中国地区近20年云的变化特征及其与模拟结果的对比

【作者】 段皎；

【导师】 刘煜；

【作者基本信息】 中国气象科学研究院 ， 环境工程， 2010， 硕士

【摘要】 气候变化是当前倍受各国政府和科学界关注的重大问题。但由于目前认知的不足,使得我们无论是对过去的气候还是对未来气候的了解都存在很大的不确定性。地球的绝大部分能量来自于太阳,云通过影响地气系统的辐射从而对整个地气系统的能量平衡具有强烈的调节作用。云的辐射特性不仅依赖于云量及其分布,还依赖于光学厚度、云水含量、有效半径及云的其它微物理特性。本论文主要关注于中国地区云的变化趋势及气溶胶对云的影响,具体包含以下两个主要研究内容:一.分别利用ISCCP (International Satellite Cloud Climatology Project)最新的D2云气候资料集,以及MODIS (MODerate-resolution Imaging Spectro-radiometer)最新的云资料,给出总云量、高云量、中云量、云光学厚度和有效半径在我国地区的分布特征,分别对季节平均和年平均的时间序列进行线性趋势分析,并进行信度检验。结果表明:(1)近20年以来中国大部分地区总云量没有显著的变化趋势,然而,在华南地区和西北部分地区的总云量有增加的趋势,青藏高原中部的总云量有所减少;在不同季节,各地总云量、高云量和中云量的变化趋势是不同的。(2)综合云的光学厚度和云的有效半径的变化趋势可以发现,与云量变化情况相对应,夏季云的光学厚度和有效半径变化趋势最显著,这可能暗示云的有效半径的变化对云光学厚度的影响可能在夏季最大,即气溶胶的间接气候效应可能在夏季最强;云量、云的光学厚度和有效半径的变化也表明在长江以南地区和青藏高原地区可能是气溶胶间接气候效应比较显著的地区。(3)中国地区冰云光学厚度与有效直径的相关具有很强的区域特征,说明冰云的微物理机制比水云更复杂。二.在前人的工作基础上,将两个国际上比较先进的模式即由NCAR/UCAR联合开发的新一代大气环流模式Community Atmospheric Model3.0(CAM3.0)与加拿大气溶胶模块Canadian Aerosol Module(CAM)进行单向在线耦合,在模式中采用Abhul-Razzak等[2002]发展的气溶胶活化方案,最终目的是研究暖云有效半径的分布和变化。采用了IPCC AR5 2005年的排放源资料,模式从1980年1月1日开始到1996年12月30日模拟了16年,分析后10年的资料。通过模式结果与卫星资料的对比评估模式,从中可以看到:(1)模式可以较好的模拟全球总云量的季节和年平均分布特征,尤其对赤道地区及海洋上空的总云量模拟的较好。模式模拟的全球高云量的分布基本体现了实际情况,在赤道及低纬度地区,模拟的高云量偏大,在两极则偏小。模式模拟的全球中云量的分布较好地再现了观测结果,只是在两极地区偏差较大。模式对总云量模拟效果最好。(2)模式模拟的中国地区总云量分布形势与卫星资料比较相似,但云量偏低;模式模拟的中国地区高云量分布基本反映了高云的分布特点,但是模拟的云量偏高,尤其在青藏高原地区;模式模拟中国地区中云的分布与观测有较大差异,主要是在青藏高原地区。更多还原

【Abstract】 Climate change has raised the concern of the current governments and scientific community. However, the past and future climate simulations are considered uncertainly with the lack of awareness and knowledge. Most of the solar radiation to the earth makes the climate effects through clouds in climate system, which also plays a strong regulatory role of the radiation effect to the entire earth-atmosphere system. Direct climate effects of clouds has been understood more clearly, however, the radiation characteristics of cloud depends not only on its distribution, but also on cloud cover, optical thickness, cloud water path, effective radius and other cloud microphysical properties, then these factors would indirectly affect on climate. This paper would contain the following two main research contents.Firstly,the temporal and spatial characteristics of cloud over China have been analyzed using the ISCCP (International Satellite Cloud Climatology Project) monthly mean D2 data from July 1983 to June 2005 and MODIS ( MODerate-resolution Imaging Spectro-radiometer) monthly mean MOD06 data from 2000 March to 2009 June. The results show that: (1) over the past 20 years, total cloud amount has little change in trend in most parts of China; in the South China and the northwest of China, the total cloud amount over there is in an increased trend, while it has been decreased trend in the central part of Qinghai-Tibet Plateau. (2) It is also found that the total cloud amount in different seasons has different trend. The changes in cloud effective radius have the greatest effect to the cloud optical thickness during summer, which means that aerosol indirect climatic effect may be the strongest during summer. The changes of cloud optical thickness and effective radius also show that the cloud over the Yangtze River region and the Qinghai-Tibet Plateau region may be caused prominently by aerosol indirect climatic effects. (3) Besides, the ice cloud optical thickness and effective diameter are associated with strong regional characteristics in China, indicating that the ice cloud micro-physical mechanism is more complex than the water cloud.Secondly, with the previous work, the CAM3.0 model we used is based on comparison of two internationally advanced models, one of which is the NCAR/UCAR joint development of new generation atmospheric general circulation models Community Atmospheric Model3.0 (CAM3.0), and the other is the Canadian Aerosol Module Canadian Aerosol Module (CAM) for one-way online interaction. The model has also used the theory of Hayder Abhul-Razzak et al. which provides the aerosol activation progress, as Aerosols-Climate coupled model simulation, and it uses AeroCom 2009 pollution source data. By CAM3.0 model simulation from January 1, 1980 to December 30, 1996, the later 10 years data has been analyzed and several major conclusions have been drawn, with the comparisons to the satellite data.(1) Model can simulate the global total cloud amount of seasonal and annual distribution, especially over the equatorial region and marine region. The simulation of the global distribution of high cloud reflects the basic reality; in the equatorial and low latitude regions, the simulated valu is lager than the satellite data, while in the polarization it is smaller. The simulation of the middle cloud amount global distribution approaches the observations, but larger deviations in the Polar Regions. The best Model analysis is the simulation of the total cloud amount.(2) Model simulated total cloud amount distribution in China is similar to the observations, but the valu is lower; model simulated high cloud amount distribution in China basically reflects the distribution of reality, but the value is higher than observation, especially in Tibetan Plateau; model simulated the distribution of middle cloud amount in China are quite different from observations, mainly in the Tibetan Plateau.更多还原