Influence of two convection schemes on the radiative energy budget

The Gridpoint Atmospheric Model of the State Key Laboratory of Numerical Model ing for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), version 1.0 (GAMIL1.0) was used to investigate impac ts of two different convective schemes on the energy budget. The two convective schemes are presented by Zhang and McFarlance/Hack (ZM) and Tiedtke/Nordeng (T N). Two simulations are performed: one with the ZM scheme (EX -ZM) and the other with the TN scheme (EX-TN). The results indicate that, during the convective process, the assumption that the deep and shallow co nvection clouds can happen at the same time in the ZM scheme is the main reason for more consumption of vapor and more release of heat in the low layers in EX-ZM, while only one type of convection is allowed to take place in the TN scheme . Hence, the relative humidity of the atmosphere in EX-TN is larger than that in EX_ZM after the convection. The relative humidity of the atmosphere is very i mportant for cloud formation and cloud microphysics processes: the larger the re lative humidity is, the more cloud and more condensation there are. Therefore th e moister atmosphere favors low cloud formation and largescale condensation, a nd mo re low cloud fraction, cloud water mixing ratio and deeper cloud extinction opti cal depth are simulated, reflecting more solar radiation flux in EX-TN. This explains why the TN scheme underestimates the net shortwave radiation flux at the top of the atmosphere and at surface. In addition, convection influences longwave radiative, surface sensible and latent heat fluxes through changes in cloud emi ssivity and precipitation.