1. 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 am
    Conference Room Bldg 815E

    Hosted by: Mike Jensen

    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.