粤西北对流性大风的物理参数及雷达回波特征

为了解粤西北对流天气的特点,对2015—2020年粤西北发生的60个大风和冰雹天气个例的物理参数、雷达产品的特征进行分析,结果表明:粤西北对流性大风的物理参数有明显的季节性和地域性,其中在春季K指数为27~40℃,出现冰雹时普遍≥32℃,TT为30~55℃,t₇₀₀-t₅₀₀>14℃、t₈₅₀-t₅₀₀>22℃,IQ为2800~5000 g·hPa·kg^-1;夏季K指数为35~42℃,TT为42~46℃,IQ为4200~6600 g·hPa·kg^-1。沙氏指数、垂直风切变、特殊高度层等物理参数在对流性大风、冰雹的潜势预报指示意义有一定的局限性。对流性大风的雷达回波春季多为带状和块状,夏季以点状、块状发展为主,径向速度>12 m/s、ET为10~13 km、VIL值30 kg/㎡以上并有急增或急降现象;出现冰雹时多为超级单体,有三体散射现象、V形缺口等特征,回波强度>60 dBz、径向速度>18 m/s、Z_DR>2.4、K_DP>2.8 dBz。

Physical Parameters and Characteristics of Radar Echoes for Convective High Winds in Northwestern Guangdong Province

For the purpose of understanding the convective weather in northwestern Guangdong,the physical parameters and characteristics of radar products are analyzed of 60 cases of high winds and hails that happened in this part of the province from 2015 to 2020.The result is shown as follows.The physical parameters of convective high winds in this area are highly seasonal and regional.In spring,the K index is between 27 and 40℃,which is generally greater than or equal to 32℃with hails.The TT is between 30 and 55℃,with t₇₀₀-t₅₀₀>14℃and t₈₅₀-t₅₀₀>22℃.The IQ is between 2800 and 5000 g·hPa·kg^-1.In summer,the K index is between 35 and 42℃,the TT is between 42 and 46℃,and the IQ is between 4200 and 6600 g·hPa·kg^-1.Such physical parameters as the SI,VWS and special altitude layer are just mildly indicative in predicting the potential of convective high winds and hails.The radar echoes of convective high winds are mostly strip-and lump-shaped in spring but mostly spot-and lump-shaped in summer,with the radial velocity greater than 12 m/s,the ET between 10 and 13 km and the VIL value above 30 kg/m;,which increases or decreases rapidly.Super cells mostly occur with hails,showing the characteristics of three-body scattering and V-shaped gaps with echo intensity above 60 dBz,radial velocity above 18 m/s,ZDR above 2.4 and KDP above 2.8 dBz.