nasa-gesdisc/es-publications-researchareas huggingface dataset:
Flux and composition of settling particles across the continental margin of the Gulf of Lion: the role of dense shelf water cascading (2010)

Abstract. Settling particles were collected using sediment traps deployed along three transects in the Lacaze-Duthiers and Cap de Creus canyons and the adjacent southern open slope from October 2005 to October 2006. The settling material was analyzed to obtain total mass fluxes and main constituent contents (organic matter, opal, calcium carbonate, and siliciclastics). Cascades of dense shelf water from the continental shelf edge to the lower continental slope occurred from January to March 2006. They were traced through strong negative near-bottom temperature anomalies and increased current speeds, and generated two intense pulses of mass fluxes in January and March 2006. This oceanographic phenomenon appeared as the major physical forcing of settling particles at almost all stations, and caused both high seasonal variability in mass fluxes and important qualitative changes in settling material. Fluxes during the dense shelf water cascading (DSWC) event ranged from 90.1 g m2 d1 at the middle Cap de Creus canyon (1000 m) to 3.2 g m2 d1 at the canyon mouth (1900 m). Fractions of organic matter, opal and calcium carbonate components increased seaward, thus diminishing the siliciclastic fraction. Temporal variability of the major components was larger in the canyon mouth and open slope sites, due to the mixed impact of dense shelf water cascading processes and the pelagic biological production. Results indicate that the cascading event remobilized and homogenized large amounts of material down canyon and southwardly along the continental slope contributing to a better understanding of the off-shelf particle transport and the internal dynamics of DSWC events.

Research areas: Validation
Feedback between dust particles and atmospheric processes over West Africa during dust episodes in March 2006 and June 2007 (2010)

Abstract. We used the comprehensive model system COSMO-ART to quantify the impact of mineral dust on the radiative fluxes, the temperature and the feedback between dust particles and their emissions. We simulated two dust storms over West Africa in March 2006 and in June 2007. Simulations with and without coupling of the actual dust concentration with the radiative fluxes and the thermodynamics were carried out for each case. The model results for the 2006 case were compared with observations of the AMMA campaign.  At the surface the shortwave radiative effect of mineral dust can be described by a linear relation between the changes in net surface radiation and the aerosol optical depth (AOD). For an AOD at 450 nm of 1 the average shortwave radiation reduction amounts 140 W m2 during noon. The longwave radiative effect of mineral dust is nonlinear, with an average increase of +70 W m2 for an AOD (450 nm) of 1. At the top of the atmosphere the effect of the dust layer with an AOD of 1 on radiative fluxes is not as significant as at the surface. It is slightly positive for the shortwave and approximately 26 W m2 for the longwave radiation.  The height range and the extension of the dust layer determine the effect of dust particles on the 2 m temperature. When the dust layer is attached to the surface and lasts for several days it leads to an increase of the surface temperature even during daytime. In case of an elevated dust layer there is a decrease in 2 m temperature of up to 4 K during noon.  It is shown, that the temperature changes caused by mineral dust may result in horizontal temperature gradients which also modify near surface winds. Since surface wind thresholds decide the uptake of dust from the surface, a feedback on total emission fluxes is established. The coupled model provides an increase in the total emission fluxes of dust particles by about 16% during the dust storm in March 2006 and 25% during the dust episode in June 2007.

Research areas: Atmospheric/Ocean Indicators
Evaluation of aerosol distributions in the GISS-TOMAS global aerosol microphysics model with remote sensing observations (2010)

