nasa-gesdisc/es-publications-researchareas huggingface dataset:
Solar global horizontal and direct normal irradiation maps in Spain derived from geostationary satellites (2015)

Solar radiation derived from satellite imagery is a powerful and highly accurate technique for solar resource assessment due to its maturity and to the long term database of observation images available. This work presents the methodology developed at CIEMAT for mapping solar radiation from geostationary satellite information and it also shows solar irradiation maps of global horizontal and direct normal components elaborated for Spain. The maps presented here have been developed from daily solar irradiation estimated for eleven years of satellite images (20012011). An attempt to evaluate the uncertainty of the presented maps is made using ground measurements from 27 meteorological stations available in Spain for global horizontal irradiation obtained from the World Radiation Data Centre. In the case of direct normal irradiation the ground measurement database was scarce, having available only six ground stations with measurements for a period of 4 years. Yearly values of global horizontal irradiation are around 1800kWhm2 in most of the country and around 19502000kWhm2 for annual direct normal irradiation. Root mean square errors in monthly means were of 11% and of 29% for global horizontal and direct normal irradiation, respectively.

Research areas: Sun-Earth Interactions
Soil moisture and precipitation thresholds for real-time landslide prediction in El Salvador (2015)

Described is the development of a regional forecasting system for landslide hazard threat level, suitable for use operationally by forecasting and disaster management agencies. The system utilizes spatially distributed operational hydrologic models to estimate depth-integrated soil moisture on basin scales of order 160 km2, with forcing of remotely sensed and on-site precipitation data. The depth-integrated soil moisture data and the precipitation forcing are used together with regional databases of landslide occurrence to develop threshold curves in the precipitation/soil moisture space that allow the prediction of landslide hazard threat level on satellite-derived rainfall pixel scales. Predetermined susceptibility maps may then be used together with the real-time prediction of hazard threat level for a particular rainfall pixel to determine the slopes within the pixel that are more likely to fail in real time and to characterize a given pixel as susceptible or non-susceptible to landsliding for real-time prediction. The operational system development requires global satellite precipitation estimates with short latency, real-time precipitation data from sparse rain gauges in the region, and a regional database of historical landslide events with location and timing information. Parametric databases that support the operational hydrologic model consist of soil texture by depth and land-use/land-cover information. The case study presented is for the country of El Salvador. The study shows the feasibility of the regional system development and the validation of the assumed existence of a threshold curve in two-dimensional space consisting of the depth-integrated soil moisture and of the forcing precipitation. The resulting threshold curve, when examined with data from the period 20062011 in El Salvador, resulted in warnings of landslide occurrence with frequency that spanned the range between 1 and 5 % of the days for the basins identified to be susceptible to landsliding.

Research areas: Land Surface/Agriculture Indicators
Sex-Specific Habitat Utilization and Differential Breeding Investments in Christmas Island Frigatebirds throughout the Breeding Cycle (2015)

In seabirds, equal bi-parental care is the rule, as it is considered crucial for raising chicks successfully because seabirds forage in an environment with unpredictable and highly variable food supply. Frigatebirds forage in poor tropical waters, yet males reduce and even stop parental care soon after chick brooding, leaving the female to provision the chick alone for an extended fledging period. Using bird-borne tracking devices, male and female Christmas Island Frigatebirds (Fregata andrewsi) were investigated during the brooding, late chick rearing and post-fledging period to examine whether sexes exhibit foraging strategies that may be linked to differential breeding investments. During brooding, males and females showed similar foraging behaviour under average marine productivity of oceanic waters close to the colony, but males shifted to more distant and more productive habitats when conditions deteriorated to continue with reduced chick provisioning. During the late chick rearing period, females progressively increased their foraging range to the more distant but productive marine areas that only males had visited during brooding. Birds spent the non-breeding period roosting in highly productive waters of the Sunda Shelf. The sex-specific utilisation of three different foraging habitats with different primary productivity (oceanic, coastal, and shelf areas) allowed for temporal and spatial segregation in the exploitation of favourable habitats which seems to enable each sex to optimise its foraging profitability. In addition, post-fledging foraging movements of females suggest a biennial breeding cycle, while limited information on males suggests the possibility of an annual breeding cycle.

