Stratocumulus Cloud Transitions in the Southeast Pacific from GOES Observations

We use data from the GOES-16 (East) Advanced Baseline Imager (ABI), and NOAA’s HYSPLIT trajectory model, to track the evolution of the planetary boundary layer (PBL) height and cloud cover in the Southeast Pacific, as marine air parcels advect equatorward in subtropical trade winds, transitioning from shallow overcast stratocumulus to trade cumulus cloud regimes. Along the trajectory of each parcel we follow three key quantities: (1) the PBL height; (2) the rate of change of the PBL height; and (3) the cloud cover. These observations will be combined with occasional coincident observations from GPS radio occultations that provide precise PBL height estimates and a bulk measure of the ‘decoupling’ of the PBL water vapor profile (how much the water vapor varies from the top to the bottom of PBL). From these observations, our goal is to make estimates of the cloud top entrainment, which is related to the time rate of change of the deepening of the PBL. By tracking the evolution of each trajectory we examine the time lagged relationships between the entrainment, cloud cover transition and water vapor decoupling.