Toward a more accurate estimate of global stratospheric aerosol surface area density. Is it important?

T. Deshler, J. L. Mercer, M. Kovilakam, J. M. RosenUniv. of Wyoming, Laramie, WY D. J. Hofmann, S. Solomon, J. F. Lamarque, P. J. YoungNOAA Earth System Research Laboratory, Boulder, CO

History of stratospheric aerosol (UW in situ instruments)Present climatology SAGE II+ and times of concern1971 - 1984Post Pinatubo low aerosol loadingWhy we care Comparison with in situ measurements and fixing the climatologyComparisons over LaramieBroadcasting (Surface area discrepancies (SAGE/UW)Using the new climatology results from Chem-CAM (3D) 1970sNOx, ClOx, Ozone Conclusions (Whats new)

SummaryPresent aerosol surface area density climatology has some deficiencies, < 1980, 1981-1984, > 2000A new climatology corrected with in situ measurements is available along with the in situ measurements used to develop it. See: http://www-das.uwyo.edu/~deshler/First results with the new climatology show differences in NOx, ClOx and OH leading to 0.5% for global average ozone in the 1970s when stratoshperic chlorine was 1500 2000 ppt. A total of 1% change does not sound like much, but recall globally the mid latitude ozone loss through the 1980s was on the order of 5%.Future workFix blanks at pressures > 100 hPa in El Chichon periodSmooth climatology at pressures < 20 hPa, where signal is very weakUse the new climatology in model runs, 1980-1985, and 1991-2010There are many people and agencies to thank for these resultsFunding over the last 40 years NSF, NSF, NSF, NASA, NRL, ...The pioneers Jim Rosen and Dave Hofmann, and their (and my) engineers, technicians, scientists and students necessary to complete the measurements.Susan Solomon for the invitation to a sabbatical and providing the means to get introduced to the world of atmospheric models, and to Jean Francois Lamarque and Paul Young for guiding me into the details

Update through 2009 of Figure 1 from Deshler, T. (2008), A Review of Global Stratospheric Aerosol: Measurements, Importance, Life Cycle, and Local Stratospheric Aerosol, Atmos. Res., 90, 223-232.SAGESAGE IISatellite RecordFour LidarRecordsIn Situ Record Two altitudes

Periods of concernCurrent Surface area densityused in Atmospheric models

Why we careN2O5 + H2O(aer) 2HNO3Consequences of this conversionLess N2O5 for: N2O5 + h NO2 + NO3 Less NO2 for: NO2 + ClO + M ClONO2NO2 + OH + M HNO3More ClO for HO2 + ClO HOCl + 02, HOCl + hv OH + ClCl + 03 ClO + 02More OH for:OH + 03 H02 + O2HO2 + 03 OH + 02 + 02Net result Less ozone from reactions with ClO and OHMore ozone from reduction in loss from NOx

Revising the climatology using In Situ Aerosol Profiles University of Wyoming with particular thanks to Jim Rosen and Dave Hofmannhttp://www-das.uwyo.edu/~deshler/US_Laramie_41N_105W (1971 - 2009)AU_Mildura_34S_142W (1972 - 1980)NZ_Lauder_45S_170E (1991 - 2001)Ant_McMurdo_78S_167E (1989 - 2008)SE_Kiruna_68N_21E (1991 - 2004)MiscellaneousBrazil, Niger, France

Aerosol concentration for particles > 0.01, 0.15, 0.25 mOct 1971Oct 1974 Fuego

Mar 1991July 1991 PinatuboAerosol concentration for particles > 0.01, 0.15, 0.25, 2.0/10.0 m

Fixing the climatologySurface Area Comparisons over Laramie with SAGE IIResultant ratios UW : SAGEBroadcasting Comparison with far flung measurementsMildura Australia (1972-1980)Lauder New Zealand (1991-2001)Led to determining rate of latitudinal spread and weighting functions for dispersal from eruptions

Fuego

Post - PinatuboModerate aerosol loadParticles large enough to Allow extinction Measurements representSurface area

Low aerosol loadExtinction measurementsCant see the small particles Controlling surface area

1988 1991 Pre PinatuboAerosol load high enough for extinction meas. to obtain good estimates of surface areaPeak of PinatuboSAGE blindedDecay of Pinatubo aerosol in good range for extinction measurementsPost Pinatubo low aerosol load

Comparison of revised climatology with measurements

Comparison of revised climatology with measurements

Periods of concernPeriod investigatedWith CAM - chem

NOxNew / OldClimatologyResults CAM chem run through 1970s

Revised Climatology FuegoNOx Profiles 40 NNew / OldClimatologyResults CAM chem run through 1970s

Revised Climatology FuegoNOx profiles 40 SNew / OldClimatologyResults CAM chem run through 1970s

Results CAM chem run through 1970s

ClONew / OldClimatologyResults CAM chem run through 1970s

Revised Climatology FuegoClO 40 NNew / OldClimatologyResults CAM chem run through 1970s

Revised Climatology FuegoClO 40 SNew / OldClimatologyResults CAM chem run through 1970s

OzoneNew / OldClimatologyResults CAM chem run through 1970s

Revised Climatology FuegoOzone 40 NNew / OldClimatology40 S is similarResults CAM chem run through 1970s

Revised Climatology FuegoTotal ozone global averageNew / OldClimatologyResults CAM chem run through 1970s

Wyoming Optical Particle Counter, r > 0.2 - 10.0 mWhitelightPumpPMTsPHAProcessorOptical ChamberAerosolin

Low GainMid GainHigh Gain

Initial MeasurementSizes1971 - 19901990 - presentPostEl Chichon

Sources of ErrorSize Aerosol index of refraction and shapeUniformity of illuminationPMT response pulse width broadeningNumber concentrationFlow rateCoincidencePoisson counting uncertainty

Estimates of differential surface area (m2 cm-3), extinction (km-1) , and volume (m3 cm-3) for insitu measurements in 1993

and 1999Evolution of Pinatubo Aerosol

Radius dependence of SAD and surface area kernel

Comparison of SAGE v6.0 and 6.1 with UWOPC extinction 525 1020 nm