Study on the Characteristics of Sea-Air Flux Variations in the Xisha Region of the South China Sea During Winter and Summer

Abstract Based on observational data collected during clear-sky conditions in the Xisha region during winter and summer of 2024, this study systematically analyzes the variability characteristics and driving mechanisms of key air-sea interface fluxes in this area. Results indicate significant diurnal variations in total solar radiation, with upward longwave radiation consistently exceeding downward longwave radiation, indicating net energy release from the ocean to the atmosphere. During summer, latent heat flux dominates air-sea heat exchange, while sensible heat flux remains weak. Winter sensible heat flux significantly intensifies to over ten times the summer value, primarily driven by sea surface temperature differences and strong winds. CO₂ flux exhibits seasonal variation characterized by “winter uptake and summer release,” functioning as a carbon sink in winter and a carbon source in summer, jointly regulated by water temperature, nutrients, and sea-air pCO₂ differences. This study reveals the seasonal sensitivity of energy and carbon exchange at the sea-air interface in the South China Sea, providing scientific basis for optimizing regional climate models.