Regional Climate Simulation And Prediction Over CORDEX East Asia Domain Using WRF Model

East Asia with the unique geographic location, vegetation distribution and monsoon climate have relatively largest climate variability in the world, meanwhile the simulation difficult is also larger than other domain. Because the regional climate models (RCMs) have the higher horizontal resolution and better physical parameterization schemes, it became a widely used tool to improve the spatial detail of the General Circulation Models (GCMs) and global reanalysis data in regional climte simulating. This paper assesses the performance of spectral nudging technique by WRF model in simulating the present climate over Coordinated Regional Climate Downscaling Experiment East Asia (CORDEX-EA) domain with larger spatial range and longer time scales. Furthermore the changes of climatology and extreme events in the future are also predicted.Firstly, the paper presents a19-year (1989-2007) simulation using WRF model driven by ERA-Interim reanalysis data over CORDEX-EA domain. Compared to observation, experiment with spectral nudging can effectively redused the surface air temperature systematic bias over eastern China and northern India peninsula in winter as well as over India peninsula and southern China in summer. Systematic bias of winter precipitation also has been redused in most areas. By using spectral nudging, WRF model can give a better performance in simulating the inter-annual charateristic of surface air temperature and precipitation. Moreover, the correlations between observation and simulated results show the large improvement. Simulated extreme events over East Asia are also tested, bias of daily maximum and minimum temperature have been redused in most India peninsula and China, as well as the probability distributions are in better agreement with observation. Simulated numbers of different precipitation intensity days show much more consistency with observation than the experiment without spectral nudging.Then, the paper gives the both simulations using WRF model nesting in one-way mode within ECHAM5data. Two sets simulation for present climate (1978-2000) under real C02Scenario and mid-21st century climate (2038-2069) under IPCC A1B Scenario over CORDEX-EA domain are conducted. Present climate simulation results indicate that WRF model has the good capability to reduce the cold bias of surface air temperature. Meanwhile, bias of precipitation is also reduced obviously but not including the summer precipitation. In most areas the inter-annual charateristic of precipitation show the better agreement though in northern East Asia the bias of surface air temperature still exist. Spectral nudging technique also plays the role on reducing the root mean square error of surface air temperature and precipitation. Meanwhile, probability distributions of daily maximum and minimum temperature show more consistency with observation in sub-regions of Northeast China, North China, Yangtze-Huai River Basin and South China. Simutated bias for number of days in little rain, moderate rain and heavy rain are also reduced.The climate change results under IPCC A1B Scenario indicate that surface air temperature will increase with a stronger amplitud in winter and north East Asia, warming centers in summer are concentrated in western China, western Mongolia and southern Russia, moreover the warming amplitud in western Tibetan Plateau is abnormal dramatic. Winter precipitation will increase in northern land area and southeastern ocean area as well as decrease in Yangtze-Huai River Basin. Simulated changes of precipitation in India peninsula and Indo-china peninsula are different among ECHAM5and WRF results. Summer precipitaiton will decrease in northern China and Mongolia but increase in southern East Asia. Extreme events prediction results show that growing season length, heat wave duration index and total number of warm night days will increase in future, meanwhile total number of frost days show the decreasing amplitudes. Changes of inter-annual extreme temperature range will be different between southern and northern East Asia. Extreme precipitation events indicate that maximum5-day precipitation total will increase over East Asia besides the northern area. Maximum number of consecutive dry days will decrease in most China, Indo-china peninsula and the Bay of Bengal, which the simulated results in southern and western China are different between models. At the same time, ECHAM5results show that heavy rainy days will decrease in northern East Asia and increase in south, in contrast, experiment without spectral nudging indicate the decreasing magnitude in eastern China and Indo-china peninsula. Simple daily intensity index will enhance in a wide range besides Mongolia. Total extrem precipitation index show the increasing magnitude in most East Asia.