Dependence of atmospheric transport into the Arctic on the meridional
extent of the Hadley cell
Abstract
Recent studies have shown a large spread in the transport of atmospheric
tracers into the Arctic among a suite of chemistry climate models, and
have suggested that this is related to the spread in the meridional
extent of the Hadley Cell (HC). Here we examine the HC–transport
relationship using an idealized model, where we vary the mean
circulation and isolate its impact on transport to the Arctic. It is
shown that the poleward transport depends on the relative position
between the northern edge of the HC and the tracer source, with maximum
transport occurring when the HC edge lies near the middle of the source
region. Such dependence highlights the critical role of near–surface
transport by the Eulerian mean circulation rather than eddy mixing in
the free troposphere, and suggest that variations in the HC edge and the
tracer source region are both important for modeling Arctic composition.