Abstract. The Aerosol Optical Depth (AOD) and Angstrom Coefficient (AC) predictions in the GISS-TOMAS model of global aerosol microphysics are evaluated against remote sensing data from MODIS, MISR, and AERONET. The model AOD agrees well (within a factor of two) over polluted continental (or high sulfate), dusty, and moderate sea-salt regions but less well over the equatorial, high sea-salt, and biomass burning regions. Underprediction of sea-salt in the equatorial region is likely due to GCM meteorology (low wind speeds and high precipitation). For the Southern Ocean, overprediction of AOD is very likely due to high sea-salt emissions and perhaps aerosol water uptake in the model. However, uncertainties in cloud screening at high latitudes make it difficult to evaluate the model AOD there with the satellite-based AOD. AOD in biomass burning regions is underpredicted, a tendency found in other global models but more severely here. Using measurements from the LBA-SMOCC 2002 campaign, the surface-level OC concentration in the model are found to be underpredicted severely during the dry season while much less severely for EC concentration, suggesting the low AOD in the model is due to underpredictions in OM mass. The potential for errors in emissions and wet deposition to contribute to this bias is discussed.

Research areas: Validation
Estimation of Indian summer monsoon rainfall using Kalpana-1 VHRR data and its validation using rain gauge and GPCP data (2010)

In the present study, an attempt has been made to estimate and validate the daily and monthly rainfall during the Indian summer monsoon seasons of 2008 and 2009 using INSAT (Indian National Satellite System) Multispectral Rainfall Algorithm (IMSRA) technique utilizing Kalpana-1 very high resolution radiometer (VHRR) measurements. In contrary to infrared (IR), microwave (MW) rain rates are based on measurements that sense precipitation in clouds and do not rely merely on cloud top temperature. Geostationary satellites provide broad coverage and frequent refresh measurements but microwave measurements are accurate but sparse. IMSRA technique is the combination of the infrared and microwave measurements which make use of the best features of both IR- and MW-based rainfall estimates. The development of this algorithm included two major steps: (a) classification of rain-bearing clouds using proper cloud classification scheme utilizing Kalpana-1 IR and water vapor (WV) brightness temperatures (Tb) and (b) collocation of Kalpana-1 IR brightness temperature with Tropical Rainfall Measuring Mission (TRMM)-Precipitation Radar (PR) surface rain rate and establishment of a regression relation between them. In this paper, the capability of IMSRA as an operational algorithm has been tested for the two monsoon seasons 2008 and 2009. For this, IMSRA has been used to estimate daily and monthly rainfall and has been intercompared on daily and monthly scales with TRMM Multisatellite Precipitation Analysis (TMPA)-3B42 V6 product and Global Precipitation Climatology Project (GPCP) rain product during these two monsoon years. The daily and monthly IMSRA rainfall has also been validated against ground-based observations from Automatic Weather Station (AWS) Rain Gauge and Buoy data. The algorithm proved to be in good correlation with AWS data over land up to 0.70 for daily rain estimates except orographic regions like North-East and South-West India and 0.72 for monthly rain estimates. The validation with Buoys gives the reasonable correlation of 0.49 for daily rain estimates and 0.66 for monthly rain estimates over Tropical Indian Ocean.

Research areas: Validation
Effects of Ocean Ecosystem on Marine Aerosol-Cloud Interaction (2010)

Using satellite data for the surface ocean, aerosol optical depth (AOD), and cloud microphysical parameters, we show that statistically significant positive correlations exist between ocean ecosystem productivity, the abundance of submicron aerosols, and cloud microphysical properties over different parts of the remote oceans. The correlation coefficient for remotely sensed surface chlorophyll a concentration ([Chl-a]) and liquid cloud effective radii over productive areas of the oceans varies between and . Special attention is given to identifying (and addressing) problems from correlation analysis used in the previous studies that can lead to erroneous conclusions. A new approach (using the difference between retrieved AOD and predicted sea salt aerosol optical depth, ) is developed to explore causal links between ocean physical and biological systems and the abundance of cloud condensation nuclei (CCN) in the remote marine atmosphere. We have found that over multiple time periods, 550 nm (sensitive to accumulation mode aerosol, which is the prime contributor to CCN) correlates well with [Chl-a] over the productive waters of the Southern Ocean. Since [Chl-a] can be used as a proxy of ocean biological productivity, our analysis demonstrates the role of ocean ecology in contributing CCN, thus shaping the microphysical properties of low-level marine clouds.

