nasa-gesdisc/es-publications-researchareas huggingface dataset:
The climatology of dust aerosol over the arabian peninsula (2015)

Abstract. Dust storms are considered to be a natural hazard over the Arabian Peninsula, since they occur all year round with maximum intensity and frequency in Spring and Summer. The Regional Climate Model version 4 (RegCM4) has been used to study the climatology of atmospheric dust over the Arabian Peninsula from 1999 to 2012. This relatively long simulation period samples the meteorological conditions that determine the climatology of mineral dust aerosols over the Arabian Peninsula. The modeled Aerosol Optical Depth (AOD) has been compared against ground-based observations of three Aerosol Robotic Network (AERONET) stations that are distributed over the Arabian Peninsula and daily space based observations from the Multi-angle Imaging SpectroRadiometer (MISR), the Moderate resolution Imaging SpectroRadimeter (MODIS) and Ozone Monitoring Instrument (OMI). The large scale atmospheric circulation and the land surface response that lead to dust uplifting have been analyzed. While the modeled AOD shows that the dust season extends from March to August with two pronounced maxima, one over the northern Arabian Peninsula in March with AOD equal to 0.4 and one over the southern Arabian Peninsula in July with AOD equal to 0.7, the observations show that the dust season extends from April to August with two pronounced maxima, one over the northern Arabian Peninsula in April with AOD equal to 0.5 and one over the southern Arabian Peninsula in July with AOD equal to 0.5. In spring a high pressure dominates the Arabian Peninsula and is responsible for advecting dust from southern and western part of the Arabian Peninsula to northern and eastern part of the Peninsula. Also, fast developed cyclones in northern Arabian Peninsula are responsible for producing strong dust storms over Iraq and Kuwait. However, in summer the main driver of the surface dust emission is the strong northerly wind ("Shamal") that transport dust from the northern Arabian Peninsula toward south parallel to the Arabian Gulf. The AERONET shortwave Top of Atmosphere Radiative Forcing (TOARF) and at the Bottom of Atmosphere Radiative Forcing (BOARF) have been analyzed and compared with the modeled direct radiative forcing of mineral dust aerosol. The annual modeled TOARF and BOARF are 3.3 and 12 W m2, respectively. However, the annual observed TOARF and BOARF are significantly different at 10 and 52 W m2, respectively. The analysis of observed and modeled TOARF agrees with previous studies in highlighting the need for more accurate specification of surface albedo over the region. Due to the high surface albedo of the central Arabian Peninsula, mineral dust aerosols tend to warm the atmosphere in summer (JuneAugust).

Research areas: Air Quality
The anthropogenic contribution to atmospheric black carbon concentrations in southern Africa: a WRF-Chem modeling study (2015)

Abstract. South Africa has one of the largest industrialized economies in Africa. Emissions of air pollutants are particularly high in the Johannesburg-Pretoria metropolitan area, the Mpumalanga Highveld and the Vaal Triangle, resulting in local air pollution. This study presents and evaluates a setup for conducting modeling experiments over southern Africa with the Weather Research and Forecasting model including chemistry and aerosols (WRF-Chem), and analyzes the contribution of anthropogenic emissions to the total black carbon (BC) concentrations from September to December 2010.  The modeled BC concentrations are compared with measurements obtained at the Welgegund station situated ca. 100 km southwest of Johannesburg. An evaluation of WRF-Chem with observational data from ground-based measurement stations, radiosondes, and satellites shows that the meteorology is modeled mostly reasonably well, but precipitation amounts are widely overestimated and the onset of the wet season is modeled approximately 1 month too early in 2010. Modeled daily mean BC concentrations show a temporal correlation of 0.66 with measurements, but the total BC concentration is underestimated in the model by up to 50 %.  Sensitivity studies with anthropogenic emissions of BC and co-emitted species turned off show that anthropogenic sources can contribute up to 100 % to BC concentrations in the industrialized and urban areas, and anthropogenic BC and co-emitted species together can contribute up to 60 % to PM1 levels. Particularly the co-emitted species contribute significantly to the aerosol optical depth (AOD). Furthermore, in areas of large-scale biomass-burning atmospheric heating rates are increased through absorption by BC up to an altitude of about 600hPa.

