The long record of HALOE data allows mapping of the 3-dimensional structure of water vapor
in the lowest stratosphere. The figure below shows the latitude-longitude distribution of water
vapor on the 390 K isentrope in January.  Relatively dry air is observed over latitudes ~10 S to 30 N,
and the lowest values (<3.0 ppmv, denoted by shading) are found to occur north of Indonesia and
over Central America.  These water vapor minima appear to be related to regions of maximum
convection (the heavy dark lines), but clearly displaced northward.  The water vapor patterns are
also displaced from the regions of coldest tropopause temperatures, which are approximately
centered over the equator.  This  northward displacement of water vapor minima may be linked
to the local Hadley circulation (northward flow) associated with the convective maxima
(as illustrated in this cross section through the western Pacific region).
 

Similar spatial patterns are observed in ozone near the tropical tropopause.  The figure
below is derived from Stratospheric Aerosol and Gas Experiment II (SAGE II) observations.
There is a small but distinct minimum in ozone nearly coincident with the water vapor minimum.
These low ozone values are a signature of recent communication with the (ozone-poor)
troposphere.