Abstract:

Based on the conventional meteorological data and visibility observed by visibility meter, the climate characteristics and causes of heavy fog in Jinzhou area during 1999-2018 were investigated.The results show that the annual number of fog days in Jinzhou has 12-year, 6-year and 3-year cycles, and its climatological normal is 33 days.The typical fog process in Jinzhou area shows an obvious diurnal variation, and is mainly divided into weak low pressure trough type and weak high pressure type after rain according to weather classification.Before the fog occurs, T-T_d is between 4-14 ℃, the wind speed is generally below 4 m·s^-1, the southerly, the northerly and the static wind account for 50%, 38%, and 12%, respectively.During the fog development phase, T-T_d is between 0 and 4 ℃, the average wind speed is 2.2 m·s^-1, the southerly and the northerly winds account for 58% and 42%, respectively.During the dense fog phase, T-T_d is between 0 and 2 ℃, the average wind speed is 1.9m/s, the southerly and the northerly winds account for 58% and 42%, respectively.However, during the fog weakening to the dissipating phase, T-T_d is gradually rising and is over 8.1 ℃, the average wind speed is 3.3 m·s^-1, and the northerly wind accounts for 58%.As the dense fog appears, temperature inversion and wet layer occur in the atmosphere.

Key words: Heavy fog, Periodicity, Abruptness, Synthetic analysis, Horizontal physical quantity, Vertical physical quantity