Meridional heat transports and the general circulation: from global scale to extremes

Online seminar by Dr. Valerio Lembo from Institute of Atmospheric Sciences and Climate, CNR, Italy

26 January 2023
KST 17:00 – 18:00

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Poleward meridional heat transports are the fundamental driver of the inhomogeneous solar radiation absorption by the Earth’s climate system that sets the general circulation of the atmosphere and ocean in motion. A careful characterization of their climatological features and how they respond to an external forcing is thus crucial, in order to correctly detect changes in the dynamics attributable to distinct factors.

In this talk, I will first address globally the poleward meridional heat transports and how these are assessed in state-of-the-art climate models. In particular, I will focus on the role of historical anthropogenic aerosol forcing for energy budget asymmetries and consequent cross-equatorial transports, how this relates to albedo asymmetries, the role of clouds and the double Inter-Tropical Convergence Zone (ITCZ) bias in climate models.

I will then shift to extratropical dynamics and the role of baroclinic eddies for the transport of energy between the subtropical regions and the Poles. Amplifying baroclinic waves are in fact fundamentally intermittent and sporadic, and this has a signature on the net seasonal transport across latitudes. I propose a zonal wavenumber decomposition in order to highlight the role of different eddy scales in different seasons and regions of Northern Hemisphere midlatitudes. Through a Generalized Extreme Value (GEV) methodology, a rigorous algorithm for extreme events detection is implemented, allowing for isolating extreme meridional heat transports and their partitioning into wavenumbers. A weather regime clustering applied on 500 hPa maps is then presented, allowing for attribution of such extreme events to modes of mid-latitudinal atmospheric dynamics.