Expert team on Upper Air System Intercomparisons, Agenda 5.1 Comparison of Snow White and RS90 measurements from WMO GPS Radiosonde Test, Alcantara , Brazil Richard Smout,Darren Lyth, John Elms John Nash Met Office, Exeter, Devon, UK

Inside a Snow White used in Brazil

Comparison of daytime measurements

Comparison of daytime measurements

Dewpoint comparison

Sample of temperature and relative humidity data from WMO GPS Radiosonde Comparison

Snow white overheating after entering thin cloud at minute 60

Conclusions Both Snow White and the Vaisala RS90 suffered problems during the Brazilian test. Hence, more reliable systems need to be deployed in future tests. Neither system should be considered an absolute reference, but both fall into the category of higher quality radiosonde relative humidity measurements