Abstract:

From January to June 2023, meteorological droughts of varying degrees occurred in southwestern China, eastern North China, northern East China, central southern China, southern South China, and central Northeast China, seriously affecting agricultural production and restricting local economic development. To improve the ability to respond to drought disasters, timely carry out disaster prevention and reduction work, and conduct real-time summaries of drought situations. This article uses K index, MCI index, T-N flux and CABLE land surface model, as well as meteorological observation data, reanalysis data, soil moisture data to comprehensively analyze the spatiotemporal distribution characteristics and causes of regional drought events. The results are as follows: (1) In the first half of 2023, severe regional drought occurred in southwestern China and eastern Inner Mongolia. The southwestern region experienced atransition from sustained to sudden drought, while Inner Mongolia continued to experience drought. (2) During the same period, the 500hPa geopotential height field showed a two trough and two ridge pattern at mid to high latitudes. The western Pacific subtropical high pressure abnormally extended westward and uplifted northward, and the Rossby waves at mid latitudes in Eurasia were abnormally weak, resulting in a weakening of the influence of flat westerly winds and cold air in mid to high latitudes, resulting in less precipitation in the southwest and eastern Inner Mongolia, leading to regional drought. (3) In the first half of 2023, the winter La Niña event shifted to the spring El Niño event, resulting in weak convective activity in the southwest region and triggering sustained hot and dry weather; The distribution of sea surface temperature sensitive areas in Inner Mongolia has led to the stability of its upstream high-pressure ridge, resulting in drought and limited rainfall in the eastern region of Inner Mongolia.

Key words: the first half of 2023, meteorological drought characteristics, atmospheric circulation factor, ocean forcing factor

摘要：

2023年1—6月我国西南、华北东部、华东北部、华中南部、华南及东北中部等地均发生不同程度的气象干旱，严重影响农业生产、制约当地经济发展。为提高应对旱灾能力，及时开展防灾减灾工作，应对旱情进行实时总结，本文利用 K干旱指数、MCI指数、T-N通量和 CABLE 陆面模式，以及气象观测数据、再分析数据、土壤水分资料等，综合分析区域性干旱事件的时空分布特征及成因。结果显示：（1）2023年上半年，中国西南和内蒙古东部地区发生严重区域性干旱，西南地区经历了从持续型到骤发型的干旱转变，而内蒙古地区则持续干旱。（2）同期 500 hPa高度场在中高纬度呈“两槽两脊”型，西太平洋副热带高压异常西伸北抬，欧亚中纬度Rossby波异常偏弱，导致中高纬地区的平直西风和冷空气影响减弱，造成西南地区和内蒙古东部地区降水偏少，进而引发区域性干旱。（3）2023年上半年，冬季La Niña事件转为春季El Niño事件，导致西南地区对流活动偏弱，诱发持续高温干旱天气；内蒙古地区的海温敏感区分布导致其上游高压脊稳定，造成内蒙古东部地区干旱少雨。

关键词: 2023年上半年, 气象干旱特征, 大气环流因子, 海洋强迫因子