Reply to Comment on “Nucleation of Mesospheric Cloud Particles: Sensitivities and Limits”

摘要

A comment by Megner (2019; M19) aims at resolving the discrepancies between the results of Megner (2011, https://doi.org/10.1016/j.jastp.2010.08.006; M11) and Wilms et al. (2016, https://doi.org/10.1002/2015JA021764; WRK16). M11 concluded that the observable properties of noctilucent clouds are close to insensitive to the concentration of meteoric smoke particles (MSPs), whereas WRK16 concluded that there is a sensitivity. M19 argues that the differences arise due to the different ranges of MSP number densities, which were analyzed in the two studies. Additionally, M19 claims that both studies show a limited sensitivity when the number density of condensation nuclei is 100 cm~(-3) or more. However, this is not confirmed in our simulations.We show that the range of MSP number densities in WRK16 is similar to the range considered by M11. In this range, the simulations of WRK16 are highly sensitive to the number of MSPs: Observable properties such as ice column mass are linearly related to the number of available condensation nuclei.We explain the different sensitivities by different vertical wind amplitudes. Our results suggest that the relative contribution of vertical wind and vertical diffusion to the vertical transport of mesospheric ice particles is the decisive factor. If vertical diffusion dominates, as in M11, there is only limited sensitivity. If vertical wind dominates, as in WRK16, noctilucent cloud properties are directly coupled to the nucleation conditions.