1961-2013年辽宁省不同等级霾现象时空分布特征及其气候成因

Temporal and spatial characteristics of haze days with different intensities and the climatic factors during 1961—2013 in Liaoning Province

利用辽宁省52个地面气象观测站的观测资料,对辽宁省不同等级霾日时空变化特征和气候成因进行分析.结果表明,辽宁省霾日在空间上存在一个高值中心(沈阳)和两个副高值中心(锦州西南部和朝阳东部),年平均霾日在50 d以上,辽西山区和东北部山区年平均霾日最少在10 d以下.辽宁省霾日主要集中在冬秋季,占全年霾日60%以上,夏季次之,春季最少;1961—2013年辽宁省平均霾日呈明显增加趋势(3.5d/10 a),轻微霾日、轻度霾日和中度霾日也呈显著增加趋势,重度霾日无明显变化.不利的气候条件加剧了霾日的出现,霾日数与降水日数呈显著负相关,降水日数的显著减少(-2.6 d/10 a)导致大气对污染物的沉降能力减弱,而静风日数增加(5.1 d/10 a)、年平均风速减小(-0.2m·s-1/10 a)和大风日数的减少(-10.1 d/10 a)则使得空气中污染物不易扩散,增加了霾天气形成的概率.

Temporal and spatial characteristics of haze days with varied intensity and the possible climatic factors have been analyzed by applying meteorological data from 52 surface weather stations in Liaoning Province between 1961 and 2013. In terms of spatial distribution,there is a high-value center located in Shenyang City and two sub-high-value centers in the southwest of Jinzhou City and in the east of Chaoyang City,where annual total haze events generally exceed 50 days. The number of haze days in the western and northeastern mountainous areas is the lowest with less than 10 days a year.Haze events are more frequently observed in winter and autumn,accounting for over 60% of annual total,followed by summer and least frequently in spring. Averaged number of annual haze days in Liaoning Province have a significant increasing trend of 3. 5 d / decade during 1961—2013. Days with slight,mild and moderate haze increase significantly,but the days with severe haze have no significant change. Unfavorable climate conditions exacerbated the occurrence of haze events. Significantly negative correlation is found between haze days and precipitation days,and the precipitation days show an obvious decreasing trend in the province,probably reducing the wet-depositing capacity of atmospheric pollutants. On the other hand,the reduced mean wind speed and strong wind days lead to the reduction of pollutants diffusion capacity.