Present-Day Antarctic Climatology Of the NCAR Community Climate Model Version 1

Five-year seasonal cycle output produced by the NCAR Community Climate Model Version 1 (CCM 1) with R15 resolution is used to evaluate the ability of the model to simulate the present-day climate of Antarctica. The model results are compared with observed horizontal syntheses and point data. Katabatic winds, surface temperatures over the continent, the circumpolar trough, the vertical motion field, the split jet stream over the Pacific Ocean, and the snowfall accumulation are analyzed. The results show that the CCM1 with R15 resolution can well simulate to some extent the dynamics of Antarctic climate not only for the synoptic scale, but also for some mesoscale features (mesoscale cyclogenesis). This is reflected in the zonal-mean pattern of vertical motion by the presence of two convergence centers. The finding suggests that the CCM1 might also capture the split jet stream over New Zealand in winter, but the evidence is mixed. This is inferred to be due to inadequate simulation of the thermal forcing over high southern latitudes. The CCM1 can also capture the phase and amplitude of the annual and semiannual variation of temperature, sea level pressure, and zonally averaged zonal (E-W) wind. That the CCM1 can simulate some characteristics of the semiannual variation may be due to the improved radiation treatment compared to the earlier CCM0. The most dramatic shortcomings were associated with the model's anomalously large precipitation amounts at high latitudes, which result from the scheme to suppress negative moisture values. The simulations of cloudiness and the atmospheric heat balance are adversely affected. A greatly refined moisture budget scheme is needed to eliminate these problems and may allow the split jet-stream feature over the New Zealand area in winter to be accurately reproduced. A coupled mesoscale-CCM1 model may be needed to adequately simulate the feedback from mesoscale cyclones to synoptic-scale weather systems, and the katabatic wind circulation.