天津地区能见度变化特征及影响因素研究

Variation trends and affect factors of visibility in Tianjin

能见度是一个重要的衡量大气透明度状况的气象指标。能见度下降是重要的城市大气环境问题之一,低能见度天气会给人们的日常生活带来诸多不便,如车辆受阻、航班延误等,并可能造成严重的交通事故。近几年天津地区雾霾低能见度天气明显增加,研究该地区能见度变化特征及影响因素,对于改善大气能见度具有指导意义。利用天津1980—2010年能见度,相对湿度及2010年PM2.5观测数据分析天津地区大气能见度长期变化趋势以及天津地区大气能见度变化与PM2.5污染和气象条件的关系。结果表明:1980—2010年能见度变化趋势为市区表现为先恶化再好转,1993年以前下降趋势明显,1993—2003年变化不大,2003年以后呈现好转,2010年恢复到10 km以上。塘沽站表现为明显的持续恶化,表现为每10年下降2.6 km,2010年能见度年均值与市区接近为11.5 km;蓟县表现为1991年前下降再保持波动性的稳定,2010年能见度维持在15.6 km左右。市区、塘沽和蓟县能见度在11—1月和6—8月较低,相对湿度和污染是影响能见度变化的主要条件。颗粒物的质量浓度和大气能见度之间存在着复杂的非线性关系,随着颗粒物粒径的变小,能见度与颗粒物浓度之间的相关系数明显提高,细粒子是影响天津地区能见度变化的主要污染物。

Visibility is an important meteorological index measuring atmospheric transparency. Reduced visibility is one of the important atmospheric environment problem in big city, low visibility bring a lot of troubles to people＇s daily life, such as blocked traffic and flight delay, sometimes even cause serious traffic accident. Low visibility events increased in recent years in Tianjin, research on the variation trends and affect factors of visibility is important for improving visibility. Long-term variation trends of visibility, as well as relationships with NOx, 03, PM10, PM2.5, PM1.0 pollution and meteorological conditions were analyzed using visibility and humidity data between 1980-2010 and the observed hourly visibility, relative humidity, and particulate concentration data at atmospheric boundary station in 2010. Visibility at urban site exhibited decreasing trend before 1993, then slight fluctuation from 1993 to 2003, since then visibility shows increasing trend and is above 10km in 2010. Visibility at Tanggu site performance obvious continually reduced trend with deterioration rate of 2.6 km/year and visibility is 11.5 km in 2010. Visibility at Jixian site decreased before 1991 and then maintained stability at about 15.6 km. Visibility was lower in Nov and Jan, Jun and Aug, humidity and pollution was the main factors influencing visibility. Complex non-linear relationship existed between the mass concentration of particulate matter and atmospheric visibility, as the particle size became smaller, the correlation coefficient improved obviously, fine particles affected visibility most in Tianjin area.