ISSI Working Group on Atmospheric Water Vapor, 11 Feb 2008ISSI Working Group on Atmospheric Water Vapor, 11 Feb 2008

Holger VömelHolger Vömel

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

University of ColoradoUniversity of Colorado

Water vapor observations Water vapor observations using the CFHusing the CFH

OverviewOverview• Science issues:Science issues:

Trend (stratosphere / upper troposphere)Trend (stratosphere / upper troposphere)SupersaturationSupersaturationUse in forecasting and modelsUse in forecasting and models

• Measurement issues:Measurement issues:Absolute accuracyAbsolute accuracyIn-cloud measurementsIn-cloud measurementsFrostpoint above 0CFrostpoint above 0C

• Logistical issues:Logistical issues: World wide coverage World wide coverage Instrument availabilityInstrument availabilityCostCostRadiosonde manufacturer interactionRadiosonde manufacturer interaction

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

• >300 soundings>300 soundings

Detector

IR LED

μ Controllerμ Controller

Cryogen

Air flow

Lens

Mirror

Heater

Frost layer

Thermistor

Science issue: TrendsScience issue: Trends

Boulder trendBoulder trend

From Scherer et al., ACPD 2007

Boulder trendBoulder trend

From Scherer et al., ACPD 2007

Where to measure trend?Where to measure trend?

Processes controllingentry of water

into stratosphere

Methane oxidationand PSCs

From Holton et al., Rev. Geophys. 1995

Science issue: SupersaturationScience issue: Supersaturation

Supersaturation from WB-57Supersaturation from WB-57

From Gao et al., Science, 2003

Harvard Lyman alpha - CFHHarvard Lyman alpha - CFH

RH ice from tropical CFH soundingsRH ice from tropical CFH soundings

Supersaturation in cloudSupersaturation in cloud

Measurement issue: Absolute accuracy Measurement issue: Absolute accuracy

2 4 6 8 10 12 14

Mixing Ratio (ppmv)

1

10

100

Pre

ssur

e (h

Pa)

Sep 2004 Sep 2005Ft Sumner (~35ºN) Balloon comparisons

Aura MLS / FIRS-2 / MkIV / NOAA FP

10

100

2 4 6 8 10 12 14

Mixing Ratio (ppmv)

Pre

ssur

e (h

Pa)

1

Frostpoint vs balloon remote sensingFrostpoint vs balloon remote sensing

CFH vs ACE-FTSCFH vs ACE-FTS

CFH vs MLSCFH vs MLS

CFH vs FISHCFH vs FISH

CFH vs WB-57 instrumentsCFH vs WB-57 instrumentsJPL TDLJPL TDL

CFH vs. FLASHCFH vs. FLASH

TC4 Costa Rica August 2007TC4 Costa Rica August 2007

CFH vs. FLASHCFH vs. FLASH

AMMA/Ticosonde Veranillo: Niger vs Costa Rica August 2006AMMA/Ticosonde Veranillo: Niger vs Costa Rica August 2006

CFH vs WB-57 instrumentsCFH vs WB-57 instrumentsHarvard Lyman alphaHarvard Lyman alpha

CFH must be considered an absolute CFH must be considered an absolute reference instrumentreference instrument

Measurement issue: In (liquid) clouds Measurement issue: In (liquid) clouds

Measurement in cloudsMeasurement in clouds

Wet bias with liquid phase?Wet bias with liquid phase?

Comparison with groundbased GPS PWVComparison with groundbased GPS PWV

Comparison with groundbased GPS PWVComparison with groundbased GPS PWV

Condensate phaseCondensate phase

Liquid :

Coarse frost:

Fine frost:

Logistical issues: World wide coverageLogistical issues: World wide coverage

CFH Observation sites (campaign based)CFH Observation sites (campaign based)

Instrument availabilityInstrument availability

Instrument needs (low estimate):Instrument needs (low estimate):

6 sites (2 tropical, 2 mid latitude, 2 polar)6 sites (2 tropical, 2 mid latitude, 2 polar)

2x per month2x per month

144 soundings per year144 soundings per year

Industrial manufacturingIndustrial manufacturing

Instrument availabilityInstrument availability

BUT conflict ofBUT conflict of

Business interestsBusiness interests• ProfitProfit• Trade secretsTrade secrets

Science interestsScience interests• Economical observationsEconomical observations• Understanding of instrumentUnderstanding of instrument• Open access policyOpen access policy

Discussion pointsDiscussion points• CFH observations provide highest level of CFH observations provide highest level of

confidenceconfidence

• Improve confidence in observations by cross Improve confidence in observations by cross checks of observations (ground and balloon checks of observations (ground and balloon based, satellites, aircraft)based, satellites, aircraft)

• Science issues to be addressed need large Science issues to be addressed need large number of soundingsnumber of soundings

• Need to address industrial production issue, Need to address industrial production issue, involvement of radiosonde manufacturersinvolvement of radiosonde manufacturers