nasa-gesdisc/es-publications-researchareas huggingface dataset:
Variations of methane in the Antarctic atmosphere in 2009-2017 by ground-based and satellite data (2020)

The article presents the results of systematic measurements (20092017) of the total column abundances of methane (TC_CH4 ) and the column-averaged concentration (X_CH 4 ) at the Antarctic station Novolazarevskaya. Solar radiation is recorded in the range 2990  3006 cm 1 using a diffraction spectrometer with 0.2 cm 1 resolution. The inverse task CH 4 total column determining is achieved using the SFIT4 v0.9.4.4 code. The analysis shows that during the measurement period the average TC_CH4 was (3.40.8).10 19 molecules/cm 2 during the measurement period, and the average X_CH 4 is (166334) ppbv. TC_CH 4 trend is (4.52.2).10 15 molecules/cm 2 /month, and X_CH4 trend is (0.28  0.11) ppbv/month. The average TC_CH 4 values and trend at Novolazarevskaya are in good agreement with the measurements by the Brucker120HR instrument at the Arrival Heights station. Seasonal variations of atmospheric methane have the maximum in OctoberNovember and the minimum in MayJuly. The trends of surface methane concentrations at Sywa, the Halley station and the Amundsen-Scott South Pole station are 0.59  0.61 ppbv/month and exceed the trend of the column-averaged concentration at Novolazarevskaya and AIRS trends for the troposphere (0.24  0.32) ppbv/month, due to a decrease in the maximal values of TC_CH4 in the period after 2014. The closest agreement of X_CH 4 variations at Novolazarevskaya with AIRS data is observed at the levels of 150200 hPa. Significant semiannual harmonics varied with height are characteristic of CH4 variations according to the AIRS data. The interference of annual and semiannual harmonics leads to the appearance of two maxima in the seasonal variations of methane with relative position to each other varies with height. The statistical model is developed for all the series considered. It approximates the trend, annual and semi-annual components of CH4 oscillations.

Research areas: Greenhouse Gases
Seasonal Shift of the Diurnal Cycle of Rainfall Over Medellin's Valley, Central Andes of Colombia (1998-2005) (2019)

The spatiotemporal variability of precipitation in regions of complex mountainous terrains constitutes one of the most challenging research topics of geosciences. This paper explores hourly precipitation data from a set of 25 stations spanning the period 1998 to 2005 within northwestern Colombia, in the Aburra Valley and the neighboring San Nicolas plateau (75.16W-6N and 75.66W-6.6N) which accounts for a land area of approximately 4000 km2. Our aim is to identify the main features of the diurnal cycle of precipitation over this complex terrain. We found that the average diurnal cycle of rainfall in the study region is bimodal at regional scale although it results from the superposition of two unimodal diurnal cycles shifting its phase throughout the seasons of the year. From October to April, average diurnal rainfall peaks in the afternoon hours (13:00-16:00 LST) but from May to September, the phase of the diurnal cycle changes to midnight hours (22:00-02:00 LST). Three low-level jets (LLJs), namely Caribbean, CHOCO, and the so-called Corriente de los Andes Orientales (CAO), are relevant to explain the seasonal shift of the diurnal cycle given their modulation of the seasonal variation of moisture sources and transport over this region. During June-July-August, moisture from afternoon evaporation processes at the bottom of the inter-Andean Magdalena Valley, located at the east of the study region, is transported by anabatic and easterly trade winds and contribute to explain the midnight and early morning peak. The life cycle of convective processes influences the orographic nature of rainfall distribution and timing in the region since deep convective cores are related with the afternoon peak, whereas wide convective cores with the early morning peak.

