Third Santa Fe Conference on Global and Regional Climate Change Santa Fe, New Mexico, October 31 November 2, 2011 Characterization and Direct Radiative Impact of Arctic Aerosols: observed and modeled R. S. Stone Cooperative Institute for Research in Environmental Sciences University of Colorado-Boulder NOAA Earth System Research Laboratory Global Monitoring Division Transport of aerosols into the Arctic Measurement strategy Results; radiative forcing efficiency The role of black carbon (soot)
Acknowledgments: NOAA Global Monitoring Division: E. Dutton, J. Augustine, D. Longenecker, J. Wendell, D. Nelson, B. Andrews, A. Jefferson, J. Ogren, G. Anderson (AFRL); Station technicians Many co-authors (see reference list) Other contributors; noted on slides NOAA Arctic Research Program A. Herber V. Vitale J. Burkhart
Source regions of aerosol transported into the Arctic haze dust H Oceanic DMS, sea salts L L smoke volcanoes
deposition along path leaves small particles mixing inhibited by inversion Arctic inversion layer pollutants smoke volcanic sea salt sulfate dust Barrow; Oct-May (Tomasi et al. 2011)
JOK Institute of Atmospheric Sciences and Climate SOD HRN ALO NYA SUM ALT EUR TIK GAW BRW POLAR-AOD project: characterize the climate-forcing properties of aerosols in polar regions
Sun photometry
Optical Depth I = I o e - /cosθ o (Beer s Law) TOA; airmass 1 I o Rayleigh O 3 NO 2 L θ o H 2 O I SP
Inter Calibration Campaign ~ Oct. 2008 Izana, Tenerife accuracy: Mean Bias Difference ~ 0.004 (Mazzola et al., 2011)
SWD = DIRECT(θ 0 ) + DIFFUSE DIFFUSE AOD(λ) DIRECT Barrow Observatory
NETsw = SWD - SWU Albedo = SWU/SWD SWU Barrow Albedo Rack
30 June 2004 Barrow H Brooks Range
noon midnight noon midnight Height (Km) Aerosol Optical Depth 8 6 4 2 2 July 3 July Barrow DOE/ARM MPL 0
DARF (or radiative forcing efficiency) is defined as the change in NETsw in response to a unit increase in AOD at 500 nm negative slope => cooling at the surface
NET shortwave irradiance (W m -2 ) Direct Aerosol Radiative Forcing (over snow at BRW) solar elevation dust haze Smoke 28 24 ΔNET sw AOD -1 (W m -2 AOD -1 ) -14-38 18 15 15 10 9 Volcanic? (Young et al., 2011) -30-16 -31-30 -23 AOD(500 nm)
50 G. Anderson (AFRL) B. Andrews 55 60 65 80 observed Closure modeled
radiative forcing efficiency (W m -2 AOD -1 ) cooling warming Aerosol radiative forcing in the Arctic TOA 2008 BRW surface 2010 Fourmile Canyon fire ocean tundra sea ice snow surface albedo (adapted from Stone et al., 2008; Fig. 10) Simulations of the direct radiative forcing by boreal smoke for a solar zenith angle of 50 º.
Altitude (km) 5 4 3 2 1 0 6 5 4 Total Heating Total Heating 3 smoke 2 WARMING 1 0 COOLING -5-4 -3below -2-1 0 1 2 3 4 5-5 -4-3 -2-1 0 1 2 3 4 5 bkg heating AO ~0.1 (adapted from Stone et al., 2008; Fig. 5) Simulations of heating rate profiles for smoke over tundra for a solar zenith angle of 65 º. 6 AOD(500) within the layer Heating Rate (K day -1 ) heating AOD.2 0.10 bkg heating AOD ~0.1 0.28 heating AOD=.3 heating AOD.28 0.35 heating AOD=.6 0.60 heating AOD=.35 heating AOD=.6 0.72 heating AOD=.7 1.00 heating AOD=.72 heating AOD = 1.0 1.10 heating AOD = 1.0 heating AOD =1.1 heating AOD =1
semi-direct effect increases atmospheric stability may suppress cloud formation normal cloud formation cloud suppressed soot Temperature (Lindeman, et al. 2011)
Fourmile Canyon Fire ~ Boulder, CO 6-7 Sept. 2010 Radiative forcing efficiency sunset noon see poster
Arctic aircraft investigations Longyearbyen, Svalbard - 1 April 2009
Sun photometer mated to a Schulz solar tracker; Polar-5 K-H Schulz
N36 Polar-5 Flight ~ April 2009
Flight provided a 3-D snapshot of Arctic aerosols more than 80,000 spectra were obtained (1 s resolution) Arctic Haze hangs over Svalbard ~ April 2009
Arctic Enhancement background haze MLO (3400m) Hawaii
26 March, 2009 eruption of Mount Redoubt, (AP photo; A. Grillo) Hofmann et al., 2009 > emissions from China Solomon et al., 2011 > minor volcanoes Globally, stratospheric aerosols have increased in abundance since 2000. Volcanic aerosols were lofted at times to over 60,000 ft and carried east and northward into the Arctic
Barrow, AK ~ long-term record of AOD(500) FWNIP SP clean background only El Chicon Pinatubo (adapted from Tomasi et al., 2011; in review) upper atmosphere AOD has increased during last decade
The role of black carbon (soot) (Shindell and Faluvegi, 2009) suggest: black carbon has contributed ~ 0.5-1.4 ºC to Arctic warming, in part due to Asian emissions (Flanner et al., 2009) suggest: surface darkening caused by particles mixed with snow outweighs the dimming influence of particles in the atmosphere. findings underlie UN recommended mitigation policy
Q. Is soot contributing to the rapid decline in Arctic sea ice? A. probably NOT NSIDC data/ucar image
2009 Polar-5 SP-2 BC profiles (S-M Li) ARCTAS ~ April 2008 median (smoke) NOAA 1983-86 AGASP Hanson and Novakov, 1989 The atmospheric burden of black carbon has diminished since the mid-1980s NP36 profile background (Warneke et al., 2010) Z A B (Matsui et al., 2011; adapted from Fig. 10b) Barrow, A. Jefferson Alert, S. Sharma Zeppelin, K. Eleftheriadis
EBC, ngm -3 1200 1000 800 600 400 Alert Barrow Ny Alasund (S. Sharma, et al., 2006) 2011 update; unpublished Barrow ~ A. Jefferson Zeppelin ~ K. Eleftheriadis 200 0 Apr 09 Apr 10 11 1990 1995 2000 2005 2010 Decimal Year
Snow surveys
International Polar Year survey (Doherty et al., 2010) 1983-1984 1200 vs. 60 observations. it is doubtful that BC in Arctic snow has contributed to the rapid decline of Arctic sea ice in recent years.
Conclusions: Arctic AOD is highly variable, depending on transport Radiative forcing (direct, indirect and semi-direct) is highly dependent on solar geometry and surface type SW effects (cooling) increase as melt progresses The recent increase in background AOD is attributed to minor volcanoes, possibly coal burning in China [BC] has decreased significantly in the Arctic; thus is an unlikely contributor to the loss of sea ice
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