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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Connecting Space to Village: Tethys Adoption Within SERVIR

The SERVIR program, a joint development initiative of National Aeronautics and Space Administration (NASA) and United States Agency for International Development (USAID), works in partnership with leading regional organizations world-wide to help developing countries use information provided by Earth observing satellites and geospatial technologies for managing climate risks and land use. SERVIR empowers decision-makers with tools, products, and services to act locally on critical issues related to four key areas: Food Security and Agriculture, Water and Water-related Disasters, Land Use/Land Cover and Ecosystems, Weather and Climate. SERVIR is improving awareness, increasing access to information, and supporting analysis to help people in West Africa, Eastern and Southern Africa, Hindu Kush-Himalaya (HKH), the Lower Mekong, South America and Mesoamerica. NASA funds an Applied Sciences Team (AST), composed of experts from universities and research institutions around the United States. Through AST, SERVIR adopted the Tethys platform introduced by Brigham Young University (BYU) for the implementation of tools to deliver scientific data to stakeholders in the Hindu Kush-Himalaya region. Several Tethys applications developed within SERVIR have raised interest amongst decision makers in the countries served by our regional hubs. They see these new apps as key vehicles to disseminate complex information related to weather models, hydrological models, and air quality monitoring, and as such the scope of our Tethys efforts continue to expand to other regions. As of July 2019, each one of the SERVIR hubs (with the exception of Amazonia, which has only recently started), have stood up Tethys portals and have at least one individual trained in the implementation and maintenance of a Tethys portal and in the creation of basic applications. HKH, with BYU's valuable support, has implemented very sophisticated applications that showcase the possibilities and the benefits that the Tethys platform brings.

Tethys↗
NASA NTRS2019

Aerosol Properties Over Tibetan Plateau From a Decade of AERONET Measurements: Baseline, Types, and Influencing Factors

In this study, a decade long measurement of aerosol optical properties at two AERONET stations (Nam Co during 2006–2016 and QOMS during 2009–2017) in the Tibetan Plateau (TP), a region sensitive to climate change and human perturbation, is presented. The baseline value of aerosol optical depth (AOD) was 0.029 and 0.027 at Nam Co and QOMS, respectively, which are comparable to or even lower than those at some Arctic and remote ocean locations. The seasonality of AOD values were the order of spring > summer > winter > autumn. Based on AOD and Ångström exponent (α), major aerosol types over the TP were further identified as continental background, biomass burning, and dust. Although continental background aerosol was the main feature in remote areas of TP, biomass burning plumes frequently occurred, especially during spring (March–April). In one of such biomass burning event in April 2014, MODIS observations demonstrated that intensive open fires occurred in South Asia, covering the foothills of Himalayas and Indo‐Gangetic Plain. The air mass back trajectories and CALIOP observations further revealed that biomass burning plume could be uplifted to higher altitudes and reach the Himalayas. Moreover, an occasional dust event detected in April 2008 over the TP demonstrated that the dust from Taklamakan Desert may impact the main body of TP episodically, although the local dust from the inside of TP cannot be excluded and warrants further study.

Manisha Pokharel↗
DOE OSTI2021

Hydrologic Regionalization under Data Scarcity: Implications for Streamflow Prediction

Continuous streamflow prediction is crucial in many applications of water resources planning and management. However, streamflow prediction is challenging, particularly in data-scarce regions. Here, we demonstrate an approach to regionalize the flow duration curve for predicting daily streamflow in the data-scare region of the central Himalayas. We developed a regression-based model to estimate streamflow at various segments of a flow duration curve by incorporating basin characteristics and climate variables. This study analyzes the sensitivities of proximity and characteristics between the donor (gauged) and receptor (ungauged) basins for time-series streamflow prediction. Our results show that regionalization techniques perform better in low to medium flows over high flows. Our findings are significant in the central Himalayan regional context to inform operational and management decisions in water sector projects like hydropower plants, which generally rely on low-to-medium streamflow information. Although the quantitative results are region-specific, the approach and insights are generalizable to the Himalayan region.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2016

Monitoring Intense Thunderstorms in the Hindu-Kush Himalayan Region

Some of the most intense thunderstorms on the planet routinely occur in the Hindu-Kush Himalaya region(HKH) region where many government organizations lack the capacity needed to predict, observe and effectively respond to the threats and hazards associated with high impact convective weather. This project combines innovative numerical weather prediction, satellite-based precipitation and land imagery techniques into a high impact weather assessment toolkit (HIWAT) that will build the capabilities of national meteorological departments and other weather sensitive agencies in the HKH region to assess the potential threats and impacts of high impact convective weather.

