The results show that a warm high ridge at the middle level and transformed surface cold high over the plain provide a good background condition ; a cooling process produced by net surface radiation fluxes is the trigger and strengthening mechanism for the fog event ; the subsidence flow at the middle and low tropospheric levels is favorable for the setting - up and maintenance of stable stratification at the boundary layer and weak wind condition at the ground layer over the fog region ; the transportation of weak warm advection at lower levels and weak lift motion at the boundary layer play a very important role to the long maintenance of the fog event ; the intrusion of north wind accompanied by cold advection is a main dynamic factor of the fog dissipation 結(jié)果表明:在中高層暖性高壓脊及地面變性冷高壓穩(wěn)定維持的大尺度背景條件下,地表凈輻射引起的近地層冷卻是大霧過程的觸發(fā)和加強機制;中低空下沉氣流的存在有助于近地層的弱風(fēng)條件和穩(wěn)定層結(jié)的建立;低層暖平流的輸入和邊界層的淺層抬升是大霧長時間持續(xù)的原因;伴隨冷空氣南下的偏北大風(fēng)是驅(qū)使大霧消散的動力因子。