Proceedings with Extended Abstracts (single PDF file) - Radio ...

was present, or precipitation was present in only small quantities, the period was assigned avalue of 0. This parameter is called the precipitation index.Fig. 2. S-band radar map of precipitation, 16 September. 2003, 0600UT.Results.A comparison of these two parameters for the period from Oct. 18 to Nov. 18 is shown in fig.3. It is apparent from this graph that for most of the time frame, incidences of enhancedisotropy correspond to occurrences of precipitation. Vertical broken lines show times whereprecipitation starts shortly after the onset of an increase in θ s to values in excess of 20 o .Fig. 3. Plots of the isotropy index (upper graph) and precipitation index (lower graph) as afunction of time in October and November, 2002. In the upper graph, the solid line shows theraw values of the isotropy index, and the gray shading shows the 5-point running mean.446Fig. 3 shows that if the isotropy index equals 3 or 4, precipitation is generally found. If theprecipitation index is 2, there may be some precipitation (e.g., case C) or there may be none(cases A and B). If the isotropy index is 0, there is no precipitation. Generally the isotropyparameter increases before the precipitation index rises to 1, so that enhanced isotropy is aprecursor to the precipitation. The delay varies between 3 and 12 hours. The incidences ofenhanced θ s often also persist for a short time after the precipitation has disappeared.