nasa-gesdisc/es-publications-researchareas huggingface dataset:
Surface transport detected by pairs of COSMO-SkyMed ScanSAR images in the Qingdao region (Yellow Sea) during a macro-algal bloom in July 2008 (2010)

In early summer 2008 an extended macro-algal bloom in the Qingdao coastal area caused the presence of huge algal aggregates at the sea surface clearly visible in SAR images. The event was observed by WideRegion ScanSAR data (X-band) acquired in July 2008 by the two currently operative COSMO-SkyMed satellites. The current constellation (two of four satellites operative by 2010) provides pairs of overlapping images with a time shift of 48 min, with a repeat time from 12 to 24 h. The full constellation will allow a peak daily acquisition capability of 24 min in the ScanSAR mode. The double acquisition with a short time lag, similar to a time derivative in the overlapping area, allows an accurate feature tracking and automated extraction of the surface transport not previously available. Considering that SAR images are unaffected by cloud cover, accurate surface transport patterns greatly improve the forecasting capability in the case of marine environmental emergencies.

Research areas: Ecosystems
Study of Data-Merging and Interpolation Methods for Use in an Interactive Online Analysis System: MODIS Terra and Aqua Daily Aerosol Case (2010)

Data merging with interpolation is a method of combining near-coincident satellite observations to provide complete global or regional maps for comparison with models and ground station observations. We investigate various methods and limitations of data merging (or data fusion), with and without interpolation, as a first step toward merging data sets archived in the National Aeronautics and Space Administration Goddard Earth Sciences Data and Information Services Center and made public through the Goddard Interactive Online Visualization and ANalysis Infrastructure (Giovanni) data portals. As a prototype for the data-merging algorithm, this paper uses daily global observations of aerosol optical thickness (AOT), as measured by the MODerate resolution Imaging Spectroradiometer onboard the Terra and Aqua satellites. The goal is to develop a very fast and accurate online method of data merging for implementation into Giovanni. We demonstrate three different methods for pure merging (without interpolation): simple arithmetic averaging (SAA), maximum likelihood estimate (MLE), and weighting by pixel counts. All three methods are roughly comparable, with the MLE (SAA) being slightly preferable when validating with respect to the AOT standard deviations (AOT means). To evaluate the merged product, we introduce two confidence functions, which characterize the percentage of the merged AOT pixels as a function of the relative deviation of the merged AOT from the initial Terra and Aqua AOTs. Eight combinations of merging-interpolation are applied to scenes with regular and irregular data gap patterns. Our results show that the merging-interpolation procedure can produce complete spatial fields with acceptable errors.

Research areas: Validation
Sources of light-absorbing aerosol in arctic snow and their seasonal variation (2010)

Abstract. Two data sets consisting of measurements of light absorbing aerosols (LAA) in arctic snow together with suites of other corresponding chemical constituents are presented; the first from Siberia, Greenland and near the North Pole obtained in 2008, and the second from the Canadian arctic obtained in 2009. A preliminary differentiation of the LAA into black carbon (BC) and non-BC LAA is done. Source attribution of the light absorbing aerosols was done using a positive matrix factorization (PMF) model. Four sources were found for each data set (crop and grass burning, boreal biomass burning, pollution and marine). For both data sets, the crops and grass biomass burning was the main source of both LAA species, suggesting the non-BC LAA was brown carbon. Depth profiles at most of the sites allowed assessment of the seasonal variation in the source strengths. The biomass burning sources dominated in the spring but pollution played a more significant (though rarely dominant) role in the fall, winter and, for Greenland, summer. The PMF analysis is consistent with trajectory analysis and satellite fire maps.

