Assessment And Reconstruction Of East Asian Winter Atmospheric Circulation Based On Cmip3Climate Models

Climate model plays important roles on climate simulation, prediction and projection. Due to the rapid development and improvement of the climate model, its performance in simulating the climate has been significantly improved. However, there are still lots of uncertainties in both climate simulation and climate projection because of the complexity of the climate system as well as the systematic errors of the climate model itself. So it is fundamental for the climate modeling, prediction and projection to evaluate the performance of the climate. Based on1960-1999reanalysis data of40-year reanalysis datasets (ERA40) from European Center for Medium-range Weather Forecasting (ECMWF) and model outputs of20th century Climate Simulation experiments given by21Coupled Ocean-Atmosphere General Circulation Models (CGCMs) of Phase3of the Coupled Model Intercomparison Project (CMIP3), evaluated are the capabilities of the climate model in simulating winter atmospheric general circulation over East Asia, in both the aspects of the climatology and interannual variability. The reconstruction capability of superensumble using the21models to simulate SLP,850hpa wind,500hPa geopotential height, East Asian winter monsoon systems (Aleutian low and Mongolia high), monsoon index based on land-sea pressure difference, index of winter monsoon intensity and westerly wind in East Asia was also explored. Results are as following:(1) Despite the slight bias still existing in the model results, the basic spatial patterns of the climatology of sea level pressure (SLP),850hPa zonal wind (u), meridional wind (v) and500hPa geopotential height are well captured by all the models. On the whole, the simulation of500hPa potential height is the best, and the simulation of v on850hPa is relatively poor;(2) Most models can basically reproduce the main variation of500hPa geopotential height in winter of the recent40years, but fail to capture the interannual change of winter SLP,850hPa u and v. At the same time, the capabilities of the models in simulating the variations of the intensities of the Aleutian low and Mongolia high as well as East Asian winter monsoon are indeed poor.(3) Results have benn significantly improved by using the superensumble of the21climates models, compared with either a single model or the simple ensemble mean of21models. According to the reconstruction of two main East Asian winter monsoon circulations (Aleutian low and Mongolia high), five East Asian monsoon indexes, and the composite analysis of SLP,850hpa wind,500hPa geopotential height in strong and weak monsoon years, the results indicate that the superensumble can well rebuild the variability of East Asian atmospheric general circulations in time and space and East Asian monsoon trend over the past40years.