Research areas: Ecosystems
Separating aerosol microphysical effects and satellite measurement artifacts of the relationships between warm rain onset height and aerosol optical depth (2015)

AbstractThe high resolution (375 m) of the Visible Infrared Imaging Radiometer Suite on board the Suomi National Polar-Orbiting Partnership satellite allows retrieving relatively accurately the vertical evolution of convective cloud drop effective radius (re) with height or temperature. A tight relationship is found over SE Asia and the adjacent seas during summer between the cloud-free aerosol optical depth (AOD) and the cloud thickness required for the initiation of warm rain, as represented by the satellite-retrieved cloud droplet re of 14 m, for a subset of conditions that minimize measurement artifacts. This cloud depth (T14) is parameterized as the difference between the cloud base temperature and the temperature at the height where re exceeds 14 m (T14). For a unit increase of AOD, the height of rain initiation is increased by about 5.5 km. The concern of data artifacts due to the increase in AOD near clouds was mitigated by selecting only scenes with cloud fraction (CF) < 0.1. For CF > 0.1 and T14 > 20C, the increase of T14 gradually levels off with further increase of AOD, possibly because the AOD is enhanced by aerosol upward transport and detrainment through the clouds below the T14 isotherm. The bias in the retrieved re due to the different geometries of solar illumination was also quantified. It was shown that the retrievals are valid only for backscatter views or when avoiding scenes with significant amount of cloud self-shadowing. These artifacts might have contributed to past reported relationships between cloud properties and AOD.

Research areas: Atmospheric/Ocean Indicators
Seascape genetics along environmental gradients in the Arabian Peninsula: insights from ddRAD sequencing of anemonefishes (2015)

Understanding the processes that shape patterns of genetic structure across space is a central aim of landscape genetics. However, it remains unclear how geographical features and environmental variables shape gene flow, particularly for marine species in large complex seascapes. Here, we evaluated the genomic composition of the two-band anemonefish Amphiprion bicinctus across its entire geographical range in the Red Sea and Gulf of Aden, as well as its close relative, Amphiprion omanensis endemic to the southern coast of Oman. Both the Red Sea and the Arabian Sea are complex and environmentally heterogeneous marine systems that provide an ideal scenario to address these questions. Our findings confirm the presence of two genetic clusters previously reported for A. bicinctus in the Red Sea. Genetic structure analyses suggest a complex seascape configuration, with evidence of both isolation by distance (IBD) and isolation by environment (IBE). In addition to IBD and IBE, genetic structure among sites was best explained when two barriers to gene flow were also accounted for. One of these coincides with a strong oligotrophic-eutrophic gradient at around 16-20 N in the Red Sea. The other agrees with a historical bathymetric barrier at the straight of Bab al Mandab. Finally, these data support the presence of interspecific hybrids at an intermediate suture zone at Socotra and indicate complex patterns of genomic admixture in the Gulf of Aden with evidence of introgression between species. Our findings highlight the power of recent genomic approaches to resolve subtle patterns of gene flow in marine seascapes.

Research areas: Ecosystems
Water column productivity and temperature predict coral reef regeneration across the Indo-Pacific (2015)

Predicted increases in seawater temperatures accelerate coral reef decline due to mortality by heat-driven coral bleaching. Alteration of the natural nutrient environment of reef corals reduces tolerance of corals to heat and light stress and thus will exacerbate impacts of global warming on reefs. Still, many reefs demonstrate remarkable regeneration from past stress events. This paper investigates the effects of sea surface temperature (SST) and water column productivity on recovery of coral reefs. In 71 Indo-Pacific sites, coral cover changes over the past 1-3 decades correlated negative-exponentially with mean SST, chlorophyll a and SST rise. At six monitoring sites (Persian/Arabian Gulf, Red Sea, northern and southern Galapagos, Easter Island, Panama), over half of all corals were <31 years, implying that measured environmental variables indeed shaped populations and community. An Indo-Pacific-wide model suggests reefs in the northwest and central Indian Ocean, as well as the central west Pacific, are at highest risk of degradation and those at high latitudes the least. The model pinpoints regions where coral reefs presently have the best chances for survival. However, reefs best buffered against temperature and nutrient effects are those that current studies suggest to be most at peril from future ocean acidification.

