nasa-gesdisc/es-publications-researchareas huggingface dataset:
Joint spatial variability of aerosol, clouds and rainfall in the Himalayas from satellite data (2010)

Abstract. Satellite-based precipitation, Aerosol Optical Depth (AOD), Cloud Optical Depth (COD), and Aerosol Index (AI) data were used to characterize the linkages among landform and the intra-annual variability of aerosols, cloudiness and rainfall in the Himalayas using empirical orthogonal function (EOF) analysis. The first modes of AOD and AI show the presence of two branches of dust aerosol: over the Indus river basin and the Thar desert with a sharp west-east gradient parallel to the southern slopes of the Himalayas  the Southern Branch; and the second against the slopes of the Tian Shan and over the Takla Makan desert in the Tibetan Plateau-the Northern branch. The third EOF mode of AOD accounts for about 7% of overall variance of AOD. It is attached to the foothills of the Himalayas east of the Aravalli range peaking in April-May-June followed by a sharp decrease in July during the first active phase of the monsoon. The first and second EOF modes of COD and precipitation show consistent patterns against the central and eastern Himalayas and along the ocean-land boundaries in western India and the Bay of Bengal. The break in cloudiness and rainfall between the winter and the monsoon seasons is captured well by the second EOF mode of COD and rainfall concurrent with the aerosol build up mode (AprilMay) over the region depicted by the third mode of AOD. The results show that the Aravalli range separates the two different modes of aerosol variability over northern India with dust aerosols to the west and polluted mixed aerosols to the east consistent with its role in regional circulation and precipitations patterns as per Barros et al. (2004) and Chiao and Barros (2007). SVD analysis between rainfall, COD and AOD showed a pattern of aerosol loading (resembling EOF3 of MODIS AOD) extending from 80 E~90 E that peaks during the winter and pre-monsoon seasons and decays abruptly during the monsoon: the regions of aerosol buildup during the pre-monsoon season and the areas of high rainfall/cloudiness during the monsoon are collocated and have opposite signs suggesting aerosol-cloud-rainfall interaction. It is proposed that the third EOF of AOD maps the area where aerosol-cloud-rainfall interactions play an important role in the regional hydro-climatology.

Research areas: Atmospheric/Ocean Indicators
Intra-annual variability of extremely rapid sedimentation onto Gardar Drift in the northern North Atlantic (2010)

North Atlantic sediment drifts are valuable archives for paleoceanographic reconstructions spanning various timescales. However, the short-term dynamics of such systems are poorly known, and this impinges on our ability to quantitatively reconstruct past change. Here we describe a high-resolution 319-day time-series of hydrodynamics and near-bottom (4m) particulate matter flux variability at a 2600m deep site with an extremely high sediment accumulation rate on the southern Gardar Drift in the North Atlantic. We compare our findings with the actual deposits at the site. The total annual particle flux amounted to 360gm2yr1, varied from 0.15 to >5.0gm2day1 and displayed strong seasonal compositional changes, with the highest proportion of fresh biogenic matter arriving after the spring bloom in June and July. Flux variability also depended on the changing input of lithogenic matter that had been (re)suspended for a longer time (decades). Active focussing of material from both sources is required to account for the composition and the magnitude of the total flux, which exceed observations elsewhere by an order of magnitude. The enhanced focussing or increased delivery appeared to be positively related to current velocity. The intercepted annual particle flux accounted for only 60% of the sediment accumulation rate of 60020gm2yr1 (0.200.07cmyr1), indicating higher intra- and inter-annual variability of both the biogenic and lithogenic fluxes and/or advection of additional sediment closer to the seafloor (i.e. <4m). This temporal variability in the composition and amount of material deposited highlights intra-annual changes in the flux of lithogenic material, but also underscores the importance of (reworked) sediment focussing and seasonality of the biogenic flux. All should be taken into account in the interpretation of the paleorecord from such depositional settings.

Research areas: Water Quality
Inherent optical properties and satellite retrieval of chlorophyll concentration in the lagoon and open ocean waters of New Caledonia (2010)

The retrieval of chlorophyll-a concentration from remote sensing reflectance (Rrs) data was tested with the NASA OC4v4 algorithm on the inner New Caledonian lagoon (Case 2) and adjacent open ocean (Case 1) waters. The input to OC4v4 was Rrs measured in situ or modeled from waters inherent optical properties (20012007). At open ocean stations, backscattering and absorption coefficients were correlated with chlorophyll (R2=0.310.51, respectively), in agreement with models for Case 1 waters. Taking spectrofluorometric measurement as reference, the OC4v4 model leads to an average underestimation of 33% of the chlorophyll concentration. For the lagoon waters, OC4v4 performed inadequately because the backscattering coefficient, highly correlated with turbidity and suspended matter (R2=0.98), was poorly correlated to chlorophyll (R2=0.42). The OC4v4 performance was better in deep lagoon waters for stations with a TDT index (Tchladepth/turbidity) higher than 19mgm2 NTU1 (R2=0.974, bias=10.2%). Global Imager Rrs provided a good estimate of Tchla (R2=0.79, N=28) in the deeper part of the lagoon.

