Intraseasonal atmospheric variability under climate trends

Area of Science:

• Atmospheric Science
• Climate Dynamics
• Nonautonomous Dynamical Systems

Background:

• Low-order climate models are crucial for understanding low-frequency atmospheric variability.
• Anthropogenic climate change may significantly affect this variability.
• Conceptual models offer insights into complex atmospheric dynamics.

Purpose of the Study:

• To investigate the impact of seasonal and climate change forcing on mid-latitude atmospheric circulation using a conceptual model.
• To analyze changes in atmospheric attractors and their predictability under different forcing scenarios.
• To assess the robustness of climate models in representing internal variability shifts.

Main Methods:

• Bifurcation analysis of an autonomous model with time-independent forcing.
• Study of a nonautonomous system with seasonally varying heat flux.
• Comparison of attractors between autonomous and seasonally forced models.
• Analysis of forward attractors under climate change trends (time-dependent forcing).

Main Results:

• Seasonal forcing alters attractor shape, reducing summer predictability and favoring winter energy transport.
• Climate change forcing shows jet speed may not consistently follow thermal contrast changes.
• Changes in eddy energy transport are observed under climate trends.
• Chaotic behavior can be suppressed or induced, and circulation patterns may shift or disappear.

Conclusions:

• The forward attractor analysis in time-dependent forcing is a robust tool for studying climate trend impacts on internal variability.
• Seasonal forcing significantly modifies atmospheric circulation dynamics and predictability.
• Climate change can lead to non-intuitive responses in jet speed and eddy energy transport.