CLOUD SYSTEM EVOLUTION IN THE TRADES (CSET): Following the Evolution of Boundary Layer Cloud Systems with the NSF–NCAR GV

• Published in: Bulletin of the American Meteorological Society 2019-01, Vol.100 (1), p.93-122
• Main Authors: Albrecht, Bruce, Ghate, Virendra, Mohrmann, Johannes, Wood, Robert, Zuidema, Paquita, Bretherton, Christopher, Schwartz, Christian, Eloranta, Edwin, Glienke, Susanne, Donaher, Shaunna, Sarkar, Mampi, McGibbon, Jeremy, Nugent, Alison D., Shaw, Raymond A., Fugal, Jacob, Minnis, Patrick, Paliknoda, Robindra, Lussier, Louis, Jensen, Jorgen, Vivekanandan, J., Ellis, Scott, Tsai, Peisang, Rilling, Robert, Haggerty, Julie, Campos, Teresa, Stell, Meghan, Reeves, Michael, Beaton, Stuart, Allison, John, Stossmeister, Gregory, Hall, Samuel, Schmidt, Sebastian
• Format: Article
• Language: English
• Subjects: Aerodynamics; Aerosols; Airborne remote sensing; Aircraft; Atmospheric aerosols; Atmospheric models; Atmospheric research; Boundary layer evolution; Boundary layer transition; Boundary layers; Chemical precipitation; Cloud precipitation; Cloud systems; Clouds; Drizzle; Environmental research; ENVIRONMENTAL SCIENCES; Evolution; Experiments; Flight; Flight plans; General aviation aircraft; In situ measurement; Jet aircraft; Lidar; Precipitation; Properties; Radar; Smoke; Stratocumulus clouds; Studies; Trade winds; Trajectory planning; Transition zone; Turbulence; Wildfires; Wind
• ISSN: 0003-0007; 1520-0477
• DOI: 10.1175/BAMS-D-17-0180.1

The Cloud System Evolution in the Trades (CSET) study was designed to describe and explain the evolution of the boundary layer aerosol, cloud, and thermodynamic structures along trajectories within the North Pacific trade winds. The study centered on seven round trips of the National Science Foundation–National Center for Atmospheric Research (NSF–NCAR) Gulfstream V (GV) between Sacramento, California, and Kona, Hawaii, between 7 July and 9 August 2015. The CSET observing strategy was to sample aerosol, cloud, and boundary layer properties upwind from the transition zone over the North Pacific and to resample these areas two days later. Global Forecast System forecast trajectories were used to plan the outbound flight to Hawaii with updated forecast trajectories setting the return flight plan two days later. Two key elements of the CSET observing system were the newly developed High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) and the high-spectral-resolution lidar (HSRL). Together they provided unprecedented characterizations of aerosol, cloud, and precipitation structures that were combined with in situ measurements of aerosol, cloud, precipitation, and turbulence properties. The cloud systems sampled included solid stratocumulus infused with smoke from Canadian wildfires, mesoscale cloud–precipitation complexes, and patches of shallow cumuli in very clean environments. Ultraclean layers observed frequently near the top of the boundary layer were often associated with shallow, optically thin, layered veil clouds. The extensive aerosol, cloud, drizzle, and boundary layer sampling made over open areas of the northeast Pacific along 2-day trajectories during CSET will be an invaluable resource for modeling studies of boundary layer cloud system evolution and its governing physical processes.