Sea Surface Temperature-Forced Monsoon Evolution and Variability in West Africa

西非季风在短暂但密集的雨季中为萨赫勒地区带来了大部分的年降雨量。由于农业仍然是占人口百分比的主要经济活动，因此了解和预测季风季节的大小和时间的变化尤为重要，如果没有准备好，可能会造成破坏性后果。这项工作将直接有助于改进季风降雨的季节性到年际预测。这项工作的结果将与有兴趣帮助萨赫勒地区的气候预测组织高度相关，如国际气候与社会研究所及其在西非的长期合作伙伴。通过各种渠道，该研究的信息可以为气候信息的应用提供信息，以便在萨赫勒地区更好地做出决策。这项工作也将支持一名研究生。从这项研究中收集的知识也将有助于哥伦比亚大学国际和公共事务学院（SIPA）课程的气候和社会教学。该项目的目标是提高对西非夏季季风的理解和预测，特别是对周围热带海洋海面温度变化的反应。关于海洋表面温度波动的资料是经常可以得到的，对气候预测很重要。萨赫勒季风的季节性降雨量每年都不一样，有时会下降到干旱程度，对社会造成严重影响。这种变化与偏远和附近海域的海面温度波动有关。过去的研究表明，当热带太平洋东部海面温度相对温暖时，夏季季风降雨往往会减弱，有时会失败，这种状态被称为厄尔尼诺现象。在拉尼娜阶段，当热带太平洋东部相对凉爽时，降雨往往是强劲而丰富的。然而，这种联系并不稳定，因为该区域对其他盆地的温度变化也很敏感，如热带大西洋和印度洋。利用大气全球气候模式，其中不同的海表温度的情况下，在全球海洋模拟观测中发现的，这项研究将阐明季风如何响应本地和远程海表温度的变化在不同的盆地，单独和共同作用。通过了解作为时间函数的动量、热量和水分输送的响应模式和机制，预计将提高根据季节前海面温度条件预测季风降雨的可能性。这个实验方法也提供了一个测量季风降雨的“信噪比”的方法。从这个角度来观察将有助于更好地确定预测的不确定性，也有助于提高季风季节预测的质量。

The West African monsoon delivers most of the annual rainfall to the Sahel region in a short but intense rainy season. Since agriculture remains the dominant economic activity in terms of percent of population engaged, understanding and predicting the variability in both the magnitude and timing of the monsoon season is especially important and potentially devastating if not prepared for. This work;will directly contribute to improving seasonal to interannual prediction of monsoon rainfall. The results of this work will be highly relevant to climate prediction organizations interested in helping the Sahel such as the International Research Institute for Climate and Society and its long-standing partners in West Africa. Through various channels, information from the study can inform applications;of climate information for better decision-making in the Sahel. The work will also support a graduate student. Knowledge gathered from this study will also contribute to the teaching of climate and society in the School for International and Public Affairs (SIPA) at Columbia University programs.The goal of this project is to improve the understanding and prediction of the West African summer monsoon, specifically response to changes in sea surface temperatures in the surrounding tropical oceans. Information on sea surface temperature fluctuations is routinely available and is important for climate prediction. The seasonal amount of Sahel monsoon rains, varies from year to year sometimes dropping to drought levels with serious effects on society. This variability has been linked to sea surface temperature fluctuations in remote and nearby ocean areas. Past studies have shown a that summer monsoon rains tend to weaken and sometimes fail when eastern tropical Pacific sea surface temperatures are relatively warm, a state known as the El Niño. Rains tend to be strong and plentiful when the east tropical pacific are relatively cool, during the La Nina phase. However, this association is not steady because the region is also sensitive to temperature changes in other basins, such as the tropical Atlantic and the Indian Oceans. Utilizing an atmospheric global climate model, in which different sea surface temperature scenarios are prescribed in the global ocean mimicking what is found in observations, this research will elucidate how the monsoon responds to changes in local and remote sea surface temperature changes in different basins, acting separately and together. By understanding the response pattern and the mechanisms of momentum, heat and moisture transport as a function of time, it is anticipated that possibilities of prediction of monsoon rainfall, based on pre-season sea surface temperatures conditions, will be advanced. This experimental method also provides a measure of "signal-to-noise" ratio in the monsoon rainfall. Putting the observations in that perspective will help frame better the prediction uncertainties, also helping advance the quality of monsoon season prediction.