Himalayas↗
DOE OSTI2023

Reciprocal transplants reveal asymmetric local adaptation of Himalayan Rhododendron approaching elevational range limit

Abstract As plant species expand their upper limits of distribution under current warming, some retain both traditional climate space and biotic environment while others encounter novel conditions. The latter is the case for Rhododendron campanulatum , a woody shrub that grows both above and below treeline at our study site in the Eastern Himalayas where a very conspicuous, stable treeline was defined by a nearly contiguous canopy of tall Abies spectabilis trees, many of which are over a century old. Prior work showed that treeline had remained static in this region while R. campanulatum expanded its elevational range limit. We tested local adaptation of R. campanulatum by performing reciprocal transplants between the species' current elevational range limit (4023 m above sea level [asl]) and just above treeline (3876 m asl). Contrary to expectation, the coldest temperatures of late winter and early mid‐spring were experienced by plants at the lower elevation: R. campanulatum at species' limit (upper site) were covered by snow for a longer period (40 more days) and escaped the coldest temperatures suffered by conspecifics at treeline (lower site). The harsher spring conditions at treeline likely explain why leaves were smaller at treeline (15.3 cm 2 ) than at species limit (21.3 cm 2 ). Contrary to results from equivalent studies in other regions, survival was reduced more by downslope than by upslope movement, again potentially due to extreme cold temperatures observed at treeline in spring. Upslope transplantation had no effect on mortality, but mortality of species limit saplings transplanted downslope was three times higher than that of residents at both sites. A general expectation is that locals should survive better than foreign transplants, but survival of locals and immigrants at our species limit site was identical. However, those species limit saplings that survived the transplant to treeline grew faster than both locals at treeline and the transplants at species limit. Overall, we found asymmetric adaptation: Compared with treeline saplings, those at species limit (147 m above treeline) were more tolerant of extremes in the growing season but less tolerant of extremes in winter and early mid‐spring, displaying local adaptation in a more complex manner than simply home advantage, and complicating predictions about impacts of future regional climate change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Weather radar in Nepal: opportunities and challenges in a mountainous region

Extreme rainfall is one of the major causes of natural hazards in the central Himalayan region, including Nepal. The performance of strategies to manage hazards and related risks relies on the accuracy of quantitative hydrometeorological prediction. Rain gauges have traditionally been used to measure the rainfall amount. However, point measurements with limited gauge coverage cannot accurately represent spatial precipitation variability in complex topography. Weather radar have shown potential for useful information on accurate areal rainfall estimates. The Department of Hydrology and Meteorology (DHM) in Nepal installed their first weather radar in 2019 in the western region of the country. Two more radars will be added to the planned radar network in the near future, in the country's central and eastern regions, respectively. We highlight both the opportunities and challenges with radar installation and observation in the mountainous regions. Radar-rainfall estimates across the Himalayas can be useful to inform decision-making in a broad range of infrastructure sectors, including water, energy, construction, transportation, and agriculture.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

A review of black carbon in snow and ice and its impact on the cryosphere

Black carbon (BC) has emerged as an important short-lived climate forcer. Due to its light absorption properties, BC can darken the snow/ice surface, affect the energy balance, and further lead to acceleration of the cryospheric melting. By reviewing the recent published literatures, we present an overview of the historical changes, spatial distribution of BC in snow/ice, and how these changes are related to the melting of the cryosphere (e.g., glaciers, snow cover, and sea ice). Ice core records show an abrupt increase of BC concentrations that began in the 1850s and continued throughout the 20th century, which is consistent with an increase in BC emissions owing to industrialization. A decrease in the amount of BC since 1970s in Arctic and European ice cores has been partially attributed to the Clean Air Act. However, in the Himalayas, BC records show a continuous increase during this period. BC concentrations in snow and ice in the mid-latitude regions are one to two orders of magnitude higher than those in the polar regions. In particular, BC concentrations in aged snow and granular ice in ablation areas of mountain glaciers are one to three orders of magnitude higher than those in fresh snow or snowpits in the glacier accumulation areas due to BC accumulation during melting season. BC in the surface snow/ice is responsible for about 20% of the albedo reduction in the Tibetan Plateau during glacier melt season. Globally, observations and modeling results indicate that radiative forcing (RF) induced by BC in snow and ice is highest in the mid-latitudes, ranging from several W m–2 in fresh snow to hundreds of W m–2 in aged snow and granular ice in glacier ablation areas. The large BC-in-snow RF and associated snow albedo feedback lead to an acceleration in the total glacier melt (approximately 20%) and/or a reduction in the duration of the snow cover by several days, resulting in an increase of glacier discharge. Given our limited understanding of the role of BC in cryospheric melting, it is important to synthesize the existing research on the multi-scale processes related to BC in snow and ice to identify the gaps in our understanding of these processes and to propose a path forward to improve the quality of our observations of the aforementioned phenomena to fill these gaps.

