[Eoas-seminar] MET Seminar Thursday September 29 3:00-4:15 PM: Dr. Yair Cohen (Climate Modeling Alliance, Caltech)

[eoas-seminar at lists.fsu.edu]

Thursday September 29, that is :-)


——————————————————
Allison Wing, Ph.D.
Associate Professor
Earth, Ocean and Atmospheric Science
Florida State University
awing at fsu.edu<mailto:awing at fsu.edu>




On Sep 23, 2022, at 9:50 AM, eoas-seminar--- via Eoas-seminar <eoas-seminar at lists.fsu.edu<mailto:eoas-seminar at lists.fsu.edu>> wrote:

Dear all,

Please join us for our next Meteorology Seminar, which will be given next Thursday September 29 by Dr. Yair Cohen<https://climate-dynamics.org/people/ycohen/>, a research scientist at the Climate Modeling Alliance at Caltech. Dr. Cohen will speak about “Combining physics and machine learning in the turbulence-convection parameterization of the CliMA climate model”.

Dr. Cohen will be joining us virtually but we will gather in EOA 1044 to participate in the seminar. If you cannot attend in person due to a medical reason or approved work out of town, please contact Allison Wing (awing at fsu.edu<mailto:awing at fsu.edu>) for remote access. Otherwise, we look forward to seeing everyone in 1044! Please join us at 3 PM for refreshments prior to the beginning of the talk at 3:15 PM.

Graduate students are invited to participate in a student-only Q&A with the speaker at 2:15 PM in EOA 6067. This is a great opportunity to meet the speaker and discuss science and work/life/career topics in an informal setting. Dr. Cohen is available for other virtual meetings between 8 - 11 AM on Thursday; please contact Allison Wing (awing at fsu.edu<mailto:awing at fsu.edu>) if you would like to meet with him during that time. If you would like to meet with Dr. Cohen at a different time next week, please get in touch with him directly.

DATE: Thursday September 29
TIME: Refreshments at 3 PM, Talk 3:15 PM - 4:15 PM.
LOCATION: EOA 1044 (speaker remote)
SPEAKER: Dr. Yair Cohen<https://climate-dynamics.org/people/ycohen/>

TITLE: Combining physics and machine learning in the turbulence-convection parameterization of the CliMA climate model

ABSTRACT: The representation of turbulence and convection at the subgrid scale of climate models by various parameterization schemes is one of the largest sources of model uncertainty in long term climate predictions. The crux of these parameterization schemes is the formulation of closure functions for processes that cannot be observed or simulated in high resolution models. In this talk I will present a hybrid approach that combines a physics based parameterization scheme with physical and machine learning (ML) closures. Such a hybrid approach cannot be trained using backpropagation typical to neutral networks, as this requires partial derivatives of the physics+ML setup in parameter space. Instead we use a gradient free (ensemble) method to train physics+ML setup from high resolution LES data. The hybrid approach ensures conservation properties, allows for straightforward interpretability of its data driven components and reduces the degrees of freedom to allow us to train from spares data. The physical model is based on the extended Eddy Diffusivity/Mass Flux (EDMF) scheme, derived by a systematic coarse-graining of the equations of motion and includes subgrid scale memory and prognostic equations for first and second moments. The closures for this scheme combine physical arguments with nondimensional functional forms that can be learned from data using various ML architectures. Our parameterization, in a single column of a climate models, reproduces well the corresponding LES of the full spectrum of boundary layer and turbulent motions: from polar boundary layers (vertical scale of 300m), through the stratocumulus-topped boundary layer (vertical scale of 1km), shallow convection (vertical scale of 3km), and deep convection (vertical scale of 15km). Furthermore, using ML closures we show that a hybrid model is able to extrapolate by training on current climate simulations to a validation set from 4K climate warming scenario.

Cheers,

Allison

On behalf of the MET Seminar Committee



——————————————————
Allison Wing, Ph.D.
Associate Professor
Earth, Ocean and Atmospheric Science
Florida State University
awing at fsu.edu<mailto:awing at fsu.edu>




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