Science highlights from the CAP-MBL field campaign at Graciosa Island

 

Authors


Robert Wood — University of Washington
Christopher S. Bretherton — University of Washington
Pavlos Kollias — Stony Brook University
Mark A. Miller — Rutgers University
Jasmine Remillard — McGill University
Edward Luke — Brookhaven National Laboratory
Virendra Prakash Ghate — Argonne National Laboratory
Anne Jefferson — NOAA- Earth System Research Laboratory
Yanluan Lin — Tsinghua University
Cecile Hannay — National Center for Atmospheric Research (NCAR)
Rabindra Palikonda — Science Systems and Applications. Inc./NASA - LRC

Category

Field Campaigns

Description

The Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) experiment used the comprehensive instruments of the ARM Mobile Facility deployment at Graciosa Island in the Azores from May 2009 to January 2011. This platform produced a rich set of coincident and continuous atmospheric measurements of meteorology, aerosols, clouds, precipitation, and radiation in a relatively remote maritime region. Here we highlight several research results from CAP-MBL.

About half of all clouds observed in CAP-MBL had detectable precipitation falling below their bases, and 20–40% of measured precipitation accumulation originated from clouds with tops lower than 3 km. We show new methods that use the radar Doppler spectrum to characterize and separate precipitation drops from cloud droplets in low clouds. They reveal the cloud structures responsible for the initiation of precipitation in marine stratocumulus clouds.

Cloud-forming aerosol concentrations at the Azores vary by over two orders of magnitude, from dirty air masses associated with continental pollution to ultra-clean collapsed marine boundary layers with some of the lowest CCN concentrations yet measured. The long duration of CAP-MBL allows us to explore the time evolution of aerosol concentrations and look for relationships between aerosol and cloud and precipitation processes.

We also show how the CAP-MBL data can be used to locally test the GFDL AM3p9 and CAM5.1 climate models running in forecast mode and show the strengths and weaknesses of these models in simulating the marine boundary layer and aerosol and precipitation processes.