Some Potential Errors in Satellite Wind Estimates Using the Geostrophic Approximation and the Thermal Wind

Abstract : Current and planned passive sensors on meteorological satellites measure radiances that are converted directly into temperature and humidity soundings. In turn, wind velocity is derived from the temperature soundings and other derived variables (for example, geopotential heights). Current operational methods involve either the geostrophic wind or the thermal wind approximation. This report presents some information and sample calculations on the types of errors that may be expected when either approximation is used to estimate the actual wind from data gathered by passive satellite sensors. The assumption is that no additional data are available (that is, only satellite sounding data from sensors of the type found on present day environmental satellites). This report does not treat the improvements that should occur when data from other sources of data (for example, radar profilers, ground-based