Abstract：This study set Beijing (BJ), Tianjin (TJ), Hebei (HB) and Shanxi (SX) among the areas around the capital as example to compare three methods on calculating haze or mist (fog) days. The three methods include single value method, daily mean method and 14:00PM moment method. The main results are as below: the regional haze days’ distribution during the past 60years in North China calculated by the three methods showed difference. The rank of the haze day numbers was single value method, daily mean method and 14:00PM moment method, with the ratio of about 1:0.54:0.45. But the regional trends appeared similar for the three methods. The long term trends of haze days for the typical cities were quite similar. The long term trends of mist (fog) days calculated by three methods turns out that single value method counted obviously more fog days and presented a long term decreasing trend, while the values gained by daily mean method and 14:00PM moment method had no significant difference, both with no significant long term trends and showed clear the interannual and inter-decadal variation. The long term trends calculated by the three methods presented obvious difference in some cities in North China. For the long term trends of seasonal variation, the seasonal distributions obtained by the three methods were similar although the difference in numbers. One outstanding feature was that there were obviously more haze days in summer besides in the heating season, mainly concentrated in June to September, especially in July to August, occurring at the same time as the sultry weather. This distribution was a unique phenomenon in North China, which was quite different from most of the other cities in China. Calculating by the single value method will include all haze processes, i.e. wide and lasting haze, which is related to the specific synoptic systems and near-surface diffusion conditions, or some other formed by decreased visibility under higher relative humidity caused by radiative cooling at the stable clear night. Calculating by the daily mean method will result in more wide and lasting haze processes, while using 14:00PM moment method can highlight the wide and lasting haze processes but neglect the haze with poor visibility caused by humidity rising in the morning and at night.
吴兑, 陈慧忠, 吴蒙, 廖碧婷, 王迎春, 廖晓农, 张小玲, 权建农, 刘伟东, 古月, 赵秀娟, 孟金平, 孙丹. 三种霾日统计方法的比较分析[J]. 中国环境科学, 2014, 34(3): 545-554.
WU Dui, CHEN Hui-Zhong, WU Meng, LIAO Bi-Ting, WANG Ying-Chun, LIAO Xiao-Nong, ZHANG Xiao-Ling, QUAN Jian-Nong, LIU Wei-Dong, GU Yue, ZHAO Xiu-Juan, MENG Jin-Ping, SUN Dan. Comparison of three statistical methods on calculating haze days-taking areas around the capital for example. CHINA ENVIRONMENTAL SCIENCECE, 2014, 34(3): 545-554.