Research areas: Air Quality, Environmental Impacts
Source attribution and interannual variability of Arctic pollution in spring constrained by aircraft (ARCTAS, ARCPAC) and satellite (AIRS) observations of carbon monoxide (2010)

Abstract. We use aircraft observations of carbon monoxide (CO) from the NASA ARCTAS and NOAA ARCPAC campaigns in April 2008 together with multiyear (20032008) CO satellite data from the AIRS instrument and a global chemical transport model (GEOS-Chem) to better understand the sources, transport, and interannual variability of pollution in the Arctic in spring. Model simulation of the aircraft data gives best estimates of CO emissions in April 2008 of 26 Tg month1 for Asian anthropogenic, 9.4 for European anthropogenic, 4.1 for North American anthropogenic, 15 for Russian biomass burning (anomalously large that year), and 23 for Southeast Asian biomass burning. We find that Asian anthropogenic emissions are the dominant source of Arctic CO pollution everywhere except in surface air where European anthropogenic emissions are of similar importance. Russian biomass burning makes little contribution to mean CO (reflecting the long CO lifetime) but makes a large contribution to CO variability in the form of combustion plumes. Analysis of two pollution events sampled by the aircraft demonstrates that AIRS can successfully observe pollution transport to the Arctic in the mid-troposphere. The 20032008 record of CO from AIRS shows that interannual variability averaged over the Arctic cap is very small. AIRS CO columns over Alaska are highly correlated with the Ocean Nino Index, suggesting a link between El Nino and Asian pollution transport to the Arctic. AIRS shows lower-than-average CO columns over Alaska during April 2008, despite the Russian fires, due to a weakened Aleutian Low hindering transport from Asia and associated with the moderate 20072008 La Nina. This suggests that Asian pollution influence over the Arctic may be particularly large under strong El Nino conditions.

Research areas: Air Quality, Environmental Impacts
Seasonal variation of diel vertical migration of zooplankton from ADCP backscatter time series data in the Lazarev Sea, Antarctica (2010)

Ten-month time series of mean volume backscattering strength (MVBS) and vertical velocity obtained from three moored acoustic Doppler current profilers (ADCPs) deployed from February until December 2005 at 64S, 66.5S and 69S along the Greenwich Meridian were used to analyse the diel vertical zooplankton migration (DVM) and its seasonality and regional variability in the Lazarev Sea. The estimated MVBS exhibited distinct patterns of DVM at all three mooring sites. Between February and October, the timing of the DVM and the residence time of zooplankton at depth were clearly governed by the daynight rhythm. Mean daily cycles of the ADCP-derived vertical velocity were calculated for successive months and showed maximum ascent and descent velocities of 16 and 15mms1. However, a change of the MVBS pattern occurred in late spring/early austral summer (October/November), when the zooplankton communities ceased their synchronous vertical migration at all three mooring sites. Elevated MVBS values were then concentrated in the uppermost layers (<50m) at 66.5S. This period coincided with the decay of sea ice coverage at 64S and 66.5S between early November and mid-December. Elevated chlorophyll concentrations, which were measured at the end of the deployment, extended from 67S to 65S and indicated a phytoplankton bloom in the upper 50m. Thus, we propose that the increased food supply associated with an ice edge bloom caused the zooplankton communities to cease their DVM in favour of feeding.

Research areas: Ecosystems
Seasonal Variability of the Organic-Walled Dinoflagellate Cyst Production in the Coastal Upwelling Region Off Cape Blanc (mauritania): A Five-Year Survey1 (2010)

