The Dynamics of an Upper-Level Trough in the Baroclinic Westerlies: Analysis Based upon Data from a Wind Profiler Network

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Abstract Hourly wind data from the National Oceanic and Atmospheric Administration's demonstration network of 404-MHz profilers in the central United States and hourly wind data from the standard National Weather Service surface network are used to determine the validity of the geostrophic momentum (GM) approximation in the vicinity of a sharp trough in the baroclinic westerlies by using observations alone. The ageostrophic and geostrophic components of the wind are retrieved from time-filtered and objectively analyzed wind data and from kinematically computed vertical velocities using the inviscid form of the horizontal equations of motion in pressure coordinates. The success of the retrieval technique is discussed critically in terms of the difference between the horizontal divergence of the wind and the horizontal divergence of the retrieved ageostrophic wind and in terms of the retrieval of the geostrophic wind field from simulated wind data using a primitive equation numerical model of a growing baro...