以南京市19542012年的逐日气象数据分析南京市灰霾天的长时间变化规律并从气候角度探讨其变化原因。南京市的霾日数近60 a来呈现明显上升趋势,从20世纪50年代的40 d /a已增加至21世纪的230 d /a左右,气象行业标准界定的霾日与人工观测的霾日长期变化趋势一致,前者在南京市具有较好的适用性。南京市雾霾混合日呈现出先增加后下降的趋势,其对应的相对湿度在不断降低,这可能是雾霾日向霾日转换,雾霾日数降低而霾日数增多的关键因素。南京地区能见度不断降低,近30 a里约下降8.4 km,霾日数与能见度相关系数高达- 0.91,随着能见度的降低,灰霾天数几乎线性增加。南京地区的年平均相对湿度在1985年以后大幅降低,已从约80%下降至68%左右,湿度与霾日的相关系数为- 0.72,随着湿度的降低,霾日呈上升趋势。南京年平均温度1985年后明显上升,升高了1.8 ℃,其中冬季上升幅度最大,夏季上升幅度最小;年均温度与霾日数呈现出明显正相关,和相对湿度呈现明显负相关,温度的升高将造成相对湿度的降低,进而造成霾日增多。南京的年平均风速1978年后不断降低,到20世纪末约降低1.5 m/s,风速与霾日呈现出显著的负相关,随着平均风速的降低,霾日数不断增多。在全球变暖的大气候背景下,南京市霾的长时间变化受到各种气候因子的影响,能见度、相对湿度、温度和风速都是重要的影响因素。
英文摘要:
With the continuous development of China's economy,haze pollution is a serious issue that urgently requires in-depth investigation. To date,very few haze pollution studies have focused on the formation and causal variation from the point of view of climate change. Against the background of a rapidly increasing number of haze days and global warming,we studied the long-term variation in haze days and discussed the reasons for the change from the climate perspective in the city of Nanjing. The study is vitally important for a deeper understanding of the formation and variation of haze. Based on daily meteorological data from the climate reference station of the China Meteorological Bureau in Nanjing from 1954 to 2012, the long-term variation in haze days was calculated using two methods: haze days identified according to the standards of meteorological industry,and haze records from the observations of meteorological observers. The number of haze days showed a clear increasing trend,from 40 d yr - 1 in the 1950s to 230 d·yr - 1 in the 21st century. The variation in haze days according to the two methods had a similar change trend, indicating favorable applicability of the standards of meteorological industry in Nanjing. During the study period, the number of fog-haze days increased and then decreased in Nanjing,accompanied by a continuing decrease in visibility,which reduced by around 4 km,as well as a decrease in relative humidity,which reduced by around 4%,changing from 89.5% in the 1950s to 85.5% currently. The change in relative humidity may be a key factor for the reduction in fog-haze days and the increase of haze days, indicating a shift from the former to the latter. The visibility in Nanjing gradually decreased by 8.4 km in the last 30 years. The annual average visibility of haze days also decreased and the proportion of severe haze increased. The correlation coefficient between haze days and visibility reached - 0.91,with haze days increasing almost linearly with the decrease in visibility. The annual average relative humidity in Nanjing declined by a large margin from 1985,changing from around 80% to 68% by the end of the study period. The change in the average relative humidity on haze days was very similar to the annual change. The correlation coefficient between haze days and relative humidity was - 0.72. The number of haze days increased as the humidity decreased. The annual average temperature in Nanjing increased obviously by approximately 1.8 ℃rom 1985. The warming trend was greatest in winter, increasing by approximately 2.1 ℃and smallest in summer(approximately 0.7 ℃. The annual average temperature was positively correlated with haze days and negatively correlated with relative humidity. The rise in temperature caused a decrease in relative humidity, which then resulted in more haze days. The annual average wind velocity decreased gradually from 1978, reducing by approximately 1.5 m·s - 1 by the end of the 20th century. The wind speed presented a significant negative correlation with the number of haze days. With a reduction in wind speed,pollutants diffuse less easily and accumulate in the atmosphere,which results in an increase in particulate matter and the frequency of haze days. In summary,against the background of global warming, the long-term variation in haze days in Nanjing is influenced by many climatic factors,among which the visibility, relative humidity, temperature and wind velocity are all particularly important.