Intra‐Annual Variability in the Fine Structure of Sea–Land Breeze Over Typical Coastal City Qingdao, China

The seasonal variation of the sea‐land breeze (SLB) circulation is investigated in a typical coastal city Qingdao, China, using continuous 2‐year observation data from Doppler LiDAR. The frequency of SLB varies seasonally, peaking in July and bottoming in January. The establishment time of the sea breeze is primarily concentrated between 08:00 LST and 12:00 LST, with its onset occurring approximately 1 hr earlier in spring and summer compared to autumn and winter. The top of the land‐breeze circulation is lower than that of the sea‐breeze circulation in all seasons and shows a decreasing trend over time. The top height of the sea‐breeze circulation, apart from a gradual decline in spring, exhibits complex curvilinear changes in other seasons. It should be noted that a negative sea‐land temperature difference (SLTD) is not a necessary condition for the formation of SLB in this study. Instead, the inversion layer structure is commonly found during the nocturnal hours of SLB days, resulting in a significant reduction in the atmospheric boundary layer height (ABLH) compared to the average, with a decrease of about 50% in winter and 10%–30% in other seasons. This stable ABL structure suppresses turbulent activity and enhances the wind speed difference between the lower and upper layers during the day, as well as the momentum transfer, which can be used to explain the development mechanism of the SLB circulation.