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- Author or Editor: C. A. McLinden x
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Abstract
The authors have used CPFM (composition and photodissociative flux measurement) polarized limb radiance measurements combined with a vector radiative transfer model to estimate stratospheric aerosol number density, extinction coefficient profiles, and size distribution. The CPFM spectroradiometer is flown on board the NASA ER-2 high-altitude research aircraft. The vertical and horizontal polarization components of limb radiance, nadir radiance, and horizontal flux are measured in the wavelength range 300–770 nm from approximately 5°–10° above to 5°–10° below the local horizon. Results from two flights during April and May 1997 as part of the Photochemistry of Ozone Loss in the Arctic Region in Summer campaign are presented. Aerosol characteristics are determined by forcing the model radiances and polarization to match the measurements. Results indicate number densities at 20 km are roughly 5–6 cm−3 with an effective radius of 0.17–0.20 μm. Number, surface area, and volume densities compare favorably with two in situ particle counters also flown on the ER-2.
Abstract
The authors have used CPFM (composition and photodissociative flux measurement) polarized limb radiance measurements combined with a vector radiative transfer model to estimate stratospheric aerosol number density, extinction coefficient profiles, and size distribution. The CPFM spectroradiometer is flown on board the NASA ER-2 high-altitude research aircraft. The vertical and horizontal polarization components of limb radiance, nadir radiance, and horizontal flux are measured in the wavelength range 300–770 nm from approximately 5°–10° above to 5°–10° below the local horizon. Results from two flights during April and May 1997 as part of the Photochemistry of Ozone Loss in the Arctic Region in Summer campaign are presented. Aerosol characteristics are determined by forcing the model radiances and polarization to match the measurements. Results indicate number densities at 20 km are roughly 5–6 cm−3 with an effective radius of 0.17–0.20 μm. Number, surface area, and volume densities compare favorably with two in situ particle counters also flown on the ER-2.
On 20 February 2001, a converted Russian ICBM delivered Odin, a small Swedish satellite, into low Earth orbit. One of the sensors onboard is a small Canadian spectrometer called OSIRIS. By measuring scattered sunlight from Earth's horizon, or limb, OSIRIS is able to deduce the abundance of trace gases and particles from the upper troposphere into the lower thermosphere. Designed and built on a modest budget, OSIRIS has exceeded not only its 2-yr lifetime but also all expectations. With more than a decade of continuous data, OSIRIS has recorded over 1.8 million limb scans. The complexities associated with unraveling scattered light in order to convert OSIRIS spectra into highquality geophysical profiles have forced the OSIRIS team to develop leading-edge algorithms and computer models. These profiles are being used to help address many science questions, including the coupling of atmospheric regions (e.g., stratosphere–troposphere exchange) and the budgets and trends in ozone, nitrogen, bromine, and other species. One specific example is the distribution and abundance of upper-tropospheric, lightning-produced reactive nitrogen and ozone. Arguably OSIRIS's most important contributions come from its aerosol measurements, including detection and characterization of subvisual cirrus and polar stratospheric and mesospheric clouds. OSIRIS also provides a unique view of the stratospheric aerosol layer, and it is able to identify and track perturbations from volcanic activity and biomass burning.
On 20 February 2001, a converted Russian ICBM delivered Odin, a small Swedish satellite, into low Earth orbit. One of the sensors onboard is a small Canadian spectrometer called OSIRIS. By measuring scattered sunlight from Earth's horizon, or limb, OSIRIS is able to deduce the abundance of trace gases and particles from the upper troposphere into the lower thermosphere. Designed and built on a modest budget, OSIRIS has exceeded not only its 2-yr lifetime but also all expectations. With more than a decade of continuous data, OSIRIS has recorded over 1.8 million limb scans. The complexities associated with unraveling scattered light in order to convert OSIRIS spectra into highquality geophysical profiles have forced the OSIRIS team to develop leading-edge algorithms and computer models. These profiles are being used to help address many science questions, including the coupling of atmospheric regions (e.g., stratosphere–troposphere exchange) and the budgets and trends in ozone, nitrogen, bromine, and other species. One specific example is the distribution and abundance of upper-tropospheric, lightning-produced reactive nitrogen and ozone. Arguably OSIRIS's most important contributions come from its aerosol measurements, including detection and characterization of subvisual cirrus and polar stratospheric and mesospheric clouds. OSIRIS also provides a unique view of the stratospheric aerosol layer, and it is able to identify and track perturbations from volcanic activity and biomass burning.