Kang, Shichang↗
DOE OSTI2021

Characterizing uncertainties in ground “truth” of precipitation over complex terrain through high-resolution numerical modeling

Ground observation of precipitation over complex terrain is subject to large uncertainties due to inadequate sampling. This study explores a method that combines limited gauge data and a high-resolution numerical simulation to quantify the precipitation uncertainties in central Himalaya. Specifically, the Coefficient of spatial Variability (CV) of precipitation and the minimum Number of Required Stations (NRS) to obtain areal-mean precipitation ground truth values within a 0.25-degree area are investigated using fine-scale meteorological simulation at 1.5 km grid spacing. Evaluation over a densely-gauged area demonstrates comparable CV and NRS values between station observations and simulations. The simulated CV and NRS values in a larger area show a strong and positive dependence on each other and an expected positive (negative) correlation with topographic complexity (temporal scale). The proposed method sheds lights on evaluating precipitation products and holds promise for informing the layout of rain gauge networks in complex terrain.

Ouyang, Lin↗
DOE OSTI2023

Incorporating the Effect of Large‐Scale Vertical Motion on Convection Through Convective Mass Flux Adjustment in E3SMv2

Abstract Recent observational studies suggest that the large‐scale dynamical forcing (vertical motion) plays important roles in deep convection development. In this study we propose a convective mass flux adjustment (MAdj) approach to represent the dynamical effects of large‐scale vertical motion on convection in the Department of Energy's Energy Exascale Earth System Model version 2 (E3SMv2). With MAdj, convection is enhanced (suppressed) when there is large‐scale ascending (descending) motion at the planetary boundary layer top. The coupling of convection with large‐scale circulation significantly improves the simulation of climate variability in E3SMv2 across multiple scales from the diurnal cycle, convectively coupled equatorial waves, to the Madden‐Julian Oscillation (MJO). The standard E3SMv2 tends to simulate overly weak diurnal amplitude of precipitation and overly weak variance of convectively coupled equatorial Kelvin and westward inertio‐gravity (WIG) waves. It also fails to simulate the essential characteristics of the MJO: continuous eastward propagation. With MAdj, the amplitude of diurnal cycle of precipitation is systematically increased and its probability density distribution is much closer to observations. The MAdj can also simulate more realistic eastward propagation of the MJO and much stronger convectively coupled Kelvin and WIG waves. Moreover, the MAdj approach slightly improves the climatology simulations in precipitation, cloud, radiation, circulation, temperature, and moisture fields, with overall root‐mean‐square error (RMSE) of major climatological fields reduced by about 2%. The MAdj approach suppresses excessive grid‐scale precipitation, reducing precipitation wet biases over South China Sea, Philippine Sea, Himalayas, and South Pacific Convergence Zone in western Pacific in summer.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Permafrost in the Cretaceous supergreenhouse

Earth’s climate during the last 4.6 billion years has changed repeatedly between cold (icehouse) and warm (greenhouse) conditions. The hottest conditions (supergreenhouse) are widely assumed to have lacked an active cryosphere. Here we show that during the archetypal supergreenhouse Cretaceous Earth, an active cryosphere with permafrost existed in Chinese plateau deserts (astrochonological age ca. 132.49–132.17 Ma), and that a modern analogue for these plateau cryospheric conditions is the aeolian–permafrost system we report from the Qiongkuai Lebashi Lake area, Xinjiang Uygur Autonomous Region, China. Significantly, Cretaceous plateau permafrost was coeval with largely marine cryospheric indicators in the Arctic and Australia, indicating a strong coupling of the ocean–atmosphere system. The Cretaceous permafrost contained a rich microbiome at subtropical palaeolatitude and 3–4 km palaeoaltitude, analogous to recent permafrost in the western Himalayas. A mindset of persistent ice-free greenhouse conditions during the Cretaceous has stifled consideration of permafrost thaw as a contributor of C and nutrients to the palaeo-oceans and palaeo-atmosphere.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Structural basis for saxitoxin congener binding and neutralization by anuran saxiphilins

