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.

将检查最先进的大气/海洋耦合全球模型的输出，以评估模型捕获西非降雨变化的独特模式的能力。例如，当东大西洋（几内亚湾）温暖时，非洲南部（几内亚）海岸的夏季季风降水尤其强烈。与此同时，北部萨赫勒地区的降雨量往往远低于正常水平，导致农作物歉收和人民的严重困难。过去对模型和观测中这种变化模式的研究已经确定了导致降雨的物理过程。这种偶极沉淀响应。沿海降水增加是由于温暖的几内亚湾南部蒸发增加，因为赤道（东/西）沃克环流及其在海湾上空的下沉分支的存在阻止了与温暖有关的局部对流增强。海面。萨赫勒地区降水量减少是由于从 700 hPa 附近的撒哈拉高空向赤道流动的温暖、干燥空气的下沉增强，以及该气流的位涡守恒的要求。将检查模型输出，以了解模型模拟降水偶极子及其分辨率和物理处理的能力。大气湿度收支、涡度和潮湿静态能量收支分析将用于评估模拟变化的机制。随着海洋温度的上升，未来偶极子模式将更频繁地发生或永久建立的可能性将得到研究。这项研究将有助于我们对萨赫勒地区干旱如何发生的基本了解，并提高在所有时间尺度上预测非洲干旱的能力。它还将为环境管理者和政策制定者提供有关世界该地区气候预测质量的指导。