GCOS Upper Air Workshop, 22 May 2006GCOS Upper Air Workshop, 22 May 2006

Holger VömelHolger Vömel

Cooperative Institute for Research in Environmental SciencesCooperative Institute for Research in Environmental Sciences

University of ColoradoUniversity of Colorado

Water vapor observations in the upper Water vapor observations in the upper troposphere and lower stratospheretroposphere and lower stratosphere

OverviewOverview

• Frost pointFrost point

• Lyman-Lyman-αα

• TDLTDL

• Polymer (Vaisala RS92)Polymer (Vaisala RS92)

• SummarySummary

Cryogenic Frostpoint Hygrometer (CFH)Cryogenic Frostpoint Hygrometer (CFH)

• Microprocessor controlMicroprocessor control

• Vertical Range: surface to ~28 kmVertical Range: surface to ~28 km (surface to ~25 km on ascent) (surface to ~25 km on ascent)

• Uncertainty: troposphere: > 4% MRUncertainty: troposphere: > 4% MR stratosphere: ~ 9 % stratosphere: ~ 9 %

• Phase sensitive detector: Phase sensitive detector: electronic sunlight filter electronic sunlight filter

• No liquid/ice ambiguityNo liquid/ice ambiguity

• Weight: ~ 400 grWeight: ~ 400 gr

• Currently interfaced with ECC ozone Currently interfaced with ECC ozone

sonde and Vaisala RS80 sonde and Vaisala RS80

• Based on NOAA/CMDL frost pointBased on NOAA/CMDL frost point hygrometer hygrometer

• 162 soundings162 soundings

Detector

IR LED

μ Controllerμ Controller

Cryogen

Air flow

Lens

Mirror

Heater

Frost layer

Thermistor

Water vapor mixing ratioWater vapor mixing ratioTicosonde 2006, Jan 4 – Mar 4, 2006Ticosonde 2006, Jan 4 – Mar 4, 2006

Tropical tropopause dehydrationTropical tropopause dehydration

Ticosonde 2006Ticosonde 2006 Jan 4 - Mar 4, 2006Jan 4 - Mar 4, 2006

Ticosonde 2005Ticosonde 2005July 8-24, 2005July 8-24, 2005

CFH AdvantagesCFH Advantages

• Measurement based on simple physicsMeasurement based on simple physics• Measurement not calibrated for water Measurement not calibrated for water

vapor, but rather for temperaturevapor, but rather for temperature(assume vapor pressure equation is correct)(assume vapor pressure equation is correct)

• Extremely large dynamic rangeExtremely large dynamic range

• Long history for technologyLong history for technology

CFH LimitationsCFH Limitations

• Instrument may fail completely in “thick” liquid Instrument may fail completely in “thick” liquid clouds or highly ice-supersaturated airclouds or highly ice-supersaturated air

• High costHigh cost• Availability of cryogenAvailability of cryogen• Instrument needs minor preparationInstrument needs minor preparation• Data product needs understanding of instrumentData product needs understanding of instrument

Snow White frostpoint hygrometerSnow White frostpoint hygrometer

• Peltier coolingPeltier cooling

• Vertical Range: surface to < tropopauseVertical Range: surface to < tropopause

• Uncertainty: 0.1Uncertainty: 0.1°C DP/FP°C DP/FP realistic 0.5°C DP realistic 0.5°C DP

• Sunlight sensitive detector Sunlight sensitive detector

• Liquid/ice ambiguityLiquid/ice ambiguity

• Weight: ~ 400 grWeight: ~ 400 gr

• Currently interfaced with SRS34,Currently interfaced with SRS34, Sippican or Tmax/Vaisala RS80 Sippican or Tmax/Vaisala RS80

Snow White frostpoint hygrometerSnow White frostpoint hygrometer

Snow White comparisonsSnow White comparisons

NOAA/CMDLNOAA/CMDLGalapagos/Huntsville/Boulder/WatuskosekGalapagos/Huntsville/Boulder/Watuskosek

CFHCFHAWEX OklahomaAWEX Oklahoma

Snow White AdvantagesSnow White Advantages

• Measurement based on simple physicsMeasurement based on simple physics

• Measurement not calibrated for water Measurement not calibrated for water vapor, but rather for temperaturevapor, but rather for temperature

• Large dynamic rangeLarge dynamic range

• Simple operationSimple operation

Snow White LimitationsSnow White Limitations

• Highly sensitive to cloud contaminationHighly sensitive to cloud contamination• Occasional unexplained failureOccasional unexplained failure• Moderate costModerate cost• Limited to below tropopauseLimited to below tropopause• Limited to RH Limited to RH ≥≥ 3-6% 3-6%• Data product needs understanding of instrumentData product needs understanding of instrument

FLASH - Lyman-FLASH - Lyman-αα

• Fluorescent Lyman Alpha Stratospheric Fluorescent Lyman Alpha Stratospheric Hygrometer (FLASH) Hygrometer (FLASH)

• Vertical Range: upper troposphere to Vertical Range: upper troposphere to stratosphere stratosphere (0.5 to 500 ppmv) (0.5 to 500 ppmv)

• Calibrated against reference frost point Calibrated against reference frost point

