Local and Remote Influences on the Intertropical Convergence Zone in a Hierarchy of Models

在过去的十年里，一项新的、富有成效的研究已经发展起来，这表明即使在远离热带的地方，热带降雨也对影响很敏感。即使是高纬度地区的加热异常，也会通过温带外涡旋能量输送的变化轻松地向赤道扩散。在热带地区，异常的哈德利环流是对加热的反应，将热量从半球输送出去，这些热量在半球的上部分支更温暖，但水汽通过其下方分支的环流进入温暖的半球。该研究组最近的研究结果使用了一种基于温带对热带降水影响的新的归因方法，以揭示双重热带辐合带(ITCZ)问题的一个令人惊讶的潜在主要原因，为ITCZ在北半球的原因发展了一种新的理论，并发现并归因于20世纪末部分由于气溶胶强迫而导致的降水南移。在这个项目中，这项工作将扩展到研究几个更重要的问题，涉及到对工业园区的本地和远程影响。首先，印度洋的降水是独一无二的，因为它的峰值位于赤道以南。气候模型将被用来测试这是由于当地的海洋热量输送，季节性循环中的大陆相互作用，还是其他因素。其次，将通过一系列理想化的模式实验研究气溶胶吸收对ITCZ漂移的影响。最后，将通过模拟修正云和水汽对热带辐射的影响，研究热带辐射异常对热带和温带以外地区引起的ITCZ移动的影响。

A new and fruitful line of research has developed over the last decade, which has shown that tropical rainfall is sensitive to influences even far away from the tropics. Even heating anomalies in high latitudes spread equatorward with ease via changes in extratropical eddy energy transports. In the tropics, an anomalous Hadley circulation develops in response to heating, fluxing heat out of the hemisphere that is warmed more in its upper branch, but moisture into the warmed hemisphere by the circulation in its lower branch. Recent results undertaken by the research group has used a new attribution procedure based on the idea of extratropical influence on tropical precipitation to uncover a surprising potential primary cause of the double intertropical convergence zone (ITCZ) problem, to develop a new theory for why the ITCZ is in the Northern Hemisphere and to discover and attribute a late 20th century southward shift in precipitation in part due to aerosol forcing. In this project, this line of work will be extended to study several more important issues involving local and remote influences on the ITCZ. First, precipitation in the Indian Ocean is unique in that it peaks south of the equator. Climate models will be used to test whether this is due to local ocean heat transport, continental interactions over the seasonal cycle, or other factors. Second, the effect of absorbing aerosols on ITCZ shifts will be studied in a series of idealized model experiments. Finally, the impact of tropical radiation anomalies on ITCZ shifts induced from the tropics and extratropics will be examined, via simulations that fix clouds and water vapor impacts on radiation in the tropics.