我国冬季气温日较差的时空变化特征及其可能成因

Temporal and Spatial Variation Characteristics and Possible Causes of Daily Temperature Range in Winter in China

摘要: 本文基于1970~2020年中国地面气候资料日值数据集、同期NCEP/NCAR逐月再分析大气环流资料以及NOAA逐月海表温度资料，采用线性趋势分析、经验正交函数分解(EOF)、相关和回归分析等方法研究了我国冬季气温日较差(DTR)的时空变化特征及其可能成因，所得结论如下：1) 我国冬季DTR呈线性减小趋势，其中40˚N以北地区减小趋势最大，这主要是因为，在全球变暖情况下，最低气温增暖速率远大于最高气温而造成的；2) 我国冬季DTR异常存在两个主要模态，第一模态表现为40˚N以南地区的一致型变化，时间序列具有显著的年际变化特征，第二模态则主要表征40˚N以北地区的DTR变化，以年代际变化为主；3) 进一步分析表明，两模态与同期海表温度异常密切相关，第一模态对应显著的热带中东太平洋海温异常，即El Niño (La Niña)年冬季，受异常大气环流的影响，我国南方地区云量增多(减少)，水汽含量增加(减少)，使得DTR容易偏小(偏大)，第二模态则与太平洋年代际振荡(IPO)有关，当IPO为正(负)位相时，东亚大槽显著减弱(增强)，东北地区水汽含量增多(减少)，导致DTR显著减小(增大)。

Abstract: Based on the daily data set of China’s surface climate data from 1970 to 2020, the monthly reanalysis of atmospheric circulation data by NCEP/NCAR in the same period and the monthly sea surface temperature data by NOAA, used linear trend analysis, empirical orthogonal function decomposition (EOF), correlation and regression analysis are used to analyze the temporal and spatial variation characteristics and possible causes of winter temperature range (DTR) in China. The conclusions are as follows: 1) In China, the winter DTR shows a linear decreasing trend, and the decreasing trend is the largest in the area north of 40˚N, which is mainly due to the fact that the warming rate of the lowest temperature is much higher than that of the highest temperature in the case of global warming. 2) there are the two principal modes of the winter DTR anomaly in China. The first mock exam is the uniform change of the 40˚N south area, and the time series has significant interannual variability. The second mode mainly represents the DTR variation in the north of 40˚N, with the interdecadal variation as the main factor. 3) Further analysis shows that the two modes are closely related to the sea surface temperature anomaly. The first mode corresponds to the significant tropical Pacific mean SST anomaly, that is, El Niño (La Niña) in the winter, under the influence of anomalous atmospheric circulation, the amount of cloud cover increased (decreasing) and the water vapor content increased (decreasing) in southern China, making DTR easy to be smaller (larger). The second mode was related to the Pacific Decadal Oscillation (IPO). When IPO was a positive (negative) phase, the East Asian Trough weakened significantly (enhanced), and the water vapor content in the northeastern region increased (decreasing), resulting in significant DTR decrease (increase).