Dinoflagellates and cyanobacteria produce saxitoxin (STX) and ~50 congeners that disrupt bioelectrical signals by blocking voltage-gated sodium channels (NaVs). Consuming seafood carrying these toxins causes paralytic shellfish poisoning (PSP). Although NaVs and anuran STX binding proteins (saxiphilins, Sxphs) use convergent STX binding modes, the structural basis for STX congener recognition is unknown. Here, we show that American bullfrog (Rana catesbeiana) RcSxph and High Himalaya frog (Nanorana parkeri) NpSxph sequester STX congeners using a ‘lock and key’ mode shared with STX. Importantly, functional studies demonstrate that Sxph ‘toxin sponges’ reverse NaV block by multiple STX congeners and detect these toxins in a radioligand binding assay (RBA) used for environmental testing. Together, our study establishes how Sxphs sequester select neurotoxins and uncover STX congener-specific interactions distinct from NaVs. These findings expand understanding of toxin sponge action and provide a foundation for strategies to monitor and mitigate the harmful effects of STX congeners.

Zakrzewska, Sandra↗
DOE OSTI2023

Influence of monsoon low pressure systems on South Asian disasters and implications for disaster prediction

Transient atmospheric vortices called monsoon low pressure systems (LPS) generate a large fraction of total rainfall over South Asia and often produce extreme precipitation. Here, we assess the influence of these storms on the occurrence of disasters, using information from the Emergency Events Database (EM-DAT) that we geocoded and then associated with LPS tracks. We show that more than half of hydro-meteorological disasters over South Asia during summer are associated with these LPS events. Weaker LPS (which are called monsoon lows) occur more frequently than stronger LPS (called monsoon depressions), but the stronger LPS produce a larger number of disasters. Furthermore, although many prior studies have shown that the peak rainfall in LPS falls southwest of the vortex centre, the disasters are concentrated on the northern edge of the LPS tracks, along the Himalayas and upper basins of the Ganga and Brahmaputra rivers. Observations show a sharp peak in rainfall on the day of disasters, confirming the physical link between LPS and these hydro-meteorological disasters. A similar peak in rainfall is found in weather forecasts made up to five days before the disaster, suggesting that short-term precipitation forecasts can be useful in disaster preparation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

A Climatology of Clear-Air Turbulence and Mountain Wave Turbulence Throughout the Stratosphere Using MERRA-2 Data

Forty years of MERRA-2 reanalysis data is used to calculate twenty-nine unique indices for both clear-air turbulence (CAT) and mountain wave turbulence (MWT) throughout the stratosphere. The indices are combined into a single estimate of turbulence intensity for both CAT and MWT for five latitudinal domains. These indices have previously been applied at commercial flight levels, but this work is the first time such indices have been evaluated for estimating turbulence throughout the entire stratosphere. The results indicate that turbulence throughout the stratosphere is generally around four-times more intense in the winter season and increases in intensity with altitude. The data suggests the strongest source of CAT in each hemisphere is the polar vortex in the winter stratosphere above 50 hPa. The strongest sources of MWT are the Himalayas and the Andes in the lower stratosphere. The relationship between CAT and the quasi-biennial oscillation is also examined and indicates that easterly tropical winds are associated with the most intense turbulence. The trends in the climatology of CAT over forty years were compared indicating a significant increase in turbulence intensity in the upper stratosphere, and a weaker but still significant decrease in turbulence intensity in the lower stratosphere.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Farmers’ Perception of Climate Change and Its Impacts on Agriculture

