CALIPSO observations of stratospheric aerosols: a preliminary assessment L. W. Thomason, M. C. Pitts, and D. M. Winker 1NASA Langley Research Center, Hampton, VA, USA
Abstract. We have examined the 532-nm aerosol backscatter coefficient measurements by
the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations
(CALIPSO) for their use in the monitoring of stratospheric aerosol. CALIPSO
makes observations that span from 82° S to 82° N each day and, for
each profile, backscatter coefficient values reported up to ~40 km.
The possibility of using CALIPSO for stratospheric aerosol monitoring is
demonstrated by the clear observation of the 20 May 2006 eruption of
Montserrat in the earliest CALIPSO data in early June as well as by
observations showing the 7 October 2006 eruption of Tavurvur (Rabaul).
However, the very low aerosol loading within the stratosphere makes routine
observations of the stratospheric aerosol far more difficult than relatively
dense volcanic plumes. Nonetheless, we found that averaging a complete days
worth of nighttime-only data into 5-deg latitude by 1-km vertical bins
yields a stratospheric aerosol distribution that is fairly consistent with
past measurements by spaceborne instruments. Based on comparisons with 2004
data from the Stratospheric Aerosol and Gas Experiment, the derived values
are close to expectation except in the tropics where they are larger by
about a factor of 2. The cause of the difference in the tropics is not
readily apparent but is most likely related to difficulties in the lidar
calibration process currently found in the CALIOP data at tropical latitudes.
Citation: Thomason, L. W., Pitts, M. C., and Winker, D. M.: CALIPSO observations of stratospheric aerosols: a preliminary assessment, Atmos. Chem. Phys., 7, 5283-5290, doi:10.5194/acp-7-5283-2007, 2007.