Research areas: Validation
Influence of solar proton events during the declining phase of solar cycle 23 on the total ozone concentration in India (2010)

Depletion of ozone under the influence of solar proton events (SPEs) is an important natural phenomenon affecting the middle mesospheric and upper stratospheric ozone content. When the Sun went through the declining phase of its activity in solar cycle 23, it unleashed a series of large eruptions, which were unusually intense flares, and accelerated particles to unprecedented energy levels. The severe impact of these events was felt in the Earth's atmosphere, not only at higher latitudes but also at the middle latitudes and tropics. The impact of nine such SPEs, having different proton flux and time duration on the total ozone content at Indian latitude belts, was studied using the ozone data obtained from Earth Probe Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument. It is observed that, for high proton flux, the depletion in ozone levels extended up to low latitudes. The observed depletion in ozone was found to be higher for longer time duration of the SPE.

Research areas: Sun-Earth Interactions
Influence of a Tropical Cyclone Gonu on Phytoplankton Biomass (Chlorophyll a) in the Arabian Sea (2010)

Tropical cyclones could gradually affect the physical, chemical, and biological processes in the upper layer of the ocean. In terms of biological consequences, the cyclone wind field causes local mixing which results in the injection of nutrients into the upper layer of the ocean and triggering phytoplankton bloom (Subrahmanyam et al. 2002). In some cases, the magnitude of the hurricane-induced bloom could reach a gradual (30-fold) increase in the surface chlorophyll a concentration, as well as an increase in the primary production (Lin et al. 2003; Smitha et al. 2006). In the regions where cyclones often occur, their propagation could chiefly influence the annual productivity of the ocean. For example, an average of 14 cyclones pass over the South China Sea annually, which suggests the contribution of cyclones to annual production to be as much as 20-30% (Lin et al. 2003).

Research areas: Severe Storms, Ecosystems
Impact of satellite based PAR on estimates of terrestrial net primary productivity (2010)

Biospheric productivity regulates the supply of food for mankind and therefore, there is a need to estimate its magnitude. The productivity is controlled by the process of photosynthesis driven by solar radiation, primarily in the visible part of the spectrum (0.40.7 m), known as the photosynthetically active radiation (PAR). Current methods to estimate terrestrial net primary production (NPP) use remotely sensed information on vegetation dynamics. Satellite based estimates of PAR are available at a global scale but have seldom been used for estimating NPP. In this study we show that the use of PAR information from satellites does have an impact on estimates of NPP and that there are detectable differences when compared to similar estimates based on conventional PAR information. Net primary production tends to be higher when compared to estimates based on total shortwave (SW) radiation with PAR assumed to be a constant fraction of SW. We focus on the United States during 2004. Net primary production is generally underestimated in regions with mesic environment while overestimated in areas with xeric environment. The most pronounced underestimated region is the southeast United States. The study demonstrates the usefulness of the satellite-based estimates of PAR for modelling terrestrial primary productivity.

Research areas: Ecosystems
Impact of Alaskan Stream eddies on chlorophyll distribution in the North Pacific (2010)

The impact of the Alaskan Stream (AS) eddies on the chlorophyll a (chl-a) distribution in the central subarctic North Pacific was investigated through analysis of chl-a and altimetry data from satellite observations. Altimetry observations provided the locations of mesoscale eddies in time and space within the maps of chlorophyll distributions. The climatological chl-a distributions averaged in the area and time showing presence of AS eddies suggested that AS eddies contributed significantly to the chl-a distribution in the deep-sea region of the subarctic North Pacific. The chl-a distribution was closely related to the AS eddies regardless of whether the eddy was located in or detached from the AS. A combination of two or three AS eddies sometimes formed high chl-a concentration belts that injected chlorophyll and coastal nutrient-rich waters southward from the Aleutian Islands far into the deep-sea region of the subarctic North Pacific. These results indicate that chl-a distribution in the central subarctic North Pacific was strongly impacted by AS eddies.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Impact of agriculture crop residue burning on atmospheric aerosol loading  a study over Punjab State, India (2010)

Abstract. The present study deals with the impact of agriculture crop residue burning on aerosol properties during October 2006 and 2007 over Punjab State, India using ground based measurements and multi-satellite data. Spectral aerosol optical depth (AOD) and Angstrom exponent () values exhibited larger day to day variation during crop residue burning period. The monthly mean Angstrom exponent "" and turbidity parameter "" values during October 2007 were 1.310.31 and 0.360.21, respectively. The higher values of "" and "" suggest turbid atmospheric conditions with increase in fine mode aerosols over the region during crop residue burning period. AURA-OMI derived Aerosol Index (AI) and Nitrogen dioxide (NO2) showed higher values over the study region during October 2007 compared to October 2006 suggesting enhanced atmospheric pollution associated with agriculture crop residue burning.

