海南岛热带孤立对流云系特征

Characteristics of tropical isolated convective clouds in Hainan Island

孤立对流云系是海南岛一种重要的对流云系形态,深入研究其发展演变规律有助于对流云系识别追踪及提升人工影响天气作业效率。基于2015—2020年海南岛S波段双偏振多普勒天气雷达(CINRAD/SA-D)探测资料,对典型孤立对流云系个例的双偏振特征以及全岛范围内孤立对流云系的发展演变特征开展综合分析,结果表明:海南岛孤立对流云系典型个例(2020年7月26日)在发展阶段出现明显差分反射率(ZDR)柱和差分相移率(KDP)柱,证明云系内部对流运动较强。2015—2020年3—9月海南岛共计发生475次孤立对流云系个例,占对流云系个例(4017次)的11.82%;西南低压槽、变暖高压脊及南下冷锋3种天气系统较易触发孤立对流云系。3—6月孤立对流云系高发,占比76.84%,明显高于其他月份;3月是孤立对流云系个例发生频次最多的月份,孤立对流云系占对流云系的47.48%。一日之中,14:00—17:00孤立对流云系出现频次最多,占总次数(475次)的72.84%。海南岛孤立对流云系在西南及中部山区高发,占比约88.84%;移向以偏东北及偏东南方向为主,主要受偏西风、偏南风影响;移动速度主要集中在6~20 km·h−1,移动距离主要为6~20 km,超过半数的孤立对流云系移动距离未超过20 km。

Isolated convective cloud system is one of the important convective cloud forms in Hainan Island,it’s significant to study the evolution characteristics for identifying,tracking convective clouds and improving the efficiency of weather modification.Based on the S-band dual-polarization Doppler weather radar(CINRAD/SA-D)data of Hainan Island from 2015 to 2020,the dual-polarization characteristic of typical isolated convective clouds case and the evolution of isolated convective clouds over the island are analyzed.The results show that the radar data of the typical case of isolated convective clouds in Hainan Island(July 26,2020)present obvious differential reflectivity(ZDR)and specific differential phase shift(KDP)column phenomena during the development phase,which means the convective motion in the clouds was strong.The total number of isolated convective clouds case in Hainan Island from 2015 to 2020 is 495 times,accounting for 11.82%of the total convective cloud cases(4017 times).The southwest low pressure trough,the warming high pressure ridge and the southward cold front are three weather systems triggering isolated convective clouds easily.The isolated convective clouds from March to June are more,accounting for 76.84%of the total cases.It is significantly higher than that of other months.March is a high-incidence month for isolated convective clouds,in which isolated convective clouds account for 47.78%of the total cases.In one day,the period from 14:00 to 17:00 is the period of high occurrence of isolated convective clouds in Hainan Island,accounting for 72.84%of the total cases(475 times).The frequency of isolated convective clouds in southwestern and central mountain⁃ous areas in Hainan Island is higher,accounting for about 88.84%of the total cases(475 times).The movement direction of isolated convective clouds is mainly northeast and southeast,which is mainly affected by westerly and southerly winds.In addition,the move⁃ment speed of isolated convective clouds is mainly concentrated between 6 and 20 km·h−1 and the movement distance of isolated con⁃vective clouds is mainly distributed between 6 and 20 km.More than half of isolated convective clouds in movement distance are less than 20 km.