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Measuring Atmospheric Changes in the Arctic
Christopher J CoxUniversity of Idaho, Geography
Acknowledgments• Von Walden (UI), Penny Rowe (UI), Matt Shupe (UC, Boulder
• Mike Town (UW), Ed Eloranta (U Wisconsin)
• Funding by National Science Foundation (NSF)
• NOAA SEARCH, CANDAC, ARM, SSEC, IGRA, NSIDC
Outline
• What is climate change?
• The Arctic Climate System
• Instrumentation
• Preliminary research
• Conclusion
What is Climate Change?Scientific Consensus
“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level” (WGI 3.9, SPM)
•Intergovernmental Panel on Climate Change (IPCC)
Climate change no longer a scientific debate, but a societal issue
What is Climate Change?The Greenhouse Effect
What is Climate Change?The Greenhouse Effect
Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide (all greenhouse gases) have
increased markedly as a result of human activities since 1750.
IPCC WG1.2 Figure 1
What is Climate Change?The Greenhouse Effect
B1 “Green” Scenario (550 ppm)
A1B “Medium” Scenario (700 ppm)
} Natural Variability
PotentialHuman
Contribution
A1Fl “Aggressive” Scenario (850 ppm)
What is Climate Change?The Greenhouse Effect
So what about Arctic?
Primarily as a result of a strong ice-albedo postive feedback, the Polar Regions are very sensitive to a warming climate.
But, they are also poorly quantified!
Previous Research
Arctic atmosphereSurface Heat Budget of the Arctic (SHEBA)
Intrieri et al (2002) An annual cycle of Arctic surface cloud forcing at SHEBAShupe et al (2005) Arctic mixed-phase cloud properties from surface-based sensors at SHEBA
OtherKey et al (2004) “Cloud distributions over the coastal Arctic Ocean: surface-based and satellite observations”Shupe & Intrieri (2003) “Cloud Radiative Forcing of the Arctic Surface: The Influence of Cloud Properties, Surface Albedo, and Solar Zenith AngleTjernstrom et al (2004) “The Summertime Arctic Atmosphere: meteorological measurements during the Arctic Ocean Experiment 2001”Verlinde et al (2004) “Mixed-Phase Arctic Cloud Experiment (M-PACE)”
Recent Sea Ice MeltDrobot et al (2008) “Evolution of the 2007-2008 Arctic sea ice cover and prospects for a new record in 2008”Kay et al (2008) “The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum”Perovich et al (2008) “Sunlight, water,and ice: Extreme Arctic sea ice melt during the summer of 2007”Schweiger et al (2008) “Did unusually sunny skies helpdrive the record sea ice minimum of 2007?”
Zhang et al (2008) “What drove the dramatic retreat of arctic sea ice during summer 2007?”
The Arctic Climate System
• Cloud properties
– not well known
– climate models
• Downwelling Infrared– Atmospheric properties
– Temperature, Humidity
• Upwelling Infrared– Surface prop (, Ts)
– Satellite validation
Signs of Arctic Climate Change
National Snow and Ice Data Center (NSIDC)
Polar Atmospheric Emitted Radiance Interferometer
Arctic High Spectral Resolution Lidar (AHSRL)Ed Eloranta (SSEC. U. Wisconsin-Madison)
Millimeter Cloud Radar (MMCR)NOAA ERL, Boulder, CO
Microwave Radiometer (MWR) - total column water vaporNOAA ERL, Boulder, CO
Radiosondes from the Eureka Weather Office
http://lidar.ssec.wisc.edu/
Instruments now in the Arctic
Arctic High Spectral Resolution Lidar (AHSRL) LIDAR – Light Detection and Ranging 40 ns pulse width
Wavelength: 523 nm
http://lidar.ssec.wisc.edu/
Instrument SpecsAHSRL
http://arm.gov/
http://lidar.ssec.wisc.edu/
Instrument SpecsMMCR
Millimeter Cloud RadarZenith pointing radarOperates at 35 Ghz
Used to determine cloud boundaries
www.arm.gov
http://arm.gov/
http://lidar.ssec.wisc.edu/
Instrument SpecsMWR
Microwave RadiometerMeasure microwave emission from water (liquid/vapor)
Reports column integrated amounts
www.arm.gov
http://lidar.ssec.wisc.edu/
Instrument SpecsPAERI
Polar Atmos. Emitted Radiance InterferometerSpectral infrared radiance from 3 to 20 m (1 cm-1)
Two detectors: MCT - LW and InSb - SWVery accurate [1% (3) of ambient radiance]
PAERI
PAERI
CO2
H2O
CH4,
N2O
O3
Cloud
PAERI
What can we use PAERI output for?
