A nudging scheme to assimilate satellite brightness temperature in a meteorological model: Impact on representation of African mesoscale convective systems

• Published in: Quarterly journal of the Royal Meteorological Society Vol. 136; no. 647; pp. 462 - 474
• Main Authors: Orlandi, E., Fierli, F., Davolio, S., Buzzi, A., Drofa, O.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2010; Wiley
• Subjects: African monsoon; AMMA; Assimilation; Brightness temperature; Computer simulation; Convection modes; Dynamical systems; Dynamics; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; METEOSAT; Physics of the high neutral atmosphere; precipitation; Precipitation (meteorological); Representations; Sahel; West Africa; Sahel; Africa; Initialization; models; temporal distribution; rainfall; atmospheric precipitation; Mesoscale convective system; sensitivity analysis; Nudging; African monsoon; METEOSAT; precipitation; Mesoscale; Spatial distribution; brightness temperature; Analysis of meteorological field; Geographic distribution; Forcing; monsoons; AMMA; Sahel; Data assimilation
• ISSN: 0035-9009; 1477-870X; 1477-870X
• DOI: 10.1002/qj.549

The study presents the implementation of a nudging procedure in a mesoscale meteorological model, and its evaluation in improving the representation of mesoscale convective systems in the region of West Africa. The generation and development of convection are related to processes with different spatial scales, making it often difficult for meteorological models to reproduce their dynamics. The assimilation approach is based on the continuous assimilation of METEOSAT infrared brightness temperatures within the model in order to trigger convection, where observations show the presence of large convective systems. The nudging also inhibits convection, when the model reproduces unrealistic convective precipitation and coherently modifies the dynamical fields. Model sensitivity to the nudging scheme has been tested to evaluate the role of the forcing term. The nudging improves the geographical distribution and time evolution of mesoscale convective systems reproduced by the model; the impact of assimilation is positive up to 13 h after the end of the nudging period. It is also shown that the nudging improves the simulated amount and spatial distribution of precipitation. Finally, the assimilation is performed throughout the entire simulation, showing how the proposed approach can be used to improve meteorological analyses in terms of convective activity and rainfall. Copyright © 2010 Royal Meteorological Society