Research areas: Air Quality, Environmental Impacts
Temporal variation in intertidal community recruitment and its relationships to physical forcings, chlorophyll-a concentration and sea surface temperature (2015)

We investigated the recruitment of intertidal barnacles and mussels at three temporal scales (months, weeks and days), and its relationships to physical forcings, chlorophyll-a concentration (Chla) and sea surface temperature (SST), at both a local (km) and a regional (10100 km) resolution. The study was conducted in the South Brazilian Bight, a subtropical region influenced by upwelling and meteorological fronts, where recruitment rates were measured monthly, biweekly and daily, from 2012 to 2013 using artificial substrates fixed in the intertidal zone. The strength of the relationship between recruitment and physical forcings, Chla and SST depended on the temporal scale, with different trends observed for barnacles and mussels. Barnacle recruitment was positively correlated with wind speed and SST and negatively related to the wind direction, cold front events and Chla. Wind direction was positively correlated with mussel recruitment and negatively covaried with SST. We calculated net recruitment (NR) to estimate the differences in recruitment rates observed at longer time scales (months and weeks), with recruitment rates observed at shorter time scales (weeks and days), and found that NR varied in time and among taxa. These results suggest that wind-driven oceanographic processes might affect onshore abundance of barnacle larvae, causing the observed variation in recruitment. This study highlights the importance of oceanicclimatic variables as predictors of intertidal invertebrate recruitment and shows that climatic fluctuations might have different effects on rocky shore communities.

Research areas: Ecosystems
Temporal variability of MODIS aerosol optical depth and chemical characterization of airborne particulates in Varanasi, India (2015)

Temporal variation of airborne particulate mass concentration was measured in terms of toxic organics, metals and water-soluble ionic components to identify compositional variation of particulates in Varanasi. Information-related fine particulate mass loading and its compositional variation in middle Indo-Gangetic plain were unique and pioneering as no such scientific literature was available. One-year ground monitoring data was further compared to Moderate Resolution Imaging Spectroradiometer (MODIS) Level 3 retrieved aerosol optical depth (AOD) to identify trends in seasonal variation. Observed AOD exhibits spatiotemporal heterogeneity during the entire monitoring period reflecting monsoonal low and summer and winter high. Ground-level particulate mass loading was measured, and annual mean concentration of PM2.5 (100.0  29.6 g/m3) and PM10 (176.1  85.0 g/m3) was found to exceed the annual permissible limit (PM10: 80 %; PM2.5: 84 %) and pose a risk of developing cardiovascular and respiratory diseases. Average PM2.5/PM10 ratio of 0.59  0.18 also indicates contribution of finer particulates to major variability of PM10. Particulate sample was further processed for trace metals, viz. Ca, Fe, Zn, Cu, Pb, Co, Mn, Ni, Cr, Na, K and Cd. Metals originated mostly from soil/earth crust, road dust and re-suspended dust, viz. Ca, Fe, Na and Mg were found to constitute major fractions of particulates (PM2.5: 4.6 %; PM10: 9.7 %). Water-soluble ionic constituents accounted for approximately 27 % (PM10: 26.9 %; PM2.5: 27.5 %) of the particulate mass loading, while sulphate (8.09.5 %) was found as most dominant species followed by ammonium (6.08.2 %) and nitrate (5.57.0 %). The concentration of toxic organics representing both aliphatic and aromatic organics was determined by organic solvent extraction process. Annual mean toxic organic concentration was found to be 27.5  12.3 g/m3 (n = 104) which constitutes significant proportion of (PM2.5, 1719 %; PM10, 1120 %) particulate mass loading with certain exceptions up to 50 %. Conclusively, compositional variation of both PM2.5 and PM10 was compared to understand association of specific sources with different fractions of particulates.

