[1] Meteoric material entering Earth's atmosphere ablates in the mesosphere and is then expected to recondense into tiny so-called ''smoke particles.'' These particles are thought to be of great importance for middle atmosphere phenomena like noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. Commonly used one-dimensional (1-D) meteoric smoke profiles refer to average global conditions and yield of the order of a thousand nanometer sized particles per cubic centimeter at the mesopause, independent of latitude and time of year. Using the first two-dimensional model of both coagulation and transport of meteoric material we here show that such profiles are too simplistic, and that the distribution of smoke particles indeed is dependent on both latitude and season. The reason is that the atmospheric circulation, which cannot be properly handled by 1-D models, efficiently transports the particles to the winter hemisphere and down into the polar vortex. Using the assumptions commonly used in 1-D studies results in number densities of nanometer sized particles of around 4000 cm À3 at the winter pole, while very few particles remain at the Arctic summer mesopause. If smoke particles are the only nucleation kernel for ice in the mesosphere this would imply that there could only be of the order of 100 or less ice particles cm À3 at the Arctic summer mesopause. This is much less than the ice number densities expected for the formation of ice phenomena (noctilucent clouds and polar mesospheric summer echoes) that commonly occur in this region. However, we find that especially the uncertainty of the amount of material that is deposited in Earth's atmosphere imposes a large error bar on this number, which may allow for number densities up to 1000 cm À3 near the polar summer mesopause. This efficient transport of meteoric material to the winter hemisphere and down into the polar vortex results in higher concentrations of meteoric material in the Arctic winter stratosphere than previously thought. This is of potential importance for the formation of the so-called stratospheric condensation nuclei layer and for stratospheric nucleation processes.Citation: Megner, L., D. E. Siskind, M. Rapp, and J. Gumbel (2008), Global and temporal distribution of meteoric smoke: A twodimensional simulation study,

[1] We investigate the link between the cold summer mesopause region and the dynamics in the stratosphere. In particular, we use Odin observations of noctilucent cloud (NLC) properties as a proxy for the state of the summer mesosphere and ECMWF winter stratospheric temperatures as a proxy for the residual circulation in the stratosphere. Large areas of strong anticorrelation between winter stratospheric temperature and summer mesospheric NLC indicate that there is an interhemispheric connection. Timelagged cross correlation shows that the wave activity flux at 100 hPa leads the NLC response by several weeks. The presented findings are consistent with recent model studies where the modulation of the mesospheric gravity wave drag by the stratospheric planetary waves yields an interhemispheric stratosphere-mesosphere coupling.Citation: Karlsson, B., H. Körnich, and J. Gumbel (2007), Evidence for interhemispheric stratosphere-mesosphere coupling derived from noctilucent cloud properties, Geophys. Res. Lett., 34, L16806,

[1] We present results of in situ measurements of charged nanoparticles, electrons, and positive ions obtained during a sounding rocket flight in October 2004 from Kiruna, Sweden, under nighttime conditions. The particle measurement reveals positive charge signatures in the altitude range between 80 and 90 km corresponding to peak charge number densities of $100 e/cm 3 at around 86 km. Aerodynamical analysis of the sampling efficiency of our instrument reveals that the particles must have been larger than 2 nm assuming spherical particles with a density of 3 g/cm 3 . The plasma environment of the observed particles is dominated by negative and positive ions, with only few free electrons. A calculation of the mean particle charge expected for particles in a plasma consisting of electrons and positive and negative ions shows that the presence of sufficiently heavy and numerous negative ions (i.e., m n > 300 amu and l ! 50) can explain the observed positive particle charge. Citation:

Abstract. Meteoroids entering the Earth's atmosphere experience strong deceleration and ablate, whereupon the resulting material is believed to re-condense to nanometre-size "smoke particles". These particles are thought to be of great importance for many middle atmosphere phenomena, such as noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. The properties and distribution of meteoric smoke depend on poorly known or highly variable factors such as the amount, composition and velocity of incoming meteoric material, the efficiency of coagulation, and the state and circulation of the atmosphere. This work uses a one-dimensional microphysical model to investigate the sensitivities of meteoric smoke properties to these poorly known or highly variable factors. The resulting uncertainty or variability of meteoric smoke quantities such as number density, mass density, and size distribution are determined. It is found that the two most important factors are the efficiency of the coagulation and background vertical wind. The seasonal variation of the vertical wind in the mesosphere implies strong global and temporal variations in the meteoric smoke distribution. This contrasts the simplistic picture of a homogeneous global meteoric smoke layer, which is currently assumed in many studies of middle atmospheric phenomena. In particular, our results suggest a very low number of nanometre-sized smoke particles at the summer mesopause where they are thought to serve as condensation nuclei for noctilucent clouds.

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