Air-Ocean Interaction and Cloud Variability over the Chilean Coastal Region

Large variability of Chilean coastal low-level jet has great impact on the structure and variability of stratocumulus over the Southeast Pacific (SEP). Using the two-way-coupled COAMPS/NCOM system with the NCODA ocean data assimilation, we found that during the strong coastal jet period, the strong oceanic upwelling and turbulent heat transfer from the atmosphere to the ocean along the coast lead to cooler sea surface temperatures (SST). The cooler sea surface temperature feeds back to increase cloud liquid water path, since it increases the lower troposphere stability and limit the entrainment. Variance analysis indicates that the correlation between the SST and the strong coastal jet is over 76% and between the SST and the liquid water path is over 60%. Since the oceanic responses to the coastal jet with time lag, the correlation increases with one-day lag, resulted a complex concomitant cyclic change between the strong coastal jet, SST and clouds. Forcing mechanisms for the cloud variability related to the oceanic upwelling are discussed. The results from the coupled simulation are compared with the uncoupled simulation and available observation from the VAMOS Ocean Cloud Atmosphere Land Study (VOCALS).