The Transport Characterization And Climate Effect Of Black Carbon In China

This paper consists of two main contents as follows:Firstly, an online Aerosol-Climate model has been developed by coupling Canadian Aerosol Module(CAM) with GCM CAM3.0. Using this coupled Aerosol-Climate model, we have studied the model results in China from the different black carbon(BC) inventories(data from GEIA, David Streets et al., in 2000 and 2004,respectively) and compared the results with observations in China and analyzed the reason of uncertainty. At last, according to above comparing, the transported characterization of BC in China has been described.Secondly, the climate effect induced by BC and sulfate aerosols has been studied. That is, the effect on East Asia summer monsoon due to BC, sulfate and both BC and sulfate aerosols only in China has been investigated with CAM3.0 itself aerosol assimilation system. This kind of climate effect of aerosols is a forefront scientific problem in the world, so it is very significant to probe.Through above research, we have gained these conclusions as follows:1. GEIA-experiment shows the global distributions of BC aerosol are consistent with BC source intensity. Global transport of BC is driven by atmospheric general circulation. In China, on the model lowest level, BC transported distance is farther in winter than summer.2. The BC source intensity of GEIA-exp. is two times higher than that of Streets-exp. while Streets2000-exp. is similar to Streets2004-exp. Compared with observations in China, we conclude the modeling BC concentration is lower than observation especially on high polluted regions or West of China, however, it is consistent with observation on background station. Generally speaking, the model result of GEIA-exp. is the most identical with observation.3. BC transport in China has seasonal change because it is driven by East Asia monsoon system. In general, on surface, it is transported from the south to the north in winter while opposite in summer. Besides, the long distant transport across the Pacific Ocean is more prominent in winter than summer. Above 500hpa, BC is transported from the west to the east driven by west wind zone. The intensity of the transport is different in each season, and it is stronger in summer and autumn than spring and winter. On the whole model levels, BC transport is also stronger in summer and autumn than spring and winter. Besides, the long distant transport zone is moving from spring to winter. It moves the northernmost region in summer and then move to the south, when winter, it is southernmost. Long distant transport is prominent above 500hpa and the amount of BC above 500hpa accounts for much portion of that on the whole levels.4. Using aerosol assimilation system of CAM3.0, we have acquired these conclusions: Chinese sulfate and BC aerosols can bring global radiation force to -0.25W/m~2 and +0.13W/m~2 , respectively; In the northern China (about the north of 25°N) , the surface temperature universally drops due to sulfate aerosols. There are 3 noticeable decreased temperature regions in Si Chuan province, northeast and northwest of China corresponding with sulfate aerosols high concentration regions, where the temperature decreased by 0.7°C. BC can induce the decrease of surface temperature in China except for in Tibet, Qinghai, the middle of Xinjiang, Yunnan and Guangxi province where the temperature is increased. Both sulfate and BC aerosols can lead to the increase of sea surface temperature. Therefore, the surface temperature and pressure differences between land and sea reduce. Then they weaken East Asian Summer monsoon and the precipitation. Sulfate aerosols have much greater effect on weakening East Asian Summer monsoon than BC so that sulfate aerosols lead to decreasing precipitation in China while BC increase precipitation in middle backward position of the Changjiang River, which is also indicated by the index of monsoon intensity. Sulfate aerosols can restrain the convection while BC aerosol can enhance it especially in southeast of China. Except above reasons to weaken East Asian Summer monsoon, the factor of the surface latent heat flux difference induced by precipitation difference between land and sea cannot be ignored, either.