4:30 PM - 4:45 PM
[AAS02-11] Impact of Precipitating Ice Hydrometeors on Longwave Radiative Forcing Estimated by a Global Cloud-system Resolving Model
Keywords:cloud ice, cloud resolving model, radiation, Nonhydrostatic Icosahedral Atmospheric Model
An offline radiation model is employed to break down cloud radiative effects into amount and altitude of each ice category. Results show that the snow radiative effect reaches 2 W m−2 in the tropics, which is about half that estimated by previous studies. This effect is strongly dependent on the vertical separation of ice categories, and it is partially generated by differences in terminal velocities, which are not represented in GCMs with diagnostic precipitating ice. Results from sensitivity experiments that change the categories and the existing altitudes of precipitating ice showed that the simulated longwave heating profile and longwave radiation field are sensitive to the treatment of precipitating ice in models. The long-term circulation behavior in models may change due to the heating behavior changes. This study emphasizes that it is the important for cloud and radiation schemes in GCMs to incorporate appropriate treatments for the radiative effects of precipitating ice in order to simulate cloud radiative effect by upper-level clouds.
Interannual variability of high clouds and their future changes will also examined by comparing NICAM simulations and observations.