Environmental & Climate Sciences Department Seminar

"Using satellite observations to evaluate the representation of clouds in climate models"

Presented by Gregory Cesana, Jet Propulsion Laboratory

Friday, October 28, 2016, 11:00 am — Conference Room Bldg 815E

The ubiquitous presence of clouds within the troposphere (global total cloud frequency about 70%) strongly characterizes the radiative balance of the earth-atmosphere system. Knowledge of the distribution of clouds and their response to a warmer climate are crucial to anticipate the evolution of our future climate. Yet, this challenge remains subject to large uncertainties in climate modeling, wherein the vertical structure of clouds plays a crucial role. Due to the potential for significant variations in the height, temperature and microphysical properties of a cloud, there is a significant range of radiative impacts from clouds.

In this presentation, I will take advantage of active sensor observations from the CALIPSO satellite and recent climate simulations from multi-model experiments to characterize systematic biases in the representation of clouds and cloud microphysics in contemporary climate models. To this end, I will introduce the satellite simulator approach, which reduces uncertainties related to instrument biases and ensures a consistent comparison between models and observations. Then, I will show a couple of examples of model biases focused on the vertical structure of clouds and the transition between supercooled liquid clouds and ice clouds. Finally, I will determine whether these biases are systematic or not, and explore their origin.

Hosted by: Mike Jensen

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