Abstract
The present study investigates how changes in the Hadley Cell (HC) intensity impact the stationary Rossby waves energy propagation in the Southern Hemisphere (SH) extratropics. Composites for weak and strong HC Intensity Index (HCI) were used in this analysis. The results for weak HC cases showed a wave train emanating from the subtropical central-west Indian Ocean in an arc-like route, with zonal wavenumber three in the polar jet waveguide, and reaching the north of South America. For strong HC cases, the wave train is also trapped inside the polar jet waveguide with zonal wavenumber four, emanating from subtropical central-east Indian Ocean and reaching the subtropical west coast of Africa. A weaker zonally oriented wave train with zonal wavenumber five has been found in the subtropical region with opposite polarity for weak and strong HC cases. Over the South America, the results show that an HC weakening can lead to a very cold and rainy winter in the southwest of the continent and a mild warm and dry winter on Brazilian states of Minas Gerais and Bahia. A pattern almost opposite was observed when the CH strengthens.
Highlights
The Hadley Cell (HC) plays a key role in the climate system
Using six strong and eight weak HC cases, selected from 1979–2010 time series of normalized HC Intensity Index (HCI) for JJA climatology, this study has shown how the Rossby waves that propagate from the tropics into the extratropics in a westerly background are affected by changes in the intensity of the Hadley circulation
When analyzing separately the two Rossby wave source (RWS) terms have been found for both cases that the vortex stretching (VS) term is the most contributor for the total RWS and the most important influence of AV term is associated with anticyclonic anomaly sources in the subtropics
Summary
Defined as the zonal mean meridional mass circulation in the atmosphere bounded roughly by 30◦S and 30◦N, with warmer air rising in the tropics and colder air sinking in the subtropics, this circulation transports momentum flux to the subtropics and heat from the tropics to the subtropics and to high latitudes through extratropical eddies. Both heat and momentum transports have important influences on subtropical jet streams, which impact on waves and atmospheric circulations at middle and high latitudes [1]. Tropical variability affects the extratropical atmospheric circulation due to the generation of Rossby waves that propagate from the tropics into the extratropics in a westerly background flow [2,3,4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
