An analysis of observation and GCM simulations of seasonal cycle of monsoon climate in Southeast Asia and Tibet Plateau

Atmospheric general circulation models have been used for climate study. Evaluation of the GCM ability to simulate the observed climate features can identify the models' inadequacy so that further improvement can be made. The research diagnoses GCM simulation of East Asian Climate, and is a part of a subproject in the Atmospheric Model Intercomparison Program and Coupled Model Intercomparison Program. We used three AMIP models and two CMIP models. Four land and oceanic regions in East Asia are chosen for the diagnostic study. In addition, the Tibetan Plateau is included due to its importance to the monsoon system. Monthly observational data and GCM simulations for the AMIP period 1979–1993 are used. The work focuses on seasonal cycles of surface temperature and precipitation, although other climate parameters such as outgoing longwave radiation, wind and surface energy balance components are also examined.; ECHAM4 seasonal cycles fit observation the best, with correlation coefficients above 0.9 for precipitation and almost 1.0 for surface temperature. Other model performances are fair. NTU-GCM can simulate particular detailed seasonal cycles: the precipitation summer retreats in the South China Sea and the Indo-China Peninsula. But at the same time its precipitation cycle is 78% larger in the Bay of Bengal, showing its inconsistency for different domains. NCAR-CCM3 systematically underestimates the seasonal cycle strength in the oceanic domains. Particularly, it underestimates the precipitation seasonal cycle 75% in the South China Sea and the Tropical Western Pacific.; NCAR-CSM simulates SST seasonal cycles well compared with observation, within 5% discrepancy and improves substantially the summer precipitation of CCM3. Especially in the South China Sea and the Tropical Western Pacific, CSM has summer precipitation of 11.6 and 12.2 mm/day, compared with observation 11.1 and 9.4 mm/dcy (CCM3 has 5.37 and 5.49 mm/day respectively). The improvement in summer precipitation is mainly due to improved surface wind (from 2.6 ms −1 in CCM3 to 10.4 ms−1 in CSM, which enhances the latent heat flux). Therefore the effect of air-sea interaction plays an important role in NCAR GCM.; However, the comparison of MPI GCMs does not show the similar improvement for including the air-sea interaction.