The paper assesses the difficulties of running an operational NWP model in the resolution range of 3-8 km. In this case, deep convection cells are neither much smaller than the grid box as assumed by most parameterization schemes, nor completely resolved as would be required for them to be treated explicitly. A specific approach is proposed, with an integrated sequential treatment of resolved condensation, deep convection, and microphysics together with the use of prognostic variables. It currently allows for the production of consistent and realistic results at resolutions ranging from a few tens of kilometers down to less than 4 km. Model skill scores and an example of an operational forecast at different resolutions are presented.

SUMMARYThe adaptation of a convective parametrization to high resolution has been successfully performed, to a certain point, by refinements in the representation of the entrainment, detrainment and some other features of the original general-circulation-model oriented scheme. But, passing to resolutions below 10 km requires dispensing with some fundamental hypotheses, starting with quasi-equilibrium and the assumption of negligible up-and downdraught mesh fractions. A prognostic scheme has been used for the draughts' vertical velocities and mesh fractions. The prognostic closure of the convective scheme has many benefits, but additional enhancements are required, starting with a coherent treatment of the cloud condensates and a more integrated combination of the different schemes producing condensation, cloud and precipitation.

ABSTRACT:The integration into a coherent package of the main 'moist' parametrizations -deep convection, resolved condensation, and microphysics -of a limited-area model is presented. The development of the package is aimed at solving efficiently the problem of combining 'resolved' and 'subgrid' condensation at all resolutions, in particular in the range between 10 km and 2 km where deep convection is partly resolved, partly subgrid. The different schemes of the package are called in cascade, with intermediate updating of internal variables, so that, for instance, the initial profiles passed to the deep-convection scheme are already balanced with respect to resolved condensation effects. Further on, the clean separation of the contributions to the closure of the updraught and downdraught from the initial vertical profile from which they evolve prevents double counting. The convective parametrization works with a prognostic mass-flux scheme, and acts on the resolved variables through condensation and convective transport. It detrains condensates that are added to the prognostic resolved condensates. A sensitivity study in a single-column model, and further validation in three-dimensional experiments at different resolutions, are presented.

Using the regional climate model ALARO-0, the Royal Meteorological Institute of Belgium and Ghent University have performed two simulations of the past observed climate within the framework of the Coordinated Regional Climate Downscaling Experiment (CORDEX). The ERA-Interim reanalysis was used to drive the model for the period 1979-2010 on the EURO-CORDEX domain with two horizontal resolutions, 0.11 and 0.44 •. ALARO-0 is char-acterised by the new microphysics scheme 3MT, which allows for a better representation of convective precipitation. In Kotlarski et al. (2014) several metrics assessing the performance in representing seasonal mean near-surface air temperature and precipitation are defined and the corresponding scores are calculated for an ensemble of models for different regions and seasons for the period 1989-2008. Of special interest within this ensemble is the ARPEGE model by the Centre National de Recherches Météorologiques (CNRM), which shares a large amount of core code with ALARO-0. Results show that ALARO-0 is capable of representing the European climate in an acceptable way as most of the ALARO-0 scores lie within the existing ensemble. However, for near-surface air temperature, some large biases, which are often also found in the ARPEGE results, persist. For precipitation , on the other hand, the ALARO-0 model produces some of the best scores within the ensemble and no clear resemblance to ARPEGE is found, which is attributed to the inclusion of 3MT. Additionally, a jackknife procedure is applied to the ALARO-0 results in order to test whether the scores are robust , meaning independent of the period used to calculate them. Periods of 20 years are sampled from the 32-year simulation and used to construct the 95 % confidence interval for each score. For most scores, these intervals are very small compared to the total ensemble spread, implying that model differences in the scores are significant.

Closure is a problem of defining the convective intensity in a given parameterization. In spite of many years of efforts and progress, it is still considered an overall unresolved problem. The present article reviews this problem from phenomenological perspectives.

The physical variables that may contribute in defining the convective intensity are listed, and their statistical significances identified by observational data analyses are reviewed. A possibility is discussed for identifying a correct closure hypothesis by performing a linear stability analysis of tropical convectively coupled waves with various different closure hypotheses. Various individual theoretical issues are considered from various different perspectives. The review also emphasizes that the dominant physical factors controlling convection differ between the tropics and extra-tropics, as well as between oceanic and land areas.

Both observational as well as theoretical analyses, often focused on the tropics, do not necessarily lead to conclusions consistent with our operational experiences focused on midlatitudes. Though we emphasize the importance of the interplays between these observational, theoretical and operational perspectives, we also face challenges for establishing a solid research framework that is universally applicable. An energy cycle framework is suggested as such a candidate