Figure 4: Illustration of the proposed pressure-push mechanism driving the southern branch of the western Pacific ITCZ in the Asia-Pacific realm.
From: Obliquity pacing of the western Pacific Intertropical Convergence Zone over the past 282,000 years
This illustration is based on the condition of high Southern Hemisphere summer insolation (high precession). (a) High obliquity. A strong pressure gradient between intensified SH and AL enhances cross-equatorial and flow reinforces the southward shift of the ITCZ rain belt to the southernmost position in boreal winter. The net effect is to increase precipitation in North Australia, with compensated amounts in PNG. (b) Low obliquity. The cross-equatorial ‘pressure-push’ forcing is weak at low-obliquity and the centre of ITCZ rain belt stays in the north, relative to high-obliquity cases in boreal winter. As a result, PNG experiences enormous rainfall while North Australia receives less rainfall.AL, Australian low; SH, Siberian high; light blue arrow, surface wind intensity; solid white line, core position of the western Pacific ITCZ1; blue circle, marine sediment core MD05-2925 site; brown circle, Gregory Lakes38.
