Horizontal gradients in the wet path delay derived from four years of microwave radiometer data

We have analyzed four years of inferred wet path delay data from a microwav e radiometer operating at 21.0 and 31.4 GHz. We have applied a four paramet er gradient model to the wet delays, using different lengths of the time se ries for the gradient estimation. The mean gradient, averaged over 15 to 14 40 minutes, varies between 0.9 and 0.4 mm End has a preferred direction tow ards the north-east. Increasing the averaging time causes the estimated gra dient to decrease. The 15 minutes mean gradient is 1.3 mm for the summer mo nths and 0.7 mm for the winter months. Structure function results are also presented.