Relationships between intense convection, lightning, and rainfall over the interior Congo Basin using TRMM data

Abstract

The lack of in situ observations across equatorial Africa creates forecasting challenges for regional populations affected by extreme weather events and makes accurate hydrological monitoring within the Congo Basin difficult. Due to the high mean convective intensity in this region, lightning observations may be particularly useful for improving satellite-based surface precipitation monitoring and forecasting. Therefore, this study aims to quantify the relative frequency of the most intense convective events in the Congo and their associated lightning – precipitation relationships through the analysis of high-resolution Tropical Rainfall Measuring Mission (TRMM) radar and lightning observations for the years 1998–2013. Lightning and precipitation measurements associated with observed echoes were isolated and assigned to one of four categories of intense convective-stratiform echo types. Results show that only 2.7% of observed echoes were classified as intense convective-stratiform, yet they produced 36.6% of observed lightning flashes and 27.4% of estimated rain totals. Significant spatial correlations were also found between total rainfall and intense convective-stratiform rain (coefficient r = 0.56). Linear relationships between lightning and echo rain rates are shown to depend heavily on the convective category. As a result, a simple linear regression cannot be made for all intense convective echoes. However, lightning can be used to retrieve a lower-bound approximation with respect to convective rain rates. Results suggest that if properly implemented, the addition of lightning data may help to improve or constrain satellite derived convective intensity and rainfall estimations.