nasa-gesdisc/es-publications-researchareas huggingface dataset:
Seasonal Variation of Long-Chain Alkyl Diols Proxies in Suspended Particulate Matter of the Changjiang River Estuary (2022)

Long-chain alkyl diols (LCDs) were applied as indicators of salinity, sea surface temperature (SST), upwelling, and nutrient conditions in marine settings. While increasing the body of most applications of LCDs proxies reconstructed paleo-environment information, few studies reported seasonal variation in LCDs and evaluated their applicability as environmental indicators in modern marine environments. Here, the composition and distribution of LCDs in suspended particulate matter (SPM) in three seasons in the Changjiang River Estuary (CRE) were analyzed to evaluate seasonal influence on the application of LCDs as environmental indicators. We found that the reconstructed temperature based on the long-chain diol index (LDI; LDI = C30 1,15-diol/(C28 1,13-diol + C30 1,13-diol + C30 1,15-diol)) was not consistent with satellite-measured SST, likely due to vertical mixing of LCDs in this region. The 1,14-diols previously used to indicate upwelling conditions, did not reflect the nutrient distribution of this region due to the Changjiang River (CR) nutrients discharge. Our results showed that the mean relative proportions of FC32 1,15-diol (FC32 1,15-diol = C32 1,15-diol  100%/(C28 1,13-diol + C30 1,13-diol + C30 1,15-diol + C32 1,15-diol)) gradually decreased from nearshore to offshore (71.1%, 37.4%, and 16.5%, respectively), suggesting that FC32 1,15-diol was a reliable proxy for riverine input to the CRE. We found that the diol index (DI; DI = C30 1,15-diol  100/(C30 1,15-diol + C32 1,15-diol)) values were correlated strongly with salinities in spring (R2 = 0.82) and summer (R2 = 0.94), indicating that DI can be considered as a useful indicator for salinity construction in this estuary.

Research areas: Ecosystems
Evaluating aquifer stress and resilience with GRACE information at different spatial scales in Cambodia (2022)

Groundwater exploitation for different sectors in Cambodia is expanding. Groundwater levels have already begun to decline in some parts of the country. Monitoring and assessing groundwater storage (GWS) change, aquifer stress and aquifer resilience will support the proper planning and management of the countrys groundwater resources; however, information regarding groundwater in Cambodia is currently scarce. Thus, GWS change in Cambodia over the 15 years from April 2002 to March 2017 was assessed using remote-sensing-based Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) datasets, with a comprehensive validation of the GRACE-derived groundwater storage anomaly (GWSA) with respect to in-situ field-based observations. The current study also investigated the impact of surface water storage (SWS) change in Tonle Sap Lake, South-East Asias largest freshwater lake, on deriving the GWS change in Cambodia. The groundwater aquifer stresses (GAS), and aquifer resilience (AR) were also evaluated. The validation results were promising, with the correlation coefficient between satellite-based estimations and ground-based measurements ranging from 0.82 to 0.88 over four subbasins. The overall decreasing rate of GWS was found to be 0.63 mm/month, with two basins having the highest declining rate of more than 1.4 mm/month. Meanwhile, the aquifer experiencing stress during the dry season had a very low ability to quickly recover from these stresses. These findings emphasise that appropriate management is urgently needed to ensure the sustainability of the groundwater resource system in this country.

Research areas: Land Surface/Agriculture Indicators
Contrasting genetic diversity and structure between endemic and widespread damselfishes are related to differing adaptive strategies (2022)

Aim Several marine biogeographical provinces meet at the Arabian Peninsula. Where and how these junctions affect species is poorly understood. We herein aimed to identify the barriers to dispersal and how these shape fish populations, leading to differing biogeographies despite shared habitat and co-ancestry. Taxon Dascyllus marginatus (endemic) and Dascyllus abudafur (widespread). Location Coral reefs from the Red Sea (RS), Djibouti, Yemen, Oman, and Madagascar. Methods We tested potential barriers to gene flow using RADseq-derived SNPs and identified whether population genetic differences on each side of these barriers were neutral or selective to relate this to the biogeography of the species. Seven locations (ranging over 5100 km) were sampled for the endemic and six (ranging over 7400 km) for the widespread species, taking 20 individuals per location, with two exceptions. Results Dascyllus marginatus populations (comprising 5648 SNPs) had an order of magnitude higher genetic differentiation compared to D. abudafur (comprising 10,667 SNPs), as well as several outlier loci that were absent in D. abudafur despite equal sampling locations. In both species, the RS and Djibouti specimens formed one genetic cluster separated from all other locations. Although ranging from the RS to Madagascar, D. abudafur was absent in Yemen and Oman. Main Conclusions Stronger genetic structure at smaller geographical scales and outlier loci in the endemic species seem associated with faster adaptation to environmental differences and selective pressure. Genetic differentiation in the widespread species is neutral and only occurs at large geographical distances. Restrictive transitions (between the Gulf of Aqaba and the RS or the RS and the Gulf of Aden) do not hinder gene flow in either species, and the environmental shift within the RS (at 22N/20N) only affected the endemic species. The genetic break in the Gulf of Aden likely reflects historical colonization processes and not contemporary environmental regimes.

