天山山区植被类型改变对新疆气候影响的模拟分析

Numerical simulation analysis on the impact of change in rangeland vegetation type on climate in the Tianshan Mountains using a Regional Climate Model

使用RegCM3区域气候模式，利用CRU资料和气象台站观测资料，验证了RegCM3区域气候模式对新疆降水和气温的模拟能力，分析了天山山区植被类型改变对新疆气候的影响。结果表明，RegCM3区域气候模式对新疆及其临近地区降水、温度的空间分布形势和季节变化特征具有较好的模拟能力。天山山区草地面积的改变，对新疆地区的降水和地面气温的影响很小。如果将天山山区43．5°～45．0°N区域内的地表类型由草地改变为耕地，即假设50％的草地被开垦为耕地，那么，天山山区降水量的变化强度在5—7月逐渐增强，然后减弱。天山植被的变化主要通过影响对流性降水并进而影响总降水的变化。天山植被类型变为农田后会造成较大的地面潜热通量差异并引起地表净热通量较大的差异，进而影响到地面气温的模拟。潜热通量的变化通过影响局地的水汽供应进而引起降水较大的变化。

The relationship of vegetation with climate change has been identified in recent studies at regional and global scales. These efforts have provided the basis for vegetation reconstruction and eco-environment restoration through research on vegetation dynamics in specific regions and on its relationship with climate change to find the key factor affecting vegetation changes. In this study, the simulations of climate （mainly temperature and precipitation distribution and changes over Xinjiang） in the Xinjiang region were carried out by RegCM3 nested into CRU data. The RegCM3 model has the ability to simulate the basic character of the spatial distribution of precipitation and temperature over Xiniiang. At the same time, the model simulation can provide more reliable information of local precipitation and air temperature for regions with few observation stations. The impact of the change in rangeland vegetation type on climate in Tianshan Mountains was analyzed by the Regional Climate Model. Using this model, we analysed the impact of vegetation change on temperature and precipitation through three sensitivity experiments. The increase in grassland area may have little effect on temperature and precipitation in the Tianshan Mountains, but vegetation type that changed from grassland to cropland resulted in an increase of temperature and precipitation in the surface layer. Half of the grass area cultivated could bring growth from May to July in the Tianshan Mountains. This study showed that latent heat release was the main factor causing the ground temperature difference. The latent heat, by influencing the water vapor contents, affected the thermo-conveetive local precipitation.