Research areas: Ecosystems
Water Supply Interruptions and Suspected Cholera Incidence: A Time-Series Regression in the Democratic Republic of the Congo (2015)

Background The eastern provinces of the Democratic Republic of the Congo have been identified as endemic areas for cholera transmission, and despite continuous control efforts, they continue to experience regular cholera outbreaks that occasionally spread to the rest of the country. In a region where access to improved water sources is particularly poor, the question of which improvements in water access should be prioritized to address cholera transmission remains unresolved. This study aimed at investigating the temporal association between water supply interruptions and Cholera Treatment Centre (CTC) admissions in a medium-sized town. Methods and Findings Time-series patterns of daily incidence of suspected cholera cases admitted to the Cholera Treatment Centre in Uvira in South Kivu Province between 2009 and 2014 were examined in relation to the daily variations in volume of water supplied by the town water treatment plant. Quasi-poisson regression and distributed lag nonlinear models up to 12 d were used, adjusting for daily precipitation rates, day of the week, and seasonal variations. A total of 5,745 patients over 5 y of age with acute watery diarrhoea symptoms were admitted to the CTC over the study period of 1,946 d. Following a day without tap water supply, the suspected cholera incidence rate increased on average by 155% over the next 12 d, corresponding to a rate ratio of 2.55 (95% CI: 1.544.24), compared to the incidence experienced after a day with optimal production (defined as the 95th percentile4,794 m3). Suspected cholera cases attributable to a suboptimal tap water supply reached 23.2% of total admissions (95% CI 11.4%33.2%). Although generally reporting less admissions to the CTC, neighbourhoods with a higher consumption of tap water were more affected by water supply interruptions, with a rate ratio of 3.71 (95% CI: 1.917.20) and an attributable fraction of cases of 31.4% (95% CI: 17.3%42.5%). The analysis did not suggest any association between levels of residual chlorine in the water fed to the distribution network and suspected cholera incidence. Laboratory confirmation of cholera was not available for this analysis. Conclusions A clear association is observed between reduced availability of tap water and increased incidence of suspected cholera in the entire town of Uvira in Eastern Democratic Republic of the Congo. Even though access to piped water supplies is low in Uvira, improving the reliability of tap water supply may substantially reduce the incidence of suspected cholera, in particular in neighbourhoods having a higher access to tap water. These results argue in favour of water supply investments that focus on the delivery of a reliable and sustainable water supply, and not only on point-of-use water quality improvements, as is often seen during cholera outbreaks.

Research areas: Public Health
Winter bloom and associated upwelling northwest of the Luzon Island: A coupled physical-biological modeling approach (2015)

For this paper, a coupled physical-biological model was developed in order to study the mechanisms of the winter bloom in the Luzon Strait (referred as LZB). Based on a simulation for January 2010, the results showed that the model was capable of reproducing the key features of the LZB, such as the location, inverted-V shape, twin-core structure and bloom intensity. The simulation showed that the LZB occurred during the relaxation period of intensified northeasterly winds, when the deepened mixed layer started to shoal. Nutrient diagnostics showed that vertical mixing was responsible for the nutrient supply to the upper 40 m layer, while subsurface upwelling supplied nutrients to the region below the mixed layer. Hydrodynamic diagnostics showed that the advection of relative vorticity (RV) primarily contributed to the subsurface upwelling. The RV advection was resulted from an offshore jet, which was associated with a northeasterly wind, flowed across the ambient RV field.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Winterspring anomalies in the stratospheric content of NO2 from ground-based measurement results (2015)

