HR: 0800h
AN: A31A-0052    [Abstracts]
TI: Low cloud amount and cosmic ray induced ionization: Correlated latitudinal variations
AU: Usoskin, I
EM: ilya.usoskin@oulu.fi
AF: Sodankyla Geophysical Observatory, Tahtela, Sodankyla, 99600 Finland
AU: Marsh, N
EM: ndm@dsri.dk
AF: Danish Space Research Institute, Juliane Maries Vej, Copenhagen, 2100 Denmark
AU: * Mursula, K
EM: kalevi.mursula@oulu.fi
AF: University of Oulu, Linnanmaa, Oulu, 90014 Finland
AU: Gladysheva, O
EM: pca00885@mail.admiral.ru
AF: Ioffe Phys.-Tech. Institute, Polytekhnicheskaya, St.Peteresburg, 194021 Russian Federation
AU: Kovaltsov, G
EM: Gena.Kovaltsov@pop.ioffe.rssi.ru
AF: Ioffe Phys.-Tech. Institute, Polytekhnicheskaya, St.Peteresburg, 194021 Russian Federation
AB: A highly significant correlation between the annual flux of cosmic rays at the Earth's orbit and the amount of low clouds has recently been found for the past 20 years. However, a comprehensive physical explanation still remains elusive. We have calculated the tropospheric ionization caused by a cosmic ray induced nucleonic-electromagnetic cascade in order to study the relation between the cosmic ray induced ionization and the global distribution of the observed low cloud amount. We find that the time evolution of the low cloud amount can be decomposed into a long-term trend and inter-annual variations, the latter depicting a clear 11-year cycle with very strong correlation (r=0.84) with cosmic ray induced ionization. We also find that the relative inter-annual variability in low cloud amount increases polewards from the equator and exhibits a highly significant one-to-one relation with inter-annual variations in the ionization over a large latitude range. This latitudinal dependence gives strong support for the hypothesis that cosmic ray induced ionization modulates cloud properties.
DE: 2104 Cosmic rays
DE: 2162 Solar cycle variations (7536)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting