基于高分辨率资料同化数据对青藏高原极端低温特征分析

Analysis of Extreme Low Temperature Characteristics on the Qinghai-Tibet Plateau Based on High-Resolution Assimilation Dataset

为进一步研究青藏高原极端低温事件的影响,本文利用WRF模式输出的2015~2020年的逐小时气温高分辨率同化数据计算了两类极端气温指数,研究了其空间分布规律,并根据指数分布规律将青藏高原分为四个区域,研究了高原极端低温的区域特征。结果表明:1) 高原整体呈现出东暖西冷的特征,气温以昆仑山脉与塔里木盆地的交界地带为低值中心,向四周逐渐增暖,霜冻日数和冰封日数也逐步减少。2) 以藏北为主的一区气温最低,以川西为主的四区气温最高,而以青海为主的二区和以藏南为主的三区气温最接近,一区和二区为年内气温变化最为剧烈的两个区域。四个区域霜冻与冰封日数的分布规律与气温相对应,一区最多,三区次之,二区较少,四区最少。3) 四个区域霜冻和冰封日数的季节变化相一致,冬季最多,春季次之,秋季较少,夏季最少。对霜冻日数而言,冬季,不同区域间日数的差异最小;温度越高的区域,霜冻日数的季节差异越明显;冰封日数与霜冻日数相反。

In order to further study the impact of extreme low temperature events on the Qinghai-Tibet Plateau, this paper calculated two types of extreme temperature indices based on the hourly temperature data of WRF reanalysis data from 2015 to 2020, and studied their spatial distribution law. According to the exponential distribution law, the Qinghai-Tibet Plateau was divided into four regions, and the regional characteristics of extreme low temperature on the plateau were studied. Major results are as follows: 1) The plateau as a whole is characterized by warmth in the east and coldness in the west, with temperatures centred on the junction of the Kunlun Mountains and the Tarim Basin as the centre of low values and gradually warming in all directions, with a gradual decrease in the number of frost and freezing days. 2) The lowest temperatures were found in Zone 1, mainly in northern Tibet, and the highest in Zone 4, mainly in western Sichuan, while Zone 2, mainly in Qinghai, and Zone 3, mainly in southern Tibet, were the closest, with Zone 1 and Zone 2 being the two regions with the most drastic temperature changes during the year. The distribution pattern of the number of frost and freezing days in the four regions corresponds to the temperature, with Zone 1 having the most, followed by Zone 3, Zone 2 having less and Zone 4 having the least. 3) The seasonal variation in the number of frost and freeze days is consistent across the four regions, with the highest number in winter, followed by spring, less in autumn and the lowest in summer. For the number of frost days, in winter, the differences in the number of days between regions were minimal;the higher the temperature, the more pronounced the seasonal difference in the number of frost days;and the opposite of frost days for the number of freezing days.