Specification Of Cloudiness And Precipitation By Multi Level Dynamical Models

Author : Frederick Sanders
Publisher :
ISBN 13 :
Total Pages : 122 pages
Book Rating : 4.3/5 (91 download)

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Download or read book Specification of Cloudiness and Precipitation by Multi-level Dynamical Models written by Frederick Sanders and published by . This book was released on 1960 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: The relationship of cloudiness and precipitation to the vertical motion as computed by quasi-geostrophic multi-level numerical models was studied. In order to determine the effects of high resolution in the vertical, both a two-parameter and a ten-level model were used. The models were applied to two storms of a contrasting nature. One was on intense northeastward-moving baroclinic cyclone and the other was a weak lee-side development under predominantly zonal conditions. Geopotential height tendencies at the 950-mb level computed by the ten-level model seemed to be more accurate than those computed by the two-parameter model, as determined by comparison with observed surface pressure tendencies. The exception was in the high elevations of the Rockies, where both models did rather poorly. Mid-tropospheric height tendencies were reasonable compared to the observed 12-hour 503-mb height changes, with the ten-level model doing slightly better than the two parameter one. Cloudiness and precipitation were best related to the vertical motion in the middle and upper troposphere. The vertical motion as calculated by the ten-level model was not significantly better correlated with observed cloudiness and precipitation than that calculated by the two-parameter model. Vertical cross sections through the frontal layers indicated a good correlation between the cloudiness, vertical motion, as computed from the ten-level model, and the orientation of the frontal zone, as shown by the potential temperature fields. This analysis was done using only the vertical motion as computed by the ten-level model, but it was believed that the two-parameter model would not have given such good resolution in the vertical. Quantitative calculations of precipitation were made for the intense storm. The computed amounts were in excess of the observed totals to the northwest of the storm center, but grossly deficient in the warm sector. It was believed these errors were due to the use of a stability parameter which was constant in the horizontal, the use of the geostrophic assumption, and to the presence of circulations on a smaller scale than that detectable by the present network of radiosonde stations.