Time Evolution of a Storm from X-POL in São Paulo: a ZH - ZDR and Titan Metrics Comparison

Dual polarization radar observations opened the possibility to classify hydrometeor types in a storm. The polarimetric radar- based determination of types and amounts of hydrometeor is important for a number of applications, both operational and for research, e.g., calibration of precipitation rates from non-polarimetric radars, initialization of hydrometeor types and amounts in storm-scale and mesoscale numerical models and verification of quantitative precipitation forecasts. In particular, the identification of particles is basic for the estimation of hydrometeor water content in the spatio-temporal evolution of precipitation, which is quite important for NWP and hydrometeorological applications. There is growing interest in polarimetric X-band radars. They are relatively smaller, suitable for mobility and allow high resolution observations to be made with antennas of moderate size. On the other hand, X-band suffers from high attenuation, a traditional major disadvantage. However, dual-polarization made it possible to mitigate the attenuation. Data used in this paper are from the polarimetric X-band mobile radar system operated in the context of the GLM-CHUVA Experiment, sited at approximately 45.9° W; 23° S near São Paulo. The paper presents a preliminary indication of the time evolution of the hydrometeor content, with an emphasis on rain, in a storm developing approximately within medium range of the radar. The storm was selected from the GLM-CHUVA project intensive campaign of the 2011/2012 summer in the Paraiba Valley, and tracked using TITAN system software. Essentially along the storm mature stage, hydrometeors as characterized in the ZH-ZDR 2D space were counted from PPIs at two elevations, for every volume scan. Each volume scan included an azimuthal scan at 89° elevation for ZDR bias correction. Boundaries for the hydrometeor characterization were chosen based on recent works found on specialized literature on hydrometeor classification with XPOL. Time evolution of the hydrometer content obtained is comparable to the corresponding TITAN metrics. Also, results indicate a compatibility with the evolution of rain in a storm observed during the COPS field phase in Central Europe. Following studies include analysis of storms producing hail at the ground.