城市化影响着局地与区域气候变化。区域气候模式是探讨城市与环境问题演变机制与城市化气候效应的重要研究手段,然而模式地表参数化方法处理地表参数时难以全面反映下垫面状况,可能影响模拟结果的合理性。因此以卫星数据源为基础,分析了 OPI方法处理下垫面参数导致的偏差,结合其导致的地表辐射收支差异说明不同空间尺度偏差的辐射收支效应,进而通过与CO_2排放关联定量分析OPI方法对城市化气候效应的影响。结果发现随着空间尺度的变大,OPI方法导致的城市面积提取误差也在变大,导致城市下垫面转变成了其周边的土地覆盖类型,增强了城市群区域的反照率,降低了城市区域的辐射收支,弱化了城市气候效应。研究发现城市地表单位面积反照率增加0.01相当于减少了2.82 kg的CO_2排放,京津冀城市群2009年案例分析表明其弱化程度相当于减少了CO_2排放2.28*10~5 t,扩展到中国区域尺度上则相当于减少了1.81*10~6 t CO_2排放。
英文摘要:
Rapid urbanization has changed surface properties of city and its surroundings,which already modified local and regional climate change. Currently regional climate models were used to analyze the climate effect influenced by urban expansion and explore its induced environmental issues. However, the Overlapping Parabolic Interpolation (OPI) method is used for surface parameterization of climate models mainly focused on the maximum information of land cover types,and it would neglect minor signals of land surface parameters,especially in highly mixture surface in city surroundings,further affected the accuracy of model simulation. In order to quantify the impact of OPI method on urban land surface parameters derivation, this study tried to examine radiative forcing of surface albedo change influenced by urban identification deviation in mega-cities of China based on Earth' s energy budget measurements, then CO_2 emission offsets from surface albedo change were used to analyze modification of OPI method on urban climate. The results showed that deviation of urban area identified by OPI method has became larger with spatial resolution increase,which resulted in urban effect underestimation for climate analysis due to surface albedo increase. Case study in the summer of 2009 showed that increasing albedos of urban area identification deviation in urban agglomeration of Beijing,Tianjin and Hebei of China will induce a negative radiative forcing equivalent to offsetting about 2. 28* 10~5 tons and 1. 81*10~6 tons of CO_2 emissions respectively.