Energetic Constraints on the Position of the Intertropical Convergence Zone
نویسندگان
چکیده
The intertropical convergence zone (ITCZ) can shift meridionally on seasonal and longer time scales. Previous studies have shown that the latitude of the ITCZ is negatively correlated with cross-equatorial atmospheric energy transport. For example, the ITCZ shifts southward as theNorthernHemisphere cools and the northward cross-equatorial energy transport strengthens in response. It has remained unclear what controls the sensitivity of the ITCZ position to cross-equatorial energy transport and what other factors may lead to shifts of the ITCZ position. Here it is shown that the sensitivity of the ITCZ position to crossequatorial energy transport depends on the net energy input to the equatorial atmosphere: the net radiative energy inputminus any energy uptake by the oceans. Changes in this energy input can also lead to ITCZ shifts. The cross-equatorial energy transport is related through a series of approximations to interhemispheric asymmetries in the near-surface temperature distribution. The resulting theory of the ITCZ position is tested in idealized general circulation model simulations with a slab ocean as lower boundary condition. In the simulations, cross-equatorial energy transport increases under global warming (primarily because extratropical latent energy fluxes strengthen), and this shifts the ITCZ poleward. The ITCZ shifts equatorward if primarily the tropics warm in response to an increased net energy input to the equatorial atmosphere. The results have implications for explaining the varied response of the ITCZ to global or primarily tropical changes in the atmospheric energy balance, such as those that occur under global warming or El Ni~ no.
منابع مشابه
Southward movement of the Pacific intertropical convergence zone AD 1400--1850
Tropical rainfall patterns control the subsistence lifestyle of more than one billion people. Seasonal changes in these rainfall patterns are associated with changes in the position of the intertropical convergence zone, which is characterized by deep convection causing heavy rainfall near 10◦ N in boreal summer and 3◦ N in boreal winter. Dynamic controls on the position of the intertropical co...
متن کاملLatitudinal Position and Trends of the Intertropical Convergence Zone (ITCZ) and its Relationship with Upwelling in the Southern Caribbean Sea and Global Climate Indices
متن کامل
A link between the double intertropical convergence zone problem and cloud biases over the Southern Ocean
The double intertropical convergence zone (ITCZ) problem, in which excessive precipitation is produced in the Southern Hemisphere tropics that resembles a Southern Hemisphere counterpart to the strong Northern Hemisphere ITCZ, is perhaps the most significant and most persistent bias of global climate models. In this study, we look to the extratropics for possible causes of the double ITCZ probl...
متن کاملEnergetic Constraints on the Width of the Intertropical Convergence Zone
The intertropical convergence zone (ITCZ) has been the focus of considerable research in recent years, with much of this work concerned with how the latitude of maximum tropical precipitation responds to natural climate variability and to radiative forcing. The width of the ITCZ, however, has received little attention despite its importance for regional climate and for understanding the general...
متن کاملControl of Saharan mineral dust transport to Barbados in winter by the Intertropical Convergence Zone over West Africa
[1] The reasons for the inter-annual variability of dust transport from the Sahara across the Atlantic are not well-understood. Here we address this issue by defining three new climate indices that capture the position and intensity of the zone of near-surface convergence over West Africa, a part of the global Intertropical Convergence Zone (ITCZ). We then relate these indices to a 38-year reco...
متن کامل