Influence of precipitation on 7Be concentrations in air as measured by CTBTO global monitoring system

• Latitudinal distribution of 7Be concentrations in air is demonstrated.
• The apparent residence time of 7Be aerosols may vary between 10 and 25 days.
• The removal of 7Be increases with increasing air humidity and precipitation.
• The significant decrease in 7Be concentrations within ITCZ is demonstrated.

Data collected by the International Monitoring System (IMS) during 2009–2012 were used to study influence of precipitation and relative humidity on changes in 7Be concentrations in atmosphere. The significant decrease in 7Be concentrations, corresponding to measurements collected by stations located within Intertropical Convergence Zone (ITCZ) is demonstrated. This effect can be attributed to the process of enhanced wet deposition within the ITCZ. To quantify this effect data collected by IMS stations within ITCZ were thoroughly analyzed. It was found that the atmospheric content of 7Be strongly decreases under the rain conditions. The rain mediated depletion of 7Be to half of its before rain value, needs about 62 h in case of light precipitation, while in the case of moderate precipitation about 38 h is needed. In addition the evaluated impact of humidity showed that increase in relative humidity by 20%, for example from 70% ± 5% to 90% ± 5% causes almost a double decrease in beryllium concentration in surface air.