Abstract
AbstractSatellite nowcasting potentially provides a vital opportunity to mitigate against the risks of severe weather in tropical Africa, where population growth and climate change are exposing an ever growing number of people to weather hazards. Numerical weather prediction demonstrates limited skill for much of Africa and weather radars are rare. However, geostationary satellites provide excellent spatial and temporal coverage of the often long‐lasting convective storms that deliver heavy rain, lightning and strong winds, presenting a valuable opportunity for satellite nowcasting. Here, we evaluate the skill of satellite nowcasting products for tropical Africa: these products are routinely generated, but to our best knowledge never routinely used in tropical Africa before the Global Challenges Research Fund African SWIFT (Science for Weather Information and Forecasting Techniques) project. Focusing in particular on convective rainfall rate (CRR) and rapidly developing thunderstorm convection warning (RDT‐CW) products, we demonstrate that both are useful nowcasting tools. The CRR product produces very different rainfall climatologies for day and night in tropical Africa. This is associated with greater skill of the product during daytime, particularly for heavier rain rates. The RDT‐CW product is able to identify around 60% of heavy (>5 mm·hr−1) rainfall events with the fraction detected increasing with increasing rainfall rate. For both products, extrapolation forwards in time (up to 90 and 60 min, respectively) maintains useful skill in tropical Africa, motivating work to develop longer lead‐time nowcasts. We conclude that widespread uptake of satellite nowcasting could provide new skilful weather predictions on short time‐scales in much of tropical Africa.
Highlights
As population growth and climate change increase exposure to weather hazards across much of the tropics, there is an urgent need to improve weather prediction and disaster early warning systems (U UNISDR, 2015; Kendon et al, 2019)
The present study aims to provide an initial estimate of the performance of the convective rain rate (CRR) and rapidly developing thunderstorm convection warning (RDT-CW) products in tropical Africa, using global precipitation measurement (GPM) (Hou et al, 2014) Integrated Multisatellite Retrievals for GPM (IMERG) (Huffman et al, 2020) as “truth.” The layout of the paper is as follows
While the Nowcasting Satellite Applications Facility (NWCSAF) software can generate a wide range of products, in the present study we focus on the two products that were identified by forecasters as most useful (i.e., CRR and RDT-CW)
Summary
As population growth and climate change increase exposure to weather hazards across much of the tropics, there is an urgent need to improve weather prediction and disaster early warning systems (U UNISDR, 2015; Kendon et al, 2019). The RDTCW product aims to identify, monitor, track and characterize convective events, thereby providing the forecaster with additional guidance on the occurrence and potential development of storms Both these products are distributed by NWCSAF and GCRF African SWIFT for the whole of Africa, for NWCSAF this does not include extrapolated CRR estimates. The present study aims to provide an initial estimate of the performance of the CRR and RDT-CW products in tropical Africa, using global precipitation measurement (GPM) (Hou et al, 2014) Integrated Multisatellite Retrievals for GPM (IMERG) (Huffman et al, 2020) as “truth.” The layout of the paper is as follows.
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