1. Water vapour soundings in the upper troposphere Geraint Vaughan University of Wales, Aberystwyth With thanks to: Clare Cambridge, Alan Phillips, Les Dean, Graham Hansford and Rod Jones

2. Comparison of three instruments Vaisala RS80-A Humicap, with Miloshevic et al (2000) correction applied Meteorlabor Snow White Frost Point Hygrometer University of Cambridge Surface Acoustic Wave FPH. 30 joint flights from Aberystwyth together with an ECC ozonesonde, using RS80 telemetry via TMAX-C interface card UTLS ozone funded project

3. Snow White, ECC and RS80 RS80 ECC ozonesonde SNOW WHITE Air inlet Peltier cooler and chilled mirror

4. Example profiles 1 Snow White (black) RS80 (Red) SAW (Green) Photo- transistor (Turquoise) Snow White is very susceptible to contamination. Left: clean profile, right: contaminated profile (based on phototransistor). SAW is the only instrument capable of stratospheric measurements. RH with respect to ice

5. Example profiles 2 Snow White (black) RS80 (Red) SAW (Green) Photo- transistor (Turquoise) Good agreement; SW control circuitry unstable near tropopause SAW measurements into the stratosphere RH with respect to ice

6. Comparison between Snow White and RS80 in UT Conclusion: No evidence of systematic bias in radiosondes. With respect to ice

7. Scatter plots, coloured by ozone amount Conclusion: frequent occurrence of high (> 120 ppbv) ozone with RH > 25 % - indicative of mixing between stratospheric and tropospheric air

8. Extension to ozonesonde database Apply Miloshevic correction to RH measured on 324 ozonesonde profiles launched from Aberystwyth between 1991 and 2002

9. Scatter plots of humidity and ozone

10. Conclusions Reasonable agreement between the three techniques RS80A profiles do not exhibit bias at high altitude if corrected according to Miloshevic et al (2000) Frequent instances of RH ice >100% at high altitudes Frequent instances of high ozone mixing ratio and RH > 25% above 10 km