Latitudinal variation of NLC particle radii derived from northern hemisphere SCIAMACHY/Envisat limb measurements

Particle radii of noctilucent clouds (NLCs) are derived from SCIAMACHY/Envisat limb-scatter measurements during the 2005 NLC season in the northern hemisphere. The NLC radii increase with increasing latitude from about 60 nm at 60°N to about 80 nm at 80°N, if a Gaussian particle size distribution with a width of σ = 12 nm is assumed. For a log-normal particle size distribution with σ = 1.4 the mean radii vary from about 30 nm at 60°N to around 50 nm at 80°N. Histograms of the NLC radii show a mono-modal structure. The size retrievals are compared to previous NLC size measurements after converting the measurements to a log-normal particle size distribution with σ = 1.4 as a common standard. The SCIAMACHY NLC radii are found to be in good agreement, but slightly larger than most of the previously published NLC radius measurements. Compared to published model simulations of NLC radii the SCIAMACHY NLC radii are systematically larger than the model results.