Research areas: Ecosystems
Global retrieval of marine and terrestrial chlorophyll fluorescence at its red peak using hyperspectral top of atmosphere radiance measurements: Feasibility study and first results (2015)

Chlorophyll fluorescence is directly linked to the physiology of phytoplankton or plants. Here, we present a new satellite remote sensing approach to retrieve chlorophyll fluorescence at its red peak (~685nm) by using measurements from the hyperspectral instruments SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) and Global Ozone Monitoring Experiment-2 (GOME-2). This method, which is based on the Differential Optical Absorption Spectroscopy (DOAS) technique, was used to exploit narrow spectral structures resulting from the filling-in of the Fraunhofer Fe I line, which originates from fluorescence. The reference spectra for chlorophyll fluorescence were calculated by the coupled oceanatmosphere radiative transfer model SCIATRAN. We compared our results on marine chlorophyll fluorescence observations with the MODIS Terra normalized Fluorescence Line Height (nFLH) product for the average of years 20032011 and year 2009. Our method also enables the retrieval of chlorophyll fluorescence above land vegetation scenes. The results for the fluorescence observed above terrestrial vegetation for July and December 2009 were compared to MODIS Enhanced Vegetation Index (EVI). The comparisons show good spatial agreement between different retrievals providing evidence for the good performance of our algorithm. The method presented is generic and can be applied to other hyperspectral instruments in the future. Having established the retrieval technique, extensive studies of chlorophyll fluorescence will improve global knowledge on physiology and photosynthetic efficiency, in both the marine and terrestrial realms, and its dependence on environmental factors.

Research areas: Validation
Geoinformatics application for assessing the potential of rainwater harvesting in arid regions. Case study: El Dabaa area, Northwestern Coast of Egypt (2015)

In the light of the current situation of water resources in Egypt, where it has a deficit in those resources, the rainwater harvesting and assessment of its potentialities became necessary. In the present study, an attempt is made to define a decision based on scientific approach for identifying the most appropriate sites for rainwater harvesting. This approach is based on GIS data layers which include DEM, landforms, geologic setting, watershed area, rainfall amounts, drainage lines, morphometric parameters, flow accumulation, flow direction, slope, and surface runoff. It also includes a verification of the site suitability through field investigations. El Dabaa area has been chosen because it has a lack of water for agriculture and drinking purposes. In addition, this area has special interest because of a planned nuclear power plant there. The obtained results reveal that the study area contains eight basins which have slightly intensive drainage network. The morphometric analyses of the studied basins reveal their opportunities for surface runoff. Three of them are showing high hazard degrees. These basins have actual runoff (Q) ranges between 16.5 and 25 mm annually resulted from average rainfall of 164 mm. Therefore, management of rainwater harvesting and protections from flash floods were recommended. Many rainwater harvesting structures, for example concert dams, alternative earth dikes, surface water reservoirs, and cisterns, should be established.

Research areas: Land Surface/Agriculture Indicators
Framework for Investigation of Karst Aquifer in an Arid Zone, Using Isotopes, Remote Sensing and GIS Applications: the Northwestern Coast of Egypt (2015)

The hydrogeology of arid regions is becoming increasingly important due to diminishing projections of water resource availability in response to global environmental change. This paper aims to investigate the karst aquifer in the study area and clarifies the different factors which affect the occurrence and quality of its groundwater. The fractures systems are the main factor which controls the groundwater occurrence in the studied aquifer. The isotope analyses reveal that the groundwater has nearly similar isotopic compositions, suggesting similar recharge conditions; they also indicate that the groundwater of karst aquifer is meteoric water and the recharging source is the rainfall. The high values of total dissolved salts (TDS) of the groundwater are attributed to the rock-water interactions which lead to dissolution processes of marine salts into the aquifer matrix. Although most of the water levels in the drilled wells are under the sea level, the isotope analyses indicate that no contribution of seawater intrusion affects the groundwater. The present study reveals that some specific regions have more priorities than others in future groundwater explorations.

