Due to the shortage of the global observational data of the terrestrial hydrological variables,the understanding of how surface hydrological processes respond to climate change is still limited.In this study,the Community Land Model(CLM4.0)with high resolution atmospheric forcing data is selected to simulate the global surface hydrological quantities during the period 1948–2006and to investigate the spatial features of these quantities in response to climate change at the regional scales.The sensitivities of evaporation and runoff with respect to the dominant climate change factors(e.g.temperature and precipitation)derived from the concept of climate elasticity are introduced.Results show that evaporation has a declining trend with a rate of 0.7 mm per decade,while runoff shows a weak increasing trend of 0.15 mm per decade over the global land surface.Analyses of the hotspots in the hydrological cycle indicate that the spatial distributions for evaporation and runoff are similar over many areas in central Asia,Australia,and southern South America,but differ largely in high latitudes.It is also found that,the evaporation hotspots in arid regions are mainly associated with the changes in precipitation.Our sensitive analysis suggests that the hydrological quantities show a rather complicated spatial dependency of response of the water cycle to the different climate factors(temperature and precipitation).
利用目前国际上应用较为广泛的两套再分析资料:NCEP/NCAR再分析的陆地表面温度(land surface temperature or skin temperature,简称LST)及欧洲中期天气预报中心ERA40表层土壤温度(ECMWF-STL1)资料,揭示了两组资料反映的春、夏季陆面热力状况分布特征及变率的异同。结果表明:1)两套资料的全球春季陆面热力状况气候态分布均反映出表面温度从赤道向两极递减的趋势,但在中低纬地区,ECMWF-STL1高于LST,高纬度地区情况相反。夏季,除格陵兰岛外,两套资料陆面热力状况气候态分布基本相同。2)春季ECMWF-STL1、LST变率类似,均表现为北半球中高纬地区表面温度变率大的特征。相比而言,欧亚大陆北部ECMWF-STL1变率较LST明显,南部相反。夏季,温度变率较大的区域主要位于非洲中部、欧亚大陆北部及美洲部分地区,其中,南北美洲两套资料温度变率差别较大。3)分析EOF第一模态发现,两套资料均表现出春季欧亚大陆热力状况南北反相变化的特征,澳大利亚及南北美洲地区两套资料空间分布型位相正好相反。对于夏季而言,两套资料均反映出欧亚大陆及非洲的一致性变化特征,而其他地区差别较大;4)春季增温显著的地区主要位于欧亚大陆中高纬,相比而言,欧亚大陆北部ECMWF-STL1升温较明显,南部LST降温较明显。夏季,非洲、欧亚以及北美洲地区,两套资料升降温趋势分布相似,但LST升降温幅度均较ECMWF-STL1大。总之,两套资料对热力状况的描述在非洲及欧亚大陆上相似性较大,而在澳大利亚、格陵兰岛及南北美洲地区有一定的差别。另外,对青藏高原地区的热力状况的描述两套资料差别较大。
Greenhouse gas emissions and land use/land cover change(LUCC)are two human activities notably affecting climate change.Will temperature and precipitation increase significantly during global warming resulting in more pronounced LUCC climatic effects?Considering the interannual forcing of these two factors,the NCAR Community Atmosphere Model(CAM4.0)was used in this study to investigate the importance of climatological background to LUCC impacts.Experiments based on the difference in the background climate,the greenhouse gas concentrations in 1850 and in the present age indicate contrary changes in climate sensitivity through estimations of the radiative forcing associated with LUCC,which are 0.54°C/(W/m2)and 0.26°C/(W/m2),respectively.Therefore,the background climate appears to play an important role in the regional impact of LUCC,especially at higher latitudes.In addition,global warming predominantly influences snow-albedo feedback in the mid-latitudes,thus determining the impact of LUCC,whereas the regional difference in precipitation caused by global warming is responsible for the differing climate response to LUCC in the tropics and subtropics.