Research areas: Validation
Kilauea lava fuels phytoplankton bloom in the North Pacific Ocean (2019)

Ocean greening off Hawai'i
From June to August 2018, the eruption of Kilauea volcano triggered a diatom-dominated phytoplankton bloom. Wilson et al. set sail to sample the plume, deploying subsea gliders and using satellite monitoring to measure the dynamics of this rare event in the nutrient-poor Pacific (see the Perspective by Ducklow and Plank). They found subsurface chlorophyll maxima not visible by remote sensing, performed transcriptome and N isotope marker analysis, and measured nutrients, partitioning of biomass into different organisms, and primary production. Much of the data are corroborated by physical modeling of the ocean dynamics. The authors conclude that the plume was fed by the lava heating subsurface water and triggering upwelling of deepwater nutrients to the surface rather than by direct injection of micronutrients from lava.
Science, this issue p. 1040; see also p. 978
From June to August 2018, the eruption of Kilauea volcano on the island of Hawaii injected millions of cubic meters of molten lava into the nutrient-poor waters of the North Pacific Subtropical Gyre. The lava-impacted seawater was characterized by high concentrations of metals and nutrients that stimulated phytoplankton growth, resulting in an extensive plume of chlorophyll a that was detectable by satellite. Chemical and molecular evidence revealed that this biological response hinged on unexpectedly high concentrations of nitrate, despite the negligible quantities of nitrogen in basaltic lava. We hypothesize that the high nitrate was caused by buoyant plumes of nutrient-rich deep waters created by the substantial input of lava into the ocean. This large-scale ocean fertilization was therefore a unique perturbation event that revealed how marine ecosystems respond to exogenous inputs of nutrients.
Volcanic eruptioninduced upwelling generated a phytoplankton bloom in nutrient-poor oceanic waters.
Volcanic eruptioninduced upwelling generated a phytoplankton bloom in nutrient-poor oceanic waters.

Research areas: Volcanic Eruptions, Water Quality
Anomalous transboundary transport of the products of biomass burning from North American wildfires to Northern Eurasia (2017)

An analysis of smoke in the atmosphere over the Russian Far East and Eastern Siberia in August 2004 was carried out. The results of the analysis indicate that the cause of the smoke in the atmosphere over these regions (with the values of aerosol optical depth exceeding 4 over the north of Kamchatka Krai) was the long-range transboundary transport of combustion products from North American wildfires. The anomalous (westward) long-range transport of the products of biomass burning was caused by atmospheric circulation characteristic for the atmospheric blocking of the dipole-type with a high-pressure region over the Chukchi Sea and a low pressure region over the south of the Bering Sea.

Research areas: Environmental Impacts, Wildfires
Hydrological differentiation and spatial distribution of high altitude wetlands in a semi-arid Andean region derived from satellite data (2011)

Abstract. High Altitude Wetlands of the Andes (HAWA) belong to a unique type of wetland within the semi-arid high Andean region. Knowledge about HAWA has been derived mainly from studies at single sites within different parts of the Andes at only small time scales. On the one hand, HAWA depend on water provided by glacier streams, snow melt or precipitation. On the other hand, they are suspected to influence hydrology through water retention and vegetation growth altering stream flow velocity. We derived HAWA land cover from satellite data at regional scale and analysed changes in connection with precipitation over the last decade. Perennial and temporal HAWA subtypes can be distinguished by seasonal changes of photosynthetically active vegetation (PAV) indicating the perennial or temporal availability of water during the year. HAWA have been delineated within a region of 12 800 km2 situated in the Northwest of Lake Titicaca. The multi-temporal classification method used Normalized Differenced Vegetation Index (NDVI) and Normalized Differenced Infrared Index (NDII) data derived from two Landsat ETM+ scenes at the end of austral winter (September 2000) and at the end of austral summer (May 2001). The mapping result indicates an unexpected high abundance of HAWA covering about 800 km2 of the study region (6 %). Annual HAWA mapping was computed using NDVI 16-day composites of Moderate Resolution Imaging Spectroradiometer (MODIS). Analyses on the relation between HAWA and precipitation was based on monthly precipitation data of the Tropical Rain Measurement Mission (TRMM 3B43) and MODIS Eight Day Maximum Snow Extent data (MOD10A2) from 2000 to 2010. We found HAWA subtype specific dependencies on precipitation conditions. A strong relation exists between perennial HAWA and snow fall (r2: 0.82) in dry austral winter months (June to August) and between temporal HAWA and precipitation (r2: 0.75) during austral summer (March to May). Annual changes in spatial extend of perennial HAWA indicate alterations in annual water supply generated from snow melt.