Research areas: Air Quality, Environmental Impacts
Hot-spots of primary productivity: An Alternative interpretation to Conventional upwelling models (2010)

The eastern Great Australian Bight (EGAB) forms part of the Southern and Indian Oceans and is an area of high ecological and economic importance. Although it supports a commercial fishery, quantitative estimates of the primary productivity underlying this industry are open to debate. Estimates range from <100 mg C m2 day1 to > 500 mg C m2 day1. Part of this variation may be due to the unique upwelling circulation of shelf waters in summer/autumn (NovemberApril), which shares some similarities with highly productive eastern boundary current upwelling systems, but differs due to the influence of a northern boundary current, the Flinders current, and a wide continental shelf. This study examines spatial variations in primary productivity in the EGAB during the upwelling seasons of 2005 and 2006. Daily integral productivity calculated using the vertically generalised production model (VGPM) showed a high degree of spatial variation. Productivity was low (<800 mg C m2 day1) in offshore central and western regions of the EGAB. High productivities (16003900 mg C m2 day1) were restricted to hotspots in the east that were influenced by the upwelled water mass. There was a strong correlation between the depth of the euphotic zone and the depth of the mixed layer that suggested that 50% of the euphotic zone lay below the mixed layer depth. As a result, high rates of primary productivity did not require upwelled water to reach the surface. A significant proportion of total productivity in the euphotic zone (57% in 2005 and 65% in 2006) occurred in the upwelled water mass below the surface mixed layer. This result has implications for daily integral productivities modelled with the VGPM, which uses surface measures of phytoplankton biomass to calculate productivity. Macro-nutrient concentrations could not be used to explain the difference in the low and high productivities (silica > 1 mol L1, nitrate/nitrite > 0.4 mol L1, phosphate > 0.1 mol L1). Mixing patterns or micro-nutrient concentrations are possible explanations for spatial variations in primary productivity in the EGAB. On a global scale, daily rates of primary productivity of the EGAB lie between the highly productive eastern boundary current upwelling systems, and less productive coastal regions of western and south eastern Australia, and the oligotrophic ocean. However, daily productivity rates in the upwelling hotspots of the EGAB rival productivities in Benguela and Humboldt currents.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Hostsymbiont recombination versus natural selection in the response of coraldinoflagellate symbioses to environmental disturbance (2010)

Mutualisms between reef-building corals and endosymbiotic dinoflagellates are particularly sensitive to environmental stress, yet the ecosystems they construct have endured major oscillations in global climate. During the winter of 2008, an extreme cold-water event occurred in the Gulf of California that bleached corals in the genus Pocillopora harbouring a thermally sensitive symbiont, designated Symbiodinium C1b-c, while colonies possessing Symbiodinium D1 were mostly unaffected. Certain bleached colonies recovered quickly while others suffered partial or complete mortality. In most colonies, no appreciable change was observed in the identity of the original symbiont, indicating that these partnerships are stable. During the initial phases of recovery, a third species of symbiont B1Aiptasia, genetically identical to that harboured by the invasive anemone, Aiptasia sp., grew opportunistically and was visible as light-yellow patches on the branch tips of several colonies. However, this symbiont did not persist and was displaced in all cases by C1b-c several months later. Colonies with D1 were abundant at inshore habitats along the continental eastern Pacific, where seasonal turbidity is high relative to offshore islands. Environmental conditions of the central and southern coasts of Mexico were not sufficient to explain the exclusivity of D1 Pocillopora in these regions. It is possible that mass mortalities associated with major thermal disturbances during the 19971998 El Nino Southern Oscillation eliminated C1b-c holobionts from these locations. The differential loss of Pocillopora holobionts in response to thermal stress suggests that natural selection on existing variation can cause rapid and significant shifts in the frequency of particular coralalgal partnerships. However, coral populations may take decades to recover following episodes of severe selection, thereby raising considerable uncertainty about the long-term viability of these communities.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Haze types in Beijing and the influence of agricultural biomass burning (2010)

