2013—2016年天津城区大气能见度的变化特征与影响因素

Analysis of variation characteristics and influencing factors of atmospheric visibility in Tianjin urban area from 2013 to 2016

  • 摘要: 采用Belfort公司生产的MODLE6000型前向散射能见度仪连续测量天津城区2013—2016年非降水期间的大气能见度,结合同期的PM2.5浓度和相关气象资料,分析大气能见度的变化特征及其影响因素。结果表明:天津城区大气能见度平均值为11.23 km,大气能见度年均值逐年提高,这与天津地区PM2.5浓度逐年下降有关;天津城区大气能见度季节变化明显,春季最高,夏季次之,秋季最低;大气能见度日变化存在显著的早晚高峰特征,PM2.5浓度和相对湿度(RH)的共同作用是造成大气能见度降低的主要原因;持续72 h以上能见度小于10 km的低能见度天气事件近年来有逐年减少趋势,但持续72 h以上能见度小于5 km的低能见度天气事件仍时有发生;低能见度天气事件主要发生在秋冬季,主要与不利扩散条件等因素有关。

     

    Abstract: Using the MODLE6000 type forward-scattering visibility meter produced by Belfort, the atmospheric visibility was measured over 2013-2016 in Tianjin urban area, and the variation characteristics and influencing factors of atmospheric visibility were analyzed, combined with the simultaneous PM2.5 concentration and related meteorological data. The results showed that the average atmospheric visibility was 11.23 km during the measurement period. The annually averaged visibility increased year by year in the 3 years, which should be related to the decrease of PM2.5 concentration in Tianjin area. The seasonal variation of atmospheric visibility in Tianjin urban area is obvious, with higher visibility in spring, lower in summer and lowest in autumn. There are significant morning and evening peaks in diurnal change of visibility, and the decrease of visibility is mainly due to joint impacts of PM2.5 concentration and diurnal variation of RH. The continuous low visibility (<10 km) weather events lasting more than 72 hours have decreased in recent years. However, the continuous low visibility (<5 km) weather events lasting more than 72 hours still occurred frequently in recent years. The low visibility weather events occurred mostly in autumn and winter, which were mainly related to the adverse diffusion conditions.

     

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