@article{8172bf13d428471684327ceddd4d8fc3,
title = "Cloud, aerosol, and boundary layer structure across the northeast Pacific stratocumulus-cumulus transition as observed during CSET",
abstract = "During the Cloud System Evolution in the Trades (CSET) field study, 14 research flights of the National Science Foundation G-V sampled the stratocumulus-cumulus transition between Northern California and Hawaii and its synoptic variability. The G-V made vertically resolved measurements of turbulence, cloud microphysics, aerosol characteristics, and trace gases. It also carried dropsondes and a vertically pointing W-band radar and lidar. This paper summarizes these observations with the goals of fostering novel comparisons with theory, models and reanalyses, and satellite-derived products. A longitude-height binning and compositing strategy mitigates limitations of sparse sampling and spatiotemporal variability. Typically, a 1-km-deep decoupled stratocumulus-capped boundary layer near California evolved into 2-km-deep precipitating cumulus clusters surrounded by patches of thin stratus that dissipated toward Hawaii. Low cloud cover was correlated with estimated inversion strength more than with cloud droplet number, even though the thickest clouds were generally precipitating and ultraclean layers indicative of aerosol-cloud-precipitation interaction were common west of 140°W. Accumulation-mode aerosol concentration correlated well with collocated cloud droplet number concentration and was typically largest near the surface. Aitken mode aerosol concentration was typically larger in the free troposphere. Wildfire smoke produced spikes of aerosol and trace gases on some flights. CSET data are compared with space-time collocated output from MERRA-2 reanalysis and from the CAM6 climate model run with winds and temperature nudged toward this reanalysis. The reanalysis compares better with the observed relative humidity than does nudged CAM6. Both vertically diffuse the stratocumulus cloud layer versus observations. MERRA-2 slightly underestimates in situ carbon monoxide measurements and underestimates ozone depletion within the boundary layer.",
keywords = "Aerosols, Boundary layer, Cumulus clouds, Precipitation, Stratiform clouds, Subtropics",
author = "Bretherton, {Christopher S.} and McCoy, {Isabel L.} and Johannes Mohrmann and Robert Wood and Virendra Ghate and Andrew Gettelman and Bardeen, {Charles G.} and Albrecht, {Bruce A.} and Paquita Zuidema",
note = "Funding Information: Acknowledgments. The success of CSET is primarily due to the dedicated staff of NCAR{\textquoteright}s Research Aviation Facility who operated the G-V and its core instrumentation, provided invaluable advice about analyzing the data, and made CSET a pleasure for its scientific participants. The authors wish to acknowledge support from NSF grants AGS-1445813, AGS-1445832, and AGS-1445831. I. McCoy was supported by the National Science Foundation Graduate Research Fellowship Program under grant DGE-1762114. V. Ghate acknowledges support from the U.S. Department of Energy{\textquoteright}s (DOE) Atmospheric System Research (ASR) under Contract DE-AC02-06CH11357 awarded to Argonne National Laboratory, and computing resources provided on Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center (LCRC) at Argonne National Laboratory. Funding Information: The success of CSET is primarily due to the dedicated staff of NCAR's Research Aviation Facility who operated the G-V and its core instrumentation, provided invaluable advice about analyzing the data, and made CSET a pleasure for its scientific participants. The authors wish to acknowledge support from NSF grants AGS-1445813, AGS-1445832, and AGS-1445831. I.McCoy was supported by the National Science Foundation Graduate Research Fellowship Program under grant DGE-1762114. V. Ghate acknowledges support from the U.S. Department of Energy's (DOE) Atmospheric System Research (ASR) under Contract DE-AC02-06CH11357 awarded to Argonne National Laboratory, and computing resources provided on Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center (LCRC) at Argonne National Laboratory. Publisher Copyright: {\textcopyright} 2019 American Meteorological Society.",
year = "2019",
month = jun,
day = "1",
doi = "10.1175/MWR-D-18-0281.1",
language = "English (US)",
volume = "147",
pages = "2083--2103",
journal = "Monthly Weather Review",
issn = "0027-0644",
publisher = "American Meteorological Society",
number = "6",
}