Impact of different radiation transfer parameterization schemes in a GCM on the simulation of the onset phase of Indian summer monsoon

JHON P. GEORGE, Z. N. BEGUM

Abstract

The impact of two radiation parameterization schemes (NASA/Goddard and GFDL) in NCMRWF T80 model on the simulation of June, 1995 is presented in this paper. Our main aim here is to understand the sensitivity of different radiation schemes on the simulation of Indian summer monsoon onset phase. At Earth's surface, the simulation using NASA/Goddard scheme produces more reasonable balance between incoming and outgoing fluxes (radiative and the turbulent heat fluxes) compared to GFDL scheme. The inclusion of cloud scattering and hence the treatment of direct and diffused radiation separately in NASA/Goddard radiation scheme resulted in changes in the net shortwave flux at surface and hence in the surface temperature. Results also indicate the high sensitivity of surface temperature in the monsoon onset simulation. Both models reasonably simulate the mean June 1995 flow patterns. Comparison between the two simulations shows that T80 model with NASA/Goddard has less forecast errors at 200 hPa, whereas in 850 hPa this simulation has slightly higher forecast errors east of 75ºE longitude over Indian latitudes.

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