On microphysical processes of noctilucent clouds (NLC): observations and modeling of mean and width of the particle size-distribution Leibniz-Institute of Atmospheric Physics at the Rostock University, 18225 Kühlungsborn, Germany
Received: 11 Dec 2009 – Published in Atmos. Chem. Phys. Discuss.: 09 Feb 2010 Abstract. Noctilucent clouds (NLC) in the polar summer mesopause region have been observed
in Norway (69° N, 16° E) between 1998 and 2009 by 3-color lidar
technique. Assuming a mono-modal Gaussian size distribution we deduce mean and
width of the particle sizes throughout the clouds. We observe a quasi linear
relationship between distribution width and mean of the particle size at the top
of the clouds and a deviation from this behavior for particle sizes larger than
40 nm, most often in the lower part of the layer. The vertically integrated
particle properties show that 65% of the data follows the linear relationship
with a slope of 0.42±0.02 for mean particle sizes up to 40 nm.
For the vertically resolved particle properties (Δz = 0.15 km) the slope is
comparable and about 0.39±0.03. For particles larger than 40 nm the
distribution width becomes nearly independent of particle size and even
decreases in the lower part of the layer. We compare our observations to
microphysical modeling of noctilucent clouds and find that the distribution
width depends on turbulence, the time that turbulence can act (cloud age), and
the sampling volume/time (atmospheric variability). The model results nicely
reproduce the measurements and show that the observed slope can be explained by
eddy diffusion profiles as observed from rocket measurements.
Revised: 18 May 2010 – Accepted: 07 Jul 2010 – Published: 21 Jul 2010
Citation: Baumgarten, G., Fiedler, J., and Rapp, M.: On microphysical processes of noctilucent clouds (NLC): observations and modeling of mean and width of the particle size-distribution, Atmos. Chem. Phys., 10, 6661-6668, doi:10.5194/acp-10-6661-2010, 2010.