Evaluation of the cloud thermodynamic phase in CMIP5 models using CALIPSO-GOCCP
Abstract
Evaluation of clouds in climate models is essential judging from the strong impact of clouds on the earth's radiation budget. Cloud phase influences many cloud properties and leads to different cloud interactions with the climate system. Thanks to a new cloud phase diagnosis in the GCM-Oriented CALIPSO Cloud Product (GOCCP) and its counterpart within the lidar simulator, we evaluated the cloud thermodynamic phase in CMIP5 climate models. Comparisons of GOCCP and LMDZ5B show that, contrary to ice clouds, liquid clouds are largely underestimated in the model. Liquid clouds occur at temperatures as cold as -40°C in the observations, but only as cold as -20°C in the model. They are dominant at temperatures warmer than -21°C in observations but only warmer than -12°C in the model. In agreement with theory, statistical observations show that liquid and ice co-exist between 0°C and -40°C, and that the cloud phase depends not only on the temperature but also on humidity. For comparison, ice and liquid do not co-exist in the model, and the modelled cloud phase does not reproduce the observed sensitivity to the atmospheric humidity. A specific focus on Arctic region shows that a lack of liquid-containing Arctic clouds contributes to a lack of 'radiatively opaque' states in LMDZ5B and CAM5 model. The surface radiation biases found in this one model are found in multiple CMIP5 models, highlighting the need for improved modelling of Arctic cloud phase. We used learning from this study to investigate how changes in the LMDZ5B and CNRM cloud phase parameterization impact the mixed phase clouds, their cloud fractions, precipitations, temperatures and radiations for inter-annual and long term simulations. Cloud Phase vertical distribution
Temperature as a function of phase- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A41M..01C
- Keywords:
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- 0321 ATMOSPHERIC COMPOSITION AND STRUCTURE Cloud/radiation interaction;
- 3337 ATMOSPHERIC PROCESSES Global climate models;
- 3360 ATMOSPHERIC PROCESSES Remote sensing;
- 3310 ATMOSPHERIC PROCESSES Clouds and cloud feedbacks