How Well Are Clouds Simulated over Greenland in Climate Models? Consequences for the Surface Cloud Radiative Effect over the Ice Sheet

• Published in: Journal of Climate
• Main Authors: Lacour, A., Chepfer, H., Miller, N., B, Shupe, M., D, Noel, V., Fettweis, X., Gallee, H., Kay, J., E, Guzman, R., Cole, J.
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS (UMR_7086)), Université Paris Diderot - Paris 7 (UPD7)-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS), Département de Géographie, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), University of Colorado Boulder, Canadian Centre for Climate Modelling and Analysis (CCCma), Environment and Climate Change Canada (ECCC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: Atmosphere; Ice sheets; Cloud forcing; Clouds; Snowmelt/icemelt; General circulation models; [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Greenland; Ice Sheet
• Online Access: https://hal.sorbonne-universite.fr/hal-01993084; https://hal.sorbonne-universite.fr/hal-01993084/document; https://hal.sorbonne-universite.fr/hal-01993084/file/jcli-d-18-0023.1_sans%20marque.pdf; https://doi.org/10.1175/JCLI-D-18-0023.1

International audience Using lidar and radiative flux observations from space and ground, and a lidar simulator, we evaluate clouds simulated by climate models over the Greenland ice sheet, including predicted cloud cover, cloud fraction profile, cloud opacity, and surface cloud radiative effects. The representation of clouds over Greenland is a central concern for the models because clouds impact ice sheet surface melt. We find that over Greenland, most of the models have insufficient cloud cover during summer. In addition, all models create too few nonopaque, liquid-containing clouds optically thin enough to let direct solar radiation reach the surface (−1% to −3.5% at the ground level). Some models create too few opaque clouds. In most climate models, the cloud properties biases identified over all Greenland also apply at Summit, Greenland, proving the value of the ground observatory in model evaluation. At Summit, climate models underestimate cloud radiative effect (CRE) at the surface, especially in summer. The primary driver of the summer CRE biases compared to observations is the underestimation of the cloud cover in summer (−46% to −21%), which leads to an underestimated longwave radiative warming effect (CRELW = −35.7 to −13.6 W m−2 compared to the ground observations) and an underestimated shortwave cooling effect (CRESW = +1.5 to +10.5 W m−2 compared to the ground observations). Overall, the simulated clouds do not radiatively warm the surface as much as observed.