NUMERICAL SIMULATIONS OF EFFECTS OF LAND SURFACE PROCESSES ON CLIMATE--IMPLEMENTING OF SSiB IN IAP/LASG AGCM AND ITS PERFORMANCE*

This is an investigation of exchanges of energy and water between the atmosphere and the vegetated continents,and the impact of and mechanisms for land surface-atmosphere interactions on hydrological cycle and general circulation by implementing the Simplified Simple Biosphere(SSiB) model in a modified version of IAP/LASG global spectral general model(L9R15 AGCM).This study reveals that the SSiB model produces a better partitioning of the land surface heat and moisture fluxes and its diurnal variations,and also gives the transport of energy and water among atmosphere,vegetation and soil explicitly and realistically.Thus the coupled SSiB-AGCM runs lead to the more conspicuous improvement in the simulated circulation,precipitation,mean water vapor content and its transport.particularly in the Asian monsoon region in the real world than CTL-AGCM runs.It is also pointed out that both the implementation of land surface parameterizations and the variations in land surface into the GOALS model have greatly improved hydrological balance over continents and have a significant impact on the simulated climate.particularly over the massive continents.Improved precipitation recycling model was employed to verify the mechanisms for land surface hydrology parameterizations on hydrological cycle and precipitation climatology in AGCM.It can be argued that the recycling precipitation rate is significantly reduced,particularly in the arid and semi-arid region of the boreal summer hemisphere,coincident with remarkable reduction in evapotranspiration over the continental area.Therefore the coupled SSiB-AGCM runs reduce the bias of too much precipitation over land surface in most AGCMs,thereby bringing the simulatedprecipitation closer to observations in many continental regions of the world than CTL-AGCMruns.