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

[摘要] Boundary layer turbulence has a profound influence on the distribution oftracers with sources or sinks at the surface. The 40-year ERA-40meteorological data set of the European Centre for Medium-range WeatherForecasts contains archived vertical diffusion coefficients. We evaluated theuse of these archived diffusion coefficients versus off-line diagnosedcoefficients based on other meteorological parameters archived during ERA-40by examining the influence on the distribution of the radionuclide²²²Rn in the chemistry transport model TM3. In total four differentsets of vertical diffusion coefficients are compared: (i) 3-hourly verticaldiffusion coefficients archived during the ERA-40 project, (ii) 3-hourlyoff-line diagnosed coefficients from a non-local scheme based onHoltslag and Boville (1993), Vogelezangand Holtslag (1996), and Beljaars and Viterbo (1999), (iii) 6-hourlycoefficients archived during the ERA-40 project, and (iv) 6-hourly off-linediagnosed coefficients based on a local scheme described in Louis (1979) and Louis et al. (1982). The diffusion scheme to diagnose the coefficientsoff-line in (ii) is similar to the diffusion scheme used during the ERA-40project (i and iii).

[学科分类] 大气科学