Relationships between atmospheric blocking and large-scale modes of climate variability: The key role of the tropical Pacific
Christina
Karamperidou
University of Hawaii
Talk
(Invited)
Large-scale modes of interannual and decadal variability of the coupled ocean-atmosphere
system, such as the Pacific Decadal Variability (PDV), the North Atlantic Oscillation (NAO), the
Atlantic Multi-decadal Variability (AMV), and the El Niño-Southern Oscillation (ENSO), modulate
and/or interact with the location, frequency, and duration of atmospheric blocking. However,
there are significant uncertainties in the strength and direction of these relationships, as well as
in the projected changes of these climate modes under future emissions scenarios. This in turn
enhances the uncertainty surrounding the characteristics of atmospheric blocking in present
and future climates. In this talk, I will first present an overview of such climate mode-blocking
relationships, and will then focus on the role of the tropical Pacific mean climate state and the
superposed interannual variability associated with ENSO. I will show the significant, and often
of opposite sign, impacts of ENSO diversity (Eastern vs. Central Pacific ENSO events) on blocking
in observations and in model simulations with historical, idealized, and pacemaker-style forcing.
I will then show that model biases in simulating ENSO diversity and its relation to the mean
state of the tropical Pacific ultimately reflect onto their simulation of atmospheric blocking at
varying degrees depending on the location, and can lead to cascading uncertainties in its
projected changes. To conclude, I will leverage paleoclimate evidence (data and model
simulations) to examine the relationship between large-scale climate modes and blocking at
longer time-scales, with the goal of constraining future blocking projections to the extent that
they interact with these modes in each region.
system, such as the Pacific Decadal Variability (PDV), the North Atlantic Oscillation (NAO), the
Atlantic Multi-decadal Variability (AMV), and the El Niño-Southern Oscillation (ENSO), modulate
and/or interact with the location, frequency, and duration of atmospheric blocking. However,
there are significant uncertainties in the strength and direction of these relationships, as well as
in the projected changes of these climate modes under future emissions scenarios. This in turn
enhances the uncertainty surrounding the characteristics of atmospheric blocking in present
and future climates. In this talk, I will first present an overview of such climate mode-blocking
relationships, and will then focus on the role of the tropical Pacific mean climate state and the
superposed interannual variability associated with ENSO. I will show the significant, and often
of opposite sign, impacts of ENSO diversity (Eastern vs. Central Pacific ENSO events) on blocking
in observations and in model simulations with historical, idealized, and pacemaker-style forcing.
I will then show that model biases in simulating ENSO diversity and its relation to the mean
state of the tropical Pacific ultimately reflect onto their simulation of atmospheric blocking at
varying degrees depending on the location, and can lead to cascading uncertainties in its
projected changes. To conclude, I will leverage paleoclimate evidence (data and model
simulations) to examine the relationship between large-scale climate modes and blocking at
longer time-scales, with the goal of constraining future blocking projections to the extent that
they interact with these modes in each region.
Presentation file
karamperidou-christina-blocking.pdf
(13.5 MB)
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