According to the results of ground-based spectrometric measurements, significant negative anomalies in the stratospheric content of NO2 were observed at a number of stations in the Northern Hemisphere during winter and spring 2011. These anomalies were accompanied by those in total ozone content (TOC) and stratospheric temperature and were caused by the transport of air masses from the region of the arctic ozone hole. The results of analysis of vertical NO2 profiles obtained at the Zvenigorod Scientific Station showed that a certain contribution to the 2011 negative anomalies of NO2 was made due to a denitrification of the polar stratosphere in the ozone-hole region. The relation between variations in the total content of NO2 and those in the TOC and temperature was analyzed for both the Northern and Southern hemispheres during winterspring periods. It was found that this relation depends on the phase of the quasi-biennial oscillation in the stratospheric equatorial wind. Such a correlation usually intensifies if only the episodes of negative anomalies caused by the transport of stratospheric air masses from the ozone-hole region are taken into consideration.

Research areas: Atmospheric/Ocean Indicators
Satellite Derived Aerosol Optical Depth Climatology over Tropical Coastal Station Machilipatnam, India (2015)

Climatological aerosol optical depths (AOD) over Tropical coastal city Machilipatnam, India have been examined to bring out the temporal heterogeneity in columnar aerosol characteristics. AOD values at 388 nm derived from the Ozone Monitoring Instrument (OMI) sensor EOS-AURA satellite, for the period of 20052013 have been analyzed for the purpose. AOD trends exhibited seasonal annual mean variations. Frequency distributions of the AOD values are examined to infer the monthly mean values. Monthly and seasonal variations of AOD are investigated in the light of regional synoptic meteorology. AODs>0.6 showed maximum occurrence in monsoon months. The mean AOD values increased towards summer reaching 0.69  0.34 and attained peak in monsoon season with a value of 0.74  0.33 and decreased during post-monsoon reaching as low as 0.73  0.3. Positive slope 0.016 observed for inter annual distribution trend line. Factors like synoptic scale circulation patterns which are causing modulations of AOD apart from local sources were discussed.

Research areas: Validation
Satellite Data Science: A Case Study for Smog Disaster Prediction from Multiple Satellite Observations (2015)

Smog Disaster studies of PM2.5PM2.5\text {PM}_{2.5} are limited by the lack of monitoring data, especially in developing countries. Satellite observations offer valuable global information about PM2.5PM2.5\text {PM}_{2.5} concentrations, but have limited accuracy and completeness. In contrast to satellite domain-driven methods for PM2.5PM2.5\text {PM}_{2.5} retrieval, our approach is satellite data-driven. Challenges and our proposed solutions discussed here in context of global scale PM2.5PM2.5\text {PM}_{2.5} estimation include (i) PM2.5PM2.5\text {PM}_{2.5} regression from Aerosol Optical Depth (AOD) data; (ii) training such a multi-view model for robust performance across multiple satellite measures; and (iii) the model for incomplete data avoids direct imputation of the missing elements. Experimental results on real-world data sets show that it significantly outperforms the existing approaches.

Research areas: Air Quality
Saharan dust as a causal factor of hemispheric asymmetry in aerosols and cloud cover over the tropical Atlantic Ocean (2015)

