Optical properties of snow and sea-ice : a field and modelling study

The work contained within this thesis is a field and laboratory study of snowpack and sea-ice optical and physical properties, and a computation modelling study of photochemical reaction rates within snowpack. The contribution of snow photochemistry to snow and atmospheric oxidative capacity is controlled in part by snow albedo and e-folding depths in snow. Albedo and e-folding depths (and thus snow photochemistry) are a function of black carbon mass ratio in snow. The work contained within this thesis demonstrates the complicated response of albedo, e-folding depth (wavelengths 300-600 run) and depth-integrated production rates of N02 and OH radicals to increasing black carbon mass ratio in well-characterised snowpacks of the Barrow OASIS campaign, Alaska. All snowpacks were reworked layered windpacks and were found to have similar responses to changes in black carbon mass ratio. The radiative-transfer calculations demonstrate two light absorption regimes: ice-dominated and black carbon dominated. The ice-dominated and black carbon dominated behaviour of albedo, e-folding depth and depth-integrated production rates with increasing black carbon mass ratios are presented. For black carbon mass ratios greater than 20 ng g-I (wavelength range of 300---600 nm), e-folding depth and depth integrated production rate have an inverse power law relationship with black carbon mass ratio. Doubling the black carbon mass ratio decreases the e-folding depth to -70% of the initial value and for solar zenith angles greater than 60°, doubling the black carbon mass ratio decreases depth-integrated production rates of N02 and OH to - 70% and - 65% of their original values respectively.EThOS - Electronic Theses Online ServiceGBUnited Kingdo