Abstract. Emissions from agricultural biomass burning (ABB) in northern China have a significant impact on the regional and global climate. The monthly average aerosol optical depth (AOD) at 550 nm in northern China in 2007 had a maximum of 0.7 in June. The AOD measurements are consistent with regional brown hazes that occurred at that time, which was a period of severe aerosol pollution. Aerosol particles were collected in urban Beijing from 12 to 30 June 2007, during a period of high haze, and studied using transmission electron microscopy with energy-dispersive X-ray spectrometry. The dominant particle types collected in the fine fraction (diameter <1 m) were ammonium sulfate, soot, K2SO4, KNO3, and organic matter, except that the K salts were minor between 21 and 30 June. K-rich particles as tracers of biomass burning, together with wildfire maps, show that intense regional ABB in northern China contributed significantly to the regional haze between 12 and 20 June. We therefore grouped the episodes into type-1 and -2 haze, with the former occurring between 12 and 20 June and the latter between 21 and 30 June. After long-range transport, ABB particles in the type-1 haze exhibited marked changes in morphology, composition, and mixing state. KCl particles were absent, presumably having been converted by heterogeneous reactions to K2SO4 and KNO3. Soot particles were mixed with the other particle types. Abundant organic matter and soluble salts emitted by ABB increased their sizes during transport and resulted in more hygroscopic aerosol particles in downwind areas, becoming additional cloud condensation nuclei. The high AOD (average value 2.2) in Beijing during 12 to 20 June is partly explained by the hygroscopic growth of fine aerosol particles and by the strong absorption of internally mixed soot particles, both coming from regional ABB emissions. Therefore, it is important to consider the origins of the haze, which in turn leads to the different particle types.

Research areas: Air Quality, Environmental Impacts
Global Modeling of the Oceanic Source of Organic Aerosols (2010)

The global marine organic aerosol budget is investigated by a 3-dimensional chemistry-transport model considering recently proposed parameterisations of the primary marine organic aerosol (POA) and secondary organic aerosol (SOA) formation from the oxidation of marine volatile organic compounds. MODIS and SeaWiFS satellite data of Chlorophyll-a and ECMWF solar incoming radiation, wind speed, and temperature are driving the oceanic emissions in the model. Based on the adopted parameterisations, the SOA and the submicron POA marine sources are evaluated at about 5 Tg ( 1.5 Tg C ) and 7 to 8 Tg ( 4 Tg C ), respectively. The computed marine SOA originates from the dimethylsulfide oxidation ( 78%), the potentially formed dialkyl amine salts ( 21%), and marine hydrocarbon oxidation ( 0.1%). Comparison of calculations with observations indicates an additional marine source of soluble organic carbon that could be partially encountered by marine POA chemical ageing.

Research areas: Water Quality
A feasibility of six-hourly rainfall forecast over central India using model output and remote sensing data (2012)

Rainfall forecast has prime importance in an agrarian country like India, wherein the agricultural production is solely dependent on monsoon rainfall. In this paper, an artificial neural network (ANN) technique is used to construct a non-linear mapping between output data from global forecast system (GFS) and rainfall from tropical rainfall measuring mission (TRMM) satellite measurements. The objective of the present study is to generate region-specific six-hourly quantitative rainfall forecast over central India using ANN and resilient propagation learning algorithm. Meteorological variables from the GFS model and precipitation product from TRMM multisatellite precipitation analysis (TMPA) are used as input data for training the network, which generate rainfall forecast for the next time step. The test was performed for central India during the summer monsoon period of 2010. In order to evaluate the potential of rainfall forecast skill over the studied region, the forecast precipitation has been intercompared with TMPA-3B42, and Kalpana-1 derived precipitation products and a statistical analysis was performed. The linear correlation between ANN forecast and TMPA-3B42 rainfall was 0.58, whereas it was 0.52 with Kalpana-1 derived precipitation estimates. The results show that the predicted precipitation by the present technique performs better than GFS model precipitation forecast, and the system indicates a potential for more accurate rainfall forecasting.

Research areas: Validation
Ciguatera fish poisoning and sea surface temperatures in the Caribbean Sea and the West Indies (2010)

Ciguatera fish poisoning (CFP) is a circumtropical disease caused by ingestion of a variety of reef fish that bioaccumulate algal toxins. Distribution and abundance of the organisms that produce these toxins, chiefly dinoflagellates of the genus Gambierdiscus, are reported to correlate positively with water temperature. Consequently, there is growing concern that increasing temperatures associated with climate change could increase the incidence of CFP. This concern prompted experiments on the growth rates of six Gambierdiscus species at temperatures between 18C and 33C and the examination of sea surface temperatures in the Caribbean and West Indies for areas that could sustain rapid Gambierdiscus growth rates year-round. The thermal optimum for five of six Gambierdiscus species tested was 29C. Long-term SST data from the southern Gulf of Mexico indicate the number of days with sea surface temperatures 29C has nearly doubled (44 to 86) in the last three decades. To determine how the sea surface temperatures and Gambierdiscus growth data correlate with CFP incidences in the Caribbean, a literature review and a uniform, region-wide survey (19962006) of CFP cases were conducted. The highest CFP incidence rates were in the eastern Caribbean where water temperatures are warmest and least variable.

Research areas: Ecosystems, Atmospheric/Ocean Indicators