Convection in Lorenz's global energy cycle with the ECMWF model
Article first published online: 22 AUG 2008
©2008 The Authors Journal compilation © 2008 Blackwell Munksgaard
Volume 60, Issue 5, pages 1001–1022, October 2008
How to Cite
STEINHEIMER, M., HANTEL, M. and BECHTOLD, P. (2008), Convection in Lorenz's global energy cycle with the ECMWF model. Tellus A, 60: 1001–1022. doi: 10.1111/j.1600-0870.2008.00348.x
- Issue published online: 24 SEP 2008
- Article first published online: 22 AUG 2008
- (Manuscript received 19 November 2007; in final form 14 May 2008)
Lorenz's global energy cycle includes the conversion rate C between available potential and kinetic energy. In traditional estimates of C only gridscale processes were evaluated; subgridscale processes were lumped into dissipation. It is argued that this is inadequate; organized subgridscale heat fluxes like deep convection cannot be treated as molecular.
Here both Cgrid and Csub are evaluated from the ECMWF Integrated Forecast System, for a 1-yr forecast in climate mode. The subgridscale fluxes are obtained from the model parametrization and the results tested for consistency; the largest contribution comes from the convection scheme. The integrand of Csub, the familiar ‘buoyancy flux’, is locally much smaller than its gridscale counterpart . However, the buoyancy flux is upward throughout, and thus representative for, the global atmosphere. The global annual means are Cgrid= (3.4 ± 0.1) W m−2 and Csub= (1.7 ± 0.1) W m−2. Further, the gridscale generation rate of available potential energy is evaluated independently and found to be Ggrid= (3.0 ± 0.2) W m−2.
These results suggest that (i) the subgridscale processes contribute significantly to the Lorenz energy cycle and (ii) the cycle, represented by the total dissipation of D= (5.1 ± 0.2) W m−2, is more intense than all earlier gridscale estimates have indicated.