Research areas: Land Surface/Agriculture Indicators
Transported Mineral Dust Deposition Case Study at a Hydrologically Sensitive Mountain Site: Size and Composition Shifts in Ambient Aerosol and Snowpack (2016)

ABSTRACTTransported mineral dust deposition to remote mountain snow decreases snow albedo and increases absorption of solar radiation, which accelerates snowpack melt and alters water supply. Mineralogy and chemical composition determine dust particle optical properties, which vary by source region. While impacts of dust deposition at remote mountain sites have been established, few studies have connected the chemical composition of ambient particles during deposition events with the properties of those deposited on the snowpack. Ambient particles and surface snow were sampled in the San Juan Mountains of southwestern Colorado, which frequently experiences dust deposition in the spring and has evidence of dust-enhanced snow melt. Individual particles were analyzed using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The number concentration and size distribution of insoluble residues in the top level of snow were determined with nanoparticle tracking analysis (NTA). During a minor dust event (April 23, 2015), the fraction of absorbing iron-enriched dust in the ambient aerosol, the number concentration, and size of insoluble residues in snow all increased. This can be traced to shifts in mineral dust source region within the Colorado Plateau, during which, there were higher wind speeds leading to increased transport. The shift in chemical composition and mineralogy of the transported dust has the potential to impact snowpack radiative forcing during dry deposition. In addition, it can also modify the snowpack through scavenging of particles during wet deposition, as well as alter the properties of clouds and orographic precipitation. Understanding these impacts is crucial to understanding the hydrological cycle at remote mountain sites.

Research areas: Cryospheric Indicators, Sun-Earth Interactions
Satellite and ground-based remote sensing of aerosols during intense haze event of October 2013 over lahore, Pakistan (2016)

Due to increase in population and economic development, the mega-cities are facing increased haze events which are causing important effects on the regional environment and climate. In order to understand these effects, we require an in-depth knowledge of optical and physical properties of aerosols in intense haze conditions. In this paper an effort has been made to analyze the microphysical and optical properties of aerosols during intense haze event over mega-city of Lahore by using remote sensing data obtained from satellites (Terra/Aqua Moderate-resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)) and ground based instrument (AErosol RObotic NETwork (AERONET)) during 6-14 October 2013. The instantaneous highest value of Aerosol Optical Depth (AOD) is observed to be 3.70 on 9 October 2013 followed by 3.12 on 8 October 2013. The primary cause of such high values is large scale crop residue burning and urban-industrial emissions in the study region. AERONET observations show daily mean AOD of 2.36 which is eight times higher than the observed values on normal day. The observed fine mode volume concentration is more than 1.5 times greater than the coarse mode volume concentration on the high aerosol burden day. We also find high values (~0.95) of Single Scattering Albedo (SSA) on 9 October 2013. Scatter-plot between AOD (500 nm) and Angstrom exponent (440-870 nm) reveals that biomass burning/urban-industrial aerosols are the dominant aerosol type on the heavy aerosol loading day over Lahore. MODIS fire activity image suggests that the areas in the southeast of Lahore across the border with India are dominated by biomass burning activities. A Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model backward trajectory showed that the winds at 1000 m above the ground are responsible for transport from southeast region of biomass burning to Lahore. CALIPSO derived sub-types of aerosols with vertical profile taken on 10 October 2013 segregates the wide spread aerosol burden as smoke, polluted continental and dust aerosols.

