Use of CALIPSO lidar observations to evaluate the cloudiness simulated by a climate model

H. Chepfer (1) , S. Bony (1) , D. Winker , Marjolaine Chiriaco (2) , J.‐l. Dufresne (1) , G. Seze (1)

1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
2 SA - Service d'aéronomie

New space-borne active sensors make it possible to observe the three-dimensional structure of clouds. Here we use CALIPSO lidar observations together with a lidar simulator to evaluate the cloudiness simulated by a climate model: modeled atmospheric profiles are converted to an ensemble of subgrid-scale attenuated backscatter lidar signals from which a cloud fraction is derived. Except in regions of persistent thick upper-level clouds, the cloud fraction diagnosed through this procedure is close to that actually predicted by the model. A fractional cloudiness is diagnosed consistently from CALIPSO data at a spatiotemporal resolution comparable to that of the model. The comparison of the model's cloudiness with CALIPSO data reveals discrepancies more pronounced than in previous model evaluations based on passive observations. This suggests that space-borne lidar observations constitute a powerful tool for the evaluation of clouds in large-scale models, including marine boundary-layer clouds.

Domaines: Planète et Univers [physics]

H. Chepfer, S. Bony, D. Winker, Marjolaine Chiriaco, J.‐l. Dufresne, et al.. Use of CALIPSO lidar observations to evaluate the cloudiness simulated by a climate model. Geophysical Research Letters, 2008, 35 (15), pp.L15704. ⟨10.1029/2008GL034207⟩. ⟨hal-03182933⟩