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Pinatubo Aerosol Global-to-Micro-Scale Evolution: A Unified Picture From Space, Air, and Ground MeasurementsWe combine a variety of measurements to develop a composite picture of the post-Pinatubo aerosol and assess the consistency and uncertainties of the measurement and retrieval techniques Satellite infrared spectroscopy, particle morphology, and evaporation temperature measurements are in accord with theoretical calculations In showing a dominant particle composition of H2SO4-H2O mature with H2SO4 weight traction of 65-80% for most stratospheric temperatures and humidities. Important exceptions are: (1) the presence of volcanic ash at all attitudes initially and in a layer just above the tropopause until at least March 1992, and (2) much smaller H2SO4 weight fractions at the low temperatures attained In high latitude winters and at the tropical tropopause. Laboratory spectroscopy and theoretical calculations yield wavelength- and temperature-dependent refractive indices for the dominant H2SO4-H2O droplets. These in turn permit derivation of particle size spectra from measured optical depth spectra for comparison to direct measurements by impactors and optical counters, All three techniques paint a generally consistent picture of the evolution of R(sub eff) the effective, or area-weighted, particle radius. In the first month after the eruption, although particle numbers increased by orders of magnitude, R(sub eff) was similar to the pre-eruption value of 0.1 to 0.2 microns because both small (r less than 0.2 microns) and large (r greater than 0.6 microns) particles increased in number. Over the next 3-6 months, R(sub eff) increased to about 0.5 microns, reflecting particle growth through condensation and coagulation. In general, R(sub eff) continued to increase for about a year after the eruption. Extinction spectra computed from in situ size distribution measurements are consistent with optical depth measurements, which show spectra with maxima initially at wavelengths of 0.42 microns or less, and thereafter progressively increasing to between 0.78 and 1 micron. Not until 1993 does optical depth spectra begin to show a clear return to the preeruption signature of maximizing at the shortest visible wavelengths or in the near UV. This coupled evolution in particle size distribution and optical depth spectra helps explain the relationship between the global maps of 0.5- and 1.0-kilometer optical depth derived from the AVHRR and SAGE satellite measurements. It also sets a context for evaluating remaining uncertainties in each of these satellite data products. We also show how the effects of wavelength-dependent refractive index on backscatter spectra can influence particle sizes retrieved from multiwavelength lidar measurements.
Document ID
20020038888
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Russell, Philip B.
(NASA Ames Research Center Moffett Field, CA United States)
Livingston, J. M.
(SRI International Corp. Menlo Park, CA United States)
Pueschel, R. F.
(NASA Ames Research Center Moffett Field, CA United States)
Pollack, J. B.
(NASA Ames Research Center Moffett Field, CA United States)
Brooks, S.
(Synernet, Inc. Fremont, CA United States)
Hamill, P.
(San Jose State Univ. CA United States)
Hughes, J.
(San Jose State Univ. CA United States)
Thomason, L.
(NASA Langley Research Center Hampton, VA United States)
Stowe, L.
(Satellite Research Lab. Washington, DC United States)
Deshler, T.
(Wyoming Univ. Laramie, WY United States)
Podolske, James R.
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Environment Pollution
Meeting Information
Meeting: American Association for Aerosol Research Annual Meeting
Location: Pittsburgh, PA
Country: United States
Start Date: October 9, 1995
End Date: October 13, 1995
Funding Number(s)
PROJECT: RTOP 665-45-51-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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