An Assessment Of Hail Detecting Ability For Yunnan Doppler Weather Radar Network And The Hail Identifying Methodology Research

Hail is one of common weather phenomena,which can be detectded by the weather radar.However,the terrain blockage has a bad effect on the ability of the weather radar detecting the hail weather.It can distort meteorological scatter echo at less blockage,and even makes the radar unable to identify the hail storm completely at severe blockage area.The purpose of this paper is to evaluate the the ability to detect the hail of Doppler radar based on several parameters such as the height of 0?,-20?,echo center and so on.On the basis of C band Doppler radar in Yunnan province and the 607 ground hail samples from 2014 to 2016,the ability of radar to detect hail is analysised and the detection effect is also classified in this paper.Compared with the actual hail weather,the results are reasonable by using the height of 0 layer and a few height difference? s to measure the detecting hail effect of radar.About 75% of areas in Yunnan is suitablefor hail cloud detecting by Doppler radar network,about 2% of the area is blocated patially,part of blockage,and around 0.2% is completely occluded.Among them,the severest blocked regions are mainly located in the northeast of Zhaotong and Lincang.After the provincial planning nine radars putting into operation,in theory,there is 90% of the hail ground can be detected,About 3% of the hail ground fall in the region where the radar can only identify when hailstorm strengthen over 8 km.And about 6% of the hail ground falls in the region where the radar coverage is only below 8 km.Even with all nine radars putting into observation network,there is 8.5% of Yunnan areas still can't be covered.In this paper,the classification discriminant analysis method and fuzzy logical method are used for hailstorm echo recognition in complex terrain.A total of 24 days hail ground true samples dataset were selected during 2014-2016 associated with the same time Storm Cell Identification and Tracking(SCIT)products which derived from weather radar Raw Data as the foundation.Based on the ground hail data and recognition criteria,the SCITs were departed into three categories: general stormcell,light hail strom and severe hail stormcell.By using the results from classification discriminant,the probability density of general stormcell,light hail strom and severe hail stormcell was calculated,and then using the results of probability density to generate fuzzy logic hail identifying method.Finally by verificating the identifying method,the results showed it improved a lot on the rate of vacancy forecas and objective score compared with NSSL algorithm.The limitation of ground hail collection is one of the factors for FAR,and the terrain occlusion and the weakness of SCIT identification small stormcell is the reason for omission of the storm.Hail recognition method based on discriminant analysis is constructed from the prior probability algorithm,which contains regional meteorology characteristics and can be used in different climate regions.this method can avoid the limitation in different areas,different climate types.Moreover,the accrancy will be improved geatly when the samples increase and accurate enough.The method of fuzzy logic index recognition is a simplified application furtherly on the basis of the discriminant method.