Atmospheric molecular hydrogen (H₂): observations at the high-altitude site Jungfraujoch, Switzerland

Abstract

Measurements of H₂ at the high-altitude site of Jungfraujoch, Switzerland are reported upon for the period of August, 2005-November, 2009. The time series consists of measurements that are primarily representative of free tropospheric background conditions. Highest background H₂ mixing ratios were observed in May, while the lowest were observed in November. The mean seasonal H₂ peak-to-trough amplitude of 21 parts per billion (ppb, 10^-9 dry air mixing ratio) at Jungfraujoch was considerably less than at other stations at similar latitudes and the seasonal minimum in November was comparatively delayed. These differences are primarily attributed to a dampening and delay of the surface soil sink signal during its vertical propagation to the free troposphere. Excess (mixing ratio minus corresponding baseline value) H₂ (₂) and excess CO (CO) displayed no significant correlation. This lacking correlation is attributed to H₂ removal by soil during transport to Jungfraujoch, thereby significantly altering the H₂CO ratio from traffic combustion sources, which is the largest source of anthropogenic H₂ influencing measurements at Jungfraujoch.