Mesoscale characteristics analysis of "parallel" dual sea breeze fronts and associated convection initiation mechanism in the Shandong Peninsula

The sea breeze front is an important system that triggers convective weather in coastal areas, but there is very little observation and research on the dual sea breeze fronts. This article uses conventional observation, Doppler radar, Himawari-9 satellite and ERA5 reanalysis data on July 9, 2023 to analyze the mesoscale characteristics of two "parallel" sea breeze fronts moving towards each other that cause severe convective weather in the eastern part of the Shandong Peninsula, and preliminarily inquiry the mechanism that triggers strong convection. The results are as follows. (1) The dual sea breeze fronts that triggered this severe convective weather are located along the coast from Fushan to Mouping (north sea breeze front) and from Haiyang to Rushan (south sea breeze front), and the surface environmental wind at the time of their appearance is southwest wind. At the initial stage of the establishment of the north sea breeze front, it showed a northwest southeast direction, and gradually turned into a northeast southwest direction parallel to the south sea breeze front as it advanced southward. (2) Peak gust can assist radar in determining the location of sea breeze front. When the dual sea breeze fronts pass through, there is a significant difference in the changes of surface meteorological elements on the north and south coasts. There is a clear north-south wind transition on the north coast, while the sharp increase in relative humidity on the south coast is the most significant. (3) In the early stage of strong convection, there were low-level atmospheric disturbances and uplifts in the sea areas on both sides of the the eastern Shandong Peninsula, which advanced inland. With the establishment of the dual sea breeze fronts, the low-level atmospheric disturbance uplift areas on both the north and south sides merged with the uplift areas of the dual sea breeze fronts, and both merged uplift areas continued to move towards each other until they merged into the strongest updrafts, which subsequently triggered short-term heavy rainfall and downburst severe convective weather.