• Cloud fraction• Trace gas measurements
• Scale radiosondes• Validate satellites
• Longwave cloud radiative forcing• more…
Instrument Sites
Eureka, Nunavut, Canada: Study of Environmental Arctic Change (SEARCH) Arctic Observing Network (AON) at Canadian Network for the Detection of Arctic Change (CANDAC) site
79º59’N, 85º57’W
Barrow, Alaska: Atmospheric Radiation Measurement (ARM) North Slope Alaska (NSA) site
71º18’N, 156º44’W
Longwave Downwelling Radiation and Arctic Sea Ice Melt
• Preliminary experimental evidence for the importance of downwelling longwave radiation to the recent decrease in sea ice concentration over the Arctic Ocean.
• Was shortwave downwelling radiation (SDW) the cause?Kay et al (2008) “The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum”Perovich et al (2008) “Sunlight, water,and ice: Extreme Arctic sea ice melt during the summer of 2007”
• Was it longwave downwelling radiation (LDW)?Schweiger et al (2008) “Did unusually sunny skies helpdrive the record sea ice minimum of 2007?”
Schweiger et al (2008)
Surface Temperature
Tropospheric Temperature
Fractional Cloud Cover
Precipitable Water Vapor
Calculating DLW Flux and LWCRF
AERI measurements made at zenith
Out of band radiance was simulated as a black body
using brightness T from 650-660 cm-1
Assume isotropic radiance (fluxes within ~5%)
Focusing on Eureka data onlyLW CRF = All – Clear
(Ramanathan et al, 1989)
FIR =π I (λ)d(λ)λ1
λ2
∫
Differences in DLW and CRF
• LWCRF depends on many variables• FCC• Optical thickness of clouds• AND Temperature of the near-surface air (in winter)
Cloud Forcing
Inter-annual Variations at Eureka
Eureka Summer Average (JJA)
Year LW-CRF (W m-2) All Sky Flux (Wm-2) FCC (%)
2006 42 275 78
2007 18 263 54
2008 27 268 63
Conclusions• The phenomenon of accelerated climate change is a scientific consensus
• The Arctic is environment is very sensitive to a warming climate and is poorly quantified
• Recent sea ice retreat may be signs of a changing climate system
• Determining the potential causes of recent sea ice decrease in the Arctic is complicated
• Experimental evidence may show that the all-sky flux has influenced sea ice retreat through an increase in the near surface temperature and/or increases in humidity
Sources• Drobot, S; Stroeve, J; Maslanik, J; Emery, W; Fowler, C, and Kay, J. 2008. “Evolution of the 2007-2008 Arctic sea ice cover
and prospects for a new record in 2008”. Geophysical Research Letters. Vol. 25(L19501), 5p.• Intrieri, JM; Shupe, MD; Uttal, T; McCarty, BJ. 2002. “An annual cycle of cloud characteristics observed by radar and lidar at SHEBA” Jounal of Geohpysical Research – Oceans. Vol. 107:C10(8030).• IPCC, 2007, Climate change (2007) Synthesis Report, Summary for Policy Makers, 22p.• Kay, J; L’Ecuyer, T; Gettelman, A; Stephens, G; and O’Dell, C. 2008. “The contribution of cloud and radiation anomalies to
the 2007 Arctic sea ice extent minimum”. Geophysical Research Letters. Vol. 25(L108503), 5p.• Perovich, DK; Richter-Menge, JA; Jones, KF; Light, B. 2008. “Sunlight, water, and ice: Extreme Arctic sea ice melt during the summer of 2007”. Geophysical Research Letters. Vol. 25(L11501), 4p.• Ramanathan, V; Cess, RD; Harrison, EF; Minnis, P; Barkstrom, BR; Ahmad, E; and Hartmann, D. 1989. “Cloud-Radiative
Forcing and Climate: Results from the Earth Radiation Budget Experiment”. Science. Vol. 243(4887), pp 57-63.• Shupe. MD and Intrieri, JM. 2003 . “Cloud Radiative Forcing of the Arctic Surface: The Influence of Cloud Properties, Surface
Albedo, and Solar Zenith Angle”. Journal of Climate. Vol. 17(3), pp.616-628.• Schweiger, AJ; Zhang, J; and Steele, M. 2008. “Did unusually sunny skies help drive the record sea ice minimum of 2007?”
Geophysical Research Letters. Vol. 35(L10503), 6p.• Tjernström, M; Leck, C; Ola, P; Persson, G; Jensen, ML; Oncley, SP; Targino, A. 2004. “The Summertime Arctic Atmosphere: Meteorological Measurements during the Arctic Ocean Experiment 2001”. Bulletin of the American Meteorological Society. Vol. 85(9), pp. 1305-1321.• Town, MS; Walden, VP; and Warren, S. 2005. “Spectral and Broadband Longwave Downwelling Radiative Fluxes, Cloud
Radiative Forcing, and Fractional Cloud Cover over the South Pole”. Journal of Climate. Vol. 18, pp. 4235-4252.• Zhang, J; Lindsay, R; Steele, M; and Scheiger, A. 2008. “What drove the dramatic retreat of arctic sea ice
during summer 2007?” Geophysical Research Letters. Vol. 25(L11505), 5p.