Diurnal evolution of the barrier layer and its local feedback in the central Taiwan Strait

Diurnal evolution of the barrier layer (BL) and its local feedback features in the central Taiwan Strait (119.2°E, 24.3°N) during summertime monsoon are investigated using in situ moored observations conducted by the “Yan-Ping 2” research vessel in late June 2005. During the initiation phase, for the non-solar radiation tends to be trapped in the upper mixed layer, whereas the solar radiation can penetrate deeply through the mixed layer approaching the thermocline, most heat is accumulated inside the BL inducing an inverse-thermal layer. Along with heat convergence inside the BL, thermal exchange increases between the BL and the overlaying mixed layer and finally, a prominently warming mixed layer is formed. Moreover, the BL is associated with a buoyancy frequency minimum with mild stability. Further analysis reveals that the BL’s local feedbacks can be divided into two aspects, on one hand, the BL can generate dramatic changes in the local sensible and latent heat fluxes; on the other hand, the sub-halocline and the thermocline serve as two interfaces during the downward transmission of the wind stirring turbulent kinetic energy (TKE) and as a result, most TKE is retarded by the shallow halocline and being trapped above the upper mixed layer, while the residual pierced through the base of the mixed layer is likewise blocked by the thermocline.