Short-term production and synoptic influences on atmospheric⁷Be concentrations

Variations of the cosmogenic radionuclide ⁷Be in the global atmosphere are driven by cooperation of processes of its production, air transports, and removal. We use a combination of the Goddard Institute for Space Studies Model E and the OuluCRAC:7Be production model to simulate the variations in the ⁷Be concentration in the atmosphere for the period from 1 January to 28 February 2005. This period features significant synoptic variability at multiple monitoring stations around the globe and spans an extreme solar energetic particle (SEP) event that occurred on 20 January. Using nudging from observed horizontal winds, the model correctly reproduces the overall level of the measured ⁷Be concentration near ground and a great deal of the synoptic variability at timescales of 4 days and longer. This verifies the combined model of production and transport of the ⁷Be radionuclide in the atmosphere. The impact of an extreme SEP event of January 2005 is seen dramatically in polar stratospheric ⁷Be concentration but is small near the surface (about 2%) and indistinguishable given the amount of intrinsic variability and the uncertainties of the surface observations.