The
figure to the right shows how satellite data can be used to monitor
the north-south, or meridional, transport of water vapor (qv). In
this figure, southward moisture transport is indicated in yellow
and red, while northward transport is in green and blue. Seasonal
mean qv for an 18 month period (6 seasons) spanning the
1987-88 El-Nino Southern Oscillation may be viewed by clicking
on the image to the right.
The meridional moisture transport is useful
in determining where the mean position of large-scale atmospheric
ridges and troughs are located in the subtropics and midlatitudes. This
is well illustrated over the United States where the line at which
qv = 0 separates northward from southward transport and
thus indicates the mean position of a ridge or trough axis. Notice
the trough axis extending southwest-northeast just south of the
Great Lakes. Often in the deep tropics the "0"
line coincides with regions where tropical convection (and thus
upper-level divergence) is observed in satellite imagery.
Last updated on: November 2, 1999