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Prediction of visibility and aerosol within the operational Met Office unified model. I: Model formulation and variational assimilation

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Clark, P. A., Harcourt, S. A., Macpherson, B., Mathison, C. T., Cusack, S. and Naylor, M. (2008) Prediction of visibility and aerosol within the operational Met Office unified model. I: Model formulation and variational assimilation. Quarterly Journal of the Royal Meteorological Society, 134 (636). pp. 1801-1816. ISSN 1477-870X

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To link to this item DOI: 10.1002/qj.318

Abstract/Summary

The formulation and performance of the Met Office visibility analysis and prediction system are described. The visibility diagnostic within the limited-area Unified Model is a function of humidity and a prognostic aerosol content. The aerosol model includes advection, industrial and general urban sources, plus boundary-layer mixing and removal by rain. The assimilation is a 3-dimensional variational scheme in which the visibility observation operator is a very nonlinear function of humidity, aerosol and temperature. A quality control scheme for visibility data is included. Visibility observations can give rise to humidity increments of significant magnitude compared with the direct impact of humidity observations. We present the results of sensitivity studies which show the contribution of different components of the system to improved skill in visibility forecasts. Visibility assimilation is most important within the first 6-12 hours of the forecast and for visibilities below 1 km, while modelling of aerosol sources and advection is important for slightly higher visibilities (1-5 km) and is still significant at longer forecast times

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:31095
Publisher:Royal Meteorological Society

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