Research areas: Air Quality
Luminescence and density banding patterns in massive Porites corals around the Thai-Malay Peninsula, Southeast Asia (2016)

We characterized the annual luminescent and skeletal density banding patterns in 51 massive Porites corals from 15 reefs from six locations around the Thai-Malay Peninsula in Southeast Asia, and explored the seasonal environmental cues/drivers of band formation. Location-specific recurrent annual luminescent banding patterns were found at all study locations with a brighter band occurring toward the end of the year (October/November/December) (at five locations) and in June (one location). Annual density banding patterns could only be discerned at four locations, and were categorized into those that formed a dense band commencing November/December, and those starting May/June. Overall, compared to luminescence, variations in skeletal density provided a less clear signal for demarcation of annual growth increments. Seasonal variations in luminescence showed clearest relationships with salinity, as a proxy for freshwater/river runoff. No convincing relationship between intra-annual luminescence intensity and density variations was found, which supports the notion that luminescent banding is due to inclusions of fluorophores into the coral skeleton rather than variations in skeletal architecture. The relationships between seasonal density variations and significant wave height and rainfall suggest density banding in this region is likely related to wave energy, or some other correlated environmental parameter/s. The large variability in skeletal banding patterns not only highlights the current relatively poor understanding of their nature and causes, but also the need for replication in their interpretation, especially in settings with complex seasonal hydrodynamic/hydrological patterns such as those found around the Thai-Malay Peninsula.

Research areas: Ecosystems, Atmospheric/Ocean Indicators
Latitudinal distribution of extant fossilizable phytoplankton in the Southern Ocean: Planktonic provinces, hydrographic fronts and palaeoecological perspectives (2016)

We present the combined abundance of all extant fossilizable planktonic groups (Dinoflagellates, Coccolithophores, Silicoflagellates, Diatoms, Parmales, Archaeomonads and micro-zooplankton) from surface waters collected along a latitudinal transect in the western Pacific sector of the Southern Ocean, ranging from ~48S, offshore New Zealand, to ~70S in the Ross Sea, Antarctica. Latitudinal shifts in species' distribution correspond with the Antarctic Circumpolar Current fronts and with the seasonal position of the ice-edge. Distinct bioprovinces are defined by clustering samples with a high degree of similarity. Our data confirm the importance of previously-defined taxa as palaeoceanographic proxies but also reveal some differences: the shift in dominance between the silicoflagellates genera Dictyocha and Stephanocha, used as a proxy of palaeo sea-surface temperatures, occurs slightly north of the Southern Sub-Antarctic Front rather than at the Polar Front; the shifts in abundance between the open-ocean diatom species Fragilariopsis kerguelensis and sea-ice related F. curta and F. cylindrus, as well as the drop in the coccolithophore Emiliania huxleyi, occur at the southern Antarctic Circumpolar Front rather than at the Polar Front. Finally, we introduce the Corona-index, based on the ratio of the coronatid to non-coronatid silicoflagellates species Stephanocha speculum, as a new proxy for sea-ice and we confirm the occurrence of abundant Archaeomonads and Parmales (Triparma laevis subsp. ramispina) in the marginal ice-edge zone.

Research areas: Ecosystems
Influence of Climate Extremes and Land Use on Fecal Contamination of Shallow Tubewells in Bangladesh (2016)

Climate extremes in conjunction with some land use practices are expected to have large impacts on water quality. However, the impacts of land use and climate change on fecal contamination of groundwater has not been well characterized. This work quantifies the influences of extreme weather events and land use practices on Escherichia coli presence and concentration in groundwater from 125 shallow wells, a dominant drinking water resource in rural Bangladesh, monitored over a 17 month period. The results showed that E. coli presence was significantly associated with the number of heavy rain days, developed land and areas with more surface water. These variables also had significant impacts on E. coli concentration, with risk ratios of 1.38 (95% CI = 1.16, 1.65), 1.07 (95% CI: 1.05, 1.09), and 1.02 (95% CI = 1.01, 1.03), respectively. Significant synergistic effects on E. coli presence and concentration were observed when land use and weather variables were combined. The findings suggest that climate extremes and land use practices, particularly urbanization, might promote fecal contamination of shallow well water, thus increasing the risk of diarrheal diseases.

