华北地区未来气候变化的高分辨率数值模拟
Simulating Future Climate Changes over North China with a High Resolution Regional Climate Model
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摘要: 使用20 km高水平分辨率的区域气候模式RegCM3,单向嵌套FvGCM/CCM3全球模式,进行了中国区域气候变化的数值模拟试验,分析华北地区夏半年4—9月的气温、降水和高温、干旱事件的变化。模式积分时间分为两个时段,分别为当代的1961—1990年和在IPCC SRES A2温室气体排放情景下的21世纪末2071—2100年。模式检验结果表明:在大部分月份,区域模式对当代气候的模拟都较全球模式更好。两个模式模拟的未来气温和降水变化,在空间分布型和量级上都有一定不同,如区域模式的升温更高,降水出现大范围减少等。此外,使用日最高气温不低于35 ℃的日数 (DT35) 和考虑了湿度因素的炎热指数 (IH) 不低于35 ℃的日数 (DHI35),分析了区域模式模拟的未来高温事件变化,结果表明:未来华北地区DT35和平原地区DHI35均有较大增加。未来华北地区的连续干旱日数 (CDD) 将增加,依照UNEP (United Nations Environment Programme) 干旱指数 (AU) 给出的气候湿润区将有较大幅度减少,而半湿润半干旱区和半干旱区面积将增加。Abstract: Multi decadal climate change simulations have been performed over China using 20 km horizontal resolution regional climate model (RegCM3) one way nested within a global model (FvGCM/CCM3, here in after called FvGCM) from NCAR/NASA. Two experiments are conducted, one for the period of 1961—1990, the other is for the future climate of 2071—2100 under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 emission scenario. The analysis focuses on the warm half of the year, from April to September. First, simulations of present climate conditions over North China by FvGCM and RegCM3 are compared with observations to assess the model performance. Results show that both models can reproduce the observed spatial patterns of surface air temperature and precipitation. Compared with FvGCM, RegCM3 shows a better performance especially in providing more spatial details of the surface variables. The changes (differences between future and present) of mean temperature and precipitation are analyzed and compared between the two models simulations. Significant warming in the end of 21st century is predicted by both models however their results are different both in spatial distribution and amount. Compared with FvGCM, a greater warming is simulated by RegCM3 in some areas of the northern part while in the southeast and the east of the region RegCM3 indicates the warming is slighter. General increase in mean precipitation is found in FvGCM simulation, in a range of less than 10% to exceeding 30%. While for RegCM3, the simulated precipitation increases in the north of Henan as well as Shandong, but changes little or even decreases in the northern part of the region is simulated. Future changes in extreme heat events simulated by RegCM3 are statistically analyzed using the days with daily maximum temperature no less than 35 ℃(DT35) and the days with a heat index which includes the humidity factor also no less than 35 ℃(DHI35). Results show a substantial increase of DT35 over the whole region and increase of DHI35over the plain areas. Increase in the maximum number of consecutive dry days (CDD) is also simulated by the model over the region, especially in the north of Hebei Province. According to the classification of UNEP drought index (AU), there will be significant less humid area and a corresponding increase of dry sub humid and semi arid, indicating the future increase of drought extent in the future over the region.
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Key words:
- climate change;
- regional climate model;
- North China
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图 2 华北地区4—9月平均地面气温和降水分布
(a) 观测气温, (b) 观测降水, (c) 全球模式模拟的气温, (d) 全球模式模拟的降水, (e) 区域模式模拟的气温, (f) 区域模式模拟的降水
Fig. 2 Mean temperature and precipitation from April to September over North China
(a) observed temperature, (b) observed precipitation, (c) temperature simulated by FvGCM, (d) precipitation simulated by FvGCM, (e) temperature simulated by RegCM3, (f) precipitation simulated by RegCM3
图 4 华北地区4—9月平均气温和降水变化
(a) 全球模式模拟的气温, (b) 区域模式模拟的气温, (c) 全球模式模拟的降水, (d) 区域模式模拟的降水
Fig. 4 Simulated mean temperature and precipitation changs from April to September over North China
(a) temperature change by FvGCM, (b) temperature change by RegCM3, (c) precipitation change by FvGCM, (d) precipitation change by RegCM3
表 1 华北地区4—9月全球和区域模式气温模拟与观测的相关系数和误差标准差
Table 1 The spatial correlation coefficient and standard deviation between the simulated and observed mean temperature from April to September over North China
表 2 华北地区4—9月全球和区域模式降水模拟与观测的相关系数和误差标准差
Table 2 The spatial correlation coefficient and standard deviation between the simulated and observed mean precipitation from April to September over North China
表 3 区域模式模拟华北区域内AU各分类气候当代、未来的分布及其变化情况
Table 3 Climate types defined by AU in RF and A2 and its change over North China simulated by RegCM3
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