中国近代土地利用变化对区域气候影响的数值模拟

A NUMERICAL SIMULATION ON IMPACT OF HISTORICAL LAND-USE CHANGES ON REGIONAL CLIMATE IN CHINA SINCE 1700

利用国家气候中心改进的高分辨率区域气候模式(RegCM-NCC)模拟研究了中国近代历史时期土地利用/覆盖变化对中国区域气候的影响,模拟结果显示,1700年以来,以森林砍伐、草地退化及相应耕地面积扩大为主的土地利用变化可能对中国区域降水、温度产生了显著影响。1700—1900年期间,由于土地利用的变化使华北、西南等地区降水呈减少趋势,其他区域变化不明显,但近50年来却使长江中下游地区、西北、东北部分地区降水有所增加。1700—1800年间的土地利用变化使得除东北及长江流域地区外的大部分地区温度呈下降趋势,1900年以后有所升高,特别是近50年来中国大部分区域平均气温升高,与这一时期由于大气中温室气体排放浓度增加造成的温度升高相一致。另外,土地利用变化不仅使大气温度、湿度发生变化,还可引起基本流场的变化,使东亚冬、夏季风气流有所增强,这主要是由于植被变化改变了地面温度,使海、陆温差进一步增大的结果。因此,土地利用变化对区域尺度气候变化的影响是不容忽视的。

By using the improved regional climate model of National Climate Center （NCC-RegCM）, a series of modeling experiments are undertaken to investigate the impacts of historical land-use changes （LUCs） on the regional climate in China. Simulations are conducted for 2 years using estimated land-use for 1700, 1800, 1900, 1950 and 1990. The conversion of land cover from forests to either grass or crops, or from grasslands to crops in these periods was extensive over China. Simulation results show that since 1700, historical LUCs, such as deforestation, degradation of grasslands, expansion of cultivated land etc, have significant impacted on regional climate change, with rainfall increasing in the low-mid Yangtze River basin, Northwest China and part of Northeast China, but decreasing to different extent in other regions. The simulated temperatures show that significant warming occurred over most areas in China in the recent hundred years, especially from 1950 to 1990, which is consistent with the warming caused by increasing greenhouse gases. On the other hand, historical LUCs have obviously affected the mean circulation, with the East Asian winter and summer monsoon becoming more intensive, which mainly results from the amplified temperature difference between ocean and land due to the vegetation change over lands.