Rossby wave propagation in the transition seasons

The study of Rossby wave propagation in strong jet stream waveguides is essential, as extreme weather events are associated with persistent atmospheric patterns at the surface which may be favored by quasi stationary Rossby waves in the upper troposphere through these pathways. But so far, all the studies are mostly for winter and summer seasons. Therefore, in the present study, we extended earlier works to the transition seasons. The waveguide patterns in both hemispheres during the spring and autumn transition seasons are explored using numerical simulations from a baroclinic model with six selected forcings in the 1979-2016 period. The results show that stronger subtropical jet streams are found in boreal and austral spring associated with stronger wave propagation. Particularly, stronger eddy kinetic energy and wave activity flux are found in boreal spring from the north of Middle East to eastern North Pacific, associated with stronger subtropical Asian jet, and in austral autumn in western Pacific region, associated with greater extension of polar jet. Interhemispheric propagation is verified in spring season in both hemispheres, through the equatorial eastern Pacific and Atlantic ducts, with a northwest-southeast orientation.