夏季亚洲季风区对流层向平流层输送的源区、路径及其时间尺度的模拟研究  

Sources,Pathways and Timescales for the Troposphere to Stratosphere Transport over Asian Monsnoon Regions in Boreal Summer

作　　者：陈斌[1,2] 徐祥德[1] 卞建春[3] 施晓晖[1] 

机构地区：[1]中国气象科学研究院灾害天气国家重点实验室,北京100081 [2]香港中文大学太空与地球信息科学研究所,香港999077 [3]中国科学院大气物理研究所中层大气和全球环境探测重点实验室,北京100029

出　　处：《大气科学》2010年第3期495-505,共11页Chinese Journal of Atmospheric Sciences

基　　金：科技部国际合作项目(编号:2007DFB20210;2009DFB20540);中国气象科学研究院基本科研业务费专项资金重点项目(批准号:2008Z006);灾害天气国家重点实验室自主研究项目(编号:2008LASWZI04;2009LASWZF02)联合资助

摘　　要：基于NCEP/NCAR分析资料和拉格朗日轨迹输送模式FLEXPART,通过气块轨迹计算,对2005年夏季亚洲季风区对流层向平流层输送(Troposphere to Stratosphere Transport,简称TST)的近地层源区、输送路径及其时间尺度问题进行了一些初步探讨。结果表明:(1)夏季亚洲季风区TST两个主要的边界层源区,一个是热带西太平洋地区;另一个是青藏高原南部、孟加拉湾以及印度半岛中北部等地区,上述两个区域与夏季强对流的分布相一致。在对流层顶高度附近(约16km高度),两个近地层源区的垂直输送贡献相当。但进一步分析发现,穿越对流层顶高度的质量输送只有约10%能够进入20～22km高度的平流层中,且主要源于以青藏高原南侧为代表的南亚季风区(约贡献75%),这进一步强调了青藏高原及其周边区域在全球TST过程中的重要地位。(2)轨迹分析显示,夏季亚洲季风区对流层进入平流层的"入口区"主要在(25°N～35°N,90°E～110°E)区域的青藏高原及其周边区域。TST路径受对流层上层南亚高压闭合环流、北半球副热带西风急流和赤道东风急流的共同控制。(3)亚洲季风区TST两个主要的过程,一个是和夏季湿对流抬升直接联系的快速输送过程,它可以使近地层大气在1～2天内输送到平流层中,贡献了整个TST的10%～30%;另一个是大气辐射加热所致的大尺度垂直输送,该输送是一个相对的慢过程,时间尺度一般为5～30天。此结果意味着,源于地表的短生命周期的大气污染物可通过光化学反应过程对该区域平流层臭氧及其他大气痕量成分平衡产生重要影响。A new subgrid-scale Stochastic Cloud Generator（SCG）,which can produce different overlap assumptions,has been implemented into the NCAR/CAM3 climate model.Four types of overlapping schemes are generated from the SCG,including Maximum Overlap（MO）,Random Overlap（RO）,Maximum-Random Overlap（MRO）,and a recently developed General Overlap（GenO）.Using GenO as a reference,the authors studied the sensitivity of radiative fields to cloud overlap changes.Results showed that the total cloud fractions generated by MRO,MO,and RO differed from that of the GenO by-0.012,-0.034 and 0.026,respectively,with MRO being closest to the GenO.The Downwelling Shortwave Radiation（DSR） at the surface was affected by the cloud overlap assumptions significantly.The largest regional differences of DSR are more than 16 W/m2 in the tropical convective area,which is about 8%-12% of the DSR for the GenO there and is statistically significant at the 95% confidence level.The second largest differences of 4-8 W/m2 occurred at middle or higher latitudes where the low cloud covers are often large.However,the differences of outgoing longwave radiation（OLR） among the four schemes are quite smaller,with the largest value over 3-4 W/m2 also located in the tropical convective area.The cloud overlap assumptions can also change the profiles of radiative heating rate and thus change the thermodynamic structure of the atmosphere.It was found that the change in longwave heating rate（with the largest value of about 0.1-0.26 K/d） is about an order higher than that in shortwave heating rate（with the largest value of about 0.01-0.025 K/d）,thus becomes the major factor influencing the thermodynamic structure.Further exploration of cloud radiative forcing（CRF） at both the surface and the top of atmosphere（TOA） and column CRF suggests that the cloud overlap assumptions affect energy absorption of the whole atmospheric column at some latitudes,through which the energy distribution at different latitudes can be systematically cha

关 键 词：对流层向平流层输送 亚洲季风区 边界层源区 输送路径 时间尺度 

分 类 号：P421[天文地球—大气科学及气象学]