Cloud representation in general-circulation models over the northern Pacific Ocean: A EUROCS intercomparison study
Article first published online: 29 DEC 2006
© Royal Meteorological Society, 2004. A. P. Lock's contribution is Crown copyright
Quarterly Journal of the Royal Meteorological Society
Volume 130, Issue 604, pages 3245–3267, October 2004 Part C
How to Cite
Siebesma, A. P., Jakob, C., Lenderink, G., Neggers, R. A. J., Teixeira, J., Van Meijgaard, E., Calvo, J., Chlond, A., Grenier, H., Jones, C., Köhler, M., Kitagawa, H., Marquet, P., Lock, A. P., Müller, F., Olmeda, D. and Severijns, C. (2004), Cloud representation in general-circulation models over the northern Pacific Ocean: A EUROCS intercomparison study. Q.J.R. Meteorol. Soc., 130: 3245–3267. doi: 10.1256/qj.03.146
- Issue published online: 29 DEC 2006
- Article first published online: 29 DEC 2006
- Manuscript Revised: 19 APR 2004
- Manuscript Received: 4 AUG 2003
The EUROCS (EUROpean Cloud Systems study) project aims to improve the treatment of cloud systems in regional and global climate and weather prediction models. This paper reports an intercomparison study of cloud representation over the Pacific Ocean for nine climate and weather prediction models. The study consists of an analysis of a June/July/August 1998 period along an idealized trajectory over the Pacific Ocean that encompasses both the ascending and descending branch of the Hadley circulation. The three cloud types that are studied by EUROCS, stratocumulus, shallow cumulus and deep-convective cloud systems, do all occur in a persistent and geographically separated way, along this trajectory.
The main focus of this study is on processes related to the hydrological cycle within the Hadley circulation. These include the large-scale dynamics (i.e. the strength of the up- and downwelling branches of the Hadley cell), the cloud processes (i.e. cloud cover, cloud amounts and precipitation), and the impact of these processes on the radiation budget both at the top of the atmosphere and at the ocean's surface.
In order to make a quantitative assessment, special care has been taken to select reliable observational datasets. The main conclusions are that (1) almost all models strongly underpredicted both cloud cover and cloud amount in the stratocumulus regions while (2) the situation is opposite in the trade-wind region and the tropics where cloud cover and cloud amount are overpredicted by most models. These deficiencies result in an overprediction of the downwelling surface short-wave radiation of typically 60 W m−2 in the stratocumulus regimes and a similar underprediction of 60 W m−2 in the trade-wind regions and in the intertropical convergence zone (ITCZ). Similar biases for the short-wave radiation were found at the top of the atmosphere, while discrepancies in the outgoing long-wave radiation are most pronounced in the ITCZ. © Royal Meteorological Society, 2004. A. P. Lock's contribution is Crown copyright