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An evaluation of clouds and precipitation in convection-permitting forecasts for South Africa

Stein, T. H. M., Keat, W., Maidment, R. I., Landman, S., Becker, E., Boyd, D. F. A., Bodas-Salcedo, A., Pankiewicz, G. and Webster, S. (2019) An evaluation of clouds and precipitation in convection-permitting forecasts for South Africa. Weather and Forecasting. pp. 233-254. ISSN 0882-8156

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To link to this item DOI: 10.1175/WAF-D-18-0080.1

Abstract/Summary

Since 2016, the South African Weather Service (SAWS) has been running convective-scale simulations to assist with forecast operations across southern Africa. These simulations are run with a tropical configuration of the Met Office Unified Model (UM), nested in the Met Office global model, but without data assimilation. For November 2016, convection-permitting simulations at 4.4-km and 1.5-km grid length are compared against a simulation at 10-km grid length with convection parametrization (the current UM global atmosphere configuration) to identify the benefits of increasing model resolution for forecasting convection across southern Africa. The simulations are evaluated against satellite rainfall estimates, CloudSat vertical cloud profiles, and SAWS radar data. In line with previous studies using the UM, on a monthly time scale, the diurnal cycle of convection and the distribution of rainfall rates compare better against observations when convection-permitting model configurations are used. The SAWS radar network provides a three-dimensional composite of radar reflectivity for northeast South Africa at 6-minute intervals, allowing the evaluation of the vertical development of precipitating clouds and of the timing of the onset of deep convection. Analysis of four case study days indicates that the 4.4-km simulations have a later onset of convection than the 1.5-km simulations, but there is no consistent bias of the simulations against the radar observations across the case studies.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:81689
Publisher:American Meteorological Society

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