nasa-gesdisc/es-publications-researchareas huggingface dataset:
Statistical intercomparison and validation of multisensory aerosol optical depth retrievals over three AERONET sites in Kenya, East Africa (2017)

Over the last two decades, a number of space-borne sensors have been used to retrieve aerosol optical depth (AOD). The reliability of these datasets over East Africa (EA), however, is an important issue in the interpretation of regional aerosol variability. This study provides an intercomparison and validation of AOD retrievals from the MODIS-Terra (DT and DB), MISR and OMI sensors against ground-based measurements from the AERONET over three sites (CRPSM_Malindi, Nairobi, and ICIPE_Mbita) in Kenya, EA during the periods 20082013, 20052009 and 20062015, respectively. The analysis revealed that MISR performed better over the three sites with about 82.5% of paired AOD data falling within the error envelope (EE). MODIS-DT showed good agreement against AERONET with 59.05% of paired AOD falling within the sensor EE over terrestrial surfaces with relatively high vegetation cover. The comparison between MODIS-DB and AERONET revealed an overall lower performance with lower Gfraction (48.93%) and lower correlation r = 0.58; while AOD retrieved from OMI showed less correspondence with AERONET data with lower Gfraction (68.89%) and lowest correlation r = 0.31. The monthly evaluation of AODs retrieved from the sensors against AERONET AOD indicates that MODIS-DT has the best performance over the three sites with highest correlation (0.710.84), lowest RMSE and spread closer to the AERONET. Regarding seasonal analysis, MISR performed well during most seasons over Nairobi and Mbita; while MODIS-DT performed better than all other sensors during most seasons over Malindi. Furthermore, the best seasonal performance of most sensors relative to AERONET data occurred during JuneAugust (JJA) attributed to modulations induced by a precipitation-vegetation factor to AOD satellite retrieval algorithms. The study revealed the strength and weakness of each of the retrieval algorithm and forms the basis for further research on the validation of satellite retrieved aerosol products over EA.

Research areas: Validation
Land susceptibility to water and wind erosion risks in the East Africa region (2020)

Land degradation by water and wind erosion is a serious problem worldwide. Despite the significant amount of research on this topic, quantifying these processes at large- or regional-scale remains difficult. Furthermore, very few studies provide integrated assessments of land susceptibility to both water and wind erosion. Therefore, this study investigated the spatial patterns of water and wind erosion risks, first separately and then combined, in the drought-prone region of East Africa using the best available datasets. As to water erosion, we adopted the spatially distributed version of the Revised Universal Soil Loss Equation and compared our estimates with plot-scale measurements and watershed sediment yield (SY) data. The order of magnitude of our soil loss estimates by water erosion is within the range of measured plot-scale data. Moreover, despite the fact that SY integrates different soil erosion and sediment deposition processes within watersheds, we observed a strong correlation of SY with our estimated soil loss rates (r2 = 0.4). For wind erosion, we developed a wind erosion index by integrating five relevant factors using fuzzy logic technique. We compared this index with estimates of the frequency of dust storms, derived from long-term Sea-Viewing Wide Field-of-View Sensor Level-3 daily data. This comparison revealed an overall accuracy of 70%. According to our estimates, mean annual gross soil loss by water erosion amounts to 4 billion t, with a mean soil loss rate of 6.3 t ha1 yr1, of which ca. 50% was found to originate in Ethiopia. In terms of land cover, ca. 50% of the soil loss by water erosion originates from cropland (with a mean soil loss rate of 18.4 t ha1 yr1), which covers ca. 15% of the total area in the study region. Model results showed that nearly 10% of the East Africa region is subject to moderate or elevated water erosion risks (>10 t ha1 yr1). With respect to wind erosion, we estimated that around 25% of the study area is experiencing moderate or elevated wind erosion risks (equivalent to a frequency of dust storms >45 days yr1), of which Sudan and Somalia (which are dominated by bare/sparse vegetation cover) have the largest share (ca. 90%). In total, an estimated 8 million ha is exposed to moderate or elevated risks of soil erosion by both water and wind. The results of this study provide new insights on the spatial patterns of water and wind erosion risks in East Africa and can be used to prioritize areas where further investigations are needed and where remedial actions should be implemented.

