SGER: Sensitivity of the West African Monsoon to Gulf of Guinea Sea Surface Temperatures (SSTs)

SGER：西非季风对几内亚湾海面温度（SST）的敏感性

• 批准号: 0446791
• 负责人: Kerry Cook
• 金额: $ 2.47万
• 依托单位: Cornell Univ - State: AWDS MADE PRIOR MAY 2010
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0446791&HistoricalAwards=false
• 关键词: SGER; Sensitivity; West; African; Monsoon

Output from state-of-the art coupled atmosphere/ocean global models will be examined to evaluate the models' ability to capture a distinct mode of rainfall variability over WestAfrica. When the eastern Atlantic (Gulf of Guinea) is warm, for example, summer monsoon precipitation is observed to be especially strong along the southern (Guinean) coast of Africa. At the same time, rainfall in the Sahel region to the north tends to be much lower than normal, bringing crop failure and severe hardship for the population.Past studies of this mode of variability in models and observations have identified the physical processes that lead to this dipole precipitation response. Enhanced precipitation along the coast is due to increased evaporation to the south over the warm Gulf of Guinea, since the presence of an equatorial (east/west) Walker circulation with its sinking branch over the Gulf prevents locally-enhanced convection in association with the warmer sea surface. Reduced precipitation over the Sahel is a consequence of the enhanced sinking of warm, dry air flowing equatorward out of the Saharan high near 700 hPa, and the requirements of potential vorticity conservation for this flow.Model output will be examined to understand the relationship between a model's ability to simulate the precipitation dipole and its resolution and physical treatments. Atmospheric moisture budget, vorticity, and moist static energy budget analyses will be used to evaluate the mechanisms of the simulated variability. The possibility that the dipole pattern will occur more frequently, or become permanently established, in the future as ocean temperatures rise will be investigated. This study will contribute to our fundamental understanding of how drought occurs in the Sahel and lead to an improved ability to predict African drought on all time scales. It will also provide guidance to environmental managers and policy makers regarding the quality of climate projections for this part of the world.

将检查最先进的耦合气氛/海洋全球模型的产量，以评估模型捕获Westafrica的独特降雨可变性模式的能力。例如，当东大西洋（几内亚湾）温暖时，沿着非洲南部（几内亚）海岸，夏季季风降水特别强。同时，北部萨赫勒地区的降雨量往往远低于正常水平，这给人口带来了农作物衰竭和严重的困难。对这种变异性模型和观察结果的研究已经确定了导致这种偶极降水反应的物理过程。沿海地区的降水增强是由于在温暖的几内亚海湾上增加了向南的蒸发，因为存在赤道（东/西）助行器循环，其下沉的分支在海湾上下沉，可防止与温暖的海面相关的本地增强对流。萨赫勒（Sahel）上的降水减少是由于从700 hpa附近的撒哈拉省高水流出的温暖，干燥的空气赤道增强的结果，并且对这种流量的潜在涡度保护的要求将检查模型输出。大气水分预算，涡度和潮湿的静态能量预算分析将用于评估模拟可变性的机制。随着海洋温度升高，偶极模式将在将来更加频繁地发生或永久建立的可能性。这项研究将有助于我们对sahel中的干旱方式的基本理解，并提高在所有时间尺度上预测非洲干旱的能力。它还将向环境经理和政策制定者提供有关世界各地气候预测质量的指导。