京津唐城市群土地利用变化的区域增温效应模拟

Modeling urban sprawl effects on regional warming in Beijing-Tianjing-Tangshan urban agglomeration

土地利用变化与大气相互作用,影响区域气候,而城市及其周边地区受人类活动影响很大,成为土地利用变化最为强烈的区域。利用耦合了城市冠层模型的中尺度大气模式(WRF/UCM),在2008年的初始大气条件和边界条件下,用20世纪70年代后期和2008年两期京津唐地区土地利用资料替换WRF/UCM模式推荐的地表覆盖数据,模拟分析不同土地利用类型及其变化对应的气候差异情况。在此过程中,利用插值方法(ANUSPLIN)得到京津唐及其周边26个气象站点观测气温的插值数据,并以此在时空尺度上对比验证了模式的模拟结果。结果表明:WRF/UCM较好地模拟出了近地表2 m的气温,无论在空间上还是在时间上都表现良好;由城市扩展主导的土地利用变化导致研究区大部分区域的增温幅度大于0.05℃,且最大的增温区域出现在城市扩展区,可达1.31℃。此外本研究初步探讨了土地利用变化的增温贡献率,结果显示研究区土地利用变化导致增温0.08℃,整体贡献率为9.88%,城市扩展区增温0.29℃,表示出了城市扩展导致的增温贡献率达到32.75%。

Land use and land cover change （ LUCC ） significantly influence regional climate as a critical aspect in the land- atmosphere interaction system. Cities and their surrounding regions tend to experience more intensive LUCC due to the high population and human activities. And the accelerating LUCC and urbanization has become an important factor which affect regional even global temperature change. In some developed countries, the space expansion rate and population growth rate all are low level. However, from the point of view of a long time （decades） and worldwide, the processes of urbanization are sustainably increasing observably. As a developing country, China is undergoing rapid urbanization, which is characterized by not only the extension of urban economy and population but also the expansion of urban land （ urban sprawl）. Urban sprawl is often presented by the conversion from original natural underlying surface to artificial architectural landscape land. Comparing with some developed countries （such as the United States） which have higher urbanization level but lower urban sprawl rate due to lower population growth rate, China is experiencing an urban sprawl process with high area ratios and magnitudes. The change process will have profound impacts on regional climate, revealed by the urban heat island （UHI） effect. Different land use types have different biophysical characters and processes, the emission of greenhouse gases only is one factor of the climatic change, the differences of surface radiation, energy and kinetic energy will directly or indirectly affect the near-surface energy balance, the local micro-meteorological conditions, the urban canopy layer, the atmospheric boundary layer and atmospheric circulation in urban and suburban areas, and affect the regional temperature changes finally. In this study, WRF/UCM （Weather Research and Forecasting Model / Urban Canopy Model ）, a meso-scale atmospheric model, which couple with an urban canopy model, was used to simulate the differences of near surface air temperature according to the different underlying surfaces, namely the land use/land cover types of 1970s and 2008 in Beijing-Tianjin-Tangshan region were used to replace the land cover data recommended by WRF itself. All the process were based on the meteorological field of 2008 and the other conditions all were the same. In the process, ANUSPLIN method was used to get interpolation data of observed temperature collected by 26 meteorological stations in the study area and its surrounding area. The study results showed that： WRF/UCM performed well on simulating the air temperature, both in the temporal or spatial scale. Almost all of the land use type transformations presented warming trend because the LUCC was dominant by urban sprawl in the area. And the warming extent over 0. 05 ℃ in most of the study area. The largest warming region appeared in the urban expansion regions, up to 1.31 ℃. The entirety warming extent of the study area led by LUCC was 0. 08 ℃, indicating that the warming contribution ratio of LUCC was 9.88%. Meanwhile, the warming extent of the urban expansion regions was 0.29 ℃, showing that the warming contribution ratio caused by urban sprawl up to 32.75%.