Index Geophysics

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

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).

Olivié, D. J. L.

Velthoven, P. F. J.

Beljaars, A. C. M.

2018-06-28

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10.5194/acp-4-2313-2004

https://acp.copernicus.org/articles/4/2313/2004/

eISSN: 1680-7324

eng