Influence of Cloud Heterogeneity in Stochastic Dynamics of Ocean Surface Wind over Subtropical Marine Stratus and Stratocumulus Regions

Persistent marine stratus and stratocumulus play important roles in marine boundary layer dynamics and air- sea coupling through cloud-surface wind interaction and turbulence driven by strong cloud top radiative cooling. The influences of boundary layer clouds and ocean surface temperature on the stochastic dynamics of ocean surface wind are addressed in this study using QuickSat and AIRS satellite observations and a conceptual model near Peruvian, Namibian, California, and Canarian regions. Nonlinear relationships exist between cloud heterogeneity and the observed high momentum. Bifurcation is a proposed mechanism for marine boundary layer dynamics. When a nondimensional cloud homogeneity parameter reaches a critical value, multiple states are observed in the subtropical MSC regions. Positive wind skewness is accompanied with negative SST skewness in the large cloud fraction regions; while small wind tendency is accompanied with positive SST skewness in the middle and low cloud fraction regions. A conceptual model is proposed to explain the observational relationship between cloud heterogeneity and surface wind dynamics based on turbulent kinetic energy balance and boundary layer physics. This study has important applications in parameterizations of temporal and spatial variability of boundary layer clouds and ocean surface wind in climate modeling.