Effects of Sea Land Breeze on Air-Sea Turbulent Heat Fluxes in Different Seasons Using Platform Observation in East China Sea

Using 2-year platform observations, this study investigates seasonal characteristics of sea land breeze (SLB) and how it influences air-sea turbulent heat fluxes (THFs) in the coastal areas of East China Sea (ECS) in different seasons. Unlike other SLB studies, this study uses hourly observation on a sea platform to explore SLB's effect on both air-sea latent heat and sensible heat transferring. The results show that sea wind (SW) does not have an obvious seasonal variation pattern while land wind (LW) is stronger in autumn and winter. The SLB day number shows a clear seasonal variation pattern, which accounts for 38.04% and 18.23% of summertime and wintertime days, reaching its peak and bottom respectively. The latent heat flux (LHF) and sensible heat flux (SHF) are high in autumn and winter while low in summer. The SLB-contributed LHF and SHF reach peaks in autumn and winter, which are 61.07 and 7.39 W/m2 respectively. The contribution importance of SLB on air-sea sensible/latent heat transferring is highest in summer while lowest in winter. On SLB days, the SHF decreases significantly by at least about 50% while LHF decreases moderately in all seasons, among which spring witnesses an inversion of sensible heat transferring direction. The warming effect of SLB is mainly responsible for the slump of SHF on SLB days. Multiple factors including relative humidity (RH), background wind field and in situ radiation cause the LHF decrease together, whose changing range varies with season. Sea land breeze (SLB) has a great impact on regional environment and meteorological fields. Turbulent heat flux (THF), including sensible heat flux (SHF) and latent heat flux (LHF), is fundamentally engaged in nearly every atmosphere-ocean interaction process and undoubtedly serve as an important driving force of global atmospheric and oceanic circulation as well as a sensitive variable when facing global climate change. However, there are few studies relating SLB to the variation of THF in the near coastal region, which is a sensitive-area to climatic changes under the effects of both natural and human variabilities. In this study, instead of using land-based data like other SLB studies, we investigate SLB's effects on air-sea THFs in different seasons based on sea-based data. We find that SLB's role in transferring air-sea energy in form of THF is most important in summer among all seasons. The SHF decreases significantly while LHF decreases moderately on SLB days in all four seasons. The warming effect of SLB is mainly responsible for the slump of SHF on SLB days, while the external factors such as background wind field, relative humidity, and in situ radiation are responsible for the LHF decrease on SLB days. The peak SLB-contributed LHF and SHF are 61.1 W/m2 in autumn and 7.4 W/m2 in winter, respectively The SHF decreases significantly while LHF decreases moderately on SLB days in four seasons The warming effect of SLB is mainly responsible for the slump of SHF on SLB days