US-Senegal Cooperative Research: Study of Interannual Variability of African Waves and Influence on Sahel Precipitation

该奖项支持Karyn Sawyer女士与大学大气研究公司（UCAR）、Wassila Thiaw博士与UCAR在国家环境预测中心（NCEP）的非洲课题组以及Saidou Sall博士与塞内加尔达喀尔大学高等理工学院大气物理实验室之间为期三年的合作研究项目。他们将研究非洲海浪的年际变化及其对萨赫勒地区降水的影响。非洲波是西非季风系统的固有组成部分。它们从非洲内陆开始，随着它们的繁殖和向西移动，中尺度对流系统（MCSs）经常在波浪中形成和发展。这些海浪在7月和8月最活跃。这也是萨赫勒地区对流降雨活跃的时期。但是人们对这些波浪的年际变化知之甚少，也不知道它们如何影响萨赫勒地区降雨的年际变化。为了确定非洲波对萨赫勒降水变率的影响，研究人员将考虑非洲波数与萨赫勒降水量之间的关系，非洲波数与热带辐合带（ITCZ）位置和强度之间的关系，以及非洲波和ITCZ位置是否对萨赫勒降水有调节作用。他们将使用NCEP-UCAR数据、卫星图像和从观测研究中获得的实地数据。将为每个时间步导出对流指数，以确定与MCSs生命周期有关的特征。然后将进行统计分析，以调查非洲海浪数量与萨赫勒地区降水之间的关系。这些结果有望促进目前对西非季风系统的理解，特别是非洲海浪的年际变化对萨赫勒降水变化的贡献。它应该促进我们对大尺度气候系统如何与局部尺度现象相互作用的理解。它结合了索耶女士的国际项目专业知识、蒂奥博士在西非估计降雨量和气候预测方面的专业知识，以及萨勒博士对对流系统的知识。

0218192Sawyer & ThiawThis award supports a three-year collaborative research project between Ms. Karyn Sawyer, with the University Corporation for Atmospheric Research (UCAR), Dr. Wassila Thiaw, with UCAR's African Desk at the National Center for Environmental Prediction (NCEP), and Dr. Saidou Sall, with the Laboratorie de Physique de l'Atmosphere of the Ecole Superieure Polytechnique at the University of Dakar in Senegal. They will study the interannual variability of African waves and influence on Sahel precipitation. African waves are inherent components of the West Africa monsoon system. They start from the African interior, and as they multiply and move westward mesoscale convective systems (MCSs) often form and develop within the waves. These waves are most active during July and August. This is also the period of active convective rains in the Sahel. But little is known about the interannual variability of the waves or how they influence the interannual variability of rainfall in the Sahel. In order to determine the influence of the African waves on Sahel rainfall variability, the investigators will consider the relationship between the number of African waves and the amount of Sahel precipitation, the relationship between the number of African waves and the position and intensity of the Intertropical Convergence Zone (ITCZ), and whether the African waves and the position of the ITCZ modulate Sahel rainfall. They will use NCEP-UCAR data, satellite imagery, and field data obtained from observation studies. A convective index will be derived for each time step to determine the characteristics associated with the life cycle of the MCSs. Statistical analyses will then be performed to investigate the relationship between the number of African waves and Sahel precipitation. The results are expected to advance the current understanding of the West African monsoon system, especially the contribution of the interannual variability in the African waves to Sahel precipitation variability. It should advance our understanding of how large scale climate systems interact with local scale phenomena. It combines the international project expertise of Ms. Sawyer, with Dr. Thiaw's expertise in estimating rainfall and climate prediction in West Africa, and Dr. Sall's knowledge about convective systems.