1961~2013年长江三角洲地区霾日季节特征及变化分析

选取长江三角洲146个观测站1961~2013年的地面观测资料,分析了霾日季节性的年际、年代际长期变化及空间分布规律。结果表明,长江三角洲霾多发时段随年际增长逐渐由冬季蔓延至春季,秋季和夏季。长三角平均霾日的季节变率从60~70年代的72.5%~78.5%,80年代跌至61.2%,到90年代跌至55.3%,而在本世纪的13 a低达52.3%,体现了长三角霾日变化季节性的年代际特征,即近53 a季节差异在不断减小,霾趋于常年化发生。霾日季节性的空间分布及年际变化特征还表明:近53 a长三角霾日呈持续上升趋势,1980年以前的2个年代增长缓慢,并维持低霾日水平,尽管1980年以后仍然增长缓慢,但维持多霾日的较高水平。霾日高发区域主要集中在南京-镇江一带、上海西南部地区、湖州-杭州-绍兴-金华一带、宁波西北部地区,高值中心依次为金华西北部兰溪市的70.2 d,江苏南京市的 40.0 d,上海金山的38.0 d以及宁波余姚市的35.5 d。长三角中部的霾日年增长率整体低于南部和北部地区,江苏中部及南部、浙江南部及东部沿海、安徽东南部地区是霾日年际增长高值区。长三角霾日年际变化趋势以夏季增长率最高,其次是秋季、春季,冬季霾日年际变化趋势普遍增长率最低,近53 a来长江三角洲大部分地区出现了霾日季节性差异变小的季节性变异特征。

SEASONAL CHARACTERISTICS AND CHANGE OF HAZE DAYS OVER THE YANGTZE RIVER DELTA REGION DURING 1961～2013

In this study by using the surface observation data (1961-2013) collected from 146 meteorological stations of the Yangtze River Delta, the seasonal characteristic of haze over the Yangtze River Delta in a recent 53 years were analyzed. The results indicated that the frequent periods of haze days have been spreading from winter to spring, autumn and even summer. The seasonal change rate of haze days in 1960s-1970s was up to 72.5%-78.5%, dropped to 61.2% in 1980s and 55.3% in 1990s, while in recent 13 years of this century was as low as 52.3%, which indicated that the seasonal differences of haze days have stable declined. Haze pollution, previously happened in winter in the Yangtze River Delta, has tended to be a frequently occurring phenomenon in all over the year. The analysis on the inter-annual and spatial variations of haze over the Yangtze River Delta in different seasons also indicated that haze days averaged over the Yangtze River Delta exhibited an increasing trend during the past 53 years, and grew slowly and maintain little haze days level before 1980, and grew slowly after 1980 but maintain more haze days levels. The regions with high frequent haze are centered over Nanjing- Zhenjiang area, southwest Shanghai, Huzhou-Hangzhou-Shaoxing-Jinhua area, and the northwest area of Ningbo city. The highest numbers of haze days in the 53-year average reached to 70.2, 40.0, 38.0, 35.5 days per year for Lanxi city in Jinhua, Nanjing city in Jiangsu, Jinshan district in Shanghai, Yuyao city in Ningbo, respectively. In terms of the geographical distributions of inter-annual variability rate of haze, central Yangtze River Delta area experienced the lower inter-annual variation rates than south Yangtze River Delta area and north Yangtze River Delta area. The large inter-annual variations of haze days concentrated over the central and south Jiangsu, the south Zhejiang and east Zhejiang coastal, as well as southeast Anhui. Seasonally, the inter-annual increase rates peaked in summer, and then followed by autumn and spring, and inter-annual increase rate in winter reached lowest in most of the Yangtze River Delta. The decreasing seasonal difference of haze is exhibited in most areas of Yangtze River Delta over the recent 53 years.