A Pressure Model Function for Scatterometers

The inverse model --- using surface winds as boundary conditions to the PBL model to yield geostrophic winds --- was very successful in producing surface pressures that were highly correlated with fields from NMC analyses. Therefore we hypothesized that the middle-man U10 might be dispensed with and a correlation between backscatter and geostrophic wind attempted.

This was done initially by Mike Freilich at OSU by simply replacing U10 in his model function correlation matrix with a pressure gradient vector taken from ECMWF analyses. The variable response of backscatter to changes in look angle and wind (pressure gradient) were as good or better than U10 correlations.

The pressure model function (PMF) has undergone extensive development from fundamental concepts directly along the lines of the U10 MF development. It produces surface pressure fields comparable to the inverse model in many situations.

Recently, the inverse model has been upgraded and extended to the tropics, making it truly a global model. Its longer heritage makes it the method of choice for our pressure fields at present.

Work continues on the PMF since it provides prospects for comparison and extension (extrapolation) to the equatorial regions.