Research areas: Ecosystems
Clustering analysis of PM2.5 concentrations in the South Sumatra Province, Indonesia, using the Merra-2 Satellite Application and Hierarchical Cluster Method (2022)


The air quality monitoring system is the most prominent tool for monitoring air pollution levels, especially in areas where forest fires often occur. The South Sumatra Province of Indonesia is one of the greatest contributors to haze events in Indonesia due to peatlands fires. It does not sufficiently possess a ground monitoring system to cover rural areas, and thus, delayed actions can result in severe air pollution within this region. Therefore, the aim of this current study is to analyze the distribution and classification of PM2.5 observed from 2019 to 2021 within the South Sumatra Province, Indonesia. The acquisition of PM2.5 data was from the Merra-2 Satellite with a spatial resolution of 0.5 
 0.625  and an hourly interval. The hierarchical cluster analysis (HCA) was applied in this study for the clustering method. The result of the study revealed that the daily mean of PM2.5 levels varied from 5.90.01 to 21.30.03 g/m3. The study area was classified into three classes: high pollution areas (HPA), moderate pollution areas (MPA) and low pollution areas (LPA), based on the HCA method. The average level of PM2.5 observed in HPA was notably higher, at 16.80.02 g/m3, followed by MPA and LPA. Furthermore, this study indicated that the highest level of PM2.5 was found during 2019, with a severe haze event in the study area due to the intensive burning of forests, bush and peatlands. As a whole, the output of this study can be used by authorities for air quality management due to forest fire events in a certain area.


Research areas: Air Quality, Wildfires
Estimation of groundwater storage change in the Helmand River Basin (Afghanistan) using GRACE satellite data (2022)

Understanding groundwater storage dynamic changes and quantifying the trends of groundwater fluctuations in the Helmand River Basin (HRB) aquifers, where the groundwater is the main source for drinking and irrigation applications, is significantly important in order to effectively manage groundwater resources. This case study quantifies the changes in groundwater storage over 18 years (i.e., from 2003 to 2021) in the HRB by employing the Gravity Recovery and Climate Experiment (GRACE) observations and Global Land Data Assimilation System (GLDAS) data due to sparse groundwater monitoring networks and lack of ground-based information. The data of observation wells was applied to validate the results of the GRACE and GLDAS outputs. The results indicate that changes in groundwater storage on average from 2003 to 2021 are equal to (-98.6  226.84 mm or -1.9  4.38 km3/year). On average, during 2003 to 2021 groundwater table decline was -2.6 m in the HRB. The study indicates relatively strong correlation (0.75) between the GRACE derived data and direct in-situ measurements. This study highlights the effectiveness of the GRACE-derived data for the reliable estimation of groundwater storage changes in the HRB and may contribute to sustainable groundwater resources management in the region.

Research areas: Land Surface/Agriculture Indicators
Dynamical Study For Aerosols Transportation For Selected Extreme Dust Storms Over Al Jazeera Region (2022)

The characteristics and classifications of aerosol properties in Iraq were studied in this paper. The 11 grid of monthly aerosol optical depth and angstrom exponent data of the period 2005 to 2017 in Iraq is used from Terra of MODIS. Moreover, the 11 grid of Aerosol Index is used and it is available from NASA's Data and Information Services Center for Earth Sciences (GESDISC). The backtrjectory for 12 dust extreme events over the Al-Jaziraregion was studied by using the Single-Particle Lagrangian Integrated Trajectory model (HySplit-4). The spatial-seasonal aerosol properties over Iraq were obtained from the EOS-Aura satellite by Ozone Monitoring Instrument. The high-high clusters of aerosol optical depth and Aerosol Index values which refer to high concentration have been found in western and southern Iraq however low-low clusters have been found in the winter season over the whole of Iraq. According to Angstrom Exponent, there are three kinds of aerosol modes: fine, mixture, and coarse. This classification shows the maximum area under fine aerosols mode has occurred in the winter with 13.6% whereas the spring season did not show any area with fine aerosols mode. Moreover, the coarse mode covers the maximum area during the summer season at 97.7% and the minimum area during the winter season at 77. 2%. To demonstrate the relationship between topography and aerosol characteristics, Aerosol Properties Index is used which shows the degree of aerosol coarseness in each pixel. Using Geographically Weighted Regression and Ordinary Least Squares, the Aerosol Properties Index geographical distribution is strongly influenced by topographic conditions. Where the maximum coefficient of determination has been observed in the spring (R2=0.91) from the Geographically Weighted Regression model, while Ordinary Least Squares show a lower coefficient of determination (R2=0.33), Geographically Weighted Regression in comparison to Ordinary Least Squares show a better coefficient of determination in all seasons. The back trajectory for extreme dust events shows that some sources of air masses and their path to the study area through two pressure levels (1000 mb, 850 mb) and the geographical desert in the area of the study are the main cause of dust storms in the study area.

