CMIP6模式对青藏高原东坡暖季降水的模拟评估

doi:10.12006/j.issn.1673-1719.2021.059

摘要/Abstract

摘要：

青藏高原东坡陡峭地形区是气候模式陆地降水模拟偏差的大值区,且这一偏差长期未得到有效改善。基于17个参加国际耦合模式比较计划第六阶段（CMIP6）的全球气候模式的日降水结果,评估了当前最新一代的气候模式对青藏高原东坡地区2000—2014年暖季（5—9月）降水气候态及其季节内演变的模拟能力。结果表明：高原东坡降水正偏差存在于大部分的CMIP6模式当中,且模式虚假降水主要源于对强降水（降水量≥6 mm/d）的过量模拟,模式对<6 mm/d的弱降水的模拟略小于观测。尽管模式对高原东坡暖季平均降水表现出一致性的高估,但不同模式对于不同月份降水的模拟存在较大不同。基于环流场的分析显示,高原东坡强降水的季节内演变与高原东坡及其以东对流层中层偏南风的演变密切相关,表明模式对于对流层中层环流的模拟虽然不是导致高原东坡强降水模拟正偏差的最主要因素,但对于环流季节内变化的合理模拟是模式能否再现高原东坡强降水逐月变化的一个关键因子。

关键词: CMIP6模式, 青藏高原东坡地区, 暖季降水, 大气环流

Abstract:

The steep terrain area in the eastern slope of the Tibetan Plateau is a large deviation area for climate models in the processes of simulating land precipitation, and this deviation has not been effectively improved for a long time. Based on the daily precipitation of 17 global climate models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6), the ability of the latest climate models to simulate precipitation climatological characteristics and their intraseasonal evolution over the eastern slope of the Tibetan Plateau during the warm season (May to September) from 2000 to 2014 was assessed. The results show that the positive precipitation deviation in the eastern slope of the Tibetan Plateau exists in most CMIP6 models, and the false precipitation center mainly comes from the over-simulation of the heavy rainfall (precipitation≥6 mm/d), and the simulation of the weak rainfall (precipitation<6 mm/d) is smaller than that of TRMM observation. Although there is a consistent over-simulation of the warm season precipitation in the eastern slope of the Tibetan Plateau, there are large differences in the simulation of precipitation for different months between models. The analysis based on the circulation field shows that the intraseasonal evolution of the heavy rainfall in the eastern slope of the Tibetan Plateau is closely related to the evolution of southerly wind anomalies in the mid-troposphere in the eastern slope of the Tibetan Plateau and east to it. The above results indicate that although the simulation of the mid-tropospheric circulation is not the main factor causing the positive deviation of the simulation of heavy rainfall in the eastern slope of the Tibetan Plateau, the reasonable simulation of the intraseasonal variation of the circulation is a key factor for a model to reproduce the month-to-month variation of heavy rainfall on the eastern slope of the Tibetan Plateau.

Key words: CMIP6 models, Eastern slope of the Tibetan Plateau, Warm season precipitation, Atmospheric circulation

张歆然, 陈昊明. CMIP6模式对青藏高原东坡暖季降水的模拟评估[J]. 气候变化研究进展, 2022, 18(2): 129-141.

ZHANG Xin-Ran, CHEN Hao-Ming. Assessment of warm season precipitation in the eastern slope of the Tibetan Plateau by CMIP6 models[J]. Climate Change Research, 2022, 18(2): 129-141.

图/表 10

表1 17个CMIP6模式的基本信息

Table 1 The information of 17 CMIP6 models

图1 降水的空间分布注：黑色等值线为500 m地形高度线;红色方框为高原东坡地区,范围为（101°~106°E,29°~34°N）。

Fig. 1 Spatial distribution of precipitation. (The black contour is the 500 m terrain height line, the red box (101˚-106˚E, 29˚-34˚N) is the eastern slope of the Tibetan Plateau)

图2 同图1,但为CMIP6各模式与TRMM观测偏差的空间分布

Fig. 2 Same as Fig. 1, but for the spatial distribution of precipitation deviation between CMIP6 models and TRMM observation

图3 29˚~31˚N平均的降水随经度的分布注：灰色竖虚线为TRMM观测强降水中心的位置。

Fig. 3 Distribution of precipitation average between 29˚N and 31˚N. (The gray vertical dashed line is the location of the TRMM observation precipitation center)

图4 CMIP6各模式与TRMM观测中降水空间分布的泰勒图(a)东亚区域（70˚~130˚E,10˚~50˚N),(b)青藏高原东侧区域（100˚~110˚E,25˚~35˚N）注：其中模式BCC-CSM2-MR（-0.06）、CAMS-CSM1-0（-0.31）和CMCC-CM2-SR5（-0.07）与TRMM观测的相关系数为负,图中未显示。

Fig. 4 Taylor diagram of the spatial distribution of precipitation between each CMIP6 model and TRMM observation. (a) East Asian region (70˚-130˚E, 10˚-50˚N), (b) the region of eastern slope of the Tibetan Plateau (100˚-110˚E, 25˚-35˚N)

图5 CMIP6各模式对青藏高原东坡地区不同强度降水的模拟(a)发生频次占总日数的百分比,(b)年累积降水量分布

Fig. 5 Simulation of each CMIP6 model for different intensity precipitation in the eastern slope of the Tibetan plateau. (a) Occurrence as a percentage of total days, (b) annual precipitation

图6 青藏高原东坡地区降水的逐月演变

Fig. 6 Monthly evolution of precipitation in the eastern slope of the Tibetan Plateau

图7 2000—2014年平均500 hPa风场的空间分布

Fig. 7 Spatial distribution of horizontal wind at 500 hPa

图8 青藏高原东坡地区日降水序列与东亚地区500 hPa日南风序列相关系数空间分布注：黑色虚框（105°~109°E,29°~34°N）为正相关大值中心。

Fig. 8 Spatial distribution of the correlation coefficients between the precipitation series in the eastern slope of the Tibetan Plateau and other regional 500 hPa southerly wind series in the East Asia region. (The black dashed box is the center of positive correlation)

图9 青藏高原东坡地区的年降水量与图8中正相关中心500 hPa南风分量的逐旬演变注：图中灰色虚线代表旬,如图中横坐标上5表示5月中旬,上一条灰色虚线表示5月上旬,后一条灰色虚线表示5月下旬。

Fig. 9 Decade-by-decade evolution of precipitation (red line) in the eastern slope of the Tibetan Plateau and the south wind (black line) in the positive correlation center in Fig. 8. (The gray dotted line in the figure represents every ten days, for example, 5 in the figure refers to mid-May, the upper gray dotted line refers to early May, and the latter gray dotted line refers to late May)

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