Subtropical anticyclones and midlatitude storm tracks are key components
of the large-scale atmospheric circulation. Focusing on the southern
hemisphere, the seasonality of the three dominant subtropical
anticyclones, situated over the South Pacific, South Atlantic and South
Indian Ocean basins, has a large influence on local weather and climate
within South America, Southern Africa and Australasia, respectively.
Generally speaking, sea level pressure within the southern hemisphere
subtropics reaches its seasonal maximum during the winter season when
the southern hemisphere Hadley Cell is at its strongest. One exception
to this is the seasonal evolution of the South Pacific subtropical
anticyclone. While winter maxima are seen in the South Atlantic and
South Indian subtropical anticyclones, the South Pacific subtropical
anticyclone reaches its seasonal maximum during local spring with
elevated values extending into summer. In this study we investigate the
hypothesis that strength of the austral summer South Pacific subtropical
anticyclone is largely due to heating over the South Pacific Convergence
Zone. Using reanalysis data, and AGCM added cooling and heating
experiments to artificially change the strength of diabatic heating over
the South Pacific Convergence Zone, our results show that increased
heating triggers a Rossby wave train over the Southern Hemisphere
mid-latitudes by increasing upper-level divergence. The propagating
Rossby wave train creates a high-low sea level pressure pattern that
projects onto the center of the South Pacific Subtropical Anticyclone to
intensify its area and strength. The southern hemisphere storm tracks
also shift poleward due to increased heating over the South Pacific
Convergence Zone.