Forcing stratocumulus clouds with internal gravity waves*

Stratocumulus clouds extensively cover Earth’s surface and subtropical oceans resulting in a net-cooling effect through reflection of sunlight. Previous studies have shown that reductions in stratocumulus lead to significant warming akin to that of greenhouse gases. Thus, it is important to understand factors that can cause the cloud deck to dissipate. 

 

A hypothesized breakup mechanism is the effect of internal gravity waves on the stratocumulus-topped boundary layer (STBL). These waves can be caused by convection or flow over topography/coastal boundaries. Utilizing large-eddy simulation with Cloud Model 1, we perform a parametric sweep of a gravity wave forcing, whose characteristics are informed by satellite observations, and study its effect in breaking the STBL. The initialization follows that of Stevens et al. 2005; we further employ a constant sea surface temperature and modify the radiation model to include a more physical representation of free troposphere cooling. Breakup is assessed by comparing the mean vertical profiles of the cloud condensate to a statistically stationary STBL. We also compare energy budgets to quantify the impact of the differing forcings on STBL breakup.