HR: 17:45h
AN: SA24A-08    [Abstracts]
TI: Three-parameter size distributions of NLC particles as measured by the ALOMAR Rayleigh/Mie/Raman lidar
AU: Baumgarten, G
EM: baumgarten
AF: Leibniz-Institute of Atmospheric Physics, Schloss-Str. 6, Kuehlungsborn, 18225 Germany
AU: * von Zahn, U
EM: vonzahn@iap-kborn.de
AF: Leibniz-Institute of Atmospheric Physics, Schloss-Str. 6, Kuehlungsborn, 18225 Germany
AB: The Rayleigh/Mie/Raman lidar of the ALOMAR observatory (located at 69 degrees N) can measure the backscatter coefficient of noctilucent clouds (NLC) and its altitude dependence in full daylight and at any local time throughout the Arctic summer at the wavelength of 532 nm. For medium and strong NLC, it can do so also at the additional wavelengths of 355 nm and 1064 nm. It so happens that in this wavelength range, scatter from the optically active NLC particles significantly deviates from Rayleigh scatter. It is this deviation from Rayleigh scatter which allows the determination of a size distribution through the measurement of backscatter coefficients at three different wavelenghts. Since 1998, the ALOMAR Rayleigh/Mie/Raman lidar has the required capability of daylight observations of NLC in three widely separated wavelengths and we have observed quite a number of NLC events for which particle size distributions could be determined. In our data analysis, we presume the NLC particles to be spherical, to consist of ice and to follow a lognormal size distribution. The latter is described by an absolute particle number density, a median radius and a radius distribution width. We will report on the results of these measurements.
UR: http://alomar.rocketrange.no
DE: 3360 Remote sensing
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0340 Middle atmosphere--composition and chemistry
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting