Abstract
This study focuses on the statistical features of dissipation flux coefficient Г in the upper South China Sea (SCS). Based on the microscale measurements collected at 158 stations in the upper SCS and derived dissipation rates of TKE and temperature variance ε and χT, via a modified method, we estimate Г and analyze its spatiotemporal variation in an energetic region and a quiescent region. We show that Г is highly variable, which scatters over three orders of magnitude from 10−2 to 101 in both regions. Г in the energetic region is slightly greater than that in the quiescent region; their median values are 0.23 and 0.17, respectively. Vertically, Г presents a clear increasing tendency with depth in both regions, though increasing rate is greater in the energetic region than in the quiescent region. In the upper SCS, Г positively depends on the buoyancy Reynolds number Reb and negatively depends on the ratio of the Ozmidov scale to the Thorpe scale, ROT, and is scaled as Г α Reb1/2. ROT−4/3, which holds for both regions. The vertical decreasing of ROT is observed, which yields parameterization of ROT =10−0.002z; this parameterization improves the performance of the Thorpe-scale method by reducing at least 50% of the bias between the observed and parameterized ε. These results shed new light on the spatiotemporal variability and modulating mechanism of Г in the upper ocean.
