Concerning the Umkehr measurements at Perth Airport (station 159):  
The instrument was moved in Oct 2000 to another site at the airport.  Some 
time shortly after that, the instrument appeared to lose sensitivity, 
and thus failed to start or complete Umkehr measurements.  This problem is 
intermittent.  The quality of the Umkehr observations also appears to less 
than before.  The instrument was checked in Lauder, New Zealand in December 
2001, but no specific problem was found. Weather conditions did not allow 
full investigations.  The sensitivity is still not good.  Umkehr data from 
October 2000 through the present is thus suspect.  A station visit is 
planned for later in 2004.

- R.D. Evans, NOAA-CMDL
  August 2003