nasa-gesdisc/es-publications-researchareas huggingface dataset:
Complex interplay of physical forcing and Prochlorococcus population in ocean (2015)

Physical forcing can replenish nutrients within the mixed layer by convective mixing or via upwelling. Conventional wisdom holds this enrichment fuels phytoplankton growth, for example ventilation of subsurface water during winter monsoon is known to enhance primary productivity in the northern Arabian Sea. One important numerically dominant phytoplankton known to have ecological niche in the ocean is Prochlorococcus. In the Arabian Sea, they occur in oligotrophic surface water and below the oxycline representing two different light and biogeochemical regimes. Here we show convective mixing in the northern Arabian Sea inhibits Prochlorococcus growth owing to change in physical environment. Pigment observations carried out during early and peak winter monsoon revealed contrasting picoplankton distribution. Divinyl chlorophyll a (a marker for Prochlorococcus) which was the most abundant picoplankton pigment during early winter monsoon was not detected with the onset of winter convection covarying with high nutrients in the surface water. We propose two possible mechanisms for such sudden disappearance which involves changes in light and biogeochemical regimes. This physico-chemical control could be critical for their existence but not limited to and can play an important role in regions experiencing such phenomenon. We also highlight the linkages between Prochlorococcus succession and basin scale dynamics from the Arabian Sea which hitherto remains poorly understood.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Comparison and evaluation of dust detection algorithms using MODIS Aqua/Terra Level 1B data and MODIS/OMI dust products in the Middle East (2015)

Dust storms have a major impact on air quality, economic loss, and human health over large regions of the Middle East. Because of the broad extent of dust storms and also politicalsecurity issues in this region, satellite data are an important source of dust detection and mapping. The aim of this study was to compare and evaluate the performance of five main dust detection algorithms, including Ackerman, Miller, normalized difference dust index (NDDI), Roskovensky and Liou, and thermal-infrared dust index (TDI), using MODIS Level 1B and also MODIS Deep Blue AOD and OMI AI products in two dust events originating from Iraq and Saudi Arabia. Overall, results showed that the performance of the algorithms varied from event to event and it was not possible to use the published dust/no-dust thresholds for the algorithms tested in the study area. The MODIS AOD and OMI AI products were very effective for initial dust detection and the AOD and AI images correlated highly with the dust images at provincial scale (p-value <0.001), but the application of these products was limited at local scale due to their poor spatial resolution. Results also indicated that algorithms based on MODIS thermal infrared (TIR) bands or a combination of TIR and reflectance bands were better indicators of dust than reflectance-based ones. Among the TIR- based algorithms, TDI performed the best over water surfaces and dust sources, and accounted for approximately 93% and 90% of variations in the AOD and OMI AI data.

Research areas: Validation
Comparing two high-resolution gauge-adjusted multisatellite rainfall products over India for the southwest monsoon period (2015)

Reliable high-resolution rainfall estimates are vital for hydrological and weather/climate-related applications and evaluation of high-resolution numerical model outputs. Multisatellite rainfall products provide immense opportunities to analyse rainfall at regular spatial and temporal scales, but suffer from large region- and season-dependent biases. Direct calibration or merging of ground-based observations with multisatellite rainfall estimates essentially provides more accurate rainfall estimates as it benefits from the relative merits of both the sources. In this study, two popular gauge-adjusted multisatellite rainfall products, the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) research monitoring 3B42 version 7 (3B42V7) and Climate Prediction Center (CPC) Rainfall Estimation Algorithm version 2 (RFE2.0) are compared with the recently released and improved gridded India Meteorological Department (IMD) gauge-based rainfall estimates over India. The comparison is done for a 13 year southwest monsoon season ranging from 2001 to 2013 at 0.25 latitude/longitude resolution. A number of skill metrics such as mean, bias, co-efficient of variation, correlation co-efficient, anomaly correlation, pattern correlation and root-mean-square error (RMSE) are computed to assess the accuracy of both the merged satellite-gauge rainfall products. The prominent Indian monsoon rainfall features are well captured by both 3B42V7 and RFE2.0 products, in general. However, they overestimate mean rainfall at the all-India scale and the overestimation is comparatively larger for RFE2.0 than for 3B42V7. Even though the interannual variability of the Indian monsoon rainfall from both the gauge-adjusted multisatellite data sets is comparable with the gauge-based estimates for the study period, RFE2.0 overestimates light rainfall and underestimates heavy rainfall. Moreover, the comparison at sub-regional scales shows that 3B42V7 overestimates rainfall over eastern India and the foothills of the Himalayas and underestimates along the west coast and over the northeast, whereas RFE2.0 underestimates monsoon rainfall over the three sub-regions except over eastern India where it overestimates rainfall by about 25%. Both the gauge-adjusted multisatellite rainfall products show larger RMSE of the order of 100% along the west coast of India, which is a cause of concern. Overall analysis suggests that 3B42V7 is superior to RFE2.0 at synoptic scale over the Indian monsoon region.

