The rain profiling algorithm “ZPHI” developed by Testud et al. (2000) was applied to the X-band polarimetric radar data. The rainfall data were collected by the observation using an X-band polarimetric radar, the MP-X radar of the National Research Institute for Earth Science and Disaster Prevention (NIED) and three J-W type disdrometers around Tsukuba city, Japan from August to September 2001.

The estimated rain rate and “normalized” intercept parameter N0* were compared with the disdrometer measurements during the rainfall period when the maximum rain rate of 121 mm/h was recorded on the ground by a disdrometer. The radar estimates were averaged horizontally within a circle of 2 km radius at each disdrometer site, then both radar and disdrometer estimates were averaged temporally using bell-shaped weighting function with 5-min window. The time variations of both from the radar and disdrometers have good similarities although the radar estimated rain rates have larger values. The reason of the overestimates is thought to be the calibration error of the MP-X radar reflectivity because the estimated N0* from the radar also show higher values than ones estimated from disdrometer measurements.

The radar calibration correction will be applied from consistency test between the rain rate estimate by “ZPHI” and an estimate combining the specific attenuation A and the differential reflectivity ZDR for more accurate rain rate estimations.