Intraseasonal interactions between the tropics and extratropics in the southern hemisphere

Journal Article · Thu Jul 01 04:00:00 EDT 1993 · Journal of the Atmospheric Sciences; (United States)

DOI:https://doi.org/10.1175/1520-0469(1993)050<1950:IIBTTA>2.0.CO;2· OSTI ID:6245809

Berbery, E H; Nogues-Paegle, J ^[1]

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1. Univ. of Utah, Salt Lake City (United States)

The mechanics of the interaction between tropical heating [estimated from outgoing longwave radiation (OLR)] and Southern Hemisphere (SH) subtropical and extratropical circulations on intraseasonal time scales are discussed. Base points are selected from teleconnectivity and teleconnection maps between OLR and zonal wind, heights, and meridional component of the divergent wind. Composites are formed for pentads with OLR anomalies at the base point greater in magnitude than one standard deviation. Enhanced convection over Indonesia is found to be associated with increases of both the southward component of the meridional divergent wind and of the westerly zonal wind to the south of the heating region during the SH summer. The increased westerly wind gradients together with increased values of the southward component of the divergent wind lead to an enhancement of the Rossby wave train evolves from this region, following the typical ray path expected from linear theory. Tropical-extratropical connections are less pronounced during SH winter than during summer, through an increase of westerly winds in the SH is found associated with enhanced convective activity in the Northern Hemisphere. The increase of the zonal wind during winter is explained by meridional overturnings that emanate from the heating regions. Isentropic trajectories are used to show that the zonal accelerations caused by the poleward motion at upper levels are in agreement with observed values. The enhancement of convective activity is also related to a southward increase of the meridional component of the divergent wind that maximizes near the equator. Since the latitudes of maximum southward component of the meridional divergent wind differ form those with maximum changes in the gradient of absolute vorticity, no increase of the Rossby wave source of excitation of Rossby waves due to tropical heating is found during this season. 33 refs., 17 figs.

• OSTI ID: 6245809
• Journal Information: Journal of the Atmospheric Sciences; (United States), Journal Name: Journal of the Atmospheric Sciences; (United States) Vol. 50:13; ISSN 0022-4928; ISSN JAHSAK
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
ASIA
ATMOSPHERIC CIRCULATION
CONVECTION
DEVELOPING COUNTRIES
EARTH PLANET
ENERGY TRANSFER
EQUATOR
HEAT TRANSFER
INDONESIA
ISLANDS
MAPS
MASS TRANSFER
PLANETS
SEASONAL VARIATIONS
SOUTHERN HEMISPHERE
TROPICAL REGIONS
VARIATIONS
WIND