Latitudinal dependence of noctilucent cloud growth



[1] The latitudinal variation of NLC particle sizes is studied using scattered solar radiation spectra from the OSIRIS instrument onboard the Odin satellite obtained during the austral summer period 1 January–17 February 2005. We show that the particles grow moderately larger when approaching the pole, with effective optical radii of 65 nm/76 nm at latitudes of 70°/90° S. Microphysical modeling suggests that particles grow larger as a consequence of a combined effect of the temperature decrease toward the pole, the available water vapor, and meridional transport times. Interestingly, at latitudes closest to the pole, NLC particle sizes show a bi-modal structure. This structure is suggested to arise from repeated growth cycles due to extended residence times in supersaturated air.