Sea surface temperature pattern influence on monsoon variability and change

气候变化可能会增加季风降雨，但会导致更大的变异和极端情况。然而，全球气候模式（GCM）不同意的热带海表温度（SST）的变暖模式以及季风降雨的区域变化。大气环流模型在当前气候中对季风和降雨量的估计也有很大的偏差，这增加了它们对未来气候预测的不确定性，尽管它们在很大程度上反映了不同大陆季风强度的相对差异。为了解释气候模式的预测，我们需要对季风如何响应不同的SST模式有一个基于物理的理解。以前的研究往往归因于亚洲季风（与非洲或南北美洲季风相比）的相对强度和可靠性的差异，在大陆面积，地形，或动力强迫射流或波的相互作用。该项目将调查SST不对称性的影响，如印度洋-太平洋暖池对季风强度的影响。该假说认为，某些离赤道的热带陆地地区上风处较暖的SST在增加相应季风的相对强度方面起着主导作用，因为它们提供了水分和近地面湿静力能，这使得降雨量增加，季风环流增强。主要问题：1.纬向海温不对称如何影响不同区域和大陆季风的相对强度？2.气候预测中不同的SST变暖模式对潜在的区域季风变化有什么影响？3.我们能否利用观测到的20世纪SST变化模式来为区域季风的未来预测提供信息或加以限制？对于这个博士项目，学生将进行研究，这将导致我们对季风降雨如何与水分来源相互作用以及未来季风如何变化的理解的提高。这项工作将涉及进行和分析全球气候模型实验，包括最先进的高分辨率过程模型模拟以及观测和较粗分辨率的模拟。学生将与埃克塞特气象局的科学家密切合作，无论是远程还是亲自访问。

Climate change will likely increase monsoon rainfall but lead to greater variability and extremes. However, global climate models (GCMs) disagree on the warming pattern of tropical sea surface temperatures (SSTs) as well as regional changes in monsoon rainfall. GCMs also have large biases in monsoon winds and rainfall in the present climate, which increases uncertainty in their climate projections for the future, although they largely capture relative differences in monsoon strength across different continents. To interpret climate model projections, we need a physically based understanding of how monsoons respond to different SST patterns. Previous studies often attributed the relative strength and reliability of the Asian monsoon (compared to African or North/South American monsoons) to differences in continental area, orography, or dynamical forcing from jet or wave interactions. This project will investigate the effects of SST asymmetries such as the Indo-Pacific warm pool on monsoon strength. The hypothesis is that warmer SSTs upwind of certain off-equatorial tropical land regions play a dominant role in increasing the relative strength of a corresponding monsoon because of the moisture and near-surface moist static energy that they supply, which allows for more rainfall and a stronger monsoon circulation.Main questions: 1. How do zonal SST asymmetries affect the relative strength of monsoons in different regions and continents? 2. What implications do different patterns of SST warming in climate projections have for potential regional monsoon changes?3. Can we use observed patterns of 20th-century SST change to inform or constrain future projections of regional monsoons?For this PhD project, the student will undertake research that will lead to improvements in our understanding of how monsoon rainfall interacts with moisture sources and how monsoons might change in the future. The work will involve performing and analysing global climate model experiments, including state-of-the-art of high-resolution process model simulations as well as observations and coarser-resolution simulations. The student will work closely with scientists at the Met Office in Exeter, both remotely and during in-person visits.