Research areas: Water Quality, Public Health, Habitat Conversion/Fragmentation, Atmospheric/Ocean Indicators
Global fine-mode aerosol radiative effect, as constrained by comprehensive observations (2016)

Abstract. Aerosols directly affect the radiative balance of the Earth through the absorption and scattering of solar radiation. Although the contributions of absorption (heating) and scattering (cooling) of sunlight have proved difficult to quantify, the consensus is that anthropogenic aerosols cool the climate, partially offsetting the warming by rising greenhouse gas concentrations. Recent estimates of global direct anthropogenic aerosol radiative forcing (i.e., global radiative forcing due to aerosolradiation interactions) are 0.35  0.5 W m2, and these estimates depend heavily on aerosol simulation. Here, we integrate a comprehensive suite of satellite and ground-based observations to constrain total aerosol optical depth (AOD), its fine-mode fraction, the vertical distribution of aerosols and clouds, and the collocation of clouds and overlying aerosols. We find that the direct fine-mode aerosol radiative effect is 0.46 W m2 (0.54 to 0.39 W m2). Fine-mode aerosols include sea salt and dust aerosols, and we find that these natural aerosols result in a very large cooling (0.44 to 0.26 W m2) when constrained by observations. When the contribution of these natural aerosols is subtracted from the fine-mode radiative effect, the net becomes 0.11 (0.28 to +0.05) W m2. This net arises from total (natural + anthropogenic) carbonaceous, sulfate and nitrate aerosols, which suggests that global direct anthropogenic aerosol radiative forcing is less negative than 0.35 W m2.

Research areas: Atmospheric/Ocean Indicators
Genetic population structure and low genetic diversity in the over-exploited sea cucumber Holothuria edulis Lesson, 1830 (Echinodermata: Holothuroidea) in Okinawa Island (2016)

Understanding genetic connectivity is fundamental for ecosystem-based management of marine resources. Here we investigate the metapopulation structure of the edible sea cucumber Holothuria edulis Lesson, 1830 across Okinawa Island, Japan. This species is of economic and ecological importance and is distributed from the Red Sea to Hawaii. We examined sequence variation in fragments of mitochondrial cytochrome oxidase subunit I (COI) and 16S ribosomal RNA (16S), and nuclear histone (H3) at six locations across Okinawa Island. We found higher haplotype diversity for mtDNA (COI: Hd = 0.69 and 16S: Hd = 0.67) and higher heterozygosity of nDNA (H3: HE = 0.39) in populations from the west coast of Okinawa compared to individuals from populations on the east coast (COI: Hd = 0.40; 16S: Hd = 0.21; H3: HE = 0.14). Overall population structure was significant (AMOVA results for COI: ST = 0.49, P 

Research areas: Ecosystems
Fossil and Nonfossil Sources of Organic and Elemental Carbon Aerosols in the Outflow from Northeast China (2016)

Source quantification of carbonaceous aerosols in the Chinese outflow regions still remains uncertain despite their high mass concentrations. Here, we unambiguously quantified fossil and nonfossil contributions to elemental carbon (EC) and organic carbon (OC) of total suspended particles (TSP) from a regional receptor site in the outflow of Northeast China using radiocarbon measurement. OC and EC concentrations were lower in summer, representing mainly marine air, than in other seasons, when air masses mostly traveled over continental regions in Mongolia and northeast China. The annual-mean contribution from fossil-fuel combustion to EC was 76  11% (0.11.3 g m3). The remaining 24  11% (0.030.42 g m3) was attributed to biomass burning, with slightly higher contribution in the cold period (31%) compared to the warm period (21%) because of enhanced emissions from regional biomass combustion sources in China. OC was generally dominated by nonfossil sources, with an annual average of 66  11% (0.52.8 g m3), approximately half of which was apportioned to primary biomass-burning sources (34  6%). In winter, OC almost equally originated from primary OC (POC) emissions and secondary OC (SOC) formation from fossil fuel and biomass-burning sources. In contrast, summertime OC was dominated by primary biogenic emissions as well as secondary production from biogenic and biomass-burning sources, but fossil-derived SOC was the smallest contributor. Distinction of POC and SOC was performed using primary POC-to-EC emission ratios separated for fossil and nonfossil emissions.

Research areas: Energy Production/Use, Environmental Impacts