Research areas: Air Quality, Environmental Impacts, Public Health
Temporal variability in epifaunal assemblages associated with temperate gorgonian gardens (2015)

The present study is one of the few that investigate the temporal variability of epifaunal assemblages associated with coral species, particularly the octocorals Eunicella gazella and Leptogorgia lusitanica in south Portugal. The results suggest time rather than colony size as a primary driver of the ecological patterns of these assemblages, which were dominated by amphipods, molluscs and polychaetes. Temporal variability was linked to changes in environmental parameters, namely temperature, chlorophyll a and particulate organic carbon. Hence, temporal variability must be taken into account for the design of future biodiversity assessment studies, as different patterns may be observed depending on the sampling time. Associated epifaunal assemblages were consistently dominated by resident species (i.e. species present in all sampling periods) and a peak of rare species was observed in the transition from spring to summer following the increase in seawater temperature. Turnover was particularly high in the transition between the spring and summer periods. In both hosts, turnover was higher in the small sized colonies, which harboured less diverse and less abundant assemblages that also differed from those inhabiting larger size colonies. The high levels of diversity associated with gorgonian colonies highlight the need for the conservation of this priority habitat.

Research areas: Ecosystems
Temporal and spatial availability of Atlantic Thread Herring, Opisthonema oglinum, in relation to oceanographic drivers and fishery landings on the Florida Panhandle (2015)

Since 1995, landings of Atlantic Thread Herring (Opisthonema oglinum) on the Florida Panhandle averaged 124 mt each spring (AprilJune) but declined to nearly zero in 199697 and 2006. To elucidate causes of recurring periods of low landings, we used generalized additive mixed models (GAMMs) to examine the relationship between Atlantic Thread Herring catch in a trawl survey on the west-central coast of Florida and four environmental variables. Chlorophyll-a was significant in the models, indicating a direct relationship between local abundance of baitfish and their planktonic food. Temperature and depth were also significant whereas salinity was not. During 2003 and 2012, synoptic satellite-derived temperature and chlorophyll-a maps were used with the GAMMs to predict monthly spatial availability on the Florida Panhandle fishing grounds (long. 8588o W and depth 1225 m). The predicted monthly availability was significantly correlated with commercial catch rates (Pearson's r = 0.26, P = 0.004, d.f. = 118). We used multiple linear regression (MLR) with lags to describe the effect of river discharge and wind (as a transport mechanism) on surface chlorophyll-a over the Panhandle fishing grounds. Discharge from local rivers was significant in all MLRs, and the Mississippi was only significant as an interaction with wind. We conclude that Atlantic Thread Herring are distributed over the Panhandle fishing grounds based on food availability that is driven by river discharge and eastward transport of Mississippi River plumes. This analysis improves our understating of baitfish dynamics, an important ecosystem component in the Gulf of Mexico.

Research areas: Agriculture, Ecosystems
Symbiodinium identity alters the temperature-dependent settlement behaviour of Acropora millepora coral larvae before the onset of symbiosis (2015)

The global distribution of marine species, many of which disperse during the larval stages, is influenced by ocean temperature regimes. Here, we test how temperature and the coral symbionts (Symbiodinium) affect survival, symbiont uptake, settlement success and habitat choice of Acropora millepora larvae. Experiments were conducted at Heron Island (Australia), where larvae were exposed to 22.5, 24.5, 26.5 and 28.5C. Within each temperature treatment, larvae were offered symbionts with distinct characteristics: (i) homologous Symbiodinium type C3, (ii) regionally homologous thermo-tolerant type D1, and (iii) heterologous thermo-tolerant type C15, as well as controls of (iv) un-filtered and (v) filtered seawater. Results show that lower instead of higher temperatures adversely affected recruitment by reducing larval survival and settlement. Low temperatures also reduced recruit habitat choice and initial symbiont densities, both of which impact on post-settlement survival. At lower temperatures, larvae increasingly settle away from preferred vertical surfaces and not on crustose coralline algae (CCA). Surprisingly, substrate preference to CCA was modified by the presence of specific symbiont genotypes that were present ex-hospite (outside the coral larvae). When different symbionts were mixed, the outcomes were non-additive, indicating that symbiont interactions modify the response. We propose that the observed influence of ex-hospite symbionts on settlement behaviour may have evolved through ecological facilitation and the study highlights the importance of biological processes during coral settlement.

