Multi-scale Analysis of Congo Basin Precipitation: Understanding the Regional Rainfall Climatology and the Potential for Change

刚果盆地热带雨林以其生物多样性和丰富的文化遗产闻名于世。但是，为人类和森林生态系统提供水资源的降雨研究不足，其行为的基本方面也没有得到充分的记录。了解流域降雨的一个挑战是缺乏观测，因为经济困难和政治不稳定阻碍了天气观测网络的发展。另一个挑战是，大部分降雨来自中尺度对流系统(MCSs)，即夏季在美国中部看到的强烈传播雷暴，很难详细观察。在该奖项下进行的研究旨在描述刚果盆地的载雨天气系统，包括它们的季节性、与大范围大气环流的联系、水分分布，以及植被繁茂的陆地表面的蒸发和蒸腾作用在多大程度上是降雨的湿润来源。这项工作利用了最近的数据集，这些数据集通过卫星和全球大气数据同化系统弥补了地面观测的不足。这些数据集具有足够高的分辨率来跟踪MCS，并确定它们的形成区域、传播路径、对降水的总贡献以及与大尺度环境的相互作用。在这里，WRF以三层嵌套结构应用于中非上空，并使用来自再分析产品的边界强迫，这确保了模拟的大尺度特征与真实世界的对应模拟。在一些模拟中，边界强迫被修改为基于全球气候模型的输出来表示未来气候变化的影响。利用潜在植被模型评估了模拟未来降水变化对雨林的影响。考虑到该地区的脆弱人口及其作为生物多样性热点的重要性，这项工作具有社会和科学意义。此外，首席调查人员还通过杰克逊学校的GeoForce计划进行当地外联，该计划通过进行实地考察和其他活动，向来自农村和市中心学校的学生介绍地球科学。地质学一直是GeoForce的主要关注点，该奖项下的推广工作将天气和气候纳入该计划所述主题的组合中。该项目还资助了两名研究生。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Congo Basin rain forest is known around the world for its biodiversity and rich cultural heritage. But the rains that provide water resources to the people and ecosystems of the forest are understudied and fundamental aspects of their behavior have not been fully documented. One challenge to understanding rainfall in the basin is lack of observations, as economic hardship and political instability have hampered development of weather observing networks. Another challenge is that much of the rainfall comes from mesoscale convective systems (MCSs), intense propagating thunderstorms like the ones seen over the central US in summer, which are difficult to observe in detail.Research performed under this award seeks to characterize the rain-bearing weather systems of the Congo Basin, including their seasonality, connections to the large-scale atmospheric circulation, moisture distribution, and the extent to which evaporation and transpiration from the vegetated land surface serves as a moisture source for rainfall. The work takes advantage of recent datasets that make up for the lack of ground-based observations through satellites and global atmospheric data assimilation systems. The datasets have high enough resolution to track MCSs and determine their formation regions, propagation paths, total contribution to precipitation, and interaction with the large-scale environment.Further research is conducted using the Weather Research and Forecasting (WRF) model, a regional model which can capture MCS dynamics. Here WRF is applied in a triply nested configuration over Central Africa with boundary forcing from reanalysis products, which ensure that the large-scale features of the simulations mimic their real-world counterparts. In some simulations the boundary forcing is modified to represent the effects of future climate change based on output from global climate models. The impact of simulated future precipitation change on the rain forest is assessed using a Potential Vegetation Model.The work is of societal as well as scientific interest given the vulnerable population of the region and its importance as a biodiversity hotspot. In addition, the Principal Investigators conduct local outreach through the Jackson School's GeoForce program, which introduces students from rural and inner-city schools to geoscience by conducting field trips and other activities. Geology has been the primary focus of GeoForce, and outreach efforts under this award bring weather and climate into the mix of topics addressed in the program. The project also supports two graduate students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.