Evaluation of the Met Office global forecast model using Geostationary Earth Radiation Budget (GERB) data

• Published in: Quarterly journal of the Royal Meteorological Society Vol. 133; no. 629; pp. 1993 - 2010
• Main Authors: Allan, Richard P., Slingo, Anthony, Milton, Sean F., Brooks, Malcolm E.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-10-2007; Wiley
• Subjects: aerosol; cloud; Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Meteorology; numerical weather prediction; Physics of the high neutral atmosphere; radiative processes; satellite data; Gulf of Guinea; North Atlantic; Atlantic Ocean; Africa; Guinea; Weather forecast; aerosols; Bias; energy balance; digital simulation; Forecast model; subtropical zone; cloud; parametrization; Radiative properties; numerical weather prediction; Outgoing longwave radiation; Cloudiness; Terrestrial radiation; aerosol; Water cloud; short period waves; Long wave; Space remote sensing; Radiation balance; Convective cloud; Satellite observation; Geostationary satellite; radiative processes; Meteosat satellites; Numerical forecast; satellite data
• ISSN: 0035-9009; 1477-870X
• DOI: 10.1002/qj.166

Simulations of the top‐of‐atmosphere radiative‐energy budget from the Met Office global numerical weather‐prediction model are evaluated using new data from the Geostationary Earth Radiation Budget (GERB) instrument on board the Meteosat‐8 satellite. Systematic discrepancies between the model simulations and GERB measurements greater than 20 Wm−2 in outgoing long‐wave radiation (OLR) and greater than 60 Wm−2 in reflected short‐wave radiation (RSR) are identified over the period April–September 2006 using 12 UTC data. Convective cloud over equatorial Africa is spatially less organized and less reflective than in the GERB data. This bias depends strongly on convective‐cloud cover, which is highly sensitive to changes in the model convective parametrization. Underestimates in model OLR over the Gulf of Guinea coincide with unrealistic southerly cloud outflow from convective centres to the north. Large overestimates in model RSR over the subtropical ocean, greater than 50 Wm−2 at 12 UTC, are explained by unrealistic radiative properties of low‐level cloud relating to overestimation of cloud liquid water compared with independent satellite measurements. The results of this analysis contribute to the development and improvement of parametrizations in the global forecast model. Copyright © 2007 Royal Meteorological Society