A 5-year sediment trap survey in the upwelling area off Cape Blanc (NW Africa) provides information on the seasonal and annual resting cyst production of dinoflagellates, their sinking characteristics and preservation potential. Strong annual variation in cyst production characterizes the region. Cyst production of generally all investigated species, including Alexandrium pseudogonyaulax (Biecheler) T. Horig. ex T. Kita et Fukuyo (cyst genus Impagidinium) and Gonyaulax spinifera (Clap. et J. Lachm.) Diesing (cyst genus Nematosphaeropsis) was enhanced with increasing upper water nutrient and trace-element concentrations. Cyst production of Lingulodinium polyedrum (F. Stein) J. D. Dodge was the highest at the transition between upwelling and upwelling-relaxation. Cyst production of Protoperidinium americanum (Gran et Braarud) Balech, Protoperidinium monospinum (Paulsen) K. A. F. Zonn. et B. Dale, and Protoperidinium stellatum (D. Wall) Balech, and heterotrophic dinoflagellates forming Brigantedinium spp. and Echinidinium aculeatum Zonn., increased most pronouncedly during upwelling episodes. Production of Protoperidinium conicum (Gran) Balech and Protoperidinium pentagonum (Gran) Balech cysts and total diatom valves were related, providing evidence of a predatorprey relationship. The export cyst-flux of E. aculeatum, P. americanum, P. monospinum, and P. stellatum was strongly linked to the flux of total diatom valves and CaCO3, whereas the export production of Echinidinium granulatum Zonn. and Protoperidinium subinerme (Paulsen) A. R. Loebl. correlated with total organic carbon, suggesting potential consumption of diatoms, prymnesiophytes, and organic matter, respectively. Sinking velocities were at least 274 m  d1, which is in range of the diatom- and coccolith-based phytoplankton aggregates and slower fecal pellets. Species-selective degradation did not occur in the water column, but on the ocean floor.

Research areas: Ecosystems
Seasonal to interannual variability and geographic distribution of the silicoflagellate fluxes in the Western Mediterranean (2010)

A total of 337 samples collected from five sediment traps located in the Gulf of Lions, Catalan margin and the Alboran Sea have been analyzed in order to study the seasonal, interannual and geographical distributions of silicoflagellate fluxes in the Western Mediterranean. As a general trend, maximum fluxes of silicoflagellate skeletons always occurred during the spring bloom; i.e. during the winterspring transition, while minimum fluxes were recorded during summer, characterised by a strong stratification and oligotrophic conditions. However, the sediment trap record of the Catalan margin did not exhibit any clear seasonal signal, probably owing to the fertilizing effect of the rivers Llobregat and Besos. Regarding interannual variability, no clear relationship between the NAO (North Atlantic Oscillation) and the silicoflagellate fluxes was found. In contrast, the silicoflagellate assemblages from the Alboran Sea and the Gulf of Lions responded with low fluxes and a delay in their annual maximum to the anomalous conditions elicited by the 199798 El Nino Event. Furthermore, the 2003 summer heat wave over the Western Mediterranean had similar repercussions on the silicoflagellate spring maximum 2004 in the Gulf of Lions. Three silicoflagellate species were identified in the samples, following the taxonomic concepts of Throndsen (1997): Dictyocha fibula (Ehrenberg), Dictyocha speculum (Ehrenberg) and Octactis octonaria (Ehrenberg) Hovasse 1946. D. fibula was cosmopolitan and the dominant species at all sites, always accounting for more than 80%. Moreover, its maximum fluxes were recorded in those sampling sites which were under the influence of high nutrient concentrations caused by the river input. D. speculum was only recorded in the northern locations, which suggests an affinity for colder water masses. In contrast, O. octonaria was restricted to the Alboran Sea stations, where temperatures reached the highest values and nutrients were scarcer.

Research areas: Ecosystems
Seasonal evolution of boundary-layer turbulence measured by aircraft during the AMMA 2006 Special Observation Period (2010)

During the African Monsoon Multidisciplinary Analysis (AMMA) field campaign, the ATR research aircraft made observations of fluxes and thermodynamics during three 15-day periods, which allowed the seasonal evolution of the atmospheric boundary-layer (ABL) characteristics to be monitored before and after the monsoon onset. As expected, temperature and humidity showed a contrast between dry warm conditions and moister cooler conditions from one period to the other. Most of the time, the wind blew from the west (northwesterly to southwesterly) in the ABL and from the east in the free troposphere. Following rainfall events occuring in July and August, surface sensible heat flux decreased and evaporation increased while the momentum flux remained large in the entire boundary layer, whatever the period. The aim of this paper is to characterize turbulence in terms of fluxes and length-scales for ABLs that exhibit particular characteristics relative to (i) entrainment at the top, (ii) wind rotation at the interface between the monsoon and the Saharan air layer and (iii) seasonal variability. In spite of the poorer accuracy of the turbulent flux estimations at the top of the ABL, the flux profiles were observed to increase or decrease linearly with altitude which enabled accurate estimates of entrainment flux ratios. It was found that the moisture flux distribution in the ABL was governed by top-down processes during the driest period and a mixture of top-down and bottom-up processes during the monsoon period. Significant differences in turbulence length-scales were also highlighted. Copyright  2009 Royal Meteorological Society

