Accession Number:

ADA533723

Title:

Using Surface Pressure to Validate Tropical Cyclone Surface Wind Retrievals From SAR

Descriptive Note:

Annual rept.

Corporate Author:

WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB

Personal Author(s):

Report Date:

2008-09-30

Pagination or Media Count:

5.0

Abstract:

The goal of this study is to develop a new method for validating surface wind and stress retrievals from oceanic synthetic aperture radar SAR imagery of tropical cyclones through the use of surface pressure data. The reason for using surface pressure measurements is that they are comparatively more reliable than wind measurements in extreme wind conditions. Surface winds are a key parameter in the exchange of momentum, heat and water vapor between the atmosphere and ocean, and the relative surface flux magnitudes play an important role in the intensity of tropical cyclones. Surface winds are notoriously difficult to measure in high wind and high sea state conditions and high resolution surface wind fields derived from SAR imagery have great potential for improving our understanding of air-sea interaction near the core of tropical cyclones. However, SAR wind retrieval techniques in such environments are in their infancy compared to those in standard use for more typical meteorological conditions. This is largely because there is little data in the high wind regime 20 m s-1 for calibration and validation of the geophysical model functions that relate microwave backscatter to the surface wind vector. Presently the best available in situ wind observations in tropical cyclones are from GPS dropsondes. However, these only provide infrequent point-wise information. A second possible source of surface winds data are the remotely sensed winds from the airborne stepped frequency microwave radiometers. These provide a narrow swath of surface winds underneath aircraft penetrations, which are routine only in the Atlantic basin.

Subject Categories:

  • Meteorology
  • Active and Passive Radar Detection and Equipment

Distribution Statement:

APPROVED FOR PUBLIC RELEASE