Extended Abstract (212K)P1.23
Single-Doppler Radar Estimation of Hurricane and Environmental Winds in the Lower Troposphere
Paul R. Harasti, NCAR, Boulder, CO
Several hurricane properties are estimated from a Principal Component Analysis (PCA) of single-Doppler radar data. These include the bearing and range to the circulation center, the radius of maximum wind, and the transition radii of the radial wind. The horizontal wind field is estimated by an extension of the VAD method, customized for hurricanes that are predominantly axisymmetric. It is assumed that the wind field can be approximated by modified, Rankine-combined vortex with a superimposed mean-environmental wind. The parameters that specify the vortex model are retrieved such that the earth-relative horizontal winds are estimated within the lowest 3 km of the troposphere. A vertical profile of the mean-environmental wind over the radar is also extracted from the results.
To demonstrate the method, results from Hurricane Bret (1999) are presented. Near-simultaneous WSR-88D data taken from Corpus Christi (KCRP) and Brownsville (KBRO) Texas, as well as a pseudo-dual Doppler wind synthesis from a NOAA P-3 research aircraft afford an ideal opportunity to inter-compare results. The estimates of the circulation center position derived from the KBRO and KCRP data agree to within the 1 km precision of the PCA. The magnitude and phase of the wind maximum agree well with the NOAA P-3 results and, in general, the absolute differences in the wind magnitudes vary from vary 0 to 10% over the horizontal domain. There are significant differences in the mean-environmental wind revealed over the ~200 km separation of the two radars. However, the average vertical profiles of the mean-environmental wind agree well with the NOAA P-3 mean wind calculated with respect to the circulation center which was located mid-way between the radars.
Poster Session 1, Tropical Cyclones, Large-scale Dynamics and Convection
Monday, 29 April 2002, 11:00 AM-12:30 PM
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