CCD Actinic Flux Spectroradiometers (CAFS)


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CAFS detector installed on the NASA DC-8.

The CCD Actinic Flux Spectroradiometers (CAFS) developed in the ARIM laboratory will be deployed on the NASA DC-8 for SEAC4RS and DC3 field campaigns. The instruments measure spectrally resolved down- and up-welling in situ ultraviolet and visible actinic flux from approximately 280-650 nm. Photolysis frequencies for photodissociation reactions for species including O3, NO2, CH2O, HONO, HNO3, N2O5, HO2NO2, PAN, H2O2, CH3OOH, CH3ONO2, CH3CH2ONO2, CH3COCH3, CH3CHO, CH3CH2CHO, CHOCHO, CH3COCHO, CH3CH2CH2CHO, CH3COCH2CH3, Br2, BrO, Br2O, BrNO3, BrCl, HOBr, BrONO2, Cl2, ClO, and ClONO2 are calculated from the radiative measurements. Careful calibration techniques and comparison to the NCAR/TUV radiative transfer model improves the accuracy and precision of the measurements. CAFS instruments have a successful heritage of radiation measurements during atmospheric chemistry and satellite validation missions including NASA AVE, PAVE, CR-AVE, TC-4 and ARCTAS campaigns on the WB-57 and DC-8 platforms and during the NSF OASIS ground campaign in Barrow, AK. Similar instruments will be deployed on the NCAR G-V platform as part of the HIAPER Airborne Radiation Package (HARP) as a part of DC3 and SEAC4RS. In situ solar radiation measurements are critical to NASA atmospheric composition research. Actinic flux radiation drives the chemistry of the atmosphere, including the evolution of ozone, greenhouse gases, biomass burning, and other anthropogenic and natural trace constituents. The evolution of boundary layer and tropospheric constituents convected to the upper troposphere and lower stratosphere requires knowledge of the complex radiative fields expected during the campaigns. The gases, in turn, control the chemical evolution of aerosols.

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