Statistical and Dynamical Exploration of Land-Ocean-Atmosphere Interactions in Two Contrasting Monsoon Regions: China and Northern Australia

季风系统覆盖了热带和亚热带的大部分地区，季风降雨为世界上许多人口提供了农业和家庭用水资源。因此，季风的变化可以有戏剧性的人类后果，更好地了解的过程，导致季风的变化是可取的。 迄今为止的研究表明，季风变化的一部分可能与遥远的海面温度（SST）异常有关，例如与厄尔尼诺事件有关的异常，这导致大气环流的大规模变化，从而调节季风地区的降雨量。 季风变化的第二个潜在原因是当地陆地表面的条件，这是受降雨的影响，并可能有进一步的影响，通过各种陆-气反馈processes.This项目的降雨量的影响，试图确定远程SST和当地陆-气相互作用调制降雨和大气条件季风区的单独效果。 研究集中在两个地区选择代表亚热带和热带季风系统，中国和北方澳大利亚分别。 首席研究员（PI）以前的工作表明，通过减少植被覆盖来改变陆地表面，在这两个地区产生相反的结果，中国的夏季风爆发较早（与更大的海洋-陆地热反差有关）和春季降雨量增加，澳大利亚北方季风延迟减弱（与植物蒸腾作用导致降水的水分来源减少有关）。该研究讨论了远程SST和当地陆地的相对作用，通过一套区域气候模式实验和统计分析，研究大气相互作用。模型模拟将通过实验研究陆地-大气反馈的作用，在实验中，陆地表面的各个方面保持不变（例如，固定叶面积，使植被在干旱条件下不会枯萎）。 统计分析使用PI开创的技术，称为广义均衡反馈分析（GEFA）。该方法使用多变量滞后相关性，以确定季风降水和强迫从远程SST和当地地表条件（包括植被叶面积指数）之间的因果关系。如上所述，季风变化有很强的人类影响，包括对作物的影响，牲畜，和澳大利亚火灾季节的持续时间。 如果成功的话，这里进行的研究可能会导致用于预测季风降水的模型的改进。 此外，PI计划领导一个为期两天的研讨会，讨论陆地-大气相互作用，区域气候建模和陆地表面建模，这将有助于向学生和早期职业科学家介绍用于研究区域气候和陆地-大气相互作用的方法。

Monsoon systems cover much of the tropics and subtropics, and monsoon rains provide the agricultural and domestic water resource for much of the world's population. Thus, variations of the monsoons can have dramatic human consequences, and a better understanding of the processes which cause monsoon variability is desirable. Research to date has shown that some portion of monsoon variability can be linked to anomalies in remote sea surface temperatures (SSTs) such as those associated with El Nino events, which cause large-scale changes in atmospheric circulation that modulate rainfall in the monsoon regions. A second potential cause of monsoon variability is the condition of the local land surface, which is affected by rainfall and can potentially have a further influence on rainfall through a variety of land-atmosphere feedback processes.This project seeks to identify the separate effects of remote SSTs and local land-atmosphere interactions in modulating rainfall and atmospheric conditions over monsoon regions. The research is focused on two regions chosen to represent subtropical and tropical monsoon systems, China and Northern Australia respectively. Previous work by the Principal Investigator (PI) suggests that modification of the land surface by a reduction in vegetation cover produces opposing results in the two regions, with an earlier summer monsoon onset in China (linked to greater ocean-land thermal contrast) and enhanced springtime rainfall, and a delayed and weaker monsoon in Northern Australia (linked to reduction in the source of moisture for precipitation due to transpiration from plants).The research addresses the relative roles of remote SSTs and local land-atmosphere interactions through a suite of regional climate model experiments and statistical analysis. The model simulations will examine the role of land-atmosphere feedbacks through experiments in which aspects of the land surface are held fixed (e.g. fixing the leaf area so that vegetation does not wilt under dry conditions). The statistical analysis uses a technique pioneered by the PI known as Generalized Equilibrium Feedback Analysis (GEFA). The method uses multivariate lagged correlation to identify causal relationships between monsoon precipitation and forcing from remote SSTs and local land surface conditions (including vegetation as represented by the Leaf Area Index).As noted above, monsoon variations have strong human impacts, including impacts on crops, livestock, and the duration of the Australian fire season. If successful, the research performed here may lead to improvements in models used to forecast monsoon precipitation. In addition, the PI plans to lead a 2-day workshop on land-atmosphere interactions, regional climate modeling and land surface modeling, which will serve to introduce students and early-career scientists to methods used for research on regional climate and land-atmosphere interactions.