西南地区城市化进程加剧局地气象条件的空间差异

Urbanization Magnifies Spatial Variations of Local Meteorological Conditions in Southwest China

土地利用覆被变化对于局地气象条件的演变具有重要影响。在过去几十年我国西南地区经历了较为明显的土地利用变化,而该区域土地利用转变背景下局地气象要素的时空差异尚缺乏定量研究。本文利用中国多时期土地利用土地覆被遥感监测数据集(CNLUCC)以及中国区域地面气象要素驱动数据集(CMFD),基于土地利用转移矩阵和距平分析方法,量化了西南地区1980—2018年的土地利用转变及典型区域下的气象要素(近地面气温、风速、向下长波辐射、降水)时间变化特征和空间差异。结果表明:(1)西南地区近四十年以城市化进程为主导,建设用地整体增加10133 km2,重庆、成都以及昆明大城市面积扩张了2~4倍;(2)以城市化进程明显的0.5°网格为中心区,3°网格为背景场,可有效刻画土地利用变化背景下的局地气象要素时空演变差异,且该差异在上述三个城市呈现出明显的地域性特征。具体来说,成都在2000年后的城市化快速发展期呈现出较大的气象条件空间差异,2000—2010年气温、长波辐射距平以及风速和降水相对变化量中心区与背景场的最大差值分别为-0.69 K、-5.2 w·m^(-2)、+22%、+20%,而2010—2018年二者差异反向,最大差值分别为+0.78 K、+4.3 w·m^(-2)、-17%、-13%。重庆大部分气象要素时空差异与成都相近,但风速呈先减小后增大的趋势,1995—2009年间中心区高于背景场达22%。昆明的土地利用较为复杂,各气象要素变化较成都与重庆存在一定差异。这可能是因为较大面积的水体对气象要素的时空变化有一定的缓冲和调节作用。本研究可为西南地区土地利用尤其是城市化发展下的用地管理和城镇规划提供参考。

Land use and land cover change(LUCC)heavily influence local meteorological and climatic conditions.Southwest China has experienced significant land use change in the past decades,but spatial variations in key meteorological factors in this region remain unclear.This study investigated LUCC in southwest China from 1980 to 2018 by land use transition matrix,based on land use data from the China Multi-Period Land Use Land Cover Remote Sensing Monitoring Dataset(CNLUCC).Over typical regions,spatial variations of local meteorological factors,i.e.near-surface air temperature,wind speed,downward longwave radiation and precipitation,were quantified by anomaly analysis,based on meteorological information from the China Meteorological Forcing Dataset(CMFD).The results suggested:(1)urbanization dominated the LUCC,with an increase of 10133 km2 in built-up areas,and large cities like Chongqing,Chengdu,and Kunming expanded by 2~4 times;(2)the spatial variations of local meteorological factors could be effectively characterized by comparing the 0.5°grid urban center with the 3°grid background area,and they were found to be different among the aforementioned cities.Specifically,Chengdu exhibited large spatial variations in meteorological factors during the rapid urbanization process.From 2000 to 2010,the differences between urban center and background area,in terms of anomaly of air temperature and downward longwave radiation,and relative changes in wind speed and precipitation,were up to-0.69 K,-5.2 w·m^(-2),+22%,and+20%,respectively.However,from 2010 to 2018 these differences were reversed,with maximum of+0.78 K,+4.3 w·m^(-2),-17%,and-13%,respectively.The temporal and spatial differences of most meteorological factors in Chongqing were similar to those in Chengdu except for wind speed,which decreased first and then increased for the entire study period,and was 22%larger in the urban center as compared to the background area from 1995 to 2009.Compared to Chengdu and Chongqing,LUCC in Kunming was more complicated,and the spatial variations of meteorological factors exhibited different patterns.This was probably due to large waterbody,which moderated the spatiotemporal evolution of local meteorological factors in this area.The findings of this study are expected to support the local development and future land use management under the context of LUCC,especially urbanization,in southwest China.