不同分辨率BCC_AGCM模式对东亚区域垂直云量的模拟

基于ISCCP(International Satellite Cloud Climatology Project)和NCEP(National Centers for Environmental Prediction)资料分析了BCC_AGCM2.1(Beijing Climate Center_Atmospheric General Circulation Model 2.1)和BCC_AGCM2.2模拟的云在东亚的垂直分布特点,并探讨了误差来源。两个模式大体上模拟出了总云量的分布形势,较好地模拟出了垂直方向上云量大值带随地形的变化特点,但模拟的总云量偏少。AGCM2.2模拟的云量整体上小于AGCM2.1,除复杂地形外AGCM2.2没有体现出高分辨率的优势。模式对中国东部环流场的模拟效果差导致模拟的云量偏少,尤其是AGCM2.2。模拟的对流层高层相对湿度明显偏大导致高层云量偏大。模式在近海面模拟的相对湿度偏小,四川盆地及周围地区冷季模拟的水汽含量偏少,因而模拟的云量偏少。模式云量对相对湿度的响应能力较好,模拟出了云量对垂直速度和稳定度的响应,但地区差异不明显。模式的云参数化方案中云与相对湿度的关系系数需要调整,应更利于云的生成。

Vertical Cloudiness over East Asia Simulated by Different BCC_AGCM Models

The ISCCP (International Satellite Cloud Climatology Project) and NCEP (National Centers for Environmental Prediction) datasets have been exploited to investigate the vertical cloudiness over East Asia simulated by BCC_AGCM2.1 (Beijing Climate Center_Atmospheric General Circulation Model 2.1) and BCC_AGCM2.2. The sources of errors are also explored in this paper. The two models generally can well simulate the distribution of total cloud amount and vertical changes in cloudiness along the topography, however, the simulated cloudiness is less than observations. The cloud cover simulated by AGCM2.2 is less than that by AGCM2.1. Despite the better representation of complex terrain, AGCM2.2 does not show any advantages of the high resolution. The poor performance of the model in the simulation of circulation fields in eastern China leads to underestimation of cloudiness, particularly in the AGCM2.2 simulation. Meanwhile, the overestimation of relative humidity in the upper troposphere results in more simulated cloudiness than observations. The underestimation of relative humidity near the ocean surface and unrealistically small moisture content simulated by the model in Sichuan Basin and its surrounding area in the cold season lead to less cloud amount in the model result. The simulated cloudiness is sensitive to relative humidity. The response of cloudiness to vertical velocity and stability is significant but has little regional difference in both models. The coefficient in the relationship between cloudiness and relative humidity in the model needs to be adjusted and should be more conducive to the production of clouds.