English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

On the potential of assimilating meteorological analyses in a global climate model for the purpose of model validation

MPS-Authors
/persons/resource/persons37144

Feichter,  Johann
MPI for Meteorology, Max Planck Society;

/persons/resource/persons37102

Bengtsson,  Lennart
MPI for Meteorology, Max Planck Society;

External Resource
No external resources are shared
Fulltext (restricted access)
There are currently no full texts shared for your IP range.
Fulltext (public)

96JD01218.pdf
(Publisher version), 2MB

Supplementary Material (public)
There is no public supplementary material available
Citation

Jeuken, A. B. M., Siegmund, P. C., Heijboer, L. C., Feichter, J., & Bengtsson, L. (1996). On the potential of assimilating meteorological analyses in a global climate model for the purpose of model validation. Journal of Geophysical Research: Atmospheres, 101, 16939-16950. doi:10.1029/96JD01218.


Cite as: https://hdl.handle.net/21.11116/0000-0006-9DD3-B
Abstract
A simple four-dimensional assimilation technique, called Newtonian relaxation, has been applied to the Hamburg climate model (ECHAM), to enable comparison of model output with observations for short periods of time. The prognostic model variables vorticity, divergence, temperature, and surface pressure have been relaxed toward European Center for Medium-Range Weather Forecasts (ECMWF) global meteorological analyses. Several experiments have been carried out, in which the values of the relaxation coefficients have been varied to find out which values are most usable for our purpose. To be able to use the method for validation of model physics or chemistry, good agreement of the model simulated mass and wind field is required. In addition, the model physics should not be disturbed too strongly by the relaxation forcing itself. Both aspects have been investigated. Good agreement with basic observed quantities, like wind, temperature, and pressure is obtained for most simulations in the extratropics. Derived variables, like precipitation and evaporation, have been compared with ECMWF forecasts and observations. Agreement for these variables is smaller than for the basic observed quantities. Nevertheless, considerable improvement is obtained relative to a control run without assimilation. Differences between tropics and extratropics are smaller than for the basic observed quantities. Results also show that precipitation and evaporation are affected by a sort of continuous spin-up which is introduced by the relaxation: the bias (ECMWF-ECHAM) is increasing with increasing relaxation forcing. In agreement with this result we found that with increasing relaxation forcing the vertical exchange of tracers by turbulent boundary layer mixing and, in a lesser extent, by convection, is reduced.