A STUDY OF HIGH-TROPOSPHERIC LAPSE RATES WITH APPLICATION TO THE CONSTRUCTION OF 300-MILLIBAR CHARTS

Herbert Riehl Univesity of Chicago

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N. LaSeur Univesity of Chicago

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Abstract

The layer of air between 700 mb and 300 mb is analyzed with the object of determining the lapse-rate patterns associated with the most important types of flow configuration in the upper westerlies. At first the average latitudinal lapse-rate gradient, which is computed as a function of mean temperature for the layer only, is subtracted from the total gradient. The residual lapse-rate gradients that remain after this subtraction show that in general the air is more stable in troughs than in ridges and that the lapse rate is less steep north of the jet-stream region than to its south. This observation makes it possible to draw some qualitative inferences concerning vertical circulation and divergence patterns associated with the jet.

The last part of the paper applies the results to an improvement of 300-mb analyses when data are sparse.

Abstract

The layer of air between 700 mb and 300 mb is analyzed with the object of determining the lapse-rate patterns associated with the most important types of flow configuration in the upper westerlies. At first the average latitudinal lapse-rate gradient, which is computed as a function of mean temperature for the layer only, is subtracted from the total gradient. The residual lapse-rate gradients that remain after this subtraction show that in general the air is more stable in troughs than in ridges and that the lapse rate is less steep north of the jet-stream region than to its south. This observation makes it possible to draw some qualitative inferences concerning vertical circulation and divergence patterns associated with the jet.

The last part of the paper applies the results to an improvement of 300-mb analyses when data are sparse.

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