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Selected results

During the SCOUT-O3/AMMA Tropical Balloon Campaign in Niamey, Niger, carried out during in September 2008, SnowWhite/COBALD and the Wyoming backscatter sonde were flown on the same balloon. In January 2009 this combined payload was launched from Sodankylä, Finland. Prior to the flights the COBALD sondes were referenced to a Wyoming sonde by night time measurements on the IAC roof. Data retrieved from the combined flights are used to compare the COBALD performance to the well-established Wyoming sonde. This poster shows the flight comparison results.

Seven SnowWhite/COBALD tandems were launched during the Lindenberg LUAMI Campaign. Example data for a cirrus cloud encountered at 12 km altitude on 6 November 2008 is shown in Figure 3. Backscatter signals are indicated by red (870 nm) and blue (455 nm) colors, the relative humidity with respect to ice is shown in cyan. The green line refers to the color index of the cloud particles only, taking the aerosol background into account. Noticeably air is supersaturated at the cirrus top while saturation is near 100% inside and below the cirrus. By the aid of Mie or T-Matrix scattering calculus the color index of 10 for the cloud particles at the cirrus top can be related to a mode radius of approximately 1.2 microns. With this, the particle backscatter ratio found at the cirrus cloud - either in the red or blue channel - corresponds to a particle concentration of 0.5 cm-3. These data lead to a kinetic relaxation time of about half an hour for the supersaturation observed. Inside the cloud the particle characterization is impeded by the fact that the color index of 15 only provides a lower limit near 3 microns for the particle size. Assuming a range between 3 and 10 microns the corresponding relaxation time is found much shorter (7 to 10 minutes). This analysis agrees with the water vapor profile observed.

Apart from clouds aerosol layers formed from high altitude injections of particulate matter or its precursors - such as volcanic activity or biomass burning - are observed frequently in the lower stratosphere. Figure 4 showing COBALD data of two soundings with a time lag of two weeks demonstrates how such a layer located near 140 hPa pressure level evolves with time. It most probably originates from the eruption of Sarychev Peak.

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© 2014 ETH Zurich | Imprint | Disclaimer | 16 March 2010
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