Lagrangian Evolution of the Northeast Pacific Marine Boundary Layer Structure and Cloud during CSET

Journal Article · 08 December 2019 · Monthly Weather Review

DOI: https://doi.org/10.1175/MWR-D-19-0053.1 · OSTI ID:1577890

Mohrmann, Johannes  ^[1]; Bretherton, Christopher S. ^[1]; McCoy, Isabel L. ^[1]; McGibbon, Jeremy ^[1]; Wood, Robert ^[1]; Ghate, Virendra ^[2]; Albrecht, Bruce ^[3]; Sarkar, Mampi ^[3]; Zuidema, Paquita ^[3]; Palikonda, Rabindra ^[4]

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1. Department of Atmospheric Sciences, University of Washington, Seattle, Washington
2. Argonne National Laboratory, Argonne, Illinois
3. Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida
4. Science Systems and Applications Inc., Hampton, Virginia

Flight data from the Cloud System Evolution over the Trades (CSET) campaign over the Pacific stratocumulus-to-cumulus transition are organized into 18 Lagrangian cases suitable for study and future modeling, made possible by the use of a track-and-resample flight strategy. Analysis of these cases shows that 2-day Lagrangian coherence of long-lived species (CO and O₃) is high ($$r$$ = 0.93 and 0.73, respectively), but that of subcloud aerosol, MBL depth, and cloud properties is limited. Although they span a wide range in meteorological conditions, most sampled air masses show a clear transition when considering 2-day changes in cloudiness (−31% averaged over all cases), MBL depth (+560 m), estimated inversion strength (EIS; −2.2 K), and decoupling, agreeing with previous satellite studies and theory. Changes in precipitation and droplet number were less consistent. The aircraft-based analysis is augmented by geostationary satellite retrievals and reanalysis data along Lagrangian trajectories between aircraft sampling times, documenting the evolution of cloud fraction, cloud droplet number concentration, EIS, and MBL depth. An expanded trajectory set spanning the summer of 2015 is used to show that the CSET-sampled air masses were representative of the season, with respect to EIS and cloud fraction. Two Lagrangian case studies attractive for future modeling are presented with aircraft and satellite data. The first features a clear Sc–Cu transition involving MBL deepening and decoupling with decreasing cloud fraction, and the second undergoes a much slower cloud evolution despite a greater initial depth and decoupling state. Finally, potential causes for the differences in evolution are explored, including free-tropospheric humidity, subsidence, surface fluxes, and microphysics.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1577890
• Journal Information: Monthly Weather Review, Journal Name: Monthly Weather Review Journal Issue: 12 Vol. 147; ISSN 0027-0644
• Publisher: American Meteorological SocietyCopyright Statement
• Country of Publication: United States
• Language: English