天津冬季相对湿度对气溶胶浓度谱分布和大气能见度的影响

于2013年1月连续在线观测天津城区气溶胶数浓度谱分布和大气能见度,并结合相关气象资料,探讨相对湿度(RH)对气溶胶浓度谱分布和大气能见度的影响.结果表明,观测期间发生了4次连续雾霾天气过程, 4次雾霾天气过程对应着气溶胶粒子数浓度的连续高值,低能见度天气系高浓度气溶胶粒子和高相对湿度协同所致;随着RH增大,PN1和PN2.5-10呈增长趋势, RH>90%后,PN1和PN2.5-10有所降低,PN1-2.5则持续增长,高RH对气粒转化和气溶胶粒子的碰并聚合作用明显;气溶胶吸湿增长因子计算表明,高RH下水汽对能见度影响很大,尤其是大雾天气下其影响甚至可能超过气溶胶粒子浓度对其的影响.

Effects of relative humidity on the aerosol size distribution and visibility in the winter in Tianjin

Taking use of the aerosol number concentration, visibility and other observation data during January of 2013 at Tianjin, the effects of relative humidity on the aerosol size distribution and visibility were analyzed. During the observation period, there were four episodes in which the visibility was continuously less than 10km. The aerosol size distribution and relative humidity were the main factors on effecting visibility. When RH was lower than 90%, number concentration of aerosol particles increased gradually as RH increased. When RH was higher than 90%, number concentration of aerosol particles between 1μm and 2.5μm in diameter increased gradually as RH increased, while number concentration of aerosol particles less than 1μm and between 2.5μm and 10μm in diameter decreased gradually as RH increased. The mean value of aerosol hygroscopic growth factors at 80% RH f (RH=80%)] was 2.04. Water vapor had a great influence on the visibility with high RH in fog and may even exceed the influence of aerosol particle concentration on visibility.