研究报告
张敏,蔡子颖,韩素芹,姚青,刘敬乐.天津污染天气边界层温度层结变化特征及预报阈值确定[J].环境科学学报,2018,38(6):2270-2278
天津污染天气边界层温度层结变化特征及预报阈值确定
- The research on threshold and regularity of temperature stratification in heavy pollution weather in Tianjin
- 基金项目：国家自然科学基金（No.41771242）；国家国际科技合作专项项目（No.2015DFA20870-02）；天津市气象局课题（No.201716ybxm10，201625ybxm18）；中国气象局预报员专项（No.CMAYBY2016-005）
- 作者
- 单位
- 张敏
- 1. 天津市环境气象中心, 天津 300074;2. 天津市气象科学研究所, 天津 300074
- 蔡子颖
- 1. 天津市环境气象中心, 天津 300074;2. 天津市气象科学研究所, 天津 300074
- 韩素芹
- 天津市气象科学研究所, 天津 300074
- 姚青
- 天津市环境气象中心, 天津 300074
- 刘敬乐
- 天津市气象科学研究所, 天津 300074
- 摘要：针对天津市大气污染防治需求，基于2016年4月1日—2017年3月31日天津255 m气象塔观测资料及数值模拟，开展天津地区污染天气边界层温度层结变化特征及预报阈值研究.结果表明：①天津地区10~250 m高度的气温递减率为0.56 ℃/100 m，当日均气温递减率小于0.4 ℃/100 m时，垂直扩散条件不利于大气污染物扩散，出现中度以上污染概率为64%，重污染概率为47%.从温度廓线和逆温频率统计分析，贴地逆温占所有逆温的55%，除贴地逆温以外逆温底部最易出现在160 m的高度，大量脱地逆温的出现不利于高架源夜间的排放.②每年10月—次年2月天津逆温频率为20%，冬季需要关注逆温情况对大气污染物扩散的影响.如秋、冬季8：00逆温仍然存在，重污染天气出现概率高达56%，中度及以上污染出现概率为72%，是重污染天气辨识的重要指标.③7：00—10：00在逆温消散或者日均气温递减率由0.6 ℃/100 m向0.4 ℃/100 m变化时，任何细微变化对大气垂直扩散有显著影响.基于天津地区PM2.5污染情况下，数值模拟显示10~250 m的气温递减率由于气溶胶的存在可减少0.06 ℃/100 m，在25个重污染过程中，日均气温递减率平均下降0.18 ℃/100 m，对大气垂直扩散条件产生显著影响.因此，在空气污染预报分析时使用不考虑气溶胶辐射效应的天气模式分析温度层结，需要适当调整阈值，尤其是在7：00—10：00逆温消散及垂直温度递减率由0.6 ℃/100 m向0.4 ℃/100 m变化时.
- Abstract：Based on the observation data and numerical simulation in Tianjin from March, 2016 to April, 2017. The research of threshold and regularity of temperature stratification under heavy pollution weather situation was conducted in Tianjin. The result showed that:1) The average temperature difference was 0.56℃/100 m between10 and 250 m. If the value of temperature difference was less than 0.4℃/100 m, the vertical diffusion condition was not conducive to the diffusion of air pollutants. Meanwhile, the probability of moderate pollution was 64%, and the probability of heavy pollution was 47%. On the basis of statistics and analysis of the temperature profile and inversion probability, the inversion temperature on ground accounted for 55% of all inversion temperature, In addition to inversion temperature on ground, the bottom of inversion was most likely to appear at the height of 160m. At night, a large number of inversion were not good for the diffusion of air pollutants about elevated sources. 2) The inversion frequency in Tianjin from October to February was 20%. The value was 1.63 times higher it between March and September. In winter, the influence of temperature inversion on air pollutant dispersion should be paid more attention. If the temperature inversion still existed at 8 AM, the probability of heavy pollution weather was 56%, which was an important indicator of heavy pollution weather. 3)When the inversion temperature collapses from 7 AM to 10 AM, or the vertical temperature lapse rate varied from 0.4℃/100 m to 0.6℃/100 m, any slight changes would bring a significant effect on atmospheric vertical diffusion. Considering the PM2.5 mass concentration in Tianjin, model simulation showed that the temperature lapse rate between 250 m to10 m reduced by 0.06℃/100 m due to aerosols. The value can even drop to 0.18℃/100 m in heavy pollution condition. It had a significant influence on atmospheric vertical diffusion conditions. It was necessary to adjust the threshold when analyzing the temperature stratification by the weather model without considering the aerosol radiation effect, especially when the inversion temperature collapsed from 7 AM to 10 AM and the vertical temperature lapse rate varied from 0.6℃/100 m to 0.4℃/100 m.
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