The influence of snow grain size and impurities on the vertical profiles of actinic flux and NOx associated emissions on the Antarctic and Greenland ice sheets

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The influence of snow grain size and impurities on the vertical profiles of actinic flux and NOx associated emissions on the Antarctic and Greenland ice sheets

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dc.contributor.advisor Alexander, Becky en_US
dc.contributor.author Zatko, Maria Christine en_US
dc.date.accessioned 2012-09-13T17:40:30Z
dc.date.available 2012-09-13T17:40:30Z
dc.date.issued 2012-09-13
dc.date.submitted 2012 en_US
dc.identifier.other Zatko_washington_0250O_10325.pdf en_US
dc.identifier.uri http://hdl.handle.net/1773/20903
dc.description Thesis (Master's)--University of Washington, 2012 en_US
dc.description.abstract We use observations of the absorption properties of black carbon and non-black-carbon impurities in near-surface snow collected near the research stations at South Pole and Dome C, Antarctica and Summit, Greenland combined with a snowpack actinic flux parameterization to estimate the vertical profile and e-folding depth of ultraviolet/near-visible (UV/near-vis) actinic flux in the snowpack at each location. We have developed a simple and broadly applicable parameterization to calculate the depth and wavelength dependent snowpack actinic flux that can be easily integrated into large scale (e.g. 3D) models of the atmosphere. The calculated e-folding depths of actinic flux at 305 nm, the peak wavelength of nitrate photolysis in the snowpack, are 8-12 cm near the stations and 15-31 cm away (> 11 km) from the stations. We find that the e-folding depth is strongly dependent on impurity content and wavelength in the UV/near-vis region, which explains the relatively shallow e-folding depths near stations where local activities lead to higher impurity levels. We calculate the lifetime of NO<sub>x</sub> in the snowpack interstitial air produced by photolysis of snowpack nitrate against escape (τ<sub>escape</sub>) from the snowpack via diffusion and wind pumping and compare this to the calculated lifetime of NO<sub>x</sub> against chemical conversion to HNO<sub>3</sub> (τ<sub>chemical</sub>) to determine whether the NO<sub>x</sub> produced at a given depth can escape from the snowpack to the overlying atmosphere. Comparison of τ<sub>escape</sub> and τ<sub>chemical</sub> suggests efficient escape of photoproduced NO<sub>x</sub> in the snowpack to the overylying atmosphere. Calculated vertical actinic flux profiles and observed snowpack nitrate concentrations are used to determine the flux of NO<sub>x</sub> from the snowpack. Calculated NO<sub>x</sub> fluxes of 4.4x10<super>8</super>-2.8x10<super>9</super> molecules cm<super>-2</super> s<super>-1</super> in remote polar locations and 3.2-8.2x10<super>8</super> molecules cm<super>-2</super> s<super>-1</super> near polar stations in January at Dome C and South Pole and in June at Summit suggest that NO<sub>x</sub> flux measurements near stations are likely underestimating the amount of NO<sub>x</sub> emitted from the clean, polar snowpack by a factor of 1.4-2.4. en_US
dc.format.mimetype application/pdf en_US
dc.language.iso en_US en_US
dc.subject actinic flux; e-folding depth; nitrate; NOx; photochemistry; photodenitrification en_US
dc.subject.other Atmospheric chemistry en_US
dc.subject.other Atmospheric sciences en_US
dc.subject.other Atmospheric sciences en_US
dc.title The influence of snow grain size and impurities on the vertical profiles of actinic flux and NOx associated emissions on the Antarctic and Greenland ice sheets en_US
dc.type Thesis en_US
dc.embargo.terms No embargo en_US


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