Martedì 3 maggio alle ore 15.30 si terrà via Zoom il sesto seminario della serie “Weather and Climate: From Fundamentals to Applications”. Maggiori informazioni sull’iniziativa, così come il modulo di pre-registrazione Zoom ed il programma completo possono essere trovati a questo link.

Il seminario, dal titolo Exploring the Manifold of the Tropical Pacific in Observations and
Models, sarà ospitato dall’Università di Trento e tenuto da Annalisa Bracco (Earth and Atmospheric Sciences, Georgia Institute of Technology).

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.