The Observation Study Of Microphysical Process Inhailstorm

For studying the microphysical process of the formation and evolution of small/wet hailstones in the typical hailstorm over northern China in quatitly and quality,utilizing four polarimetric parameters(horizontal reflectivity ZH,differential reflectivity ZDR,specific differential propagation phase KDP and copolar cross-correlation coefficient ?HV)of X-band dual-polarimetric radar(714XDP-A)and the environmental temperature T to construct the fuzzy-logic-based hydrometeor identification(HID)method(in particular,a scheme for small/wet hail in the typical hailstorm over northern China is added to study the microphysical environment characteristics of the formation and evolution of samll/wet hail).Furtherly,constructing the concept of the microphysical process in hailstorm cell during the mature and dissipated stages after validating the results of HID are consistent with theoretical researches and ground observational records.The results are as follows.(1)Because the input variables(KDP,ZH,ZDR,?HV)of HID,the quality control of ?DP,ZH,ZDR and ?HV is necessary.There is proposed a comprehensive method which is applied to running mean,median,Kalman,finite impulse response(FIR)and wavelet de-noising filters for filtering the ?DP.The results which are from once stratiform precipitation and once cumulonimbus precipitation indicate that the comprehensive wavelet de-noising(CWD)method is the best among these methods in correcting the zero errors of ?DP,remaining details of intense precipitation and smoothing.Furtherly,the evaluated KDP from filtered ?DP by CWD is so smooth that for precipitation estimation and remains the details of intense precipitation.(2)The conclusions of validating the HID results in two typical hailstorms cases combined the ground observational hailstone records,the differential reflectivity hail signal(HDR)and polarimetric variables of radar indicate that: the hydrometeor distribution of HID in vertical or horizontal is consistent with the theoretical hydrometeors distribution with temperature and the hailstones in HID is coincident with the ground observational hailstone records;the abnormal ZDR signature of hailstones under melting level will cause error recognitions of hail;the HDR can imply the hailstones which are in a low melting degree well and is consistent with HID,however,the contrary to hailstones are in a high melting degree.(3)The area of hailstones initial formed(AHIF)exists in hailstorm mature stage,the characteristics of AHIF: it is around the-20? layer(7.5-8.7 km height)and the ZH of it is 50-55 d BZ,V of it is positive.The high density graupels and abundant supercooled water revolve round it,furthermore,the embryo may not source from the bottom of AHIF by updraft.The ZDR column(i.e.,ZDR?1 dB)will shrink because the descending of ice phase particles in rear of hailstorm along the ZDR column,furtherly,the “channel”(i.e.,ZDR<1 dB)will form.There will not form the hailstones above the-10? layer in hailstorm dissipated stage.(4)The concept of microphysical process in typical hailstorm cell over northern China during the mature and dissipated stages is constructed by radar variables(ZH,ZDR,V)and HID results.In this concept,the formation and transformation of precipitation particles follow the traditional theory,and theformation and development of small/wet hail does not exist the cycle growth mechanism what is in supercell due to the intensity of updraft.This study helps fill in the applied researches of the hydrometeor identification in hailstorms based on the domestic X-band dual-polarimetric radar,and it is beneficial for understanding the microphysical processes of microphysical process in typical hailstorms over northern China during the mature and dissipated stages.Furtherly,the statistic of AHIF provides the theoretical basis and guiding significance to weather modification.