Research areas: Land Surface/Agriculture Indicators
Food abundance explains the breeding season of a tropical shorebird, the Crab Plover Dromas ardeola (2015)

The timing of breeding in birds is a life-history trait that generally depends on food availability, but other factors may play a role, particularly in tropical areas where food availability is less seasonal than in temperate or polar areas. We studied the factors affecting the breeding season of the Crab Plover Dromas ardeola, a burrownesting colonial shorebird endemic to the north-western Indian Ocean. A reduced risk of burrow flooding, high temperatures suitable for exploiting solar incubation, a reduced interference by Palaearctic shorebirds during foraging, a reduced risk of predation by Palaearctic raptors and a high food abundance are all associated with the summer breeding season of the Crab Plover in our study area in Eritrea. In addition, we collected remotely recorded data associated with these advantageous environmental factors around breeding colonies in nine well-separated areas. Only average annual chlorophyll a concentration, a proxy of marine productivity, was significantly correlated with the start of the breeding season, which varies up to one month throughout the breeding range. We conclude that food abundance, with the likely high intraspecific competition due to coloniality, is strongly supported as the critical factor determining the nesting phenology of this tropical species.

Research areas: Ecosystems
Exploring seascape genetics and kinship in the reef sponge Stylissa carteri in the Red Sea (2015)

A main goal of population geneticists is to study patterns of gene flow to gain a better understanding of the population structure in a given organism. To date most efforts have been focused on studying gene flow at either broad scales to identify barriers to gene flow and isolation by distance or at fine spatial scales in order to gain inferences regarding reproduction and local dispersal. Few studies have measured connectivity at multiple spatial scales and have utilized novel tools to test the influence of both environment and geography on shaping gene flow in an organism. Here a seascape genetics approach was used to gain insight regarding geographic and ecological barriers to gene flow of a common reef sponge, Stylissa carteri in the Red Sea. Furthermore, a small-scale (<1 km) analysis was also conducted to infer reproductive potential in this organism. At the broad scale, we found that sponge connectivity is not structured by geography alone, but rather, genetic isolation in the southern Red Sea correlates strongly with environmental heterogeneity. At the scale of a 50-m transect, spatial autocorrelation analyses and estimates of full-siblings revealed that there is no deviation from random mating. However, at slightly larger scales (100200 m) encompassing multiple transects at a given site, a greater proportion of full-siblings was found within sites versus among sites in a given location suggesting that mating and/or dispersal are constrained to some extent at this spatial scale. This study adds to the growing body of literature suggesting that environmental and ecological variables play a major role in the genetic structure of marine invertebrate populations.

Research areas: Ecosystems
Evaluation of Precipitation Climatology Derived from TRMM Multi-Satellite Precipitation Analysis (TMPA) Monthly Product over Land with Two Gauge-Based Products (2015)

The NASA/JAXA Tropical Rainfall Measuring Mission (TRMM) has been in operation for over 17 years since 1997. The length of TRMM is far shorter than those from ground observations, raising a question as to whether TRMM derived climatology products are good enough for research and applications. In this study, three climatologies derived from a blended product (the TRMM Multi-Satellite Precipitation Analysis (TMPA) monthly product or 3B43) and gauge-based ground observations (Global Precipitation Climatology Center (GPCC) and Willmott and Matsuura (WM)) are compared over land on a global scale (50 N50 S) to assess the performance and weaknesses of the TMPA-derived climatology. Results show that the 3B43 climatology matches well with the two gauge-based climatologies in all seasons in terms of spatial distribution, zonal means as well as seasonal variations. However, large variations are found in light rain (<0.5 mm/day) regions such as the Sahara Desert. At high rain rates, large negative biases (3B43 < WM < GPCC) are found in orographically influenced regions such as windward sides of monsoon mountains in JJA, which is associated with underestimation of shallow orographic rain rates in microwave radiometer algorithms and sparse gauge data for bias correction. Nonetheless, biases in 3B43 exist and vary with geographic locations due to a number of factors such as gauge availability and algorithm issues.