Research areas: Land Surface/Agriculture Indicators
Large-Scale Smoke Haze over the European Part of Russia and Belorus in July 2016 (2018)

The smoke haze over the European part of Russia (EPR) and Belorus in July 2016 has been studied with the use of aerosol optical thickness (AOT) data measured by MODIS satellite spectrometers. The AOT maximum on the territory limited by coordinates 4570 N and 2060 E reached 2.95 on July 24, 2016 with an average regional value of 0.48. The total mass of smoke aerosol without the area covered by clouds was 0.73 million tons. Analysis of the wind fields and five-day back trajectories of air mass movement showed that the smoke was transported by the northeast winds to the EPR and Belorus from western Siberia, including the Yamalo-Nenets Autonomous District, which was characterized by large forest fires from July 17 to 23. Simulation of the radiation regime of the smoky atmosphere indicated that the average radiative forcings of smoke aerosol at upper and lower boundaries of the atmosphere for the above-mentioned territory are 29 and 54 W/m2, respectively (the extreme values are 124 and 154 W/m2, respectively). A comparative analysis of the smoke haze characteristics over the EPR in July 2016 and in summer 2010 has been conducted. According to ground-based measurement data, the mass concentration of PM10 during the smoke period from July 24 to 27 in the Moscow region reached 0.25 mg/m3.

Research areas: Air Quality, Wildfires
Bajacalifornian dust deposition and atmospheric input of iron to the Gulf of California during the summer (2020)

Iron (Fe) is an essential micronutrient for all living organisms and its atmospheric supply to the surface waters of marginal seas remains poorly understood. Here we report the seasonal and spatial variability of atmospheric mineral dust deposition and Fe fluxes along the west coast of the Gulf of California (GC). Meteorological data and dust samples were collected from June 2010 to October 2013 at three sites of the eastern side of Baja California Peninsula (BCP). Evidence of an across-BCP wind component (W-E) during the warm season (MaySeptember) was found, suggesting that winds crossing the BCP from west to east were an important source of variability. Coincidently, dust deposition at the northern and center sites were significantly (p 

Research areas: Ecosystems
Reproductive cycle of the sea cucumber (Isostichopus fuscus) and its relationship with oceanographic variables at its northernmost distribution site (2017)

The brown sea cucumber Isostichopus fuscus is highly prized and intensively fished, yet no studies of its reproductive cycle at its northernmost distribution site exist. To characterize its reproductive cycle, monthly surveys (Oct 2014-Dec 2016) that included gonad collection were conducted in 118 sites along the eastern coast of Baja California, including islands from Bahia San Luis Gonzaga (29o 49 14.18 N, 114 o 356.17 W) to the 28th parallel north. A total of 2 808 sea cucumber specimens were measured (mean length  SD = 21.4  6 cm) and weighed (375.6  249 g). Seven hundred and seventeen organisms were dissected but only 553 gonads were suitable for processing through histological analysis to identify sex and developmental stage. Of these individuals, 224 were female, 162 were male, 157 were undifferentiated and 10 were hermaphrodites, resulting in a sex ratio that was significantly different from 1:1 (2 = 36.63, P = 0.03, df = 23). There was no statistical difference (p > 0.05) of either size or weight between males and females, but females were larger than males. The length-weight relationship observed was W = 0.18L2.4, r2 = 0.82, p <0.05 while the size-at-first-maturity was 16 cm. Five gonad stages were identified: 28% undifferentiated, 9% gametogenesis, 15% mature, 19% expulsion and 29% post-expulsion. The Oocyte Theoretical Diameter (OTD) was estimated by measuring the area of 10 291 oocytes, finding 2 307 individuals in oogenesis (mean  SD of 65.3  19.7 m), 3 630 in maturity (66.0  17.8 m), 3 756 in spawning (73.8  14.6 m) and 868 in post-spawning (49.18  20.7 m). Modal progression analysis shows that oocytes increase 23% in size from oogenesis to maturity, and decrease 9%in size from maturity to spawning and, on average, oocytes are 72% smaller post-spawning that during spawning. Rev. Biol. Trop. 65(Suppl. 1): S180-S196. Epub 2017 November 01.

