GC062-01
The African Rainfall Project: High resolution (1km) weather modeling at continental scale thanks to the World Community Grid

Thursday, 10 December 2020: 05:30
Virtual
Nick Van De Giesen, Delft University of Technology, Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft, Netherlands, Camille Le Coz, Delft University of Technology, Delft, Netherlands and Lloyd A. Treinish, IBM Thomas J. Watson Research Center, Environmental Science, Yorktown Heights, NY, United States
Abstract:
The goal of the African Rainfall Project (ARP) is to derive accurate rainfall estimates over Sub-Saharan Africa, with the help of a high-resolution (1km) application of the Weather Research and Forecasting Model (WRF). Such a resolution will allow the model to better represent rainfall, and in particular, convective precipitation. This is a unique experiment that has never been performed at such a scale. The model runs on the IBM World Community Grid (WCG).

ARP divides the African continent into over 35609 WRF modelling domains. For each domain, WRF is run on a personal computer of a volunteer, who shares spare computing resources via the WCG. It calculates episodes of two days’ worth of weather with output for every 15 minutes (193 total time steps each). Each WRF domain is triply nested. Hence, it first calculates at a coarse resolution of 9km x 9km covering a 468km x 468km region with historical boundary conditions from NCEP FNL (Final) Operational Global Analysis. Within the center of this domain, it calculates the next nest at the intermediate resolution of 3 km (156 km x 156 km) with the boundary conditions set by the coarser domain calculation. Finally, a domain of 52 km x 52km is calculated at the center of the intermediate domain. Vertically, the atmosphere is divided into 51 layers so that the output is produced on a 52x52x51 grid. The model is run on four staggered grids to be able to look into the variability of model outcomes. The period covered runs from 1 July 2018 until 30 June 2019.

All atmospheric parameters (wind, pressure, etc.) are calculated but only about twenty variables of direct interest are stored and uploaded to the central WCG facility. The amount of data produced is about 0.5 PB or, in more nostalgic terms, a pile of over 370 million 3.5-inch floppy disks. That pile would weigh over 6700 tons and would be over 1200 km high. These data will be stored and made available through an interactive geo-portal at SURFsara, a computational facility of Dutch universities.

The first results will be presented here, as well as a comparison of the model results with ground-based data from the Trans-African Hydro-Meteorological Observatory (TAHMO).

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