For this reason, the fresh new decimal relationships anywhere between ITCZ venue and you can AHT
Expression of your own spatial framework off wind gusts (grey arrows), meridional bulk overturning streamfunction (strong and dashed gray outlines into the positive and negative streamfunction opinions, respectively), rain (bluish contours), and you may vertically integrated atmospheric temperatures transportation (red arrows) of this Hadley cell to possess (top) boreal summer and you will (bottom) austral june. The new equator is the dashed green line.
Thus, brand new quantitative relationships anywhere between ITCZ venue and AHT
Signal of spatial design away from winds (gray arrows), meridional bulk overturning streamfunction (solid and you may dashed gray outlines to the negative and positive streamfunction values, respectively), precipitation (bluish contours), and you may vertically provided atmospheric temperature transport (yellow arrows) of Hadley mobile for (top) boreal summer and you will (bottom) austral summer. The fresh new equator ‘s the dashed green range.
(2008) in a slab ocean aquaplanet simulation where a hemispheric asymmetry in atmospheric heating was imposed by introducing a surface heating in the southern extratropics and an equal surface cooling in the northern extratropics. The ITCZ was found to shift toward the heat source and the precipitation maximum was nearly collocated with the location of zero meridional heat transport in the atmosphere, suggesting that a meridional shift of the Hadley cell was the underlying cause of the precipitation shift. Yoshimori and Broccoli (2009, 2008) found that the change in AHTEQ in response to hemispheric asymmetric forcing was closely related to the meridional shift in the Hadley cell, which itself was a response to the hemispheric asymmetry of the forcing and feedbacks. They also noted the concurrent shift in the tropical precipitation along with the Hadley cell but did not quantify the relationship between the change in AHTEQ and the meridional shift of the ITCZ. More recently, Frierson and Hwang (2012) found that the meridional shift in the ITCZ due to increased greenhouse gas concentrations in an ensemble of simulations was strongly correlated with the change in AHTEQ. They also found that AHTEQ had a large intermodel spread due to differences in extratropical cloud responses. This suggests that the extratropics play an important role in setting the ITCZ location via the interhemispheric asymmetry in energy input to the atmosphere and the associated changes in AHTEQ.
There is widespread paleoclimatic evidence for shifts and/or intensity changes of tropical precipitation in the past including a southward shift of the ITCZ during glacial times (Pahnke et al. 2007), abrupt transitions during glacial times (Wang et al. 2001; Peterson et al. 2000) associated with Dansgaard–Oeshchger and Heinrich events, a more northern location during the Holocene thermal maximum (H), and a southward shift (estimated to be approximately 5°) during the Little Ice Age (Sachs et al. 2009). Provided the same relationship between the ITCZ and AHTEQ holds across different climate states, each of the ITCZ shifts noted in the paleoclimate records would have an AHTEQ change that can be quantified. Moreover, the change in AHTEQ would have to be associated with a hemispheric asymmetry of atmospheric forcing or climate feedbacks (see Fig. 2). EQ provides a framework for comparing precipitation shifts deduced from paleoclimate data and the proposed mechanisms and/or climate forcing that are believed to have caused the precipitation changes (i.e., orbital forcing, changes in land ice and sea ice, cloud albedo changes, a shutdown of Milf Sites dating sites for free the Atlantic meridional overturning circulation, etc.). There is also widespread paleoclimatic evidence for changes in meridional gradients of tropical sea surface temperature (SST) to which the ITCZ is sensitive. Furthermore, SST gradients may be easier to reconstruct from paleoproxies than ITCZ location. Therefore, a quantification of the relationship between SST gradients and ITCZ location is an important task for paleoclimate interpretation.