Research areas: Ecosystems
Impact of SST on heavy rainfall events on eastern Adriatic during SOP1 of HyMeX (2018)

The season of late summer and autumn is favourable for intensive precipitation events (IPE) in the central
Mediterranean. During that period the sea surface is warm and contributes to warming and moistening of the
lowest portion of the atmosphere, particularly the planetary boundary layer (PBL). Adriatic sea is surrounded by
mountains and the area often receives substantial amounts of precipitation in short time (24 h). The IPEs are a
consequence of convection triggered by topography acting on the southerly flow that has brought the unstable
air to the coastline. Improvement in prediction of high impact weather events is one of the goals of The
Hydrological cycle in the Mediterranean eXperiment (HyMeX). This study examines how precipitation patterns
change in response to different SST forcing. We focus on the IPEs that occurred on the eastern Adriatic coast
during the first HyMeX Special observing period (SOP1, 6 September to 5 November 2012). The operational
forecast model ALADIN uses the same SST as the global meteorological model (ARPEGE from Meteo France), as
well as the forecast lateral boundary conditions (LBCs). First we assess the SST used by the operational atmo-
spheric model ALADIN and compare it to the in situ measurements, ROMS ocean model, OSTIA and MUR
analyses. Results of this assessment show that SST in the eastern Adriatic was overestimated by up to 10 K during
HyMeX SOP1 period. Then we examine the sensitivity of 8 km and 2 km resolution forecasts of IPEs to the
changes in the SST during whole SOP1 with special attention to the intensive precipitation event in Rijeka.
Forecast runs in both resolutions are performed for the whole SOP1 using different SST fields prescribed at initial
time and kept constant during the model forecast. Categorical verification of 24 h accumulated precipitation did
not show substantial improvement in verification scores when more realistic SST was used. Furthermore, the
results show that the impact of introducing improved SST in the analysis on the precipitation forecast varies for
different cases. There is generally a larger sensitivity to the SST in high resolution than in the lower one, al-
though the forecast period of the latter is longer.

Research areas: Atmospheric/Ocean Indicators
Total Column Ozone, Precipitable Water Content and Aerosol Optical Thickness Over Atigre Village, a Tropical Station: First Observations (2019)

In this paper, we report first-time observations of total column ozone (TCO), aerosol optical thickness (AOT) and precipitable water content (PWC) at five different wavelengths using compact, handheld, multichannel sun photometer (Microtops II ozonometer) at Atigre village (16.74N latitude, 74.37E longitude, 604 ms altitude above sea level). The three optical filters at wavelengths 305 nm, 312 nm and 320 nm are used to detect the TCO, while two optical filters 936 nm and 1020 nm are used to detect the PWC and AOT, respectively. We have been collecting data from September 1, 2017, and 122 days are selected from September 1, 2017, to December 31, 2017, to present as first observations of TCO, AOD and PWC. The mean values of TCO, AOT and PWC are found to be 261.2 ( 9.22) DU, 0.25 ( 0.04) and 1.98 ( 0.79) cm, respectively, during this period. The TCO measurements taken by the Microtops II ozonometer are compared with the ozone monitoring instrument satellite data over Atigre. We found that PWC and AOT values are negatively correlated ( 0.54) during monsoon season, while they show positive correlation (0.63) during other seasons with 90% significance level. The diurnal variation of TCO, PWC and AOT differ in monsoon and the post-monsoon season.

Research areas: Validation
Lower diversity of recruits in coastal reef assemblages are associated with higher sea temperatures in the tropical South Atlantic (2019)

Climate change will lead to community shifts and increase the vulnerability of coastal marine ecosystems, but there is yet insufficient detail of how early life stages of marine populations are linked to oceanic-climate dynamics. This study aimed to investigate how ocean-climate variability is associated with spatial and temporal changes in benthic larval recruitment of tropical reef assemblages. Recruitment (abundance, richness, and diversity) of benthic invertebrates was monitored for one year on macroalgal beds in four rocky reefs in a marine protected region in the Eastern coast of Brazil, and compared to fluctuations in meteo-oceanographic conditions at multiple temporal scales (days, weeks, and months). Our results revealed that recruitment of benthic invertebrates varies widely (up to 15 orders of magnitude) among sampled reefs and in time, with wave height, wind speed, and sea temperature being significantly related to recruitment variability. We detected strong taxonomic variability in recruitment success and ocean-climate variables, which highlights the complexity of estimating community vulnerability to climate change in benthic communities. Given that macroalgal beds are key to recruitment of some species regionally (430 km), the protection of coastal nursery habitats may be critical for marine conservation and species adaptation in a climate change scenario. Considering the projected ocean-climate change in IPCC scenarios, our study suggests that recruitment of marine populations in coastal reefs could be highly sensitive to climate change in the tropical South Atlantic Ocean.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Investigating the effects of episodic Super-cyclone 1999 and Phailin 2013 on hydro-meteorological parameters and agriculture: An application of remote sensing (2018)

