Observational analyses of a sea fog event over the northern Yellow Sea when Typhoon"Lekima"(1909)landed on Qingdao
This study focuses on the physical process of a sea fog event during Typhoon"Lekima"(1909)in the northern Yellow Sea by using observation data,reanalysis data and backward trajectory model.The analysis indic-ates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed in-land.The warm and humid southerlies from the South Yellow Sea condensed into fog on the colder sea surface be-sides the typhoon center,which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon.The"stable up and turbulent down"structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area.However,the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer,resulting in the enhanced turbulent mix-ing and the decrease of the stability in the bottom atmospheric boundary layer,which was the main cause of the fog dissipation.