基于环境模式PM_(2.5)的渤海及其西岸能见度预报技术优化研究

The research on improving visibility forecast in Bohai Sea and West Coast of Bohai Sea based on environmental model PM_(2.5)

基于2019年12月1日—2020年11月30日渤海及其西岸地区能见度观测和数值模拟,研究了该区域海岸陆能见度演变特征及其预报方法,并通过引入PM_(2.5)浓度及建立相应的消光方程,提升该地区能见度预报准确率.结果表明:渤海及其西岸地区海岸陆能见度演变特征存在差异,就年平均能见度而言,海上(含港口)高于陆地,并且前者的能见度日变化较后者更趋平缓,低能见度(<3 km)天气陆地主要出现在0:00—8:00,海上(含港口)则全天均有可能出现,海上(含港口)0~500 m低能见度天气多于陆地,500~3000 m低能见度天气少于陆地.渤海及其西岸地区能见度预报需要考虑气溶胶消光的影响,欧洲数值模式(ECMWF)和天津气象台主观能见度预报产品,在该区域预报与实况的相关系数为0.2~0.3,相对误差为40%~50%.引入天津环境模式PM_(2.5)浓度预报,基于ECMWF相对湿度和环境模式液态水含量,通过消光方程可以较好地改进预报该区域能见度的效果,其产品陆地和港口能见度预报与实况的相关系数分别为在0.8和0.5以上,相对误差分别为20%和40%左右,小于3 km小时预报准确率在50%左右,日最低能见度小于3 km的预报准确率在70%以上,海上相比陆地预报准确率偏低1/3.基于海气耦合技术和气溶胶同化技术可进一步精细提升海上和陆地能见度预报能力,冬季试验表明,增加区域海气耦合模式和气溶胶三维变分技术,渤海能见度日值预报与实况的相关系数可达到0.72,相对误差降至26.0%,陆地能见度预报与实况的相关系数为0.95,相对误差为15.5%.

Based on the observation and numerical simulation of visibility in Bohai Sea and its west coast from December 1,2019 to November 30,2020.This paper studied the evolution characteristics and prediction methods of visibility in this region.The study showed that there were differences in the evolution characteristics of visibility between the Bohai Sea and the west coast of Bohai Sea.The visibility of the sea(including ports)was higher than that of the land,and daily variation of visibility on the former was more gradual than on the latter.The low visibility weather(<3 km)mainly occursed on land from 0:00 to 8:00,while the sea(including ports)may occur all day.The low visibility weather at sea(including ports)was more than that on land from 0 to 500 m.The low visibility weather from 500 m to 3000 m was less than that on land.The visibility forecast in Bohai Sea and its west coast needed to consider the influence of aerosol enction.The correlation coefficient between observation and numerical simulation by ECMWF about visibility prediction was 0.2~0.3,and the relative error was 40%~50%.PM_(2.5) mass concentration forecast by Tianjin environmental model was introduced.Based on relative humidity by ECMWF model and liquid water content by environmental model,The extinction equation could be used to improve the visibility forecast in this area.The correlation coefficients between the visibility forecast and the actual situation on land and port were above 0.8 and 0.5,and the relative errors were about 20%and 40%.The forecast accuracy was 50%(hours less than 3 km),and the daily minimum visibility was less than 70%,which was one third lower than that on land at sea.Based on the air-sea coupling technology and aerosol assimilation technology,the visibility prediction ability at sea and on land could be further improved.The winter experiment showed that by adding the regional air-sea coupling model and aerosol three-dimensional variational technology,the correlation coefficient between visibility prediction and actual visibility in Bohai Sea could reach 0.72,and the relative error was reduced to 26.0%,while the correlation coefficient between land visibility prediction and actual visibility was 0.95,and the relative error was 15.5%.