[Faculty] Fwd: [CSRC.COLLOQUIUM] "On the Dual Nature of Chaos and Order in Weather and Climate: New Insights and Opportunities Within a Generalized Lorenz Model"

[Jose Castillo]

[image: SDSU_CSRC Logo.jpg]


DATE:
*Friday, November 6, 2020*



TITLE:

*On the Dual Nature of Chaos and Order in Weather and Climate: New Insights
and Opportunities Within a Generalized Lorenz Model*


TIME:
*3:30-4:30PM*




LOCATION:
Join Zoom Meeting -  *https://SDSU.zoom.us/j/91071174391*
<https://sdsu.zoom.us/j/91071174391>



SPEAKER/BIO:

*Dr. Bo-Wen Shen, Mathematics and Statistics, San Diego State University *






ABSTRACT:


Over 50 years since Lorenz’s 1963 study and a follow-up presentation in
1972, the statement ``weather is chaotic’’ has been well accepted. Such a
view turns our attention from regularity associated with Laplace’s view of
determinism to irregularity associated with chaos. In contrast to single
type chaotic solutions, recent studies using a generalized Lorenz model
(GLM, Shen 2019a; Shen et al. 2019) have focused on the coexistence of
chaotic and regular solutions that appear within the same model using the
same modeling configurations but different initial conditions. The results,
with attractor coexistence, suggest that the entirety of weather possesses
a dual nature of chaos and order with distinct predictability (e.g., Shen
et al. 2020). The refined view on the dual nature of weather is neither too
optimistic nor pessimistic as compared to the Laplacian view of
deterministic predictability that is unlimited and the Lorenz view of
deterministic chaos with finite predictability. The refined view may unify
our theoretical understanding of different predictability within various
types of solutions of Lorenz models and recent numerical simulations of
advanced global weather/climate models that can simulate large-scale
tropical systems (e.g., African easterly waves and Madden-Julian
Oscillations) beyond two weeks (e.g., Shen 2019b; Judt 2020).

In this study, based on the GLM, we discuss the following two mechanisms
that may enable or modulate two kinds of attractor coexistence and, thus,
contribute to distinct predictability: (1) the aggregated negative feedback
of small-scale convective processes that can produce stable non-trivial
equilibrium points and, thus, enable the appearance of stable steady-state
solutions and their coexistence with chaotic or nonlinear oscillatory
solutions, referred to as the 1st and 2nd kinds of attractor coexistence;
and (2) the modulation of large-scale time varying forcing (heating) that
can determine (or modulate) the alternative appearance of two kinds of
attractor coexistence.  Based on our results, we then discuss new
opportunities and challenges in predictability research with the aim of
improving predictions at extended-range time scales, as well as
sub-seasonal to seasonal time scales.




Host: Jose Castillo

Note: Videos of previous colloquium talks can be seen on the CSRC website
in the colloquium archive section or on the CSRC YouTube page here
<https://www.youtube.com/channel/UCN0ZEztlmyDqG2pm-Rle_Eg/feed>.




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