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Title: Aircraft millimeter-wave passive sensing of cloud liquid water and water vapor during VOCALS-REx

Journal Article · · Atmospheric Chemistry and Physics (Online)
 [1];  [2];  [3];  [4]
  1. Univ. of Miami, Miami, FL (United States). Rosenstiel School of Marine and Atmospheric Sciences
  2. Univ. of Wyoming, Laramie, WY (United States). Dept. of Atmospheric Sciences
  3. Prosensing Inc., Amherst, MA (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)

Routine liquid water path measurements and water vapor path are valuable for process studies of the cloudy marine boundary layer and for the assessment of large-scale models. The VOCALS Regional Experiment respected this goal by including a small, inexpensive, upwardpointing millimeter-wavelength passive radiometer on the fourteen research flights of the NCAR C-130 plane, the Gband (183 GHz) Vapor Radiometer (GVR). The radiometer permitted above-cloud retrievals of the free-tropospheric water vapor path (WVP). Retrieved free-tropospheric (abovecloud) water vapor paths possessed a strong longitudinal gradient, with off-shore values of one to twomm and nearcoastal values reaching tenmm. The VOCALS-REx free troposphere was drier than that of previous years. Cloud liquid water paths (LWPs) were retrieved from the sub-cloud and cloudbase aircraft legs through a combination of the GVR, remotely-sensed cloud boundary information, and insitu thermodynamic data. The absolute (between-leg) and relative (within-leg) accuracy of the LWP retrievals at 1 Hz (≈100 m) resolution was estimated at 20 gm-2 and 3 gm-2 respectively for well-mixed conditions, and 25 gm-2 absolute uncertainty for decoupled conditions where the input WVP specification was more uncertain. Retrieved liquid water paths matched adiabatic values derived from coincident cloud thickness measurements exceedingly well. A significant contribution of the GVR dataset was the extended information on the thin clouds, with 62% (28 %) of the retrieved LWPs <100 (40) gm-2. Coastal LWPs values were lower than those offshore. For the four dedicated 20° S flights, the mean (median) coastal LWP was 67 (61) gm-2, increasing to 166 (120) gm-2 1500 km offshore. Finally, the overall LWP cloud fraction from thirteen research flights was 63 %, higher than that of adiabatic LWPs at 40 %, but lower than the lidar-determined cloud cover of 85 %, further testifying to the frequent occurrence of thin clouds.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF)
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1396248
Journal Information:
Atmospheric Chemistry and Physics (Online), Vol. 12, Issue 1; ISSN 1680-7324
Publisher:
European Geosciences UnionCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 32 works
Citation information provided by
Web of Science

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Cited By (10)

The Tropical Atlantic Observing System journal May 2019
Impact of natural and anthropogenic aerosols on stratocumulus and precipitation in the Southeast Pacific: a regional modelling study using WRF-Chem journal January 2012
Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean journal January 2013
The first aerosol indirect effect quantified through airborne remote sensing during VOCALS-REx journal January 2013
Aircraft observations of cold pools under marine stratocumulus journal January 2013
Aircraft observations of aerosol, cloud, precipitation, and boundary layer properties in pockets of open cells over the southeast Pacific journal January 2014
Global and regional modeling of clouds and aerosols in the marine boundary layer during VOCALS: the VOCA intercomparison journal January 2015
Marine liquid cloud geometric thickness retrieved from OCO-2's oxygen A-band spectrometer journal January 2019
The Atmospheric radiation measurement (ARM) program network of microwave radiometers: instrumentation, data, and retrievals journal January 2013
Global and regional modeling of clouds and aerosols in the marine boundary layer during VOCALS: the VOCA Intercomparison journal January 2014

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