Lagrangian evolution of the northeast pacific marine boundary layer structure and cloud during CSET

Johannes Mohrmann, Christopher S. Bretherton, Isabel L. McCoy, Jeremy McGibbon, Robert Wood, Virendra Ghate, Bruce Albrecht, Mampi Sarkar, Paquita Zuidema, Rabindra Palikonda

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Flight data from the Cloud System Evolution over the Trades (CSET) campaign over the Pacific stratocumulusto- cumulus transition are organized into 18 Lagrangian cases suitable for study and futuremodeling,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 (+560m), estimated inversion strength (EIS; -2.2K), 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, andMBL 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 toEIS and cloud fraction. TwoLagrangian 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. Potential causes for the differences in evolution are explored, including free-tropospheric humidity, subsidence, surface fluxes, and microphysics.

Original languageEnglish (US)
Pages (from-to)4681-4700
Number of pages20
JournalMonthly Weather Review
Issue number12
StatePublished - 2019

ASJC Scopus subject areas

  • Atmospheric Science


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