The gradient wind in the mesosphere and lower thermosphere

Abstract

HRDI zonally averaged daytime temperatures are used to compute the gradient wind in the 65-105 km range. Results are compared with independently measured HRDI zonal mean zonal winds. The gradient wind captures the essential features of the observed wind field in the summertime midlatitudes, including the stratospheric easterly (westward) jet and the reversal to westerly (eastward) winds in the lower thermosphere. The consistency between HRDI and gradient winds diminishes at tropical latitudes, due to substantial tidal contamination of daytime temperatures used to compute the gradient wind.