The project EUROCS aims to improve the treatment of cloud systems in global and regional climate models. In addition, benefits will be also gained for hydrology and severe weather issues. Clouds probably remain the largest source of uncertainty affecting evaluations of climate change in response to anthropogenic change. The recent interest to develop capability to predict regional changes of climate, stress also the importance to better represent clouds in models. EUROCS concentrates its efforts on 4 major and well identified deficiencies of climate models:
I. stratocumulus over ocean,
II. diurnal cycle of cumulus,
III. diurnal cycle of precipitating deep convection over continents,
IV. sensitivity of deep convection development on the moisture profile.
This site contains results of an single column model intercomparison of Cumulus clouds and a 3D full GCM intercomparison of clouds in the Hadley circulation. More information on EUROCS can be found at the EUROCS project home page.
EUROCS is funded by the EU FP5 (EVK2 CT1999 0005) (March 2000-Febr 2003)
Intercomparison Study for Single Column Models
The present SCM intercomparison is based on the 6th GCSS WG 1 intercomparison case. This case is based on observations at the ARM site on the Southern Great Plains (USA) on 21st june 1997. During that day Cumulus clouds developed at the top of an initially clear convective boundary layer. The intercomparison case has been developed and coordinated by Andy Brown (UKMO), responsible for the LES models, and Adrian Lock (UKMO), responsible for the SCM models. The original case description by Andy Brown can be obtained here (compessed postscript).
Results of several LES models have been presented at a meeting in Boulder, January 2000. On average, the LES results agreed rather well with each other. All models produced Cumulus clouds in reasonable correspondece with the measurements. Some results of the LES models can be obtained by anonymous ftp to email.meto.gov.uk (cd pub/apr/arm).
However, results of SCMs differed more strongly, and did not match the LES results as closely. Although most SCMs were able to simulate a Cumulus cloud, the SCMs typically suffered from the following deficiencies:
- too high cloud fractions and cloud liquid water.
- difficulties to develop and maintain a conditionally unstable layer.
- considerable numerical noise
Finally, it was felt by most SCM modellers that SCMs are much more sensitive to changes in the forcing or initial profiles than LES models seem to be. The present intercomparison will be focussed on these problems.
Intercomparison Study for 3D GCM's
We want to include full GCMsin the GCSS/EUROCS framework.
Why? SCM/CRM simulations have limitations:
- there are only few cases
- we know little about theirrepresentativeness
Therefore good parametrizations can give bad results and vice versa. Errors in different parts of the modelcontribute to the total error. Hence, we propose to compare GCM simulation along a prescribed cross section representing the Sc to Cu to Cb transition.