Research areas: Ecosystems
Switch between Morphospecies of Pocillopora Corals (2015)

Pocillopora corals are the main reef builders in the eastern tropical Pacific. The validity of Pocillopora morphospecies remains under debate because of disagreements between morphological and genetic data. To evaluate the temporal stability of morphospecies in situ, we monitored the shapes of individual colonies in three communities in the southern Gulf of California for 44 months. Twenty-three percent of tagged colonies of Pocillopora damicornis changed to Pocillopora inflata morphology during this time. This switch in identity coincided with a shift to a higher frequency of storms and lower water turbidity (i.e., lower chlorophyll a levels). Seven months after the switch, P. inflata colonies were recovering their original P. damicornis morphology. All colonies of both morphospecies shared a common mitochondrial identity, but most P. damicornis colonies undergoing change were at a site with low-flow conditions. This is the first in situ study to document switching between described morphospecies, and it elucidates the influence of temporal shifts in environmental conditions on morphologically plastic responses.

Research areas: Ecosystems
Study of Aerosols Characteristics and Dynamics over the Kingdom of Saudi Arabia Using a Multisensor Approach Combined with Ground Observations (2015)

This study covers various aspects of the aerosol distribution and characteristics, namely, optical depth climatology, absorption characteristics, and their microphysical properties over four regions in Saudi Arabia using satellite and ground observations including MODIS/Terra and Aqua, OMI, MISR/Terra, AERONET, and CALIPSO for the period April 2003January 2013. The study includes cities in the North Western, Western, Eastern provinces of Saudi Arabia and in the Rub al Khali desert or Empty Quarter. Satellite and ground observations showed that the dust season extends from April to August with prominent peaks yet with high anthropogenic contribution late summer and early fall. Analysis shows an increase in the aerosol concentration during March 2009 which could be attributed to a major dust storm during that time. Comparing the AOD time series over regions 13 and region 4 (desert) we observe monthly and annual variability with no recurrence pattern over the years. The Aqua Deep Blue AOD550 data shows a single peak pattern that occurs over region 4 during the spring season known for its frequent dust events. OMI data shed the light on the presence of higher air pollution levels over region 3, representing the oil rich eastern province of Saudi Arabia.

Research areas: Air Quality
Spatiotemporal characteristics of aerosols in India: Observations and model simulations (2015)

An analysis of aerosol characteristics measured using sun photometers, MODIS and MISR, and simulated using global aerosol models (GOCART and MOZART) over six distinctly different environments in India reveal significant regional and temporal variations. Model AODs are lower than measured AODs, and exhibit a winter low and summer high, while features in measured AODs differ. MODIS and MISR AODs are higher than model simulated AODs. Differences between measured and model AODs arise due to absence of seasonal cycle in model AODs which occurs mainly due to lack of proper representation of aerosol emissions and not due to meteolorogy. In model simulations dust (>40% during premonsoon) and sulfate (40% during monsoon) contribute the maximum to total AOD. Model derived single scattering albedo (SSA) is higher than measured SSA over the study locations because simulated BC is low. The inter-annual variability in model derived SSA is lower than model-observation differences in SSA. The intra-regional variation in model AODs is lower than that of MODIS AODs. Sea salt contributes 10% to total AOD during monsoon only over Peninsular and west Central India. The underestimation of AODs by GOCART and MOZART and space-time differences with observations strongly favors improving the emission inventories of aerosol sources and removal mechanisms of aerosols in the models. Results from present study can serve as inputs to tune models because not only total AODs but also species AODs, and their amount need to be properly simulated in order to reduce the uncertainty in radiative and climate impact of aerosols.

