EUROCS

(EUROpean Cloud Systems)

Project Funded by the European Community

Summary
Objectives
Project Outline
Project Participants
Project Coordinators
Case Studies
Pacific Intercomparison Case for 3D GCMs

Summary

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:

  1.  stratocumulus over ocean,
  2.  diurnal cycle of cumulus,
  3.  diurnal cycle of precipitating deep convection over continents,
  4.  sensitivity of deep convection development on the moisture profile.
These issues are considered of great magnitude as they lead to major deficiencies in the predicted global and regional climates (Figure 1). Some of these issues have been addressed in the past, but others as of yet have not.

Figure 1: Comparison of the ECMWF Re-Analysis with
FIRE I Observations: Diurnal Variation of Marine Stratocumulus by P. G. Duynkerke and J. Teixiera.

The strategy used in EUROCS to address these issues is based on the use of a hierarchy of models and observations to integrate cloud studies across the full range of scales. Numerical models range from General Circulation Models (GCMs) through Single Column models (SCMs) to Cloud Resolving Models (CRMs) and Large Eddy Simulations (LES). Observations which will be used will vary from global satellite measurements to local observations of individual clouds through lidar and millimetric radars.

The specific aims of the project are:

To produce comprehensive 4-D data sets using several LES models and CRMs on cases defined above which address critical problems associated with the prediction of cloud in regional and global climate and Numerical Weather Prediction (NWP) models.

To use the LES/CRM data sets to investigate deficiencies in climate and NWP models using 9 different SCMs as a test bed. Specific issues to be addressed will be the general failure of climate regional and global models to predict stratocumulus amounts, the diurnal triggering of boundary layer convection and deep precipitating convection over land, and the lack of sensitivity of deep convection development on moisture profile in these models. Once the reasons of deficiency are identified, physically-grounded corrections will be brought in SCMs.

To improve climate and NWP models ability to represent both the mean structure (horizontally and vertically) as well as time variability of cloud water and cover for the critical cases defined above. Six different European climate models will be used in EUROCs making it of large benefit to the whole community.

To bring together a critical mass of the scientific community across Europe working in various areas of Cloud and Climate research, with the focused aim of improving cloud representations in climate and NWP models.

Objectives

The project mainly aims to improve the treatment of cloud systems in global and regional climate models, which directly relates to the RTD priority 2.1.3 "improved model treatment of physical processes (in particular clouds)." In addition, benefits will also be gained for hydrology and severe weather issues (RTD 1.5.2 "Improved flood and drought forecasting")..

Clouds probably remain the largest source of uncertainty affecting evaluations of climate change in response to anthropogenic change. That explains for a large part why the range of simulated temperature changes in response to a CO2 doubling (1.5 to 4.5 C) is quite invariant for almost 20 years (e.g. Report of latest Intergovernmental Panel on Climate Change: Dickinson et al. 1996). The recent interest to develop capability to predict regional climate changes stress the importance to better represent clouds in models. For example, the prediction of distributions of mean and extreme precipitation is highly dependent on the cloud representation in models. The climate community must thus give more consideration to the problem of cloud representation in General Circulation Models (GCMs) and Limited Area Models (LAMs) which are applied to climate issues. As most of European models applied to climate issues are also used to produce short and medium range forecasts, prediction of severe weather systems will directly benefit from EUROCS. 

The present investigators have chosen to concentrate their efforts on 4 major and well identified deficiencies of climate models: 

·stratocumulus over ocean,

·diurnal cycle of cumulus,

·diurnal cycle of precipitating deep convection over continents,

·sensitivity of deep convection development on the moisture profile.

Project Outline

The strategy to be used in EUROCS (Figure 2) is based on the use of a hierarchy of models and observations to integrate cloud studies across the full range of scales (Figure 1). Numerical models range from General Circulation Models (GCMs) through Single Column Models (SCMs) to Cloud Resolving Models (CRMs) and Large Eddy Simulations (LES). All these models exist in Europe but need to be applied along a coordinate way to efficiently solve the issues addressed by EUROCS. Table 1 illustrates the summary of Partners and their corresponding numbering together with the type of numerical models used in Eurocs.

Partners
Numbering
CRM/LES
SCM
GCM
CNRM-GAME (CNRS & Meteo-France)
P1
Yes
Yes
Yes
ECMWF
P2
No
Yes
Yes
UKMO
P3
Yes
Yes
Yes
IMAU (University of Utrecht)
P4
Yes
Yes
No
INM
P5
Yes
Yes
No
SMHI
P6
No
No
Yes
LMD (CNRS)
P7
No
Yes
Yes
MPI (MPG-IMET)
P8
Yes
Yes
Yes
KNMI
P9
Yes
Yes
No
UL (ICTE)
P10
No
Yes
No
Table 1: List of EUROCS Partners and their models. CRM and LES stands for Cloud Resolving Models and
Large Eddies Simulation Models respectively. SCM and CM stands for Single-Column Models and Climate
Models respectively.

