拉尼娜年影响下鄂尔多斯市冬季气候及大气环流特征

Characteristics of Ordos City under the Background of La Nina Year

利用NCEP/NCC再分析资料和1960—2018年出现拉尼娜(La Nia)年鄂尔多斯市地面气象观测的逐月和冬季平均气温、极端最低气温及降水量等历史资料,分析不同类型、不同强度拉尼娜年背景下鄂尔多斯市降水及气温时空分布特征。结果显示:冬季降水量与拉尼娜强度成正比,且东部型拉尼娜年比中部型拉尼娜年的降水量多,降水量贡献率最大的月份是1月。空间分布呈现东部型拉尼娜、强拉尼娜以及中等强度拉尼娜背景下大部地区降水偏多,而中部型拉尼娜和弱拉尼娜背景下大部地区降水偏少的特征。气温分布呈现总体偏低,偏低程度呈波动略减态势。气温偏低年份的概率与拉尼娜发生强度成正比且发生在东部类型拉尼娜概率较大。空间上不论拉尼娜强度和类型均呈现大部地区偏低的特征,其中,极端最低气温出现在西部和南部地区的频率大于其它地区。不同强度和类型的拉尼娜年,所对应的大气环流特征和高、低空配置以及地面气压场特征均不同。

Using NCEP/NCC reanalysis data and historical data such as the monthly and winter average temperature, extreme minimum temperature and precipitation of the Ordos surface meteorological observations from 1960 to 2018, analyze the temporal and spatial distribution of precipitation and temperature in Ordos City and the characteristics of high and low circulations under the background of different types and different intensities of La Ni?a years. The results show that: the winter precipitation is directly proportional to the intensity of La Ni?a, and the eastern La Ni?a has more precipitation than the central La Ni?a. The month with the largest precipitation contribution rate is January. The spatial distribution presents the characteristics of more precipitation in most areas under the background of eastern La Ni?a, strong La Ni?a and medium-intensity La Ni?a, and less precipitation in most areas under the background of central La Ni?a and weak La Ni?a. The temperature distribution is generally low, and the low degree shows a slight decrease in fluctuation. The probability of low temperature years is proportional to the intensity of La Ni?a, and the probability of La Ni?a occurring in the eastern type is greater. Regardless of the intensity and type of La Ni?a, most areas show the characteristics of low temperature. Among them, the frequency of extreme minimum temperatures in the western and southern regions is greater than in other regions. Different intensities and types of La Ni?a years have different circulation characteristics, high and low altitude configurations, and ground pressure field characteristics.