Relationship between time series cosmic ray data and aerosol optical properties: 1999–2015

High energy cosmic ray (CR) particles are capable of ionizing the Earth's atmosphere, which lead to changes in the atmospheric properties that affect its physical and chemical characteristics. One of the most important results of the interactions between the CR particles and the atmospheric molecules is the formation of aerosol and its subsequent condensation processes. In this study, the relationship between the time series of the aerosol optical properties; namely the aerosol optical depth (AOD) and Angstrom exponent (α), and the CR muons and neutrons was investigated and established. AOD and α monthly mean data were obtained from the AERONET site located in central Saudi Arabia (24.91° N, 46.41° E, 760 m), for the period of 1999–2015 and the corresponding CR data from Oulu neutron monitor were used for these investigations. Cosmic ray data for the period of 2002–2012 obtained from KACST muon detector were also used in this study. Correlation analyses between the time series of CR data (measured by NM and muon detector) and the aerosol optical properties were carried out and showed significant correlations between these variables. While AOD was positively correlated with the CR data, α showed the opposite.