and carbon dioxide emissions across Amazonia (2019)

Deforestation rates have declined substantially across the Brazilian Legal Amazon (BLA) over the period from 20002017. However, reductions in fire, aerosol and carbon dioxide have been far less significant than deforestation, even when accounting for inter-annual variability in precipitation. Our observations and analysis support a decoupling between fire and deforestation that has exacerbated forest degradation in the BLA. Basing aerosol and carbon dioxide emissions on deforestation rates, without accounting for forest degradation will bias these important climate and ecosystem-health parameters low, both now and in the future. Recent increases in deforestation rate since 2014 will enhance such degradation, particularly during drought-conditions, increasing emissions of aerosol and greenhouse gases. Given Brazils committed Nationally Determined Contribution under the Paris Agreement, failure to account for forest degradation fires will paint a false picture of prior progress and potentially have profound implications for both regional and global climate.

Research areas: Habitat Conversion/Fragmentation, Wildfires
The world's second-largest, recorded landslide event: Lessons learnt from the landslides triggered during and after the 2018 Mw 7.5 Papua New Guinea earthquake (2022)

Events characterized by widespread landslides provide rare but valuable opportunities to investigate the spatial and size distributions of landslides in relation to seismic, climatic, geological and morphological factors. This study presents a unique event inventory for the co-seismic landslides induced by the February 25, 2018 Mw 7.5 Papua New Guinea earthquake. The mainshock rupture was dominated by reverse fault motion, and this was also the case for the aftershocks. The latter also triggered widespread landslides in combination with rainfall during the period between February 26 and March 19. We mapped approximately 11,600 landslides of which, more than 10,000 were triggered by the mainshock, with a total failed planimetric area of about 145 km2. Such a large area makes this inventory the world's second-largest recorded landslide event after the 2008 Mw 7.9 Wenchuan earthquake, where the motion changed from predominantly thrust to strike-slip. Large landslides are abundant throughout the study area located within the remote Papua New Guinea Highlands. Specifically, more than half of the landslide population is larger than 50,000 m2 and overall, post-seismic landslides are even larger than their co-seismic counterparts. To understand the factors controlling the distribution of landslides' occurrence and size, we combine descriptive statistics as well as more rigorous bivariate and multivariate analyses. We statistically show that the 15-day antecedent precipitation plays a role in explaining the spatial distribution of co-seismic landslides. Also, we examine four strong aftershocks (Mw  6.0) within 9 days after the mainshock and statistically demonstrate that the cumulative effect of aftershocks is the main factor disturbing steep hillslopes and causing the initiation of very large landslides, up to ~5 km2. Overall, the dataset and the findings presented in this paper represent a step towards a holistic understanding of the seismic landslide hazard assessment of the entire Papua New Guinea mainland.

Research areas: Land Surface/Agriculture Indicators, Earthquakes
Effects of ozone and clouds on temporal variability of surface UV radiation and UV resources over Northern Eurasia derived from measurements and modeling (2020)

Temporal variability in erythemal radiation over Northern Eurasia (4080 N, 10 W180 E) due to total ozone column (X) and cloudiness was assessed by using retrievals from ERA-Interim reanalysis, TOMS/OMI satellite measurements, and INM-RSHU chemistryclimate model (CCM) for the 19792015 period. For clear-sky conditions during spring and summer, consistent trends in erythemal daily doses (Eery) up to +3%/decade, attributed to decreases in X, were calculated from the three datasets. Model experiments suggest that anthropogenic emissions of ozone-depleting substances were the largest contributor to Eery trends, while volcanic aerosol and changes in sea surface temperature also played an important role. For all-sky conditions, Eery trends, calculated from the ERA-Interim and TOMS/OMI data over the territory of Eastern Europe, Siberia and Northeastern Asia, were significantly larger (up to +58%/decade) due to a combination of decrease in ozone and cloudiness. In contrast, all-sky maximum trends in Eery, calculated from the CCM results, were only +34%/decade. While Eery trends for Northern Eurasia were generally positive, negative trends were observed in July over central Arctic regions due to an increase in cloudiness. Finally, changes in the ultraviolet (UV) resources (characteristics of UV radiation for beneficial (vitamin D production) or adverse (sunburn) effects on human health) were assessed. When defining a UV optimum condition with the best balance in Eery for human health, the observed increases in Eery led to a noticeable reduction of the area with UV optimum for skin types 1 and 2, especially in April. In contrast, in central Arctic regions, decreases in Eery in July resulted in a change from UV excess to UV optimum conditions for skin types 2 and 3.

Research areas: Public Health
Long-term eruptive trends from space-based thermal and SO2 emissions: a comparative analysis of Stromboli, Batu Tara and Tinakula volcanoes (2018)

Batu Tara (Indonesia) and Tinakula (Solomon Island) are two poorly known volcanoes with morphologies and short-term eruptive activity similar to Stromboli (Italy). However, quantitative information about their long-term eruptive behaviour is limited, making the comparisons with Stromboli descriptive and based on short periods of observations. Here, we use over a decade of satellite data to measure and compare the radiant flux (20002017) and the SO2 mass (20042017) of all three volcanoes. The combined analysis of volcanic radiant power (from MODIS data) and SO2 flux (from OMI data) reveals different long-term eruptive trends and contrasting ratios of SO2/VRP. These data indicate that the eruptive mechanisms operating at each volcano are quite different. The persistent open-vent activity of Stromboli volcano is episodically interrupted by flank eruptions that drain degassed magma stored in the very shallow portion of the central conduit. In contrast, a long-lasting exponential decay of both VRP and SO2 flux observed at Batu Tara is consistent with the eruption of undegassed magma from a deep, closed magma chamber, whilst Tinakula displays multiple year-long eruptive phases, characterised by evolving gas/thermal ratios and an eruptive intensity increasing with time. Magma budget calculations for the latter volcano are consistent with eruption from a volatile-zoned magma chamber, coupled with periods of gas/magma accumulations at depth. Our results suggest that the combined analysis of satellite thermal/gas data provides a valuable tool for decrypting the long-term volcanic dynamics that could remain hidden over shorter timescales.

Research areas: Volcanic Eruptions