The tropical cyclones (TCs) are often associated with unprecedented heavy rainfall, and have a pronounced impact over East coast states of India. This study has done comprehensive investigation on contribution of two episodic TCs rainfall to the annual rainfall using satellite based rainfall estimates from TMPA-3B42 (daily product), and rainfall data from India Meteorological Department (IMD) observations. We analyzed both rainfall distribution and inundation extent induced by two episodic severe cyclonic events (Supercyclone 1999 and Phailin 2013), and assessed their impacts on hydro-meteorological parameters and agricultural productivity. Our findings suggest that rainfall originated from two episodic TCs significantly contributed to the annual rainfall, accounting for about 525% over the coastal districts of Odisha state. Howbeit, it was subjected to underestimation owing to rainfall biases of TMPA-3B42 during TCs, which was evident when it was compared with IMD measurements. Along the TCs track, intense rainfall followed by peak discharge from the river basins caused substantial flooding and inundation of croplands over the coastal regions. The TC related rainfall, strong winds, and storm surges have diminished kharif season's agricultural production, as crops were submerged during these periods. Overall, the rice production has been diminished by 57%, and this rice production even lowered by more than 70% in some of the districts. Most severely affected districts (Ganjam, Puri, Cuttack, Jajpur, Bhadrak, Baleshwar) were located close to landfall, where croplands are dominating land use type. These results inferred that the isolated severe TCs could bring significant amount of rainfall, which would cause widespread impacts on agricultural activities. Finally, the findings of this unique study recommends that the satellite based rainfall estimate data can act as a valuable input for flood modeling and crop monitoring at different scales to alleviate hydrometeorological and agricultural impacts.

Research areas: Severe Storms, Agriculture, Floods
Recent trend in the global distribution of aerosol direct radiative forcing from satellite measurements (2020)

Global distribution of aerosol direct radiative forcing (DRF) is estimated using Clouds and Earth's Radiant Energy System (CERES) synoptic (SYN) 1 datasets. During 20012017, a statistically significant change of global DRFs is revealed with a general decreasing trend (i.e., a reduced cooling effect) at the top of the atmosphere (DRFTOA 0.017 Wm2year1) and at the surface (DRFSFC 0.033 Wm2year1) with rapid change over the land compared to the global ocean. South Asia and Africa/Middle East regions depict significant increasing trend of atmospheric warming by 0.025 and 0.002 Wm2year1 whereas, the rest of the regions show a decline. These regional variations significantly modulate the global mean DRF (5.36  0.04 Wm2 at the TOA and  9.64  0.07 Wm2 at the surface during the study period). The observed DRF trends are coincident with the change in the underlying aerosol properties, for example, aerosol optical depth, Angstrom exponent and partly due to the increasing columnar burden of SO2 over some of the regions. This indicates that increasing industrialization and urbanization have caused prominent change in the DRF during recent decades.

Research areas: Atmospheric/Ocean Indicators, Habitat Conversion/Fragmentation
Enhanced flood mapping using synthetic aperture radar (SAR) images, hydraulic modelling, and social media: A case study of Hurricane Harvey (Houston, TX) (2020)

Post event flooding maps are currently extracted from synthetic-aperture radar (SAR) and/or optical satellite images or developing using hydraulic model simulations. Several sources of uncertainties impact the accuracy of such flood maps constructed from each method, especially in urban areas. An integrated approach that combines satellite imagines of flooded areas, hydraulic models, and markers from social media that should reduce these uncertainties and allow a more accurate reconstruction of flooded urban areas, is presented in this paper. The flooding associated with Hurricane Harvey in Houston, TX was chosen as a case study. Model validations demonstrate the effectiveness of our integrated approach in reconstructing an accurate flooding map, as well as the temporal and spatial patterns of flooding. Using the experience from this case study we discuss the possibility to use satellite data, instead of ground-based rainfall gauge measurements as precipitation inputs to the hydraulic model; and possible error sources in simulating flooding in urban areas using the hydraulic model.

