C. Tyrrell et al., LINKS BETWEEN TROPICAL CONVECTION AND VARIATIONS OF THE EXTRATROPICALCIRCULATION DURING TOGA COARE, Journal of the atmospheric sciences, 53(18), 1996, pp. 2735-2748
Data from the Intensive Observation Period of the Tropical Ocean Globa
l Atmosphere Coupled Ocean-Atmosphere Response Experiment (November 19
92-February 1993) have been used to investigate the links between intr
aseasonal variations in tropical convection and those in forcing of up
per-tropospheric Rossby waves in the extratropics. The primary databas
es are Geostationary Meteorological Satellite imagery and tropical win
d analyses from the Bureau of Meteorology, Australia. A number of 5-da
y periods showing convection in different locations were chosen. For e
ach period, mean fields of divergence, cloud-top temperature, and uppe
r-tropospheric Rossby wave source are presented. Vorticity budgets are
used to demonstrate the processes responsible for the Rossby wave sou
rce patterns. The approach follows earlier studies of links between in
terannual variations of tropical convection associated with the Southe
rn Oscillation and variations of the extratropical circulation. It is
shown that the regions of tropical convection correspond to longitudin
ally localized Hadley cells. in the subtropics, at the higher-latitude
end of each cell, there is a Rossby wave source dipole with anticyclo
nic and cyclonic forcing. The anticyclonic forcing of Rossby waves is
associated with advection of vorticity by the divergent outflow, while
the cyclonic forcing is due to the region of convergence immediately
above the downward branch of the local Hadley cell. Hence, the authors
provide a dynamical basis for tropical-midlatitude interactions assoc
iated with intraseasonal variations of tropical convection.