Research areas: Air Quality
Spatio-Temporal Distribution of Aerosol and Cloud Properties over Sindh Using MODIS Satellite Data and a HYSPLIT Model (2015)

ABSTRACTIn this study, aerosols spatial, seasonal and temporal variations over Sindh, Pakistan were analyzed which can lead to variations in the microphysics of clouds as well. All cloud optical properties were analyzed using Moderate Resolution Imaging Spectroradiometer (MODIS) data for 12 years from 2001 to 2013. We also monitored origin and movements of air masses that bring aerosol particles and may be considered as the natural source of aerosol particles in the region. For this purpose, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to make trajectories of these air masses from their sources. Aerosol optical depth (AOD) high values were observed in summer during the monsoon period (JuneAugust). The highest AOD values in July were recorded ranges from 0.41 to 1.46. In addition, low AOD values were found in winter season (DecemberFebruary) particularly in December, ranges from 0.16 to 0.69. We then analyzed the relationship between AOD and Angstrom exponent that is a good indicator of the size of an aerosol particle. We further described the relationships of AOD and four cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP) by producing regional correlation maps of their data values. The analyses showed negative correlation between AOD and Angstrom exponent especially in central and western Sindh. The correlation between AOD and WV was throughout positive with high correlation values > 0.74 in whole Sindh except eastern most arid strip of the Thar Desert in the region. The correlation between AOD and CF was positive in southern Sindh and goes to negative in northern Sindh. AOD showed a positive correlation with CTP and CTT in northern Sindh and a negative correlation in southern Sindh. All these correlations were observed to be dependent on the meteorological conditions for all of the ten sites investigated.

Research areas: Atmospheric/Ocean Indicators
Spatio-temporal distribution and transport of particulate matter in the eastern tropical North Atlantic observed by Argo floats (2015)

The spatial and temporal distribution of particulate matter in the water column of the eastern tropical North Atlantic between 16.922.9N and 16.629.3W was investigated using optical measurements from transmissometers mounted on Argo floats. The corresponding profiles of beam attenuation coefficients measured from February 2008 to May 2009 were used to study particulate matter in different layers such as the surface nepheloid layer (SNL), subsurface nepheloid layer (SSNL), intermediate nepheloid layer (INL) and bottom nepheloid layer (BNL) as well as to investigate sinking particles (SP). The SNL were down to about 60m water depth at thicknesses between 20 and 60m. Our analyses verified high correlation between particulate matter and phytoplankton in the SNL. High offshore SNL extension of up to 750km was found in the area of Cape Blanc filaments in January 2009. Their typical widths ranged from 11 to 72km. Furthermore, float-borne observations even resolved atmospheric dust deposition into the surface water layer during a strong Saharan dust event in October 2008. The observed dust concentration in the mixed water layer was found to vary between 0.0021 and 0.0168gm3 depending on applied assumptions. An abrupt change from a SNL to a SSNL regime over distances of only 80 to 90km was observed. The particulate matter in the SSNL showed lateral extensions from 420 to 1020km offshore. A statistically significant correlation between the depth of subsurface particle maxima and the distance to shore was found. An averaged diameter of 30km was determined for the sharply isolated patches of INL which was consistent with model simulations of other studies. The lateral transport of particulate matter in these INL features in the area of the giant Cape Blanc filaments was found to be more pronounced than reported in earlier studies. The distribution of particulate matter within the INL filaments reached up to 610km off the shelf edge. The frequency of INL decreased with increasing distance to shore. The sinking velocity of particulate matter of one long-term observed INL was approximately 1.3mday1. Highly concentrated BNLs with beam attenuation coefficients of up to 4.530m1 were observed in the continental slope region. INLs appeared more frequently than SP events which lead to the conclusion that the lateral transport of particulate matter in INL features in the study area was more important than their passive vertical sinking.

Research areas: Ecosystems
Spatial Pattern of Hydrological Predictability of Landslide-Prone Areas (2015)

In this paper, the authors argue that integration of the hydrological model for landslide-prone areas should proceed under a soft geovisual communication in order to mitigate the uncertainty involved in downscaling rainstorm hazard mapping and geocomputational tracking. In this respect, examples of geovisualized spatial patterns for Terminio-Tuoro area affected by damaging landslide events is given by the rainstorm hazard index (RHI)kriged probability map. These findings should contribute to improving the information base needed to implement and monitor a sound strategy for warning, forecasting and planning landslide hazard.

Research areas: Land Surface/Agriculture Indicators