Datensatz

Zusammenfassung

This work reassesses the global atmospheric budget of H2 with the TM5 model. The recent adjustment of the calibration scale for H2 translates into a change in the tropospheric burden. Furthermore, the ECMWF Reanalysis-Interim (ERA-Interim) data
from the European Centre for Medium-Range Weather Forecasts (ECMWF) used in this
study show slower vertical transport than the operational data used before. Consequently,
more H2 is removed by deposition. The deposition parametrization is updated because
significant deposition fluxes for snow, water, and vegetation surfaces were calculated in
our previous study. Timescales of 1–2 h are asserted for the transport of H2 through the
canopies of densely vegetated regions. The global scale variability of H2 and ıD[H2] is
well represented by the updated model. H2 is slightly overestimated in the Southern
Hemisphere because too little H2 is removed by dry deposition to rainforests and
savannahs. The variability in H2 over Europe is further investigated using a
high-resolution model subdomain. It is shown that discrepancies between the model and
the observations are mainly caused by the finite model resolution. The tropospheric
burden is estimated at 165 ˙ 8 Tg H2. The removal rates of H2 by deposition and
photochemical oxidation are estimated at 53 ˙ 4 and 23 ˙ 2 Tg H2/yr, resulting in a
tropospheric lifetime of 2.2 ˙ 0.2 year.