Research areas: Air Quality
Mapping and Prioritizing Potential Illegal Dump Sites Using Geographic Information System Network Analysis and Multiple Remote Sensing Indices (2022)

Due to rapid urbanization and population growth, identification and management of illegal dump sites has been a global challenge. In this study, satellite imagery and geographic information system were used to map potential illegal dump sites (PIDS). An original analytical approach was developed to identify PIDS using a set of remote sensing indices and vector files. The Network Analysis tool was used to prioritize PIDS considering driving distance between PIDS and neighboring populated points. A total of five variables (Landfills, LST, HCHO, Highways, and EVI) were considered. A study area in Saskatchewan, Canada, was selected, and the identified PIDS account for about 37.3% of the total area. Road network intensity and accessibility appear important to the occurrence of PIDS. Overall road densities in identified PIDS ranged from 0.098 to 0.251 km/km2. All five variables have observable effects on the occurrence of PIDS; however, LST and highways are recommended for future studies due to their higher membership grade and spatial sensitivity. The combination of multiple remote sensing indices and network analysis on PIDS prioritization is advantageous. The proposed PIDS mapping and prioritization method can be easily employed elsewhere.

Research areas: Habitat Conversion/Fragmentation
Seasonal Variability in Present-Day Coccolithophore Fluxes in Deep Eastern Mediterranean Sea: A Multi-Year Study (20152017) of Coccolithophore Export in SE Ionian Sea at 4300 m Depth (2022)

This study is the first attempt to understand the coccolith flux and its seasonal variability at the deepest part of the Mediterranean Sea. Samples were obtained from the deepest Mediterranean time-series sediment trap (4300 m) moored in the SE Ionian Sea (Nestor site) from January 2015 to November 2017. Throughout the study period, the coccolith fluxes displayed a seasonality signal with high values during the late winterearly spring convective mixing period (February to April) and low flux values during summer except for some solitary peaks in June. The maximum coccolith flux was observed in March 2015 while the minimum value was recorded in November 2017. Among the nineteen identified species of heterococcoliths, the dominant species in all the samples was Emiliania huxleyi reaching up to 79%, followed by Florisphaera profunda that comprised up to 33% of the total coccolith count. For the annual cycle of 2015, the average coccolith flux for the Nestor Site at a relatively shallower depth (2000 m) was comparable and for some time intervals was lower than the coccolith flux recorded in the present study at 4300 m, while coccolith flux peaks appeared simultaneously in both traps indicating a fast sinking rate. The higher E. huxleyi, F. profunda, Gladiolithus flabellatus, and Calciosolenia brasiliensis coccolith flux at 4300 m compared with their corresponding fluxes at 2000 m can be attributed to lateral advection, resuspension, and/or the influence of Eastern Mediterranean Deep Waters (EMDWs).

Research areas: Ecosystems
Tracking the influence of drought events on winter wheat using long-term gross primary production and yield in the Wei River Basin, China (2023)

The Wei River Basin (WRB) is the main winter wheat-producing area in Northwest China and plays a pivotal role in national food security and economic development. Drought is the main agro-meteorological disaster affecting winter wheat yield in this region, and the accurate assessment of the drought impacts on crop growth and yield is an important part of maintaining food security. However, commonly used assessment methods, such as correlation analysis and crop model simulation, have some limitations. In this study, based on standardized precipitation evapotranspiration index (SPEI) at multiple time scales, gross primary production (GPP) and yield data from 1990 to 2018, sensitivity analysis, Pearson correlation, and superposed epoch analysis (SEA) were used to analyze the spatiotemporal characteristics of drought in the WRB and its influence on winter wheat growth and quantitatively assess the impact of drought at different levels on winter wheat yield. The results were as follows: 1) Overall, the WRB was in a dry state with a drying trend during 19902018, and the droughts in spring, summer, and winter were the main driving forces of annual drought that seriously threatened the growth and yield of winter wheat, especially in spring (MarchMay), which is the key growth period of winter wheat. 2) The average annual GPP of winter wheat in the WRB showed a significant upward trend of 0.465  10a1, and the central part of the WRB was the region where winter wheat GPP had higher sensitivity to drought. In general, winter wheat GPP during the growing season was most sensitive to SPEI-3, indicating that seasonal water deficits had the greatest impact on winter wheat growth. 3) The yield reduction of winter wheat caused by drought presented a spatial distribution that is heavy in the north and light in the south, and as the drought grade increased, the winter wheat yield decreased more significantly, even in irrigated areas. Therefore, relevant government departments still need to strengthen the risk management of agricultural droughts in the WRB and formulate reasonable policies to maintain food security.

