Abrupt seasonal variation of the ITCZ and the Hadley circulation
Article first published online: 28 SEP 2007
Copyright 2007 by the American Geophysical Union.
Geophysical Research Letters
Volume 34, Issue 18, September 2007
How to Cite
2007), Abrupt seasonal variation of the ITCZ and the Hadley circulation, Geophys. Res. Lett., 34, L18814, doi:10.1029/2007GL030950., , and (
- Issue published online: 28 SEP 2007
- Article first published online: 28 SEP 2007
- Manuscript Accepted: 30 AUG 2007
- Manuscript Revised: 22 AUG 2007
- Manuscript Received: 16 JUN 2007
- Hadley circulation;
- tropical dynamics
 Using Global Precipitation Climatology Project (GPCP) daily data, we show that the seasonal migration of the global zonal-mean intertropical convergence zone (ITCZ) is not smooth, but jumps from the winter hemisphere to the summer hemisphere. The abrupt migration is within 10 days. Detailed analyses reveal that the phenomenon of the abrupt seasonal migration of the ITCZ mainly exists over particular tropical domains, such as Indian Ocean, western and central Pacific, and South America, which gives the rise of the jump of the global zonal-mean ITCZ. Because the ITCZ constitutes the ascending branch of the Hadley circulation, we also examine whether there exists such an abrupt seasonal change in the Hadley circulation. It is found that the intensity of the Hadley cells evolves smoothly with time. However, the horizontal scales of the Hadley cells demonstrate abrupt seasonal changes, corresponding to the abrupt seasonal migration of the global ITCZ. The winter cell extends rapidly across the equator, while the summer cell rapidly narrows. This suggests that the solsticial cell is the dominant component of the Hadley circulation, and that the equinoctial symmetric pattern is ephemeral.