Controls on Marine Boundary Layer Mesoscale Structure Observed During the MAGIC Campaign

Abstract:

Marine boundary layer (MBL) clouds play a significant role in the Earth’s energy budget by reflecting a large portion of incoming solar radiation with little compensating effect on emitted terrestrial radiation. Despite this importance, large-scale models, used for climate projections, are not able to accurately represent MBL clouds and disagree on the magnitude of their feedback in a warming climate. Observations from the Marine Atmospheric Radiation Measurement (ARM) GPCI Investigation of Clouds (MAGIC) field campaign were used to investigate the relationships between thermodynamic structure and MBL cloud properties. MAGIC was the first ship-based deployment of the Second ARM Mobile facility (AMF2), making measurements from the Horizon Lines Spirit cargo ship as it traveled from Los Angeles, CA to Honolulu, HI and back from October 2012 through September 2013. Our analysis concentrates on observations from regular radiosonde launches from AMF, vertically pointing Ka-band ARM cloud radar observations and coincident scenes from the Geostationary Operational Environmental Satellite (GOES). MBL cloud mesoscale structure is quantified from satellite observations via the effective cloud diameter for a GCM-sized grid-box centered on the Spirit and related to boundary layer thermodynamic structure and cloud boundary statistics. Preliminary results suggest a bimodal relationship between lower tropospheric stability and MBL cloud mesoscale structure.