Influence of Galactic Cosmic Rays on atmospheric composition and dynamics

• Published in: Atmospheric Chemistry and Physics
• Main Authors: M. Calisto, I. Usoskin, E. Rozanov, T. Peter
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2011
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Greenland; polar night; Siberia
• Online Access: https://doi.org/10.5194/acp-11-4547-2011; https://doaj.org/article/b497ad81dde34c6f8bf8e6458e19b730

This study investigates the influence of the Galactic Cosmic Rays (GCRs) on the atmospheric composition, temperature and dynamics by means of the 3-D Chemistry Climate Model (CCM) SOCOL v2.0. Ionization rates were parameterized according to CRAC:CRII (Cosmic Ray induced Cascade: Application for Cosmic Ray Induced Ionization), a detailed state-of-the-art model describing the effects of GCRs in the entire altitude range of the CCM from 0–80 km. We find statistically significant effects of GCRs on tropospheric and stratospheric NO x , HO x , ozone, temperature and zonal wind, whereas NO x , HO x and ozone are annually averaged and the temperature and the zonal wind are monthly averaged. In the Southern Hemisphere, the model suggests the GCR-induced NO x increase to exceed 10 % in the tropopause region (peaking with 20 % at the pole), whereas HO x is showing a decrease of about 3 % caused by enhanced conversion into HNO 3 . As a consequence, ozone is increasing by up to 3 % in the relatively unpolluted southern troposphere, where its production is sensitive to additional NO x from GCRs. Conversely, in the northern polar lower stratosphere, GCRs are found to decrease O 3 by up to 3 %, caused by the additional heterogeneous chlorine activation via ClONO 2 + HCl following GCR-induced production of ClONO 2 . There is an apparent GCR-induced acceleration of the zonal wind of up to 5 m s −1 in the Northern Hemisphere below 40 km in February, and a deceleration at higher altitudes with peak values of 3 m s −1 around 70 km altitude. The model also indentifies GCR-induced changes in the surface air, with warming in the eastern part of Europe and in Russia (up to 2.25 K for March values) and cooling in Siberia and Greenland (by almost 2 K). We show that these surface temperature changes develop even when the GCR-induced ionization is taken into account only above 18 km, suggesting that the stratospherically driven strengthening of the polar night jet extends all the way down to the Earth's surface.