天津地区霾天气特征研究

基于2014~2017年天津地区PM_2.5质量浓度,能见度和相对湿度监测数据开展霾天气特征研究.结果表明：天津中度以上霾过程分为五类：高压后部型,北部弱高压型,低压槽型,均压场型和锋前低压型.在现行标准下,中度霾一般对应重度污染天气,重度霾对应重度到严重污染天气;五级重度污染天气一般有中-重度霾发生,六级严重污染天气有重度霾天气发生.2013年“大气污染防治行动计划”开展以后,天津PM_2.5质量浓度和霾日均显著减少,2017年相比2013年霾日减少了55%,中度及其以上霾日由2013年的41d下降到2017年的20d,下降幅度超过50%.基于实况监测的PM_2.5质量浓度,能见度和相对湿度,可以较好的构建区域能见度计算方程.统计数据显示,其估算的能见度和实况值相关系数为0.94,相对误差为18.6%,非霾日辨识准确率为85%,霾日辨识准确率为95.6%,轻微霾辨识准确率为83%,轻度霾辨识准确率为78%,中度霾辨识准确率为93%,重度及以上霾辨识准确率为94%,对于判断霾等级,有较强的适用性.将该方程与空气质量模式结合开展霾等级预报,2015~2017年24h预报产品检验显示：能见度预报值与实况值相关系数为0.75,预报均值13.9km,实况均值14.1km,相对误差为29.6%,FAC2（预报值在实况值两倍范围内百分比）为98.1%,霾日预报准确率81.4%,霾日漏报率18.6%,霾日空报率20.6%,如果容错1级,轻微霾日预报准确率为96%,轻度霾日预报准确率为85%,中度及以上霾日预报准确率为69%,可有效支撑天津霾等级预报的开展.

Research on characteristics of haze weather in Tianjin

A research was carried out on characteristics of the haze weather in Tianjin based on the monitoring data of PM_2.5 mass concentration, visibility and relative humidity in the area from 2014 to 2017, The findings showed that there are five types of haze processes above moderate degree in Tianjin:that in the rear of high pressure, that caused by weak high pressure from north, that caused by low pressure trough, that caused by uniform pressure field and that caused by low pressure before front. As per the current standards, moderate haze generally corresponds to severely polluted weather; severe haze corresponds to severely to untra-severely polluted weather. Moderate to severe haze usually occurs in Level V severely polluted weather, and severe haze occurs in Level VI ultra-severely polluted weather. After "Air Pollution Prevention Action Plan" was implemented in 2013, PM_2.5 mass concentration and haze days were significantly reduced, by 2017, the number of haze days had decreased by 55% compared with 2013, moderate and above haze days decreased by 50% from 41d in 2013 to 20d in 2017. Based on the monitoring data of PM_2.5 mass concentration, visibility and relative humidity, the calculation equation of regional visibility can be well constructed. Statistics showed that the correlation coefficient between visibility and real value in the estimation is 0.94, with the relative error 18.6%, identification accuracy rate of the non-haze day is 85%, that of the haze days 95.6%, that of the ultra-slight haze days 83%, that of the slight haze days 78%, that of moderate haze days 93% and that of severe and above haze days 94%, which is greatly applicable for judgement of haze level. This equation was combined with the air quality model to predict the haze level. Inspection of the forecasting product showed:the correlation coefficient between the forecast values and real values of visibility is 0.75, with average forecast value 13.9km and the average real value 14.1km, and the relative error rate 29.6%, the FAC2 (the ratio of the forecast value to two times the real value) is 98.1%, the forecast accuracy rate, forecast missing rate and false rate of the haze days are 81.4%, 18.6% and 20.6%, respectively. Let the tolerance be of Level I, the forecast accuracy rates of ultra-slight haze days, the slight haze days and the moderate and above haze days are 96%, 85% and 69%, respectively, which may effectively support the haze level forecast in Tianjin.