Research areas: Validation
Collapse of zooplankton stocks during Liriope tetraphylla (Hydromedusa) blooms and dense mucilaginous aggregations in a thermohaline stratified basin (2015)

A growing number of studies report an increase in jellyfish populations worldwide that may have consequences for marine planktonic food web dynamics. The principal objective of this study was to understand the changes in a zooplankton community during blooms of Liriope tetraphylla and subsequent mucilage events in the Sea of Marmara, a small highly stratified transitional basin between the Black and Aegean Seas. Liriope blooms observed in 2006 and 2007 reached a maximum abundance of 2978 ind.m3, following the species' first observation in 2005. Jellyfish species are known to play a key guild role by restructuring plankton communities and in the Sea of Marmara Liriope caused a temporal regime shift from a crustacean- to a jellyfish-controlled system. A rapid decline in abundance of most important zooplankton species followed the Liriope increase, together with a drastic shift in community structure. The dominant summerautumn species Penilia avirostris (Cladocera) vanished in the autumn of 2006 and was diminished 30-fold in 2007 when compared with years without Liriope. The decline in zooplankton and the devastating effects of mucilage on pelagic ecosystem and socio-economics through restricting commercial fisheries implied sensitivity of the already perturbed Marmara ecosystem to changes in predator densities and environmental stability.

Research areas: Ecosystems
Coastal climate and beach dynamics at Ponta do Ouro, Mozambique (2015)

Annual field surveys conducted at Ponta do Ouro in Southern Mozambique have determined that coastal variability is driven by high wave energy and consequent northward longshore drift. There is a log-spiral headland-bay system marked by 80 m tall forested dunes in the south that give way to a broad flat sandy beach. Marine climate processes that affect coastal erosion and accretion are studied using local and remote data sets. Since surveys began, the climate has undergone a prolonged dry spell (2002-2007) followed by increased run-off and easterly winds (2010-2013) that have re-built the beaches. Sand grain sizes vary from 240 - 410 m (coarser south  finer north) and are mobilized by frequent longshore wind events > 10 m/s. Ocean drifters reveal a northward current in the outer surf zone of 0.6 m/s and an onshore gyre of 0.1 m/s in the recessed bay. Wave-driven sand transport is estimated at 5 106 kg/yr/m. While the upper beach has flattened due to pedestrian traffic and urban development, the lower beach has recovered from erosion due to a greater frequency of easterly waves and rainy weather.

	 

	Key words: Beach, coastal erosion, marine climate.

Research areas: Land Surface/Agriculture Indicators
Climatic controls on the interannual to decadal variability in Saudi Arabian dust activity: Toward the development of a seasonal dust prediction model (2015)

The observed climatic controls on springtime and summertime Saudi Arabian dust activities during 19752012 are analyzed, leading to development of a seasonal dust prediction model. According to empirical orthogonal function analysis, dust storm frequency exhibits a dominantly homogeneous pattern across Saudi Arabia, with distinct interannual and decadal variability. The previously identified positive trend in remotely sensed aerosol optical depth since 2000 is shown to be a segment of the decadal oscillation in dust activity, according to long-duration station record. Regression and correlation analyses reveal that the interannual variability in Saudi Arabian dust storm frequency is regulated by springtime rainfall across the Arabian Peninsula and summertime Shamal wind intensity. The key drivers of Saudi Arabian dust storm variability are identified. Winter-to-spring La Nina enhances subsequent spring dust activity by decreasing rainfall across the country's primary dust source region, the Rub' al Khali Desert. A relatively cool tropical Indian Ocean favors frequent summer dust storms by producing an anomalously anticyclonic circulation over the central Arabian Peninsula, which enhances the Shamal wind. Decadal variability in Saudi Arabian dust storm frequency is associated with North African rainfall and Sahel vegetation, which regulate African dust emissions and transport to Saudi Arabia. Mediterranean sea surface temperatures (SSTs) also regulate decadal dust variability, likely through their influence on Sahel rainfall and Shamal intensity. Using antecedent-accumulated rainfall over the Arabian Peninsula and North Africa, and Mediterranean SSTs, as low-frequency predictors, and tropical eastern Pacific and tropical Indian Ocean SSTs as high-frequency predictors, Saudi Arabia's seasonal dust activity is well predicted.

