2023年秋季我国气候异常特征及成因分析

利用NCEP/NCAR再分析数据集和中国2400个站的气候观测数据，对2023年秋季我国气候异常特征及其成因进行分析。2023年秋季全国平均气温为1961年以来历史同期最高；全国平均降水量接近常年同期，但空间分布不均且季节内变化明显。秋季欧亚中高纬环流呈“两槽一脊”型，造成我国气温显著偏高；9月呈“两脊一槽”型，巴尔喀什湖低槽活动导致西北地区降水增多；10月呈“两槽一脊”型，导致北方地区偏暖加强；11月呈“西高东低”型，东路冷空气增强，东北地区气温偏低、降水偏多。西太平洋副热带高压总体较常年偏强、偏西，脊线9月异常偏北、10月偏南、11月接近常年。印缅槽9月显著偏强，10—11月接近常年。9月印缅槽偏强与副热带高压异常偏北共同导致了长江中下游以北至黄河下游地区多雨；10—11月东部地区水汽条件整体偏差。9—10月近海台风频繁活动，造成华南地区降水偏多。2023年秋季我国气候受到大气季节内变化的显著作用，热带海温异常的影响不典型。

Features and Possible Causes of Abnormal Climate over China in Autumn 2023

Based on the NCEP/NCAR reanalysis data and climate observations from 2400 stations of China, the characteristics of climatic anomalies over China in autumn 2023 and the possible causes are analyzed. The results denote that, in autumn 2023, the average temperature in China peaked the record in the same period since 1961, and the average precipitation was close to the climatic mean, but had uneven spatial distribution and significant intra-seasonal variability. The circulation in the mid-high latitudes of Eurasia showed a “negative-positive-negative” pattern on the seasonal mean scale, leading to the abnormal warming in China. In September, the circulation was in a “positive-negative-positive” pattern that caused the frequent activity of the trough near Balkhash Lake and the increase of precipitation in Northwest China; in October, the “negative-positive-negative” pattern of circulation caused further warming in northern China; and in November the circulation pattern of “positive in west and negative in east” formed, enhancing the cold air in the east and causing the temperature in Northeast 〖JP2〗China to drop to below normal and precipitation〖JP〗 to be more than normal. The Western Pacific subtropical high (WPSH) was stronger and more westward than usual overall, and its ridge line swung frequently in the meridional direction, that is, the ridge line was abnormally further north than usual in September, further south than usual in October and close to normal position in November. The India-Burma trough was significantly stronger in September and near normal during October-November. In September, the stronger Indo-Burma trough and the northerly WPSH jointly contributed to the heavy〖JP2〗 rainfall in the region between the middle and lower reaches of Yangtze〖JP〗 River and the lower reaches of Yellow River. The basic water vapor transport condition in eastern China became negative from October to November. In addition, typhoon activities in southern coastal area of China were frequent in September and October, resulting in more precipitation in South China. These results reveal that the climate anomaly in autumn 2023 was significantly affected by the intra-seasonal variation of the atmosphere, and it did not match the typical responses to the tropical SST anomaly.