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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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12 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Insights of Boundary Layer Turbulence Over the Complex Terrain of Central Himalaya from GVAX Field Campaign

Limited observations hinder understanding of turbulent characteristics in mountainous terrain resulting from heating or cooling of slopes, wind, vertical motions, and heat or moisture advection, which disperse aerosols and other pollutants over the region. In this study, the 1290 MHz radar wind profiler data are utilized to compute the boundary layer height (BLH), the refractive index structure constant (C n 2 ), and the energy dissipation rate (ε) over the central Himalayan site for the period of November 2011 to March 2012, from the intense Ganges Valley Aerosol Experiment (GVAX) field measurements. The radar wind profiler (RWP) based estimation of BLH and ε is validated against the radiosonde, representing the effectiveness of the datasets for further investigation. The strong seasonal variation of log C n 2 and log ε, with average values of ≈ -12 m -2/3 and -2 m 2 s -3 , respectively, is associated with the mountain-induced local circulations and stability in the atmospheric boundary layer. The weak stratification during weak flow is found to be responsible for deep mixing, particularly in the nocturnal boundary layer in spring. Furthermore, the level of cloud cover significantly impacts the strength of turbulence, with the highest cloud cover resulting in a substantial increase in log C n 2 (approximately -11 m -2/3 ) due to intense updraft and downdraft motions compared to clear skies. Additionally, the distribution of aerosol loading across the site, coupled with the behavior of BLH, atmospheric stability, and orographic-induced circulations, implies distinctive seasonal mechanisms for transporting aerosols toward the mountains. This study offers valuable insights into the diurnal and seasonal patterns of turbulent mixing and the mechanisms behind the transport of pollutants through boundary layer processes over the region.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1983

Capabilities and limitations of the Sondrestrom radar for ST observations

The Sondrestrom radar is located on the western side of Greenland near the U.S. air base and Danish community at Sondre Stromfjord. The radar was previously located at Chatanika, Alaska where its primary role was incoherent-scatter studies of the auroral ionosphere. Stratosphere/troposphere studies have occupied a very small portion of the radar observing schedule. The high operating frequency (1290 MHz) implies that the radar may only be used for turbulence-scatter studies in the troposphere and lower stratosphere. While the inner scale sizes of turbulence imply that the radar should be able to obtain data up to at least 20 km, in practice about 15 km seems to be the usual limit, due to lack of system sensitivity. However, this upper height limit varies from day to day and data have been obtained up to 23 km when a long (50 micro sec) pulse has been used. At high latitudes the tropopause is typically about 8 to 11 km altitude, therefore the radar is particularly suited to studies at tropopause heights. Additionally capabilities and limitations are discussed along with transmitter, receiver and antenna characteristics.

Watkins, B. J.↗
NASA NTRS2017

An Analysis of Coordinated Observations from NOAA's Ronald Brown Ship and G-IV Aircraft in a Landfalling Atmospheric River over the North Pacific During CalWater-2015

To gain a more complete observational understanding of atmospheric rivers (ARs) over the data-sparse open ocean, we used a diverse suite of mobile observing platforms deployed on NOAAs Ronald H. Brown (RHB) research vessel and G-IV research aircraft during the CalWater-2015 field campaign to describe the structure and evolution of a long-lived AR modulated by six frontal waves over the northeastern Pacific on 20-25 January 2015. Satellite observations and reanalysis diagnostics provided synoptic-scale context, illustrating the warm, moist southwesterly airstream within the quasi-stationary AR situated between an upper-level trough and ridge. The AR remained offshore of the U.S. West Coast but made landfall across British Columbia where heavy precipitation fell. Forty-seven rawinsondes launched from the RHB provided a comprehensive thermodynamic and kinematic depiction of the AR, including uniquely documenting an upward intrusion of strong water-vapor transport in the low-level moist southwesterly flow during the passage of frontal waves 2 through 6. A collocated 1290-MHz wind profiler showed an abrupt frontal transition from southwesterly to northerly flow below 1 km MSL coinciding with the tail-end of AR conditions. Shipborne radar and disdrometer observations in the AR uniquely captured key microphysical characteristics of shallow warm rain, convection, and deep mixed-phase precipitation. Novel observations of sea-surface fluxes in a midlatitude AR documented persistent ocean-surface evaporation and sensible-heat transfer into the ocean. The G-IV aircraft flew directly over the ship, with dropsonde and radar spatial analyses complementing the temporal depictions of the AR from the RHB. The AR characteristics varied, depending on the location of the cross section relative to the frontal waves.

atmospheric rivers↗