• Uncertainty: 9% MRUncertainty: 9% MR

• Night time (descent) onlyNight time (descent) only

• Weight: ~ 1 kgWeight: ~ 1 kg

• Currently interfaced Vaisala RS80Currently interfaced Vaisala RS80

• 45 soundings45 soundings

FLASH - Lyman-FLASH - Lyman-αα

FLASH - Lyman-FLASH - Lyman-αα

FLASH AdvantagesFLASH Advantages

• Calibrated against frost point standardCalibrated against frost point standard

• High measurement precisionHigh measurement precision

• Very fast sensorVery fast sensor

• Largely insensitive to cloudsLargely insensitive to clouds

• Large dynamic range (low mixing ratios)Large dynamic range (low mixing ratios)

FLASH LimitationsFLASH Limitations

• Instrument measures properly on descentInstrument measures properly on descent• Can only measure during night timeCan only measure during night time• Full moon limits data rangeFull moon limits data range• High costHigh cost• Measurement range : 0.5 to 500 ppmvMeasurement range : 0.5 to 500 ppmv• Currently can’t check calibration in the fieldCurrently can’t check calibration in the field

MayComm TDLMayComm TDL

• Tunable Diode LaserTunable Diode Laser

• Vertical Range: mid troposphere to Vertical Range: mid troposphere to stratosphere stratosphere

• Calibrated against reference frost point Calibrated against reference frost point

• Uncertainty: 5% MRUncertainty: 5% MR or 0.5 ppmv or 0.5 ppmv

• Payload weight: ~ 1 kgPayload weight: ~ 1 kg

MayComm TDLMayComm TDLCosta RicaCosta RicaJanuary/February 2006January/February 2006

5 TDL soundings5 TDL soundings

MayComm TDL vs CFHMayComm TDL vs CFHCosta RicaCosta RicaJanuary/February 2006January/February 2006

13 CFH soundings13 CFH soundings

MayComm TDL – CFH comparisonMayComm TDL – CFH comparison

MayComm TDL VariabilityMayComm TDL Variability

TDLTDL CFHCFH

MayComm TDL AdvantagesMayComm TDL Advantages

• High measurement precisionHigh measurement precision

• Very fast sensorVery fast sensor

• Insensitive to cloudsInsensitive to clouds

• Large dynamic range (low mixing ratios)Large dynamic range (low mixing ratios)

• Easy to useEasy to use

MayComm TDL LimitationsMayComm TDL Limitations

• Prototype onlyPrototype only• High costHigh cost• No lower troposphere No lower troposphere

(Can extend to surface with second path)(Can extend to surface with second path)• No stable interface/telemetry system yetNo stable interface/telemetry system yet

Polymer sensor (Vaisala RS92)Polymer sensor (Vaisala RS92)

• Capacitive polymer sensorCapacitive polymer sensor

• Vertical Range: lower to upper Vertical Range: lower to upper troposphere (?) troposphere (?)

• Uncertainty: 2-5% RHUncertainty: 2-5% RH

• Payload weight: ~ 250 gPayload weight: ~ 250 g

• Sensors go through undocumented Sensors go through undocumented changes changes

Polymer sensor (Vaisala RS92)Polymer sensor (Vaisala RS92)

AWEX, OklahomaAWEX, Oklahoma

Nov 2003Nov 2003

Lautlos, FinlandLautlos, Finland

Feb 2004Feb 2004

TCSP, Costa RicaTCSP, Costa Rica

Jul 2005Jul 2005

Night time comparisons RS92 vs CFHNight time comparisons RS92 vs CFH

Polymer sensor (Polymer sensor (Vaisala RS92Vaisala RS92))

Day time comparison RS92 vs CFHDay time comparison RS92 vs CFH

TCSP, Costa RicaTCSP, Costa Rica

Jul 2005Jul 2005

Polymer sensor (Polymer sensor (Vaisala RS92Vaisala RS92)) Advantages Advantages

• Very low costVery low cost

• Largely insensitive to cloudsLargely insensitive to clouds

• Easy to useEasy to use

• Vaisala RS92: One of the best of the Vaisala RS92: One of the best of the polymer sensorspolymer sensors

Polymer sensor (Polymer sensor (Vaisala RS92Vaisala RS92)) Limitations Limitations

• Very large solar radiation sensitivityVery large solar radiation sensitivity• Good measurements need third party correctionsGood measurements need third party corrections• Very hard to trace calibration changes Very hard to trace calibration changes • Very hard to trace sensor changesVery hard to trace sensor changes

  Claimed Claimed accuracyaccuracy CalibrationCalibration LimitationsLimitations

Dynamic Dynamic rangerange HistoryHistory CostCost

Ease of Ease of useuse

EngineeringEngineeringstatusstatus

CFHCFH0.5°C DP/FP

4-9% ++ No "wet" clouds ++ + - (o) o

research /small series

Snow WhiteSnow White 0.1°C DP/FP +Some cloudsRH > 3-6%

No stratosphereo + o ++

productionsmall series

Lyman-alpha (FLASH)Lyman-alpha (FLASH)9%

(20% below 2 ppmv)

+Night time onlyDescent only

No lower troposphere + o -- +

research /small series

TDL (MayComm)TDL (MayComm)5%

0.5 ppmv o ? + - -- (++)

Proof of concept

Polymer (Vaisala RS92)Polymer (Vaisala RS92) 2-5% RH -

No stratosphereLarge radiation error

Chemical contaminationVery hard to trace

sensor/calibration changes

- + ++ + (++)Large scale production

Questions?Questions?