Using continuous ground-based radar and lidar measurements for evaluating the representation of clouds in four operational models

Dominique Bouniol (1) , Alain Protat (2, 3) , Julien Delanoë (4, 3) , Jacques Pelon (3) , Jean-Marcel Piriou (1) , François Bouyssel (1) , Adrian M. Tompkins (5) , Damian R. Wilson (6) , Yohann Morille (7) , Martial Haeffelin (7) , Ewan J. O'Connor (4, 8) , Robin J. Hogan (4) , Anthony J. Illingworth (4) , David P. Donovan (9) , Henk-Klein Baltink (9)

1 CNRM - Centre national de recherches météorologiques
2 CAWCR - Centre for Australian Weather and Climate Research
3 SPACE - LATMOS
4 Department of Meteorology [Reading]
5 ECMWF - European Centre for Medium-Range Weather Forecasts
6 United Kingdom Met Office [Exeter]
7 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
8 FMI - Finnish Meteorological Institute
9 KNMI - Royal Netherlands Meteorological Institute

The ability of four operational weather forecast models (ECMWF, ARPEGE, RACMO and Met Office) to generate a cloud at the right location and time (the cloud frequency of occurrence) is assessed in the present paper using a two-year time serie of observations collected by profiling ground-based active remote sensors (cloud radar and lidar) located at three different sites in western Europe (Cabauw, NL, Chilbolton, UK, Palaiseau, F.). Particular attention is given to potential biases that may arise from instrumentation differences (especially sensitivity) from one site to another and intermittent sampling. In a second step the statistical properties of the cloud variables involved in most advanced cloud schemes of numerical weather forecast models (ice water content and cloud fraction) are characterized and compared to their counterparts in the models. The two years of observations are first considered as a whole in order to evaluate the accuracy of the statistical representation of the cloud variables in each model. It is shown that all models tend to produce too many high level clouds, with too high cloud fraction and ice water content. The mid-level and low-level cloud occurrence is also generally overestimated, with too low cloud fraction but a correct ice water content. The data set is then divided into seasons to evaluate the potential of the models to generate different cloud situations in response to different large-scale forcings. Strong variations in cloud occurrence are found in the observations from one season to the same season the following year as well as in the seasonal cycle. Overall, the model biases observed using the whole data set are still found at seasonal scale, but the models generally manage to well reproduce the observed seasonal variations in cloud occurrence. Overall, models do not generate the same cloud fraction distributions and these distributions do not agree with the observations. Another general conclusion is that the use of continuous ground-based radar and lidar observations is definitely a powerful tool for evaluating model cloud schemes and for a responsive assessment of the benefit achieved by changing or tuning a model cloud parameterization.

Mots clés: Radar observations; Lidar observations; Surface observations; Clouds; Model initialization

Domaines: Météorologie

Dominique Bouniol, Alain Protat, Julien Delanoë, Jacques Pelon, Jean-Marcel Piriou, et al.. Using continuous ground-based radar and lidar measurements for evaluating the representation of clouds in four operational models. Journal of Applied Meteorology and Climatology, 2010, 49 (9), pp.1971-1991. ⟨10.1175/2010JAMC2333.1⟩. ⟨hal-00477076⟩