Research areas: Atmospheric/Ocean Indicators
Climate-induced range shifts of the American jackknife clam Ensis directus in Europe (2015)

Mapping the future potential distribution of alien species has become an issue of great concern. Ecological niche models are increasingly used to forecast the spatial range of introduced species in the context of climate warming. Here, we studied the potential spread of the American jackknife clam Ensis directus into European waters. E. directus, a marine bivalve native to the American coasts, was observed in Europe for the first time in the German Bight at the end of the 1970s. Afterwards, the clam quickly colonized the surrounding waters of the North Sea. Although many studies focused on its biology, ecology and colonization, the extent to which E. directus may invade European and Nordic seas remained poorly known. In this study, we used two ecological niche models (ENMs), calibrated on the native area of the mollusk, to evaluate the potential distributional range of the bivalve over European seas. Under current environmental conditions, E. directus should continue to progress towards the southern coasts of France and may also invade new areas in the Adriatic Sea. Projections for the end of the century suggest that the probability of occurrence of E. directus increases from Denmark to France with both ENMs. The Tunisian coasts may also become a new suitable area for the mollusk but the results of the two ENMs differ for this region. Therefore, contrary to what is often observed, a southward range expansion of E. directus is probable, especially as climate will get warmer.

Research areas: Ecosystems
Characteristics of 14C and 13C of carbonate aerosols in dust storm events in China (2015)

In contrast with its decrease in western China deserts, the dust storm event in eastern China, Korea, and Japan shows an increase in frequency. Although the drylands in northeastern China have been recognized as an important dust source, the relative contributions of dust transport from the drylands and deserts are inconclusive, thus the quantification of dust storm sources in downwind area remains a challenge. We measured the 14C and 13C contents in carbonates of dust samples from six sites in China, which were collected for the duration of dust storm events in drylands, deserts, and urban areas. The 13C of the dryland dust samples considerably varied in a range of 9.7 to 5.0, which partly overlapped the desert dust carbonate 13C ranges. The 14C content of the dryland dust carbonates showed a narrow range of 60.94.0 (as an average and 1 SD of five samples) percent modern carbon (pMC), indicating the enrichment of modern carbonate. Dust samples in desert regions contained relatively aged carbonates with the depleting 14C showing of 28.83.3pMC. After the long-range transport of the western China desert dust plume, the carbonates collected at the southern China remained the depletion of 14C (33.55.3pMC) as in the desert regions. On the other hand, the samples of dust storm events at the urban areas of eastern China showed an enrichment of 14C contents (46.25.0pMC, n=7), which might be explained by the stronger contribution of modern-carbonate-rich dryland dust.

Research areas: Validation
Characteristic behavior of water radon associated with Wenchuan and Lushan earthquakes along Longmenshan fault (2015)

In China, numerous subsurface, surface water well and spring parameters are being monitored through a large network of stations distributed in China sponsored by China Earthquake Administration (CEA). All the data from these network is managed by China Earthquake Network Center (CENC). In this paper, we have used numerous data (water radon, gas radon, water level, water temperature) available through CENC for the period 20022014 and studied the behavior and characteristics of water 222radon [Rn(w)]. The observed parameters were also complemented by rainfall data retrieved from Tropical Rainfall Measuring Mission (TRMM) satellite. Our detailed analysis shows pronounced changes in the observed parameters (especially water and gas radon) prior to the earthquake. The changes in water radon, ground water level and rainfall showing characteristics behavior for Wenchuan and Lushan earthquakes. The long term data analysis of water radon and water level at various locations around epicenters of two major earthquakes along Longmenshan fault show a positive and negative relation of water radon and water level prior to these earthquakes. It is difficult to find any trend of water radon and changes in water radon pattern with these two earthquakes that could prove as a reliable precursor of earthquakes. Changes in the water radon concentrations from one location to other may be associated with the changes in ground water regime and geological settings in the epicentral and surrounding regions.

Research areas: Earthquakes
Changes in the distribution of Al and particulate Fe along A16N in the eastern North Atlantic Ocean between 2003 and 2013: Implications for changes in dust deposition (2015)

Particulate Al and Fe and dissolved Al concentrations were analyzed in seawater samples from the upper 1000m of the eastern North Atlantic Ocean along the CLIVAR/CO2 Repeat Hydrography Program section A16N in summer 2013, repeating trace metal observations made along the A16N transect a decade earlier. Upper-ocean trace metal distributions in the equatorial and subtropical regions of the North Atlantic are heavily influenced by atmospheric aerosol sources. Using changes in the concentrations of subsurface particulate Al and Fe and mixed-layer dissolved Al in the equatorial North Atlantic, we estimate dust deposition to surface waters in the eastern North Atlantic increased by approximately 15% between 2003 and 2013. Increased concentrations of dissolved Al in subtropical mode waters suggest that dust deposition may have also increased in the western basin. Our observations are consistent with recent reports linking increasing sea surface temperatures in the tropical North Atlantic to increased removal of atmospheric dust via precipitation over the past several decades and highlight the importance of accurate representation of dust deposition processes for modeling Fe biogeochemistry.

