西太平洋副热带高压指数的修订与应用

Revision and Application of the Western Pacific Subtropical High Indices

中文关键词:  西太平洋副热带高压  副高监测指数  东亚夏季风雨带  夏季高温  全球变暖

英文关键词:Western Pacific Subtropical High (WPSH) indices  East Asian summer monsoon rainbelt  hot summer  global warming

中文摘要:

      作为东亚季风区气候异常的重要环流系统之一,西太平洋副热带高压(以下简称副高)的强弱、位置和形态对我国天气气候异常有显著影响。气候监测业务中主要通过副高指数(包括副高面积、强度、脊线、北界和西伸脊点五个指数)来反映副高的强度、位置和空间形态。受全球变暖影响,北半球副热带位势高度整体增强,导致现行的副高指数已不能准确刻画副高特征,与区域性洪涝或夏季高温等极端天气过程的对应关系也减弱,因此非常有必要对副高指数进行修订。具体修订内容包括:(1)首先确定副高的最西经度位置和北界位置,然后再计算副高的面积和强度指数；(2)考虑变暖背景下副高的西伸形态及其与我国气候异常的关系,将副高面积指数规定为西伸脊点至150°E范围内5880gpm等值线所包围区域的实际面积；(3)对副高脊线和北界指数分别补充了西段和东段指数,能够更为细致地表征副高的形态变化及其与我国降水和高温的关系。 与现行指数的对比显示，修订的副高指数提升了副高对我国气候异常演变的指示性。在变暖背景下，除副高脊线指数外，各月的副高指数显示副高明显增大、增强、北扩且西伸。其中盛夏时期副高更倾向于北扩影响我国北方地区，而其他季节副高则更倾向于西伸影响我国西部地区。修订的副高指数与我国夏季降水和高温都存在较好的对应关系，且较现行业务指数与降水的关系更为显著，尤其是西伸脊点和西段脊线指数。它们与夏季各月降水和高温的空间相关分布，体现了随着东亚夏季风的推进，降水和高温的高相关区也逐渐北抬的特征。

英文摘要:

      As one of the major circulation systems causing climate anomalies in the East Asian monsoon region, the intensity, location, and spatial morphology of the Western Pacific Subtropical High (WPSH) have a significant impact on China"s weather and climate anomalies. The WPSH is mainly described by five WPSH indices in the climate monitoring operation in the National Climate Center of CMA, including area (GM), intensity (GQ), ridgeline (GX), northern boundary (GB), and westernmost point (GD) indices. Under the background of global warming, the enhancement of the subtropical geopotential height in the Northern Hemisphere led to the fact that the current operational WPSH indices can no longer accurately depict its spatial morphology, and weaken its corresponding relationship with regional extreme weather processes such as flood or summer heat. Thus, this work proposed the necessary to improve the WPSH indices, including: (1) firstly determining the GD and GB indices, and then calculating the GM and GQ indices; (2) considering the further western extension of the WPSH and its relationship with China’s climate anomalies under the warming background, the GM index is stipulated as the area enclosed by 5880 gpm isolines from the WPSH westernmost point to 150°E; (3) adding the western and eastern GX indices, and the western and eastern GB indices, which can characterize finely the spatial variation of the WPSH and its relationship with precipitation and high temperature anomalies in China. The comparison with the operational indices shows that the revised WPSH indices improve the inductiveness of the WPSH to the evolution of climate anomalies in China. Under a warming background, the WPSH in all months significantly enlarged and strengthened, and extended northwestward, without a trend in the ridgeline location. Specifically, the WPSH expands northward to affect northern China in mid-summer, while extending westward to affect western China in other seasons. The revised indices have a better correspondence with both summer precipitation and high temperature in China than the operational indices, especially for the GD and western GX indices. Their spatial correlation distributions with summer precipitation and high temperature reflect that as the northward advance of the East Asian summer monsoon.