Walker circulation response to extratropical radiative forcing

Abstract

Walker circulation variability and associated zonal shifts in the heating of the tropical atmosphere have far-reaching global impacts well into high latitudes. Yet the reversed high latitude–to–Walker circulation teleconnection is not fully understood. Here, we reveal the dynamical pathways of this teleconnection across different components of the climate system using a hierarchy of climate model simulations. In the fully coupled system with ocean circulation adjustments, the Walker circulation strengthens in response to extratropical radiative cooling of either hemisphere, associated with the upwelling of colder subsurface water in the eastern equatorial Pacific. By contrast, in the absence of ocean circulation adjustments, the Walker circulation response is sensitive to the forcing hemisphere, due to the blocking effect of the northward-displaced climatological intertropical convergence zone and shortwave cloud radiative effects. Our study implies that energy biases in the extratropics can cause pronounced changes of tropical climate patterns.

A stronger versus weaker Walker: understanding model differences in fast and slow tropical Pacific responses to global warming

“…Similarly, they nd that extra-tropical warming is key for driving enhanced tropical warming by slowing down the Hadley cell as well as the oceanic subtropical cells, thereby reducing poleward heat transport. Kang et al (2020) similarly nd in reversed experiments that the Walker cell strengthens in response to extra-tropical cooling for simulations including a dynamic ocean.…”

“…A related question is whether the inability of GCMs to capture the observed recent temperature and wind trends is indeed caused by an inaccurate representation of the transient Indo-Paci c OT response, which may be linked to persistent GCM biases affecting the cold tongue/warm pool complex, equatorial wind stress, the equatorial undercurrent and the ITCZ (e.g. Bellinger et al 2013;Burls et al 2017;Karnauskas et al, 2020;Li and Xie, 2014) as well as extra-tropical biases (Burls and Fedorov, 2014;Thomas and Fedorov, 2017;Kang et al, 2020). To investigate the impacts of GCM biases, Seager et al (2019) use a simpler model based on thermodynamic atmosphere-ocean coupling linearized around the tropical mean state.…”

Fingerprinting shock-induced deformations via diffraction

“…5 d. Overall, these Fe results demonstrated how dislocations, phase transformations and twins collectively evolve both 1D and 2D diffractograms. By harnessing the fingerprints identified in this investigation and knowledge of local pressures and plasticity contributors from atomic-scale simulations, researchers can decouple these superimposed deformation modes when analyzing experimental diffractograms 27 .…”

“…However, researchers have just begun to harness high-speed X-ray diffraction to detail an experimental shock response in real-time 22 , 23 . Over just the last five years, this approach has resolved a long-standing controversy over the phase transformations of shocked graphite 24 , connected stacking faults to the plastic deformation of shocked Au 25 , tracked the twins and slip in shocked Mg 23 , 26 , demonstrated the pressure dependence of slip and twining for Ta 8 , and elucidated the phase transformation of BCC Fe 27 . Moreover, researchers have just begun to harness high-speed electron diffraction for even finer spatial resolution 28 – 31 .…”

Reversal Asymmetry of Rainfall Change Over the Indian Ocean During the Radiative Forcing Increase and Stabilization

“…is the ocean dynamics effect due to advection, diffusion and mixing,  E T is SST change, and the term on the left side of the equation is close to 0 in a long-term mean (Deser et al, 2010;Hwang et al, 2017;Kang et al, 2020;Xie et al, 2010;Ying et al, 2016). A more detailed derivation can be found in the Supporting Information S1.…”