Abstract:By using meteorological ground and high-resolution observation data, automatic station data, satellite imagery and ERA5 data, the temporal and spatial distribution characteristics of summer fog in the Beijing-Tianjin-Hebei Region from 2000 to 2019 are analyzed． The conceptual model of summer fog is established, and the typical cases are analyzed. The results show that there are 1-4 days of summer fog every year in most of the Beijing-Tianjin-Hebei Region． Minimum visibility tends to be relatively low when fog appears in the northwest, northeast and southeast of the region． Average minimum visibility from central Zhangjiakou to northwest Baoding, southeast Baoding to central Cangzhou and Hengshui areas can decrease to as low as 300 m． The spatial difference of duration of summer fog in plain area is small, generally 1-1.4 days, and the fog duration in mountainous area is relatively longer. The generation and dissipation of fog have obvious diurnal changes. Usually, fog occurs in high frequency in the morning before and after sunrise, and dissipates within 3 hours after sunrise． In summer, when the fog appears, the bottom height of the inversion layer is usually high, the inversion thickness is thin, the temperature difference is small and the intensity is weak. The diurnal temperature range on the ground is above 7℃, and the wind speed is 1-2.4 m·s-1. All these are the important conditions for the formation of fog． The wind direction is mainly southerly or northerly when fog occurs．Three typical conceptual models of summer fog in the Beijing-Tianjin-Hebei Region are radiation fog under the control of high pressure ridge, advection radiation fog under the control of southwest airflow in front of upper trough, and rain fog under the control of subtropical high pressure．