Evaluation of archived and off-line diagnosed vertical diffusion coefficients from ERA-40 with ²²²Rn simulations

D. J. L. Olivié (1, 2) , P. F. J. van Velthoven (2) , A. C. M. Beljaars (3)

1 TU/e - Eindhoven University of Technology [Eindhoven]
2 KNMI - Royal Netherlands Meteorological Institute
3 ECMWF - European Centre for Medium-Range Weather Forecasts

Boundary layer turbulence has a profound influence on the distribution of tracers with sources or sinks at the surface. The 40-year ERA-40 meteorological data set of the European Centre for Medium-range Weather Forecasts contains archived vertical diffusion coefficients. We evaluated the use of these archived diffusion coefficients versus off-line diagnosed coefficients based on other meteorological parameters archived during ERA-40 by examining the influence on the distribution of the radionuclide ²²²Rn in the chemistry transport model TM3. In total four different sets of vertical diffusion coefficients are compared: (i) 3-hourly vertical diffusion coefficients archived during the ERA-40 project, (ii) 3-hourly off-line diagnosed coefficients from a non-local scheme based on Holtslag and Boville (1993), Vogelezang and Holtslag (1996), and Beljaars and Viterbo (1999), (iii) 6-hourly coefficients archived during the ERA-40 project, and (iv) 6-hourly off-line diagnosed coefficients based on a local scheme described in Louis (1979) and Louis et al. (1982). The diffusion scheme to diagnose the coefficients off-line in (ii) is similar to the diffusion scheme used during the ERA-40 project (i and iii).

Domaines: Océan, Atmosphère

D. J. L. Olivié, P. F. J. van Velthoven, A. C. M. Beljaars. Evaluation of archived and off-line diagnosed vertical diffusion coefficients from ERA-40 with ²²²Rn simulations. Atmospheric Chemistry and Physics, 2004, 4 (9/10), pp.2313-2336. ⟨hal-00295554⟩