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

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

Snow White, ECC and RS80

RS80

ECC ozonesonde

SNOW WHITE

Air inlet

Peltier cooler and chilled mirror

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 RH with respect to ice

Example profiles 2Snow 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 RH with respect to ice

Comparison between Snow White and RS80 in UT

Conclusion: No evidence of systematic bias in radiosondes.

With respect to ice

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

Extension to ozonesonde databaseApply Miloshevic correction to RH measured on 324 ozonesonde profiles launched from Aberystwyth between 1991 and 2002

0

50

100

150

200

250

0 20 40 60 80 100 120 140 160Relative Humidity (ice) / %

Nu

mb

er

Relative Humidity (ice): Summer, 10-11km

0

100

200

300

400

500

0 20 40 60 80 100 120 140 160Relative Humidity (ice) / %

Nu

mb

er

Relative Humidity (ice): Winter, 10-11km

Scatter plots of humidity and ozone

40

60

80

100

120

1.5 2.0 2.5 3.0

log10

(H2O mixing ratio)/ppmv

O3 m

ixin

g ra

tio, p

pbv

Summer, 10-12km

40

60

80

100

120

1.5 2.0 2.5 3.0 3.5 4.0

log(H2O mixing ratio)/ppmv

log(

O3 m

ixin

g r

atio

)/p

pbv

Summer, 5-6km

30

50

70

90

110

1.5 2.0 2.5 3.0 3.5 4.0

log(H2O mixing ratio)/ppmv

log(

O3 m

ixin

g ra

tio)/

ppb

v

Winter, 5-6km

20

40

60

80

100

120

1.0 1.5 2.0 2.5

log(H2O mixing ratio)/ppmv

log(

O3 m

ixin

g r

atio

)/p

pbv

Winter, 10-11km

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 RHice>100% at high altitudes

• Frequent instances of high ozone mixing ratio and RH > 25% above 10 km