To evaluate and to improve cloud parameterization in GCMs, 9 different SCMs will be used. Five SCMs represent a single column of GCM with the same physical package as the full GCM. Results of SCM can thus be directly compared and the 4D dataset generated by LES/CRM used to improve the GCM/SCM parameterizations. 

The last step of the strategy is to run 5 different GCMs including improvements of cloud representations and to look at the general representation of clouds and dynamic features, focusing on diurnal variations of shallow and deep convection and stratocumulus cover as compared to available satellite observations (ERBE, ISCCP, CLAUS) and results from runs with previous cloud representation. A Limited Area Model (LAM) will also be used to look at the impact of improved cloud parameterization in the prediction of regional climate.

The project has been designed around 5 main workpackages WP1 to WP5.

WP1 and WP2 will be concerned with the production of a 4D comprehensive data set using LES/CRMs on the 4 chosen cases addressing the major issues identified above. The results of LES/CRMs will be inter-compared and observed. Activities in WP1 and WP2 will occur within the first 18 months.

WP3 and WP4 will use the datasets issued from WP1 and WP2 together with SCM to identify the reasons for deficiencies of cloud representation in GCMs. Once the reasons for deficiencies have been identified, physically-grounded corrections will be included in the SCMs. To achieve the goals of WP3 and WP4, the partners involved will need new diagnoses from LES/CRMs simulations.

WP5 will use the first improved cloud representation in 5 different GCMs and 1 LAM to provide a framework where all the interactions are present. GCMs will carry out model integrations at the seasonal time scale (3 months or more, for different seasons). Preliminary tests of new cloud schemes will also be made on 10-day periods. Some long climates at high horizontal resolution will also be performed with the regional model forced by ECMWF analysis. A first comparison of characteristics of stratocumulus, diurnal cycle of shallow and deep convection as simulated by current and improved GCMs with available satellite observations (ERBE, ISCCP, CLAUS) will be made.

The last six months of the project will be partly devoted to finalizing the improvement of cloud schemes. The comparison with satellite observations of 6 climate models will give insights on the effect of the first set of improved cloud schemes. Some deficiencies are to be expected between simulations and observations. Inter-comparison of climate models on specific points will be useful from this point of view. At this stage, it will then be important to make new changes in cloud schemes using the CRM datasets and SCMs. Final climate runs will be made with these last improvements as well as final comparisons with satellite observations. 

Project Participants

Participant (P)
Contractors
Country
P1
Centre National de la Recherche Météorologique/Groupe d’Etude de l’Atmosphere Meteorologique
France
P2
European Centre for Medium-range Weather Forecasts
United Kingdom
P3
UK Meteorological Office
United Kingdom
P4
Utrecht University
The Netherlands
P5
Instituto Nacional de Meteorologia
Spain
P6
Swedish Meteorological and Hydrological Institute
Sweden
P7 
Laboratoire de Météorologie Dynamique 
France
P8
Max-Planck-Institut fuer Meteorologie
Germany
P9
Royal Netherlands Meteorological Institute
The Netherlands
P10
University of Lisbon
Portugal
Project Coordinators

Project Coordinator:
P1Jean-Luc REDELSPERGER – CNRM-GAME

Laboratory Coordinators:
P2Anton BELJAARS - ECMWF
P3Stephen DERBYSHIRE - UK Meteorological Office
P4Peter DUYNKERKE - Utrecht University
P5Joan CUXART RODAMILANS - Instituto Nacional de Meteorologia
P6Colin JONES - Rossby Center, SMHI
P7Jean-Yves GRANDPEIX - LMD
P8Andreas CHLOND - Max Planck – Institut Für Meteorologie
P9Pier SIEBESMA - KNMI
P10Pedro MIRANDA - ICTE – Centro de Geofisica, Universidade De Lisboa 

Case Studies

I.Stratocumulus over the ocean -Peter Duynkerke & Stephan De Roode

II.Diurnal cycle of cumulus-Geert Lenderink & Pier Siebesma

III.Diurnal cycle of precipitating deep convection over continents-Françoise Guichard and Jon Petch

IV.Sensitivity of deep convection development on the moisture profile-Stephen Derbyshire

Pacific Intercomparison Case for 3D GCMsGeert Lenderink & Pier Siebesma