Thermodynamic and radiative structure of cumulus-topped tropical and sub-tropical marine boundary layers

Description

Marine boundary-layer fair weather cumulus clouds have a significant impact on the Earth’s radiation budget due to their high shortwave albedo. These clouds are also intimately tied to the turbulence in the boundary layer and help transport the enthalpy and moisture from the surface to the free troposphere. Due to their minuscule temporal and spatial scales compared to the global climate model (GCM) resolution, these clouds need to be parameterized in GCM simulations aimed at predicting the future climate.

We have used the data collected during the deployment of the Atmospheric Radiation Measurement (ARM) Climate Research Facility’s first mobile facility (AMF1) on Graciosa Island and at the Tropical Western Pacific (TWP) Manus site when single-layered boundary-layer cumulus clouds were observed at the facilities to study their thermodynamic and radiative structure. The radiosonde data was used to study the thermodynamic structure, especially to characterize the mixed-layer and the boundary-layer inversion. We have also used the data from vertically pointing cloud radars present at the site and that from other instruments to serve as an input to a 1-dimensional radiative transfer model called the Rapid Radiative Transfer Model (RRTM). The RRTM simulations were made at a high temporal (10-second) and vertical (10-meter) resolution to accurately capture the radiative impacts of the mixed-layer inversion and the boundary-layer inversion. We anticipate the results to be useful and serve as an input for studies using single-column models to test different parameterizations.