利用大气化学模式WRF-Chem建立3D_Var同化系统, 对美国西部地区一次PM2.5化学污染过程的PM2.5总量及其主要成分(黑碳、有机碳、硝酸盐、硫酸盐)进行了同化试验, 并与未同化结果和实况进行了区域、单站及时间序列的对比。结果表明, 此系统具有较好的同化效果, 同化试验结果与实况接近, 站点分布和演变趋势吻合较好; 任取3个站点进行单点时间序列演变和散点分布分析, 同化后相关系数有所增加, 均在0.85以上, 在所选3个站点中相关系数最大达0.95, 均方根误差都明显减小; 数值模拟没有模拟出的大值中心, 但经同化后能再现出来; 模式模拟PM2.5低浓度值的演变趋势及数值要好于高浓度值; 随着模式的运行, 同化前期效果最好, 同化中期和后期结果与实况偏差有所增加; 模式还存在系统偏差和奇点问题, 这些是模式需要改进的地方。
A three-dimensional variational system was established rely on the fully coupled meteorology-chemistry model (WRF-Chem) and used to carry a assimilation experiment about the ground-level PM2.5 and its main components: black carbon, organic carbon, nitrate, sulfate in Los Angeles in the west of American. At the same time we compare the area distribution, single station and temporal variations of the output with control experiment and observed. The results show that: This system has a good effect of assimilation, assimilation results and live closer to the site distribution and evolution of the trend in good agreement; take three sites for the evolution of single-point time series and scatter plot analysis, assimilation correlation coefficient increase in more than 0.85, the correlation coefficient selected three sites up to 0.95, the root mean square error has significantly reduced; numerical simulation did not simulate the large value of the center can be reproduced by assimilation; model simulations the low concentration of PM2.5 evolution of trends and values better than the high-concentration values; with the mode of operation, the pre-assimilation results is better, the deviation of assimilation in mid-period and late period and observation increase; modes also exist systematic bias and singularity, these are the areas for improvement mode.
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