Previous studies showed that, over the global ocean, there is no noticeable hemispheric asymmetry in cloud fraction (CF). This contributes to the balance in solar radiation reaching the sea surface in the northern and southern hemispheres. In the current study, we focus on the tropical Atlantic (30 N30 S), which is characterized by significant amounts of Saharan dust dominating other aerosol species over the North Atlantic. Our main point is that, over the tropical Atlantic, Saharan dust not only is responsible for the pronounced hemispheric aerosol asymmetry, but also contributes to significant cloud cover along the Saharan Air Layer (SAL). Over the tropical Atlantic in July, along the SAL, Moderate Resolution Imaging Spectroradiometer CF data showed significant cloud cover (up to 0.80.9). This significant CF along SAL together with clouds over the Atlantic Intertropical Convergence Zone contributes to the 20% hemispheric CF asymmetry. This leads to the imbalance in strong solar radiation, which reaches the sea surface between the tropical North and South Atlantic, and, consequently, affects climate formation in the tropical Atlantic. During the 10-year study period (July 2002June 2012), NASA Aerosol Reanalysis (aka MERRAero) showed that, when the hemispheric asymmetry in dust aerosol optical thickness (AOT) was most pronounced (particularly in July), dust AOT averaged separately over the tropical North Atlantic was one order of magnitude higher than that averaged over the tropical South Atlantic. In the presence of such strong hemispheric asymmetry in dust AOT in July, CF averaged separately over the tropical North Atlantic exceeded that over the tropical South Atlantic by 20%. Both Multiangle Imaging Spectroradiometer measurements and MERRAero data were in agreement on seasonal variations in hemispheric aerosol asymmetry. Hemispheric asymmetry in total AOT over the Atlantic was most pronounced between March and July, when dust presence over the North Atlantic was maximal. In September and October, there was no noticeable hemispheric aerosol asymmetry between the tropical North and South Atlantic. During the season with no noticeable hemispheric aerosol asymmetry, we found no noticeable asymmetry in cloud cover.

Research areas: Atmospheric/Ocean Indicators
Remote Sensing of Suspended Sediment Over Gulf of Martaban (2015)

AbstractGulf of Martaban is located at the north of Andaman, and is one of the world most turbid areas. The presence of suspended sediment concentration (SSC) in the water body could reduce the underwater transmittance. This study has been conducted to investigate the variation of SSC over the Gulf of Martaban. Remote sensing reflectance (Rrs) of 667 nm is used as a proxy to represent the sediment SSC variation over the study area. The data for the period of July 2002 to March 2014 acquired from MODIS Aqua 4 km resolution are used in this study. As a result, there is no obvious yearly variation in the SSC cover area. The SSC variation over this study area is found to be seasonal. High homogenous SSC covers area observably during the northeast (NE) monsoon season that occurs from December to January. The sediment cover area could reach the latitude of 15N that located at the south of the gulf. During southwest (SW) monsoon season that occurs from May to September, low and sparse SSC cover area is observed. As a consequence, the area covered by the SSC is higher during the NE monsoon season as compared to the SW monsoon season. Hence, the SSC cover area during the NE monsoon season is greater than the yearly averaged SSC cover area. Meanwhile the SSC cover area during the rainy SW monsoon season is less than the yearly and NE monsoon season.

Research areas: Water Quality
Reconciling single-chamber Mg / Ca with whole-shell 18O in surface to deep-dwelling planktonic foraminifera from the Mozambique Channel (2015)

Abstract. Most planktonic foraminifera migrate vertically through the water column during life, meeting a range of depth-related conditions as they grow and calcify. For reconstructing past ocean conditions from geochemical signals recorded in their shells, it is therefore necessary to know vertical habitat preferences. Species with a shallow habitat and limited vertical migration will reflect conditions of the surface mixed layer and short-term and mesoscale (i.e. seasonal) perturbations therein. Species spanning a wider range of depth habitats, however, will contain a more heterogeneous, intra-specimen variability (e.g. Mg / Ca and 18O), which is less for species calcifying below the thermocline. Obtained single-chamber Mg / Ca ratios are combined with single-specimen 18O and 13C of the surface-water inhabitant Globigerinoides ruber, the thermocline-dwelling Neogloboquadrina dutertrei and Pulleniatina obliquiloculata, and the deep dweller Globorotalia scitula from the Mozambique Channel. Species-specific Mg / Ca, 13C and 18O data combined with a depth-resolved mass balance model confirm distinctive migration and calcification patterns for each species as a function of hydrography. Whereas single-specimen 18O rarely reflects changes in depth habitat related to hydrography (e.g. temperature), measured Mg / Ca of the last chambers can only be explained by active migration in response to changes in temperature stratification. Foraminiferal geochemistry and modelled depth habitats shows that the single-chamber Mg / Ca and single shell 18O are in agreement with each other and in line with the changes in hydrography induced by eddies.

Research areas: Ecosystems