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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Tropical cyclone outer surface winds derived from satellite microwave sounder data

Upper tropospheric temperature anomalies are detected in brightness temperature data from the Nimbus 6 Scanning Microwave Spectrometer (SCAMS). Brightness temperature anomalies are related to surface pressure anomalies through the radiative transfer and hydrostatic equation. Surface wind speeds at outer radii are then estimated using the gradient wind equation and a shearing parameter. The method is first tested using simulated satellite data constructed from temperature, pressure and height data recorded by aircraft reconnaissance of four hurricanes. Wind speeds in the 80-95 kPa region are estimated with 2-3 m/sec accuracy. Next, 55.45 GHz SCAMS data over eight typhoons during 1975 are used to estimate the radii of 15.4 m/sec (30 kt) and 27.5 m/sec (50 kt) winds. Accuracies of about + or - 80 and + or - 70 km, respectively, are found. It is suggested that the technique be further tested using data from the Microwave Sounding Unit on board the TIROS-N and NOAA 6 satellites.

Kidder, S. Q.↗
NASA NTRS1984

Quantitative satellite applications - Tropical cyclone intensity monitoring and track forecasting

An assessment is made of the effectiveness of VISSR Atmospheric Sounder (VAS) data gathered over the North Atlantic Ocean area in the 1982 and 1983 hurricane seasons. By the end of the 1983 season, progress had been made in providing high quality analyses and displays of mass, motion and moisture patterns for evaluation. A comparison of mean forecast errors for several different operational models, official forecasts, and the VAS Trajectory model for selected cases in which VAS deep layer mean wind data were available show VAS accuracies that are comparable with those of the official forecasts.

Velden, C. S.↗
NASA NTRS1994

On the transport of trace gases by extra-tropical cyclones

Extratropical cyclones are able to transport trace gases through the whole troposphere and lower stratosphere. At mid-latitudes most of the ozone transport from the lower stratosphere down into the troposphere is accomplished by depressions. The changing the total ozone contents, associated with the variable tropopause heights, are shown to be clearly visible in satellite ozone data.

Allaart, Marc A. F.↗
NASA NTRS2001

Bathymetric Effects on a Tropical Cyclone Wave Field at Landfall

On 26 August 1998, the NASA Scanning Radar Altimeter (SRA) flew aboard one of the WP-3D hurricane research aircraft to document the sea surface directional wave spectrum in the region between Charleston, SC and Cape Hatteras, NC, as Bonnie, a large Category 3 hurricane, was making landfall near Wilmington, NC. Two days earlier, the SRA had documented the wave field spatial variation in open water when Hurricane Bonnie was 400 km east of Abaco Island, Bahamas. Bonnie was similar in size during the two flights, but the maximum speed in the NOAA Hurricane Research Division surface wind analysis was 15% lower prior to landfall (39 m/s) than it had been in the open ocean (46 m/s). This was compensated for by its faster movement prior to landfall (9.5 m/s) than when it was encountered in the open ocean (5 m/s). The slower movement matched the group velocity of waves of 65 m length, so waves at the peak of the spectrum outdistanced the storm as soon as they were generated. The higher translation speed prior to landfall matched the group velocity of waves of 230 m length, significantly increasing the effective fetch and duration of waves near the peak of the spectrum which propagated in the direction of the storm track. The open ocean wave height variation indicated that Hurricane Bonnie would have produced waves of 11 m significant wave height on the shore northeast of Wilmington had it not been for the continental shelf. The bathymetry distributed the steepening and breaking process across the shelf so that the wavelength and wave height were reduced gradually as the shore was approached. The wave height 5 km from shore was about 4 m.

Wright, C. W.↗
NASA NTRS2009

Demonstration of Effects on Tropical Cyclone Forecasts with a High Resolution Global Model from Variation in Cumulus Convection Parameterization

The Goddard Earth Observing System Model, Version 5 (GEOS-5) is a system of models that have been developed at Goddard Space Flight Center to support NASA's earth science research in data analysis, observing system modeling and design, climate and weather prediction, and basic research. The work presented used GEOS-5 with 0.25o horizontal resolution and 72 vertical levels (up to 0.01 hP) resolving both the troposphere and stratosphere, with closer packing of the levels close to the surface. The model includes explicit (grid-scale) moist physics, as well as convective parameterization schemes. Results will be presented that will demonstrate strong dependence in the results of modeling of a strong hurricane on the type of convective parameterization scheme used. The previous standard (default) option in the model was the Relaxed Arakawa-Schubert (RAS) scheme, which uses a quasi-equilibrium closure. In the cases shown, this scheme does not permit the efficient development of a strong storm in comparison with observations. When this scheme is replaced by a modified version of the Kain-Fritsch scheme, which was originally developed for use on grids with intervals of order 25 km such as the present one, the storm is able to develop to a much greater extent, closer to that of reality. Details of the two cases will be shown in order to elucidate the differences in the two modeled storms.

Miller, Timothy L.↗
NASA NTRS2010

The Representation of Tropical Cyclones Within the Global William Putman Non-Hydrostatic Goddard Earth Observing System Model (GEOS-5) at Cloud-Permitting Resolutions

The Goddard Earth Observing System Model (GEOS-S), an earth system model developed in the NASA Global Modeling and Assimilation Office (GMAO), has integrated the non-hydrostatic finite-volume dynamical core on the cubed-sphere grid. The extension to a non-hydrostatic dynamical framework and the quasi-uniform cubed-sphere geometry permits the efficient exploration of global weather and climate modeling at cloud permitting resolutions of 10- to 4-km on today's high performance computing platforms. We have explored a series of incremental increases in global resolution with GEOS-S from irs standard 72-level 27-km resolution (approx.5.5 million cells covering the globe from the surface to 0.1 hPa) down to 3.5-km (approx. 3.6 billion cells).

Putman, William M.↗