热带对流过程对北极放大现象的影响与机制

Over the past few decades, as global warming continues, surface warming has been observed to be more pronounced and rapid in Arctic than any other regions on earth. This phenomenon is so called Arctic amplification. It is shown that the characteristics and mechanism of Arctic amplification are rather complex. It is not only related to the local thermodynamic processes in the polar regions, such as sea ice melting, surface albedo change, air-sea heat exchange, clouds, radiation etc., but also affected by the mid-latitude atmospheric circulation and water vapor transport..There is strong correlations between tropical convection and Arctic warming, but the physical processes are still not clear. In this project, we will study the Rossby wave response to tropical convection on synoptic (intra-seasonal) time scale and its impact on Arctic amplification by utilizing data analysis and numerical simulation. Analysis will include Rossby wave source, Rossby wave propagation characteristics, wave-flow interaction, atmospheric circulation change, atmospheric baroclinicity change and moisture transport into Arctic. The impact of tropical convection from different locations on Arctic amplification will also be compared and evaluated in order to better understand the importance of the extra-polar atmospheric dynamic process to polar warming.

近几十年来，随着全球变暖的持续，北极地区经历了比地球上其他任何地区更快速且更强烈的表面增暖，这种现象被称为北极放大现象。已有研究表明，北极放大现象具有非常复杂的时空特征和形成原因，它不仅与北极地区局地热力过程，如海冰融化、地表反照率、海-气热量交换、云层、辐射等因素有关，而且受到中纬度大气环流和水汽输运等因素的影响。.热带对流与北极放大现象有较强相关，但具体物理过程仍不明确。本项目拟通过观测资料分析和数值模式模拟的手段从天气时间尺度分析热带对流过程激发的大气Rossby波响应，从Rossby波源位置、Rossby波向极传播的波活动特征、波流相互作用、大气环流与斜压性的改变以及向极地的水汽输运等方面揭示热带对流过程对北极放大现象的影响和机制，并定量地比较和评估热带不同区域的对流过程对北极放大现象的影响程度，阐释极地外大气动力过程对极地增暖的重要作用。

本项目通过观测资料分析和数值模式模拟的手段从天气时间尺度分析了北极增暖对应的北极地区局地大气、海冰和地表辐射等不同分量的变化特征, 以及热带对流过程激发的大气Rossby波响应. 从Rossby波源位置、Rossby波向极传播的波活动特征、波流相互作用以及向极地的水汽输运等方面揭示了热带对流过程对北极放大现象的影响和机制，并定量地比较和评估了热带不同区域的对流过程对北极放大现象的影响程度，阐释了极地外大气动力过程对极地增暖的重要作用。此外, 研究还发现, 在南半球冬季也同样存在相似的跨极地传播的Rossby波, 热带对流过程激发从热带/副热带向南极传播的Rossby波列, 在传播过程中调制南极中高纬度大气环流和向南极的水汽输送, 从而导致到达南极的水汽输运和向下的红外辐射增加, 最终造成南极大陆表层增暖。表明热带对流对极地气候变化有极其重要的影响。