Simulation of Non-Homogeneous CO2 and Its Impact on Regional Temperature in East Asia

Carbon dioxide(CO2) is an important greenhouse gas that influences regional climate through disturbing the earth’s energy balance. The CO2concentrations are usually prescribed homogenously in most climate models and the spatiotemporal variations of CO2are neglected. To address this issue,a regional climate model(RegCM4) is modified to investigate the non-homogeneous distribution of CO2and its effects on regional longwave radiation flux and temperature in East Asia. One-year simulation is performed with prescribed surface CO2fluxes that include fossil fuel emission, biomass burning, air-sea exchange, and terrestrial biosphere flux. Two numerical experiments(one using constant prescribed CO2concentrations in the radiation scheme and the other using the simulated CO2concentrations that are spatially non-homogeneous) are conducted to assess the impact of non-homogeneous CO2on the regional longwave radiation flux and temperature. Comparison of CO2concentrations from the model with the observations from the GLOBALVIEW-CO2network suggests that the model can well capture the spatiotemporal patterns of CO2concentrations. Generally, high CO2mixing ratios appear in the heavily industrialized eastern China in cold seasons, which probably relates to intensive human activities. The accommodation of non-homogeneous CO2concentrations in the radiative transfer scheme leads to an annual mean change of -0.12 W m-2in total sky surface upward longwave flux in East Asia. The experiment with non-homogeneous CO2tends to yield a warmer lower troposphere.Surface temperature exhibits a maximum difference in summertime, ranging from -4.18 K to 3.88 K, when compared to its homogeneous counterpart. Our results indicate that the spatial and temporal distributions of CO2have a considerable impact on regional longwave radiation flux and temperature, and should be taken into account in future climate modeling.