Research areas: Atmospheric/Ocean Indicators
Seasonal dynamics and regional features of MODIS-derived land surface characteristics in dust source regions of East Asia (2010)

Atmospheric mineral dust is an important component of the climate system; however, representation of dust production in the climate models poses significant challenges. Satellite remote sensing has the potential to aid in determining the surface characteristics of active dust source regions that are of importance to dust emission modeling. This study uses data from the Moderate-resolution Imaging Spectroradiometer (MODIS) in conjunction with soil texture to investigate linkages of spatial distribution of surface characteristics related to dust emission, and their dynamics, at the seasonal time scale. In addition to standard MODIS land products such as surface albedo and NDVI which are strongly linked to dust emission, we introduce a roughness index (RI) and an arid soil surface index (ASSI) to aid in land surface characterization. Three regions of northwestern China known for dust emission, the Taklamakan, Badain Jaran, and Gurbantunggut Deserts, are examined for spatial and temporal changes of surface characteristics during winterspringsummer transition FebruaryJuly 2005. A new methodology is proposed by introducing regional masking derived from MODIS Band 10 surface albedo. The analysis demonstrates regional unique temporal and spatial characteristics in the 2005 seasonal transition for these areas. Seasonal modes of response are clearly present. The soil texture correlation results demonstrate that clay fraction has a consistently high negative correlation to albedo, as does vegetation. The analysis also demonstrates that RI is a dynamic characteristic changing both with season and on much shorter time scales.

Research areas: Land Surface/Agriculture Indicators
Satellite monitoring of climatic factors regulating phytoplankton variability in the Arabian (Persian) Gulf (2010)

Possible factors regulating phytoplankton variability in the Arabian (Persian) Gulf were analyzed on the basis of satellite observations and meteorological data (19972009), including remotely-sensed chlorophyll a concentration (CHL), sea surface temperature, wind, solar radiation, precipitation, and aerosols. Shallow waters of northwestern Gulf influenced by Shatt Al-Arab River discharge were more productive than open Gulf waters, although seasonal CHL patterns in this and other shallow regions looked unrealistic likely because the CHL signal was obscured by bottom reflection. Therefore our further analyses focused on the open Gulf waters, which show a subtropical seasonal CHL cycle with maximum in winter and minimum in springsummer. This cycle, however, was decoupled from the seasonal extremes of wind mixing. Interannual variations of CHL in the open Gulf regions were correlated with precipitation and aerosol data rather than with wind and sea surface temperature, consistent with the hypothesis of atmospheric deposition as a factor regulating phytoplankton growth. The effect of dust fertilization was likely observed in 2000 and 2008, when low precipitation and aerosol properties indicating elevated level of aeolian dust transport were followed by phytoplankton blooms.

Research areas: Ecosystems
Saharan dust infrared optical depth and altitude retrieved from AIRS: a focus over North Atlantic  comparison to MODIS and CALIPSO (2010)

