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Resolving away stratocumulus biases in modern global climate models

Presentation Date
Friday, December 16, 2022 at 2:45pm - Friday, December 16, 2022 at 6:15pm
McCormick Place - Poster Hall, Hall - A



The longstanding difficulty of representing boundary layer clouds in state-of-the-art global atmospheric models limits our ability to represent aerosol-cloud radiative forcing and cloud feedbacks, and to improve future climate projections. We have shown that high vertical resolution – a missing component of current largescale models – has a major impact on the representation of low-level clouds: the marine stratocumulus bias, especially offshore, is significantly reduced when applying the kind of high vertical resolution typically used in large eddy simulations – and without tuning. In this study we use the Energy Exascale Earth System Model (E3SM) coupled with the Framework for Improvement by Vertical Enhancement (FIVE) to demonstrate significant improvement in coastal stratocumulus. FIVE embeds an auxiliary column with a fine vertical grid in the host model grid column and computes selected one-dimensional processes thereon. We show that concurrent enhancement of horizontal and vertical resolution is essential to achieve substantial reduction of persistent marine stratocumulus biases over coastal regions. We hypothesize that better resolved topography near the coast with high horizontal resolution promotes atmospheric conditions that are more conducive to stratocumulus formation. Under these conditions, the resolution of the cloud-top inversion afforded by high vertical resolution facilitates the formation and maintenance of coastal marine stratocumulus clouds.

Funding Program Area(s)