Abstract

A field program in March 1982 obtained rewinsonde data over a mesoscale network that had resolution similar to that of the temperature and moisture data simultaneously obtained from VAS (Visible and infrared spin-span radiometer Atmospheric Sounder). This provides a unique opportunity to verify objective analysis procedures used to combine standard rawinsonde and VAS soundings of temperature and moisture.

In this study, various combinations of VAS data, conventional rawinsonde data, and gridded data from the National Weather Service's (NWS) global analysis, are used in successive-correction (SC) and variations objective analysis procedures. The analysis are objectively and subjectively compared with the AVE/VAS special-network rawinsonde data, where the major discernable mesoα-scale feature at this time was a cold-air pocket at 500 mb.

The objective three-dimensional verification statistics show that the use of VAS data to supplement the NWS rawinsonde data significantly decreased the mixing-ratio error, but also significantly increased the temperature error. The SC procedure used to analyse the VAS data reduced the mixing-ratio error more than did any of the variational procedure. Compared to the error associated with the basic NWS global analysis that has not been supplemented with rawinsonde or VAS data, the use of VAS temperature and mixing-ratio data had a positive impact when combined with these global fields. The positive impact on the moisture field was considerably greater however.

Subjective verification of the temperature fields at 500 mb produced additional insight. First, the VAS retrieval data were able to modify the very smooth global analysis to produce a fairly realistic temperature minimum in the verification-network region. Also, the variational procedures were able to successfully blend the rawinsonde and VAS data to that the bed subjective verification of the cold-pocket structure was produced when both data sources wore employed.

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