Research areas: Floods, Severe Storms
Correlations among phytoplankton biomass, sea ice and wind speed in Barents Sea and the future climate trends (2020)

Global climate closely links with the Arctic Ocean ecosystem especially in the Barents Sea. The distributions and correlations among chlorophyll-a (CHL), sea ice concentration (ICE), wind speed (WIND), sea surface temperature (SST) and mixed layer depth (MLD) are studied within the region of Barents Sea (70N-80N, 30E40E) over the period 20032013. CHL increased from north to south in general. Ice melted rapidly in the southern region (70N-75N) and had less impact than SST on phytoplankton blooming. Melting ice in northern region (75N-80N) contributed significant source on phytoplankton development. WIND had negative correlations with CHL in spring blooming season and had positive correlations during autumn. Dimethylsulfide (DMS) concentration and sea-to-air DMS flux are simulated using a comprehensive biogeochemical model. The key model parameters are calibrated using a genetic algorithm under contemporary climate conditions. Environmental factors and DMS sea-air flux are compared for 1CO2 and 4CO2 climate conditions. By 4CO2, SST increases more than doubles, DMS increases 27.5%. Mean annual DMS sea-to-air flux increases 323%. The increase of DMS flux under 4CO2 conditions indicates that Arctic climate may be counteracting with the warming by 4CO2.

Research areas: Cryospheric Indicators, Ecosystems
Spatial-Temporal Assessment of Satellite-Based Rainfall Estimates in Different Precipitation Regimes in Water-Scarce and Data-Sparse Regions (2020)

Accurate precipitation measurement is very important for socio-hydrological resilience in the face of frequent extreme weather events such as cyclones. This study evaluates the performance of two satellite products: the Tropical Rainfall Measuring Mission (TRMM 3B43V7) Multi-satellite Precipitation Analysis (TMPA, hereafter: TRMM) and the Integrated Multi-satellite Retrievals for GPM (IMERG, Final Run V06, hereafter: GPM) in the Sultanate of Oman. Oman is an arid country that generally has few rainy days, but has experienced significant flash floods, tropical storms and cyclones recently, leading to the loss of lives and millions of dollars in damage. Accurate precipitation analysis is crucial in flood monitoring, hydrologic modeling, and the estimation of the water balance of any basin, and the lack of a sufficient weather monitoring network is a barrier to accurate precipitation measurement. Satellite rainfall estimates can be a reliable option in sparse network areas, especially in arid and semi-arid countries. This study evaluated monthly rainfall (hereafter: OBSERVED) levels at 77 meteorological stations from January 2016 to December 2018. The capacity of the TRMM and GPM satellite products to detect monthly rainfall amounts at varying precipitation thresholds was also evaluated. Findings included (1) overall and across the 11 Governorates of Oman, both satellite products show different spatial variability and performance to the OBSERVED at the monthly, seasonal, and annual temporal scales; (2) from the perspective of precipitation detection and frequency bias, GPM showed a similar performance to TRMM at detecting low precipitation (2 mm/month) but was poorer at detecting high precipitation (>30 mm/month) across the entire country as well as in the Northern, Interior, and Dhofar regions; (3) both products show similarities to the OBSERVED through the partitioning of their seasonal time series into a distinct number of homogenous segments; and (4) both products had difficulty reproducing OBSERVED levels in the Dhofar and Interior regions, which is consistent with studies conducted in mountainous and coastal regions. With the aim of reproducing the spatial and temporal structure of OBSERVED in a rugged terrain, the study shows that both satellite products can be used in areas of sparse rain gauges or as additional observation for studies of extreme weather events. Overall, this study suggests that for Oman, both satellite products can be used as proxies for OBSERVED with appropriate bias corrections and GPM is also a reliable replacement for TRMM as a precipitation satellite product. The findings will be useful to the countrys flood resilience and mitigation efforts, especially in areas where there is sparse rain gauge coverage.

Research areas: Validation