Research areas: Droughts, Agriculture
Effect of dust particles on lightning flash rate and polarity of dust storms over India (2022)

Six cases of dust storms that occurred over the northwestern and northern parts of India have been studied here to understand the effect of dust on the lightning characteristics of these storms. Satellite pictures show high dust content on all six storm days, and ground station data show that visibility was reduced to less than 500 m. Lightning data observed by the lightning detection network indicate that these six cases of convective dust storms produced more than 30 percent of positive CG lightning in the total CG lighting, which is considered to be very high compared to ordinary thunderstorms. Further, analysis indicates that the current carried by positive lightning is much higher than negative lightning. In some cases, the lightning flash rate reached more than 200 flashes per min (fpm). Observation shows that all these thunderstorms were accompanied by dust, and hence, incursion of the abundance of dust particles into the cloud was likely to be very high. Many earlier observations have suggested that aerosols can affect thunderstorms microphysical (such as vertical distribution of the hydrometers) and electrical characteristics. With the abundance of dust particles in the cloud and increased positive CG discharges, it has been proposed that increased dust particles can modify the vertical distribution of ice particles inside a thundercloud and affect the lightning flash rate as well as polarity.

Research areas: Atmospheric/Ocean Indicators
Trophic architecture as a predictor of ecosystem resilience and resistance in the eastern Pacific (2022)

The intricate trophic structure of marine ecosystems defines their ecological properties and network metrics; it has been used extensively to assess the development and maturity of ecosystems. The Eastern Pacific is warming due to climate change, and added human stressors are affecting the trophic architecture of its marine ecosystems. We aimed to explore the maturity of ecosystems in this region under the assumption that the trophic architecture of an ecosystem is a proxy of maturity, and that there is a direct relationship between resistance and maturity and an inverse one with resilience. We applied ecosystem network analysis to model runs of published rebuilt Ecopath models to explore the potential effects of oceanographic variables and human disturbance on the trophic architecture of 13 ecosystem models, 11 models within three different Large Marine Ecosystems (LMEs) and two models describing oceanic islands, that have an array of oceanographic conditions and are subject to different human stressors. We conclude that even when ecosystem attributes cannot conclusively assert maturity stage, they can suggest how close or far the ecosystems are from maturity. We found that the ecosystems in the Gulf of California are resilient because they have a high median trophic level, high Production/Biomass ratio, and median ascendency/capacity ratio, and because they are subject to natural variations of productivity. Upwelling ecosystems are in an intermediate stage of maturity, followed by ecosystems from the Pacific Central American Coastal LME. As expected, oceanic islands, which have a production deficit, must optimize their energy transfer. Our analysis suggests that although trophic architecture cannot serve as a direct indicator of maturity, it can help estimate ecosystem resilience and identify those systems that can withstand future impacts.

Research areas: Ecosystems
Distribution of nutrients and chlorophyll across an equatorial reef region: Insights on coastal gradients (2022)

Abstract We evaluate how the concentrations of inorganic nutrients and chlorophyll a vary in a heterogeneous area (Equatorial SW Atlantic), covering a gradient from stations closer to the coast to others more distant associated or not with turbid-zone reefs. Vertical temperature (27.9  0.10 C; mean  standard deviation) and salinity (36.2  0.14) profles showed that the water column is well mixed (0-30 m depth). The oligotrophic condition was marked by low concentrations of phosphate (0.30  0.22 M) and dissolved inorganic nitrogen (0.64  0.74 M). Moreover, dissolved reactive silicon (DSi) was low in most samples (< 2.0 M), but higher (>10 M) in nearshore stations, probably related to continental runoff and/or resuspension of the bottom sediments. The pelagic phytoplankton biomass indicated that chlorophyll a (0.25  0.08 g L-1) was low, positively correlated with light and negatively correlated with nutrients, indicating possible phytoplankton uptake. Chlorophyll a concentrations were lower in stations closer to the coast and higher in some stations near the reefs, indicating that the latter could be more prone to phytoplankton development and depletion of nutrients, especially DSi. Therefore, although oligotrophy is present along this coast, we found some unexpected heterogeneity of nutrient and chlorophyll a distributions, which were probably infuenced by benthic-pelagic coupling due to the presence of extensive reefs, sponge gardens (18-30 m depth), and the proximity to the coast. These results highlight the importance of understanding the heterogeneity of ocean productivity, especially in lesser known low-latitude areas, which showed distinct nutrient and chlorophyll a levels related to the occurrence of tropical reefs that are capable of supporting important fsh stocks and unique biological communities.

Research areas: Ecosystems