| This study analyses the impacts of greenhouse effect on regional climate in eastern China as simulated by RegCM3(ICTP) for the period of mid-21st century under IPCC A1B scenario. For policymakers, this can be a basis for preparing regional medium and long-term development program. In the 19th century, scientists realized that gases in the atmosphere cause a "greenhouse effect" which affects the planet's temperature. Human activities contribute to global warming by enhancing Earth's natural greenhouse effect. In this study, the RegCM3 is nested in one-way mode within the AOGCM(EH50M). Two sets of multi-decadal simulations at 30-km grid spacing for present day(1981-2000) and future climate(2041-2060, IPCC A1B emission scenario) are conducted. The first set can be used to examine the simulation capability of RegCM3, and the second one would be the important point which would provide us the characteristic of climate change in eastern China. The main points of this study can be summarized as follows:1) Climate is different from one region to another. At present, numerical simulation is considered to be one of the best methods to know the climate change which could be affected by both human activities and natural elements. Before we start simulation, sensitivity experiments for parameterized scheme of physical process and lateral boundary conditions would be needed. For this part, RegCM3 is used to simulate the eastern China climate for 1998. Results of experiments show that linear relaxation lateral boundary treatment and MIT-Emanuel convective precipitation scheme are more suitable than the other schemes for the simulation in eastern China.2) To examine the climate simulation capability of RegCM3, we analyzed the RegCM3's simulation of present day climate in four sub-regions of eastern China. The coupled atmosphere-ocean general circulation model—EH5OM, which is one of the most successful CMIP3 models (out of 22) in simulating the climate of the 20th century models, provides the initial field and lateral boundary condition for RegCM3. Simulation results show that this regional model can well reproduce the atmospheric circulation and some basic features of the observed mean surface climate, including surface air temperature and precipitation. In some extent, there is a cold bias in the RegCM3 simulation and the amount of precipitation simulated by model is somewhat over the observed data.3) After assessing the climate simulation ability of RegCM3 over eastern China, the regional climate model is nested in one-way mode within EH50M to simulate the future climate in the same area under IPCC A1B scenario. Our study mainly focus on the discussion of some basic features of climate, including ground temperature, precipitation, and atmospheric circulation in lower(850hPa), mid(500hPa) and upper(200hPa) level of troposphere. Comparing to present day climate, the warming of annual temperature in four sub-regions are in range of 1.02-2.85℃, while the rise is much significant in south China and the increase in east China is the smallest one when compare to other regions. We also calculate the variance of temperature in all 12 months, and it seems that temperature variance in winter will increase in all regions, in another words, the inter-annual variability of temperature will increase in winter in mid-21st century over four sub-regions. General increase in annual mean precipitation is simulated by RegCM3, and the more the precipitation increase in one region, the less air temperature rise in this region. The simulation results of atmosphere circulation show that the future 850hPa geo-potential high fields remain much the same as present day climate. However, the northward East Asian trough and subtropical high over the West Pacific at 500hPa may contribute to the change in position of rain-belts and precipitation intensity. The coverage of upper jet at 200hPa would turn broad in summer, eastward in winter, and the fluctuation of jet strength will become frequent in winter.
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