Introduction of Height Differences 
with Change in Radiosonde Type  

The charts below shows 50 hPa heights and differences for Miami and Key West, Florida for a 30 day period.  During the this period each station took 2 observations a day for a total of 60 observations. Prior to June 1, 1998 (observation #35), both stations used the VIZ-B2 radiosonde.  After this date, Miami began using the Vaisala RS80-57H radiosonde, while Key West continued using the VIZ-B2.  Note the difference in the heights once Miami began using the Vaisala radiosonde.  The differences at this level (and other levels) can be attributed to different temperature and pressure sensors used in each instrument and the solar/IR radiation corrections applied to the Vaisala temperature data before it is disseminated. VIZ-B2 temperatures are not corrected at the station, but at meteorological centers such as NCEP.