A performance evaluation of the new Vaisala RS90 radiosonde has been made using 6-hour forecasts from the Nordic High Resolution Limited Area Model (HIRLAM) prediction model at the Tikkakoski synoptic upper-air station (02935) over a period of several months in 1997 - 1998. The evaluation was performed by the Finnish Meteorological Institute (FMI). Height data for the new RS90 was compared to sounding data from several neighboring upper-air stations by using the HIRLAM model as the reference.
The RS90 Radiosonde was evaluated in two areas of performance. Firstly, the Tikkakoski upper-air station made both RS90 and RS80 soundings. These daily soundings were studied by plotting the geopotential height data for different pressure levels. Secondly, the RS90 height data were compared against those from neighboring radiosonde stations, most of which were using RS80 Radiosondes. This comparison was made by using the 6-hour forecasts first guesses as the reference.
According to the tests, the RS90 data exhibited a smaller deviation between the HIRLAM model and the observations, than when compared to RS80 data . This is an indication that the new sensors used in the RS90 radiosonde are more accurate and exhibit a faster response time than their predecessors. On the other hand, the differences between the two sonde types are relatively small when compared to the typical variance between the model and site to site radiosonde data. This demonstrates that the RS90 can be used in lieu of the RS80 radiosonde without any consideration with respect to the model.