上合组织青岛峰会期间海雾维持和消散阶段的环境场特征

Environmental field characteristics of sea fog maintenance and dissipation during the 2018 Shanghai Cooperation Organization Qingdao Summit

利用常规观测、地面加密自动站及NCEP再分析资料,针对上合组织青岛峰会的气象服务过程,对海雾维持和消散两个阶段的气象要素特征进行了分析。结果表明:1)当能见度低于1 000 m时,相对湿度为99%,能见度介于1 000～2 000 m之间时,相对湿度为95%～99%。2)近地面层30°N以北黄海海域持续吹东南风,并在青岛形成水汽辐合中心,有利于青岛形成海雾;当东南风转为东北风,水汽辐合中心减弱或消失时,海雾趋于消散。3)在海雾维持阶段,逆温层最低高度稳定在980 hPa以下,总逆温差逐渐增强,逆温梯度跃升与海雾强度增强同步;最大逆温层厚度和逆温层总厚度下降12 h后海雾逐渐减弱,逆温层最低高度上升时能见度也随之上升。4)白天逆温层之上为下沉运动,之下为上升运动,夜间700 hPa之下均为上升运动,且上升运动中心位于逆温层之下,这种垂直结构有利于逆温层和海雾的维持;当逆温强度减弱,垂直运动穿越逆温层贯穿700 hPa以下对流层时,海雾趋于消散。

Based on conventional observations,data of intensified automatic weather stations,and NCEP reanalysis data,the meteorological characteristics of the sea fog maintenance and dissipation mechanisms during the 2018 Shanghai Cooperation Organization Qingdao Summit are analyzed.The results are as follows.1)The visibility lower than 1 000 m corresponds to the relative humidity of 99%and the visibility between 1 000 m and 2 000 m corresponds to the relative humidity between 95%and 99%.2)When southeasterly winds continuously blow near the surface over the Yellow Sea above 30°N and a water vapor convergence center is formed in Qingdao,it is favorable for the formation of sea fog in Qingdao.The sea fog tends to dissipate when southeasterly winds turn to northeasterly winds and the water vapor convergence center is weakened or disappears.3)During the sea fog maintenance phase,the lowest inversion layer is stable below 980 hPa,the total temperature inversion difference gradually increases,and the sharply increasing of temperature inversion gradient synchronizes with the enhancement of the sea fog intensity.The sea fog is gradually weakened 12 hours after the decrease of the maximum and the total thickness of the inversion layers,and the visibility increases with the increase of the lowest inversion layer.4)Sinking movement happens above the inversion layer and ascending movement below it in the daytime,while ascending movement happens below 700 hPa and the center of ascending movement is below the inversion layer in the nighttime.This vertical structure is favorable for the maintenance of the inversion layer and the sea fog.When the temperature inversion intensity decreases and vertical movement happens throughout the troposphere below 700 hPa,the sea fog tends to dissipate.