Research areas: Validation
Changes in deep-sea fish and crustacean communities at 10002200m in the Western Mediterranean after 25years: Relation to hydro-climatic conditions (2015)

Long-term changes in the biomass, diversity and composition of deep-living fish and decapods from the Balearic Basin (western Mediterranean) have been compared between two periods, 19851992 vs. 20072012, based on 106 bottom trawls performed at 10002250m. Relationships have been identified between the changes in community composition and the hydroclimatic conditions (e.g. NAO, temperature, salinity and dissolved O2) of the area. We found a generalized deepening of middle-slope communities (9501250m), especially among decapods, which is suggested (from GLM results) to have been a response to the long-term increase in salinity of the Levantine Intermediate Waters (LIW), located above the level sampled to ca. 700m. Even more pronounced was the shallowing of all of the lower slope species (16002250m), accompanied by a significant decrease of biomass from 19851992 to 20072012. This last tendency would be done to a combination of factors: long-term decrease of O2 in the bottom-boundary layer, greater degradation of POM arriving on the bottom due to temperature increase in the Western Mediterranean Deep Waters (WMDW) and probably a decrease of Chl a at the surface and, thus, of production. The influence of climatic oscillations (NAO) on differences found between 19851992 and 20072012 seems secondary, likely because the NAO did not show significant differences between the two periods. Some plankton-feeding species showed an increase of density during high/positive NAO (e.g. Alepocephalus rostratus), while some benthos feeders increased during low/negative NAO (e.g. Aristeus antennatus, mainly juveniles). The increase of rainfall and advective fluxes under low/negative NAO (i.e., in 20072012) may increase the formation of the nepheloid layer identified over 12001400m in the area (Cartes et al., 2013a), linked to zooplankton aggregation in that depth range. Greater food availability could explain the generalized migration by both middle and lower slope species toward these intermediate depths that acquired greater trophic resources. Deep-sea Mediterranean fish and invertebrates, including important commercial species, seemed to undergo long-term changes in its distribution and biomass due to changes in hydro-climatic conditions, mainly a decrease of O2 in the bottom-boundary layer.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Cetacean occurrence and spatial distribution: Habitat modelling for offshore waters in the Portuguese EEZ (NE Atlantic) (2015)

In the Portuguese Economic Exclusive Zone (EEZ) (NE Atlantic), little survey effort dedicated to cetacean species has been carried out in offshore waters. As a consequence, data on their occurrence, distribution and habitat preferences is scarce. In this area, 48 sea surveys along fixed transects within Continental Portugal and Madeira Island were performed in 2012 and 2013, from July to October, using platforms of opportunity. We used an environmental envelope approach and GAM habitat models to identify the role of oceanographic, topographic and geographical variables in shaping cetacean distribution. Results demonstrate the richness of offshore waters in this area as in 10,668nmi sampled, we recorded 218 sightings from at least nine cetacean species, resulting in an overall ER of 2.04 sightings/100nmi. The interaction of topographic and oceanographic features was shown to influence the distribution of the species/groups along the routes. Among the sighted species, only common dolphin showed a preference for coastal waters, while for all the other species high seas proved to be determinant. This result reinforces the need to address conservation issues in open ocean. This preliminary assessment showed the importance of the entire area for the distribution of different cetacean species and allowed the identification of several species/group specific potential suitable habitats. Considering the Habitats Directive resolutions, ACCOBAMS priorities, EEZ extension for the area and Maritime Spatial Planning Directive, and the urgent need for management plans, we suggest that the sampling strategy here presented is a cost-effective method to gather valuable data, to be used to improve cetacean habitat models in the area.

Research areas: Ecosystems
Brown haze types due to aerosol pollution at Hefei in the summer and fall (2015)

Brown haze episodes were evaluated at Hefei in the summer (JuneAugust) and fall (SeptemberNovember) seasons, and typical haze types were identified by air-mass back-trajectories and fire spot maps. Compared with clear weather conditions, larger median single scattering albedo values of 0.82 and 0.78 at 550nm were obtained for the summer and fall haze episodes, respectively. Further, the observed lower scattering Angstrom exponents imply that more large particles than small particles dominated the haze plumes, which is in agreement with the profiles of size distribution. Particles during a haze episode in Hefei grow to a size such that the 0.10 limit for the backscattering ratio is reached, which may indicate that the aged aerosols promote the formation of haze episodes. Three typical haze types were identified: biomass burning, anthropogenic industrial and traffic emissions, and brown carbon. Less negative aerosol radiative forcing efficiencies of 12.7 and 10.9Wm2 in summer and fall were estimated, respectively, for haze impacted by biomass burning, which emphasizes an enhanced significance of biomass burning aerosols on climate forcing.

Research areas: Air Quality, Environmental Impacts