热带气旋背景下广东龙卷气候特征和环境条件

Climatic Characteristics and Environmental Conditions of Tornadoes in Guangdong under the Background of Tropical Cyclones

中文关键词:  热带气旋,龙卷,广东,时空分布特征,环境条件

英文关键词:tropical cyclone  tornadoes  Guangdong  spatial-temporal characteristics  environmental conditions

中文摘要:

      为研究热带气旋背景下广东龙卷发生的特征,利用1961—2022年广东历史龙卷灾情数据和欧洲中期天气预报中心第五代大气再分析资料(ERA5),统计广东热带气旋龙卷的时空分布、天气形势和关键热动力环境条件,并对比分析了不同热带气旋在相似路径下有/无龙卷生成的关键物理量差异。结果表明:广东热带气旋龙卷主要发生在珠三角、雷州半岛和潮汕平原。热带气旋龙卷占广东总龙卷数量的约42%,龙卷个数与影响广东的热带气旋数量呈显著正相关；8月为热带气旋龙卷的最高发月份,14-18时和06-10时为日内高发时段。这些龙卷主要发生在热带气旋中心的东北象限(或其前进方向的右后侧或深层环境风切变上切变区域)；热带气旋登陆后的2-18小时是龙卷发生的高发时段,龙卷生成时对应的热带气旋强度主要为热带风暴和热带低压。热带气旋背景下广东龙卷发生天气形势可分为偏南急流型和偏北急流型,两类天气型龙卷的生成位置超级单体复合参数(SCP)大值区和强龙卷指数(STP)大值区呈现出较好的空间匹配关系。对比热带气旋背景下龙卷与非龙卷的环境条件,发现在热带气旋中心的东北象限广东龙卷环境具有明显更大的夹卷对流有效位能(E-CAPE)和0-1km 风暴相对螺旋度(SRH1)(其差异均达到了95%置信水平的Welch t检验),E-CAPE和SRH1的组合能较好地指示热带气旋引发的龙卷潜势。对比热带气旋背景下广东龙卷与冷涡背景辽宁龙卷、热带气旋背景江苏龙卷和美国龙卷,发现广东龙卷的对流有效位能与美国相当,只有辽宁龙卷和江苏龙卷的约1/2,但广东龙卷SRH1是辽宁龙卷的2倍,约为美国龙卷的1/2。

英文摘要:

      In order to study the characteristics of tornadoes occurring in Guangdong province under the background of Tropical Cyclones (TC), using tornado disaster data in Guangdong and the fifth generation atmospheric reanalysis data (ERA5) from the European Center for Medium-Range Weather Forecasts from 1961 to 2022, the spatial-temporal distribution, weather patterns, and atmospheric environmental conditions of Guangdong tornadoes under the background of TCs are investigated. Differences between the physical parameters of tornadoes and non-tornadoes under the background of TCs are compared. The results show that TC tornadoes in Guangdong are mainly concentrated in the Pearl River Delta, Leizhou Peninsula and Chaoshan Plain. Under the background of TCs, tornadoes account for about 42% of the total number of tornadoes in Guangdong, and the number of tornadoes is significantly positively correlated with the number of TCs affecting Guangdong. August is the highest month for tornadoes in Guangdong under the background of TCs, and 14-18 p.m. and 6-10 a.m. are the peak periods for tornadoes. Guangdong tornadoes mainly occur in the northeast quadrant of the TC center, the right rear of the TC"s movement path, and the upper shear region of the environmental wind. The 2-18 hours after TC landfall are the peak period for tornadoes, and the TC intensity during tornadoes is mainly tropical storms and tropical depressions. The weather pattern of TC tornado is mainly southerly jet and northerly jet. The generating positions of tornadoes of the two weather types show a better spatial matching relationship with the large value areas of supercell composite parameters (SCP) and significant tornado parameters (STP). In the background field of TCs with similar paths, comparing atmospheric conditions with and without tornadoes, it was found that the atmospheric environment with tornadoes has significantly larger entrainment convective available potential energy (E-CAPE) and 0-1km storm relative helicity (SRH1) in the northeast quadrant of the TC center (statistically significant at the 95% level) . The combination of E-CAPE and SRH1 can better indicate the potential of tornadoes caused by TCs. The atmospheric physical parameters of Guangdong tornadoes under the background of TCs were compared with those of Jiangsu tornadoes, American tornadoes, and Liaoning tornadoes under the background of cold vortex. It was found that the CAPE of Guangdong tornadoes is equivalent to that of the United States, only about half of that of Liaoning tornadoes and Jiangsu tornadoes. However, the SRH1 of Guangdong tornadoes is twice that of Liaoning tornadoes, about half of that of American tornadoes.