Correction of radiosonde pressure and temperature measurements using simultaneous GPS height data

A method of correction for radiosonde pressure and temperature data by using simultaneous global positioning system (GPS) ellipsoidal height (z_GPS) is proposed. The correction is made by adjusting the observed pressure and temperature so that the ellipsoidal height (zPTU) calculated from integrating the hypsometric equation by using the latitude- and altitude-dependent gravity together with the observed pressure, temperature and humidity (PTU) agrees with z_GPS. The temperature bias is assumed to arise only from inaccurate radiation correction so that there is no temperature bias in the nighttime data. Under this assumption, the deviations of z_PTU from z_GPS in the nighttime data result only from observational errors in pressure. The pressure adjustment required to remove these deviations is applied also to the daytime data. The daytime temperature bias can then be estimated from the difference between z_PTU and z_GPS during the day. The biases in Vaisala RS80 pressure and temperature measurements are estimated using the Soundings of Ozone and Water in the Equatorial Region campaign data. The estimated pressure bias is positive below ~7 km and negative above it. The bias above 15 km is statistically significant. The daytime temperature bias lacks statistical significance due to fluctuations in the results.