Curvature of the Wind Profile in the Troposphere Versus Regions of CAT and Non-CAT in the Stratosphere

Abstract

A discussion of the theoretical importance of the curvature of the wind profile to the amplitude of mountain waves is presented. Mechanisms favorable for CAT are discussed in relation to such wave motions. This study shows that CAT encountered by the XB-70 aircraft in the stratosphere during expected mountain-wave conditions is related to the vertical gradient of curvature of the wind profile in the troposphere. Computations were based upon meteorological data obtained from rawinsondes and turbulence data from 17 flights of the aircraft. The results were determined from analysis of the areal variations of the vertical gradient of the curvature term in the Scorer parameter in relation to the location of the turbulent and non-turbulent regions. These results show that 89% of the turbulent regions in the stratosphere occurred in expected mountain-wave areas and that 79% were located where the vertical gradient of curvature was positive in the 10?30 000 ft layer below. For the non-turbulent regions, 74% were outside expected mountain-wave areas and 98% of these occurred where the vertical gradient of curvature was negative. In addition, all the non-turbulent regions within expected mountain-wave areas occurred where the vertical gradient of curvature was negative. Detailed discussions of the analysis techniques and of the results are presented.