Abstract. Monthly mean infrared (10 m) dust layer aerosol optical depth (AOD) and mean altitude are simultaneously retrieved over the tropics (30 S30 N) from almost seven years of Atmospheric Infrared Sounder (AIRS) observations covering the period January 2003 to September 2009. The method developed relies on the construction of look-up-tables computed for a large selection of atmospheric situations and follows two main steps: first, determination of the observed atmospheric thermodynamic situation and, second, determination of the dust properties. A very good agreement is found between AIRS-retrieved AODs and visible optical depths from the Moderate resolution Imaging Spectroradiometer (MODIS/Aqua) during the main (summer) dust season, in particular for three regions of the tropical North Atlantic and one region of the north-western Indian Ocean. Outside this season, differences are mostly due to the sensitivity of MODIS to aerosol species other than dust and to the more specific sensitivity of AIRS to the dust coarse mode. AIRS-retrieved dust layer mean altitudes are compared to the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP/CALIPSO) aerosol mean layer altitude for the period June 2006 to June 2009. Results for a region of the north tropical Atlantic downwind of the Sahara show a good agreement between the two products (360 m). Differences observed in the peak-to-trough seasonal amplitude, smaller from AIRS, are principally attributed to the large difference in spatial sampling of the two instruments. They also come from the intrinsic limit in sensitivity of the passive infrared sounders for low altitudes. These results demonstrate the capability of high resolution infrared sounders to measure not only dust aerosol AOD but also the mean dust layer altitude.

Research areas: Validation
Reproduction of the Cortes Geoduck Panopea globosa (Bivalvia: Hiatellidae) and Its Relationship with Temperature and Ocean Productivity (2010)

This article describes the timing of gametogenic development and spawning in a population of geoduck clams, Panopea globosa (Dall 1898), from the Upper Gulf of California and its relationship to temperature changes and primary productivity. Clams were collected monthly over 1 year (March 2008 to March 2009), and salinity, dissolved oxygen, and substrate type were recorded during each survey. Standard histological analyses and measurements of oocyte diameters were used to describe the timing of gametogenic development and spawning. Satellite data for temperature and chlorophyll were gathered to test a general conceptual planktonic larval development model. The results demonstrated that reproductive activity was triggered by a steep decrease in temperature 4 months prior to the peak of productivity. Thus, larval development matches favorable conditions, as predicted by Cushing's MatchMismatch Hypothesis.

Research areas: Ecosystems
Regression models for the estimation of carbon exchange in boreal forests (2010)

Based on the measurements of the carbon dioxide fluxes at a few sites of the global FLUXNET network, we developed linear regression models for the estimation of the carbon budget of boreal forests. The model estimates satisfactorily agree with the measurement data obtained in the boreal forests of Canada (Manitoba, Thompson) and Russia (Krasnoyarsk krai, Zotino). The correlation coefficient between the calculations and measurements for a coniferous forests exceeds 0.9, with the annually mean model error in the budget estimate, as compared to the experimental results, not exceeding 50 gC/m2/yr. Using satellite and ground-based meteorological data, we calculated the monthly average carbon budget of the coniferous forests of Krasnoyarsk krai in 2001. Based on the satellite classification of the vegetation cover, we plotted monthly and annually average maps of the carbon budget that reflect the spatiotemporal distribution of the CO2 uptake and emission rates. It is shown that the coniferous forests of Krasnoyarsk krai are mostly a carbon sink, uptaking as much as 300 gC/m2 throughout the growing season.

Research areas: Ecosystems
Recent Trends Towards Oligotrophication of the Northern Adriatic: Evidence from Chlorophyll a Time Series (2010)

The results of the updated and quality-checked data base of field observations on chlorophyll a (Chl a) collected in the period 1970-2007 in the Northern Adriatic Sea are presented. From the last decade, SeaWiFS satellite information was also considered. Results demonstrate a global tendency towards Chl a reduction in the period of investigation, which is more marked in the eutrophic area under the influence of the Po River. In the rest of the basin, which presents meso-or oligotrophic characteristics, long-term changes are more difficult to detect. The long-term field dataset can be divided into two periods: the last decade characterized by the strong decrease observed in the whole northern Adriatic and the earlier period with no or slight increase. The recent substantial reduction of Chl a concentrations is confirmed all over the basin (-0.11 mg m3 year1) from satellite-derived information. Results are consistent with recently evidenced decrease in concentrations of phosphate and ammonia and point to the existence of oligotrophication in the Northern Adriatic. Results indicate forcefully that the still common perception of the Adriatic Sea as a very eutrophic basin is no longer appropriate, at least for its northern part and in recent years.

Research areas: Water Quality