An investigation of vertical extrapolation of the vector horizontal wind field

Abstract

Extrapolation techniques including the geostrophic and gradient thermal wind, average wind shear from United States Weather Bureau maximum-wind analyses, and persistence were statistically compared for January 1960 over the United States. Calculations were made for layers contained between 200 mb and 40,000 or 15,000 feet, the thicknesses averaging 2100 or 6500 feet, respectively. Graphic results are presented for both speed and direction errors for each type of extrapolation. It is shown that low wind speed, cross-isobar flow, and large curvature are associated with significant extrapolation errors. The author is grateful for the patience and expert counsel of Professor R. J. Renard of the United States Naval Postgraduate School, Monterey, California.