A Scheme for the Computation of Short-Wave Surface Direct and Diffuse Irradiances in the Weather Research and Forecasting model. The Role of Aerosols in Cloudless Skies.

José A. Ruiz-AriasNCAR/MMMUniversity of Jaén, SpainShort-wave surface direct irradiance is the downward solar flux received from the sun's direction at the surface. Short-wave surface diffuse irradiance is the downward solar flux received at the surface from any other direction. Together, they make up the short-wave surface total or global downward solar flux, which is the solar flux typically computed in NWP models (it is the SWDOWN variable in the WRF's output). Surface direct and diffuse solar fluxes are important to compute the incoming irradiance for an arbitrarily oriented plane, which has implications for the surface energy budget in mountainous areas. They are a keystone for solar energy applications (flat photovoltaic, concentrating photovoltaic and concentrating solar thermal). Aerosols strongly affect the partitioning of the total radiation into the direct and diffuse fluxes in cloudless conditions. However, they are typically oversimplified or even ignored in these models because reliable and wide data bases have not been available so far.

In this talk we introduce a modeling approach for the computation of the short-wave surface direct and diffuse fluxes in the Weather Research and Forecasting (WRF) model with special focus on clear sky conditions and aerosols. We do it in a comprehensive manner, from the study of different data sources of aerosols currently available, through the bench-marking of some WRF short-wave schemes. We end the talk with the proposal of a parameterization for the aerosol optical properties that enables the accurate computation of surface solar fluxes, provided an accurate aerosol estimate is available.

**This seminar will be available via webcast at: http://www.fin.ucar.edu/it/mms/fl-live.htm                                                                                    

Thursday, 29 August 2013, 3:30PMRefreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Main Auditorium Room 1022


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Thursday, August 29, 2013 - 3:30pm