盛夏海南岛防区台风累积动能气候异常特征分析

利用1981—2018年CMA-STI热带气旋最佳路径数据集、NCEP/NCAR再分析资料和OA Flux3潜热通量数据,分析了盛夏海南岛台风累积动能(Accumulated Cyclone Energy,ACE)气候特征及异常年大气环流形势和相关物理量特征。结果表明:1981—2018年盛夏海南岛ACE呈先下降后上升的变化趋势,同时具有明显年代际特征,2010年后存在准2 a显著周期。盛夏ACE偏高(低)年,西太副高偏大(小)偏强(弱)偏西(东),其南侧伴有偏强(弱)的季风槽,台风北侧对流(不)活跃;低层防区内存在异常气旋式切变(反气旋式环流),海南受偏东(西)异常气流影响,有利(不利)于对流、水汽等向台风环流并入而加强(削弱)台风,120°~130°E越赤道气流(不)活跃;菲律宾以东至南海高空抽吸作用偏强(弱),盛行异常上升(下沉)运动,且环境风垂直切变偏小(大);东海—日本海潜热通量偏小(大),热带西太平洋及南海低层为水汽辐合(散)区。

Anomalous climatic characteristics of accumulated cyclone energy in Hainan Island defense area during midsummer

Based on the CMA-STI tropical cyclone optimal track data from 1981 to 2018, NCEP/NCAR reanalysis data and OA Flux3 latent heat flux data, the climatic characteristics of accumulated cyclone energy (ACE) in Hainan Island in midsummer and the characteristics of atmospheric circulation background and related physical quantity in anomalous years were analyzed. The results showed that, the ACE index of Hainan Island of in midsummer showed a trend of first decreasing then increasing from 1981 to 2018. Meanwhile, it presented an obvious decadal characteristic, and there was a quasi-two-year significant cycle after 2010. In the high (low) ACE years, the western Pacific subtropical high was big (small), strong (weak) and westward (eastward), with a strong (weak) monsoon trough on the south side of the subtropical high, which made the convection on the north side of the typhoon active (inactive). In the lower levels, there was abnormal cyclonic shear (anticyclonic circulation) in the typhoon protection zone, and Hainan Island was affected by abnormal easterly (westerly) flow, which was favorable (unfavorable) for convection, water vapor to merge into typhoon circulation and strengthen (weaken) the typhoon. Moreover, the equatorial flow was active (inactive) at 120°-130°E. The suction effect at high altitude was relatively stronger (weaker) from east of the Philippines to the South China Sea, and the anomalous upward (downward) movement prevails, meanwhile the vertical shear of ambient wind was weaker (stronger). The latent heat flux around the East China Sea and the Sea of Japan was relatively smaller (larger), and in the lower layer, the tropical western Pacific and the South China Sea were the moisture convergence (divergence) region.