Vertical Motion Calculations and Satellite Cloud Observations over the Western and Central United States

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  • 1 Texas A &M University, College Station, Tex.
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Abstract

Vertical motions over the western and central United States during 19–21 August 1961 were computed by several methods. The resulting angles applicable, at 700 mb or 10,000 ft (600 mb for the Joint Numerical Weather Prediction vertical motion fields) were compared both subjectively and objectively to each other, to the corresponding standard type cloud and weather observations, and to approximately synoptic TIROS nephanalyses. The results of the comparisons showed only moderate agreement among the various methods and between the vertical motion analyses and the TIROS information. The component method, based on observed winds, appeared to give the best agreement with the satellite picture indications of vertical motion, though it seemed little better than some of the other methods. The use of satellite data shows definite promise as a means of evaluating computed vertical motion fields and should eventually contribute to the improvement of the procedures used to compute motions.

A lag, or “trailing effect&rdquo, was noted in the relation between the vertical motion patterns and the cloud distribution. The regions of cloudiness often were displaced from the centers of upward motions. This effect seemed particularly evident for rapidly moving vertical motion patterns. The cloud activity was most frequently displaced in the direction from which the vertical motion patterns were moving.

Abstract

Vertical motions over the western and central United States during 19–21 August 1961 were computed by several methods. The resulting angles applicable, at 700 mb or 10,000 ft (600 mb for the Joint Numerical Weather Prediction vertical motion fields) were compared both subjectively and objectively to each other, to the corresponding standard type cloud and weather observations, and to approximately synoptic TIROS nephanalyses. The results of the comparisons showed only moderate agreement among the various methods and between the vertical motion analyses and the TIROS information. The component method, based on observed winds, appeared to give the best agreement with the satellite picture indications of vertical motion, though it seemed little better than some of the other methods. The use of satellite data shows definite promise as a means of evaluating computed vertical motion fields and should eventually contribute to the improvement of the procedures used to compute motions.

A lag, or “trailing effect&rdquo, was noted in the relation between the vertical motion patterns and the cloud distribution. The regions of cloudiness often were displaced from the centers of upward motions. This effect seemed particularly evident for rapidly moving vertical motion patterns. The cloud activity was most frequently displaced in the direction from which the vertical motion patterns were moving.

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