Seminar Announcement ESP

[Adrian Tompkins]

*Seminar Announcement*

_May 3 2022  3:30 pm CET_
*
*
*Annalisa Bracco
*/Professor at Earth and Atmospheric Sciences, Georgia Institute of 
Technology
Atlanta, U.S.A./
https://eas.gatech.edu/people/bracco-dr-annalisa*
<https://atmos.colostate.edu/~davet/>*

*"Exploring the Manifold of the Tropical Pacific in Observations and 
Models"*

_Abstract_
The climate system is multiscale, multidimensional and nonlinear. Here 
we propose a robust framework for visualizing and analyzing its 
dynamics, accounting for both dependencies and nonlinearities. At each 
time t, the system is uniquely described by a state space vector 
parameterized by N variables and their spatial variability. The dynamics 
is confined on a manifold with dimension lower than the full state space 
and a strategy for manifold learning is presented via linear and 
nonlinear algorithms. We focus on the Tropical Pacific Ocean using a 
reanalysis as observational proxy (ERA5) and two state-of-the-art models 
from the CMIP6 catalog, MPI and EC-Earth3.

The analysis spans four variables over two 40 years periods at daily 
frequency, during historical times and in the SSP585 scenario. The 
manifold learning step allows for comparing nonlinear contributions as 
well as the relative role of each variable in the system's dynamics. 
Instantaneous properties of the high dimensional attractor are then 
quantified through the local dimension and persistence metrics, recently 
introduced to the climate community.

These metrics quantify geometrical properties of the manifold and the 
stability of local motions. Both models underestimate the average 
dimension and overestimate the potential predictability of Tropical 
Pacific climate compared to ERA5, which is indicative of common and 
persistent differences between modelled and observed dynamics. These 
model's biases are nearly identical during the historical period while 
diverging in the global warming scenario analyzed.


-- 
Adrian Tompkins          | Earth System Physics
+39 040 2240579 (office) | ICTP
office 251, ex sissa bld | Strada Costiera 11
www.ictp.it/~tompkins     | 34151 Trieste, Italy