![]() ![]() While Doppler radar usage on ships is well established, the impact of ship motion on polarimetric radar variables has not been explored. However, before this can be realized it is necessary to understand the limitations that may be imposed by the deployment of such radars on a moving platform. This, and other such planned ships, will allow cloud studies around the globe in key climate regions ranging from the tropics to the deep Southern Ocean. Recent plans include the operation of polarimetric radar from ships, such as the new Australian research vessel (R/V) under construction, the R/V Investigator (details can be found at ). Ground-based polarimetric radars are providing important new information on cloud microphysics and quantitative precipitation measurement for both research and operational applications (e.g., Bringi and Chandrasekar 2001). Furthermore, the results from the scattering simulations have been used to provide equations for correction factors that can be applied to compensate for the “apparent” nonzero canting angles and nonzero elevation angles, so that drop size distribution parameters and rainfall rates can be estimated without any bias. The results show that as long as the ship movement is limited to a roll of less than about 10°–15°, the effects are tolerable. Dependence on mean volume diameter is examined as well as variations of the four main polarimetric parameters. Scattering calculations are also performed using the T-matrix method with measured drop size distributions as input. Equations are derived (i) to convert the measured differential reflectivity for nonzero mean canting angles to those for zero mean canting angle and (ii) to do the corresponding corrections for nonzero elevation angles. Scattering from a single oblate hydrometeor is considered at first. Calculations are carried out by (i) varying the “effective” mean canting angle and (ii) separately examining the elevation dependence. The effect of ship motion on shipborne polarimetric radar measurements is considered at C band.
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