Power law relationships of the form R = aAb are derived, where R is the rainfall rate, and A is the 35-GHz specific attenuation Ah or specific differential attenuation ΔA = Ah - Av, where the subscripts h and v indicate horizontal and vertical polarizations. The effects of raindrop size distribution, canting, and oscillation on these relationships are evaluated quantitatively. The drop size distributions (DSDs) are obtained from ground-based disdrometer measurements from three different geographical locations around the world. The R-Ah relationship is negligibly affected by raindrop canting and oscillation. It is affected to some extent by DSD variations, with less than 15% fractional standard error (FSE) in the estimated rainfall rate RAh. On the other hand, the R-ΔA relationship is most sensitive to raindrop oscillation, up to about 35% difference in RΔA compared to the no-oscillationcase, and the effect of canting is about 9% for a standard deviation of 10° of the polar canting angle compared with no canting. The FSE due to variations in the DSD for R < 5 mm h-1 is greater than 30% and increases with decreasing R. However, for R > 20 mm h-1, the FSE in RΔA is comparable (and even lower for R > 30 mm h-1) to that of RAh. The exceptions to this are rainfall rates with DSDs dominated by smaller raindrops (diameters less than 2.4 mm). It is also emphasized that because oscillation and canting affect ΔA but not Ah, they could be used in combination for determining the presence of drop oscillation and canting and for estimating an effective raindrop shape model (axial ratio versus size).
|Original language||English (US)|
|Number of pages||10|
|Journal||IEEE Transactions on Geoscience and Remote Sensing|
|State||Published - Nov 2002|
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering
- Earth and Planetary Sciences(all)