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.

将对最先进的大气/海洋耦合全球模式的输出进行审查，以评价这些模式捕捉西非降雨量变化的独特模式的能力。例如，当大西洋东部（几内亚湾）温暖时，沿非洲南部（几内亚）海岸沿着的夏季季风降水特别强烈。与此同时，北部萨赫勒地区的降雨量往往比正常情况下少得多，造成作物歉收，给人民带来严重困难，过去对模型和观测中这种变异模式的研究已经确定了导致这种偶极子降水反应的物理过程。沿海沿着降水增加是由于温暖的几内亚湾上空向南的蒸发增加，因为赤道（东/西）步行者环流及其下沉分支在海湾上空的存在，阻止了与温暖的海面有关的局部对流增强。萨赫勒地区的降水减少是700百帕附近撒哈拉高压向赤道方向流出的温暖干燥空气下沉增强的结果，以及这种流动的位涡守恒的要求，将检查模式输出，以了解模式模拟降水偶极子的能力与其分辨率和物理处理之间的关系。大气湿度收支、涡度和湿静态能量收支分析将用于评估模拟变率的机制。今后随着海洋温度的上升，偶极模式是否会更频繁地出现，或成为永久性的，将进行调查。这项研究将有助于我们从根本上了解萨赫勒地区干旱的发生方式，并提高在所有时间尺度上预测非洲干旱的能力。它还将为环境管理人员和决策者提供关于世界这一地区气候预测质量的指导。