On the use of outgoing longwave radiation data in incorporating divergent part of the wind in analysis

Abstract

In the present study, kinematic divergence computed using ECMWF grid point data at 850 hPa  is enhanced by  using the relationship between OLR and divergence. This new enhanced divergence is used to  compute the velocity potential and then, the divergence part of the wind is obtained from velocity potetial. To obtain the rotational part of wind, we computed the vorticity from wind data, and subsequently stream function and obtained and the rotational part of the wind from the stream function. The total wind is the combination of divergent part obtained from modified velocity potential (using OLR data) and rotational part from unmodified stream function. This total wind field is used as initial guess for univariate objective analysis by optimum interpolation scheme so that Initial Guess field contained the more realistic divergent part of the wind. Consequently, the analysed field also will contain the divergent part of the wind.