Abstract:

The effects of several important factors on the error of hail index were analyzed by a simulation test method. Using the measurement indexes of probability of detection (POD), critical success index (ICS) and false alarm ratio (RFA), the 25 hail storms and 72 non-hail storms among 12 hail processes during March of 2008 to July of 2012 were assessed based on the new generation Doppler weather radar data in Zunyi City. The results indicate that H0, the vertical profile of reflectivity factor and distance between the target and radar have great influence on POSH error, while Hm20 has insignificant influence. There are high RFA and low ICS when POH are used to recognize hail cloud. Identification effect of POSH is better than that of POH. Increasing threshold can enhance ICS and decrease RFA. The POD is low when the threshold is larger. POSH=70 is the best threshold, with which high POD and ICS and low RFA can be obtained. POD has no change when POSH and VIL>20kg·m^-2 are used together to identify hail cloud, but lower RFA and higher ICS can be obtained when the threshold of POSH is less than 90.

Key words:  Highland mountainous area, Hail index, Parameter correction