Intercomparisons of Data Derived from Nimbus 5 Temperature Profiles, Rawinsonde Observations and Initialized LFM Model Fields

Abstract

A 23?24 February 1975 case study is made comparing the results achieved using Nimbus 5 satellite temperature, profiles with those obtained from radiosonde data and the initial hour data of the Limited Area Fine Mesh (LFM) model of the National Meteorological Center. An objective analysis technique is used to construct and analyze isotropic cross sections through an intense baroclinic zone. A cross section based on 1700 GMT Nimbus 5 soundings is compared with those based on 1200 and 0000 GMT radiosonde and LFM data. Geostrophic shear calculations are used to compare the thermal gradients for various isobaric layers obtained from the three data acts. The Nimbus 5 results show somewhat less detail than those based on the radiosonde data, but wore than those obtained from the LPM data. Comparisons of the mean temperature in various isobaric layers for the three time periods indicate that the 1700 GMT Nimbus 5 data appear to be consistent with the changing synoptic pattern. Estimates of the wind components normal to the cross sections are obtained using 1) the geostrophic wind calculated from Nimbus 5 data, 2) the observed winds which are enhanced by the geostrophic shear obtained from the radiosonde data, and 3) the initial-hour LFM winds. The wind estimates also indicate that the Nimbus 5 data provide results which agree with the evolving synoptic situation. In general, the results suggest that the insertion into numerical models of satellite-derived mean thermal gradients calculated for 100?200 mb thick layers, rather than mean temperatures, may facilitate the use of satellite soundings.