Research areas: Validation
Evaluation of black carbon emission inventories using a Lagrangian dispersion model  a case study over southern India (2015)

Abstract. We evaluated three emission inventories of black carbon (BC) using Lagrangian particle dispersion model simulations and BC observations from a rural site in southern India (Gadanki; 13.48 N, 79.18 E) from 2008 to 2012. We found that 93 to 95% of the BC load at the observation site originated from emissions in India and the rest from the neighbouring countries and shipping. A substantial fraction (33 to 43%) of the BC was transported from northern India. Wet deposition is found to play a minor role in reducing BC mass at the site because of its proximity to BC sources during rainy season and relatively short rainy season over western and northern parts of India. Seasonally, the highest BC concentration (approx. 3.3 g m3) is observed during winter, followed by spring (approx. 2.8 g m3). While the model reproduced well the seasonal cycle, the modelled BC concentrations are significantly lower than observed values, especially in spring. The model bias is correlated to fire radiative power  a proxy of open biomass burning activity. Using potential emission sensitivity maps derived using the model, we suggest that underestimation of BC mass in the model during spring is due to the underestimation of BC fluxes over southern India (possibly from open-biomass-burning/forest-fires). The overall performance of the model simulations using three different emission inventories (SAFAR-India, ECLIPSE and RETRO) is similar, with ECLIPSE and SAFAR-India performing marginally better as both have about 30% higher emissions for India than RETRO. The ratio of observed to modelled annual mean BC concentration was estimated as 1.5 for SAFAR, 1.7 for ECLIPSE and 2.4 for RETRO.

Research areas: Air Quality
Estimate of errors and verification of the method of fluid location of the atmosphere (2015)

A variant of determining errors in the statistical estimate of the average effective concentration field calculated in the quasi-two-dimensional approximation by the method of fluid location of the atmosphere (FLA) is proposed. Results of the FLA verification by three methods are presented. In spite of the fact that the quasi-two-dimensional approximation has some restrictions, all the considered ways of verification point to the possibility to use the FLA method for estimating average concentration fields of fine aerosol.

Research areas: Validation
Error characterization of TRMM Multisatellite Precipitation Analysis (TMPA-3B42) products over India for different seasons (2015)

A comprehensive error characterization of satellite-based precipitation products is vital for advancement of precipitation algorithms, evaluation of numerical model outputs, and their integration in various hydro-meteorological applications. The Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) products are in high demand to users for numerous applications. The latest version 7 (V7) of TMPA products are assumed to be better than its previous versions due to substantial changes in input data sets and algorithm. The TMPA algorithm is also a benchmark algorithm for the Global Precipitation Measurement (GPM) mission multisatellite precipitation products. In this study, both near-real-time (TMPA-RT) and research-quality (TMPA-V7) TMPA data sets are extensively evaluated against gridded gauge-based data over India for pre-monsoon, monsoon, and post-monsoon seasons at daily scale for a 13-year (20012013) period. The systematic and random error components in TMPA data sets are decomposed for their wider usage in agricultural and hydrological applications. Although TMPA-V7 and RT data sets represent the mean seasonal rainfall characteristics reasonably well, both the satellite-based data sets show an overestimation of rainfall over most parts of the country except over the orographic regions. However, TMPA-V7 is better than TMPA-RT when compared with the reference observations. Both the TMPA products show larger systematic error over the mountainous regions of northeast India. TMPA-RT has larger random error than TMPA-V7 possibly due to difference in calibration methods for the development of these data sets. Both the satellite-based data sets show significant difference from the reference observations for light to moderate rainfall ranges especially in the monsoon season. Larger error associated with systematic component in both the data sets is found during the pre-monsoon season. Furthermore, bias and error in satellite-derived rainfall data show a considerable interannual variation. Overall results suggest that a suitable region and season dependent bias-correction is required in TMPA data sets before its integration in hydrological applications.

Research areas: Validation