Clear‐sky closure studies of lower tropospheric aerosol and water vapor during ACE‐2 using airborne sunphotometer, airborne in‐situ, space‐borne, and ground‐based measurements |
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| Authors: | Beat Schmid John M Livingston Philip B Russell Philip A Durkee Haflidi H Jonsson Donald R Collins Richard C Flagan John H Seinfeld Santiago Gassó Dean A Hegg Elisabeth Öström Kevin J Noone Ellsworth J Welton Kenneth J Voss Howard R Gordon Paola Formenti Meinrat O Andreae |
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| Institution: | Bay Area Environmental Research Institute, San Francisco, CA, USA;;SRI International, Menlo Park, CA, USA;;NASA Ames Research Center, Moffett Field, CA, USA;;Naval Postgraduate School, Monterey, CA, USA;;California Institute of Technology, Pasadena, CA, USA;;University of Washington, Seattle, WA, USA;;Meteorological Institute, Stockholm University, Stockholm, Sweden;;University of Miami, Miami, FL, USA;;Max Planck Institute for Chemistry, Mainz, Germany |
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| Abstract: | We report on clear‐sky column closure experiments (CLEARCOLUMN) performed in the Canary Islands during the second Aerosol Characterization Experiment (ACE‐2) in June/July 1997. We present CLEARCOLUMN results obtained by combining airborne sunphotometer and in‐situ (optical particle counter, nephelometer, and absorption photometer) measurements taken aboard the Pelican aircraft, space‐borne NOAA/AVHRR data and ground‐based lidar and sunphotometer measurements. During both days discussed here, vertical profiles flown in cloud‐free air masses revealed 3 distinctly different layers: a marine boundary layer (MBL) with varying pollution levels, an elevated dust layer, and a very clean layer between the MBL and the dust layer. A key result of this study is the achievement of closure between extinction or layer aerosol optical depth (AOD) computed from continuous in‐situ aerosol size‐distributions and composition and those measured with the airborne sunphotometer. In the dust, the agreement in layer AOD (λ=380–1060 nm) is 3–8%. In the MBL there is a tendency for the in‐situ results to be slightly lower than the sunphotometer measurements (10–17% at λ=525 nm), but these differences are within the combined error bars of the measurements and computations. |
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