WRF模拟的1980-2000年中国东北农业开发对气候的影响

利用WRF模式,基于中国东北1980年代前期和2000年的土地利用/覆盖数据,分别进行了1980-2000年的气候变化模拟试验。通过两个试验结果的对比,分析了1980-2000年中国东北农业开发对气候的影响。在冬季和春季,农业开发使地表反照率增强,地表吸收的短波辐射减少,地表感热通量相应减少,地表气温降低;在夏季和秋季,农业开发削弱了地表反照率,地表吸收的短波辐射增加,同时地表潜热通量大幅增加,且增幅大于地表吸收的短波辐射的增幅,地表感热通量则相应减少,地表气温降低。农业开发的致冷幅度大多为0.1°C~1.0°C,与同期大尺度气候变化导致的当地背景温度变幅基本相当。农业开发引起的夏季降水变化因气候年景而异,“南旱北涝”年景下,呼伦贝尔—黑龙江省中部以及吉林省中部少雨,黑、吉、蒙三省（自治区）交界处降水增加,辽、蒙交界处以及辽东湾北部降水减少;“南涝北旱”年景下,呼伦贝尔—黑龙江省中部以及吉林省中部多雨,黑、吉、蒙三省（自治区）交界处降水减少,辽、蒙交界处以及辽东湾北部降水减少。农业开发的面积极其有限,因而由其导致的温度和降水显著变化主要出现在农业开发当地,尚不足以显著影响区域平均温度和降水变化。

Simulated effects of cropland extension on climate over Northeast China from 1980 to 2000 by WRF Model

By using the land use/cover data for the early 1980 and 2000 in Northeast China, we carried out two 21-year (1980-2000) simulations, respectively, with the Weather Research and Forecast (WRF) model. This paper is aimed to investigate the effects of cropland extension on climate in Northeast China. In winter and spring, the replacement of natural grassland and forest by cropland enhanced land surface albedo, and surface net solar radiation was therefore reduced. As a consequence, the surface sensible heat flux decreased and the cooling effect occurred. Mostly, the local surface air temperature dropped by 0.1°C to 1.0°C. The cooling strength is comparable to the contemporaneous background temperature change which is induced by large circulation and sea surface temperature changes. In summer and autumn, the replacement of nature vegetation by cropland reduced land surface albedo, and surface net solar radiation was therefore increased. Meanwhile, the surface latent heat flux increased largely and the surface sensible heat flux decreased. As a result, there was also a cooling effect on local surface climate. These findings demonstrate detectable effects of land use/cover changes on local temperature. The effects of agricultural development on summer precipitation vary with background climate. In the South-Drought and North-Flood years, the decreased precipitation is detected in the Hulun Buir to central Heilongjiang province and central Jilin province and around the Liaodong Gulf while the precipitation increases in common boundary area of Heilongjiang, Jilin and Inner Mongolia. In the South-Flood and North-Drought years, the precipitation anomaly pattern is approximately reverse to the abovementioned South-Drought and North-Flood years with the exception that there is still decreased precipitation around the Liaodong Gulf. However, due to limited area with land use/cover changes, the impact on regional mean temperature is very limited.