Impacts of the January 2005 solar particle event on noctilucent clouds and water at the polar summer mesopause

H. Winkler, C. von Savigny, J. P. Burrows, J. M. Wissing, M. J. Schwartz, A. Lambert, M. García-Comas
2012 Atmospheric Chemistry and Physics Discussions  
The response of noctilucent clouds to the solar particle event in January 2005 is investigated by means of icy particle and ion chemistry simulations. It is shown that the decreasing occurrence rate of noctilucent clouds derived from measurements of the SCIAMACHY/Envisat instrument can be reproduced by one-dimensional model 5 simulations if temperature data from the MLS/Aura instrument are used. The sublimation of noctilucent clouds leads to significant changes of the water distribution in the
more » ... istribution in the mesopause region. The model predictions are in general agreement with H 2 O measurements from the MLS and the MIPAS/Envisat satellite instruments, although the modelled effect of water redistribution is stronger than the observed one. Additionally, 10 it is revealed that the water depletion due to reactions of proton hydrates during the considered solar particle event has only a minor impact on the icy particles. 15 growing particles sediment and become visible at ∼84 km before they eventually sublimate at lower altitudes (e.g., Turco et al., 1982; Jensen and Thomas, 1988; Berger and von Zahn, 2002). Typical NLC radii are in the 10 to 80 nm range (Rusch et al., 1991; von Cossart et al., 1999; Robert et al., 2009 ). The uptake of water at higher altitudes and its release at lower altitudes leads to a redistribution of water vapour inside and 20 well below the NLC layer (e.g., von Zahn and Berger, 2003). Although the temperature measurements of Lübken et al. (2009) indicate that homogeneous ice nucleation can be possible at the polar summer mesopause, it is generally believed that at typical supersaturation levels during the NLC season condensation nuclei are required for the Abstract 25 board NASA's Aura satellite. The question of changed atmospheric dynamics is not addressed here. Abstract 20 + 3.53068 ln(T ) − 0.00728332 T ) 1154 Abstract 25 Abstract 20 is assumed to linearly increase from 1.5 cm s −1 at 75 km to 4 cm s −1 at 85 km, and then linearly decrease to 2 cm s −1 at 91 km. This resembles the vertical wind profile of Rapp and Thomas (2006) . Equation (5) is solved by the means of the Crank-Nicolson Abstract 1175 Abstract 1177
doi:10.5194/acpd-12-1151-2012 fatcat:v4fwn5bv7nacxiic6qjvczst5y