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

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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.