Influences of offshore background wind on the formation of sea-land breeze and the characteristics of pollutant diffusion

The formation of sea-land breeze (SLB) is primarily affected by background wind and temperature difference between the sea and nearby land. Because the intensity of sea breeze is significantly stronger than that of land breeze, land breeze may result in more accumulated pollutants under the condition of offshore background wind (OBW) than under the condition of no OBW in coastal areas. The formation process of sea-land breeze and the dispersion trajectory and accumulation effect of pollutants are studied under different velocities of OBW with the same sea-land temperature difference by employing computational fluid dynamics (CFD). The results reveal that the depth and the duration of sea breeze decrease with the increase of the velocity of OBW. The most unfavorable velocity of OBW (0.2 m s -1 ) exists when the concentration affected by OBW is higher than that by no OBW in coastal areas. The pollutants close to the ground will be blown to the inland by sea breeze when the velocity of OBW is less than 1.0 m s -1 . When the velocity of OBW is larger than 2.0 m s -1 , the pollutants will not occur on the inland due to the influence of OBW.