Climate change and climate variability drive rapid glacier melt and snowpack loss, extreme precipitation and temperature events, and alteration of water availability in the Himalayas. There is increasing observational evidence of climate change impacts on water resource availability and agricultural productivity in the central Himalayan region. Here, we assess the farmers’ perception of climate change and its impacts on agriculture in western Nepal. We interviewed 554 households and conducted eight focus group discussions to collect farmers’ perceptions of temperature and rainfall characteristics, water availability, onset and duration of different seasons, and the impacts of such changes on their lives and livelihoods. Our results indicate that the farmers’ perceptions of rising annual and summer temperatures are consistent with observations. Perception, however, contradicts observed trends in winter temperature, as well as annual, monsoon, and winter precipitation. In addition, farmers are increasingly facing incidences of extreme events, including rainfall, floods, landslides, and droughts. These hazards often impact agricultural production, reducing household income and exacerbating the economic impacts on subsistence farmers. Integrated assessment of farmers’ perceptions and hydrometeorological observations is crucial to improving climate change impact assessment and informing the design of mitigation and adaptation strategies.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1985

On the Global Distribution of Three-Dimensional Eliassen-Palm Fluxes by Stationary Waves

The global distribution of three dimensional EP fluxes is investigated by using statistics for Dec. 1980 to Feb. 1981 and June to August 1981 calculated from operational analyses. Results at 1000 and 150 mb are given. During the Northern Hemisphere (NH) winter strong upward fluxes can be seen at 1000 mb in the lee of the Himalayas and Rockies, windward of the Canadian Rockies in the east Pacific, to the north of the Atlantic stormtrack and over the west Pacific in a region of strong land sea thermal contrast. Upward fluxes also appear near the west coasts of the Southern Hemisphere (SH) subtropical continents regions of strong land sea thermal contrast. At 150 mb (Fig. 1b) the strongest upward flux now occurs south of Alaska. The horizontal fluxes imply poleward propagation from the convection over Indonesia to 20 N, a region where the assumptions underlying EP fluxes are not well met. Equatorward propagation dominates the NH midlatitude except over the Pacific. The fluxes given offer hints of the sources of stationary waves, but also show several puzzling features and a rather cavalier disregard of regions of easterly wind. The physical meaning and interpretation of three dimensional EP fluxes is not yet clear.

White, G. H.↗
NASA NTRS1985

Geodynamical basis for crustal deformation under the Tibetan Plateau

Plate tectonics and satellite-derived gravity data are used to examine crustal deformation under the Tibetan Plateau. A spherical harmonic analysis is given for the global plate boundary system, and the crustal stresses in Tibet are calculated from satellite gravity data. A superimposed stress system is constructed. The stress patterns reveal that the cold downwelling mantle convection flow beneath southern Tibet pulls the Indian plate down but applies a bending moment on the end of the plate to uplift and support the mass of the Himalayas.

Liu, H.-S.↗
NASA NTRS1987

Jet stream velocity errors in general circulation models

The longitude and time dependence of excessive wind speed errors above subtropical jets in current GCM forecasts is studied for 14 five-day winter forecasts using the NASA Goddard Laboratory for Atmospheres fourth-order GCM. Several distinct phenomena, which may be divided into four categories, are found to contribute to the excess winds. These categories are: (1) error growth above the jet near the Himalayas; (2) error growth above the jet initiated elsewhere followed by advection; (3) tropical moisture bursts appearing in equatorial regions and migrating northeastward to merge with and distort the jet; and (4) undulatory growth of waves in the meridional component of the jet stream velocity. The results of additional sensitivity studies of the Himalayan region error are also reported.

Tenenbaum, J.↗
NASA NTRS1988

Snow cover, snowmelt and runoff in the Himalayan River basins

Not withstanding the seasonal vagaries of both rainfall amount and snowcover extent, the Himalayan rivers retain their basic perennial character. However, it is the component of snowmelt yield that accounts for some 60 to 70 percent of the total annual flow volumes from Hamilayan watersheds. On this large hydropotential predominantly depends the temporal performance of hydropower generation and major irrigation projects. The large scale effects of Himalayan snowcover on the hydrologic responses of a few selected catchments in western Himalayas was studied. The antecedent effects of snowcover area on long and short term meltwater yields can best be analyzed by developing appropriate hydrologic models forecasting the pattern of snowmelt as a function of variations in snowcover area. It is hoped that these models would be of practical value in the management of water resources. The predictability of meltwater for the entire snowmelt season was studied, as was the concurrent flow variation in adjacent watersheds, and their hydrologic significance. And the applicability of the Snowmelt-Runoff Model for real time forecast of daily discharges during the major part of the snowmelt season is examined.

Dey, B.↗