2002-2011年乌鲁木齐市API指数变化特征

Characteristics of Air Pollution Index in Urumqi From 2002 to 2011

文章利用乌鲁木齐市2002-2011年之间的空气污染指数(API)日报和同期气象要素数据,研究了API指数的变化特征,讨论了与气象要素间的相关关系。结果表明,API指数在10 a中呈下降趋势,年变化系数为-3.2。大气质量良好率在59.1%~77.4%之间变化。API指数呈显著季节差异,冬季较高,夏季最低。API指数Ⅰ级天数在春季、夏季和秋季分布占总天数的9.34%~34.82%。Ⅲ级以上天数在冬季较高,达到82.97%。月均API指数与本站气压和相对湿度呈现正相关,与风速、气温、平均水汽压和日照时数呈现负相关。而季节平均API指数与气象要素有一致的相关关系,且相关系数都有显著增大。API指数与气象要素在不同污染级别下,相关性变化较大。西北气流往往带来较低的API指数,而偏东气流往往伴随着污染日。

Based on the daily data of air pollution index(API) and the ground meteorological variables of corresponding period from 2002 to 2011, this paper has researched change characteristics of API and the correlations between API and meteo-rological variables in Urumqi. The conclusions are as follows: During the period of 2002 and 2011, the air pollution conditions have been improved gradually. The annual coefficient of API variation of-3.2. The proportion of air quality excellent varied between 59.1% to 77.4%, and the air quality in summer is the best and in winter is the worst among four seasons. The number of days in Class Ⅰ accounted for 9.34% ~34.82% of total number of days in the spring, summer and autumn. The number of days in Class Ⅲ and above is very much in winter, which reaching 82.97% of total number of days. The monthly average API has a positive correlation with air pressure and relative humidily while it has a negative correlation with wind speed, air temperature, average vapor pressure and sunshine hours. Under seasonally average size, the correlation coefficient between API and meteorological vaiables are consistent with monthly average API, and the correlation coefficient has increased significantly. The correlation coefficient between API and meteorological vaiables have larger change in the different levels of pollution. According to an analysis of the distribution of pollution days for different wind directions, Urumqi is mainly influenced by extreme wind speed and maximum wind speed from north-northwest and north in non-pollution days while from north-northeast and east in pollution days.