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

在过去的十年里，一项富有成果的新研究表明，热带降雨对远离热带的影响也很敏感。即使是高纬度地区的加热异常也容易通过温带涡旋能量输送的变化向赤道传播。在热带地区，一个反常的哈德利环流是对加热的反应，它将热量从上层分支更温暖的半球输送出去，而将湿气通过下层分支的环流输送到温暖的半球。研究小组最近取得的成果基于温带影响热带降水的思想，使用了一种新的归因程序，揭示了双热带辐合带（ITCZ）问题的一个令人惊讶的潜在主要原因，发展了一种新的理论，解释了为什么双热带辐合带在北半球，并发现了20世纪后期降水向南移动的部分原因是气溶胶强迫。在这个项目中，这方面的工作将会扩展到研究几个更重要的问题，这些问题涉及到对国际创新工业区的本地和远程影响。首先，印度洋降水的独特之处在于它在赤道以南达到峰值。气候模式将用于检验这是否是由于局部海洋热输送、大陆在季节周期中的相互作用或其他因素造成的。其次，将通过一系列理想模式实验研究气溶胶的吸收对ITCZ位移的影响。最后，将通过模拟确定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引起的ITCZ偏移的影响。

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.