ISSI Working Group on Atmospheric Water Vapor, 11 Feb 2008 Holger Vömel Cooperative Institute for Research in Environmental Sciences University of Colorado.
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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
Where to measure trend?Where to measure trend?
Processes controllingentry of water
into stratosphere
Methane oxidationand PSCs
From Holton et al., Rev. Geophys. 1995
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. FLASHCFH vs. FLASH
AMMA/Ticosonde Veranillo: Niger vs Costa Rica August 2006AMMA/Ticosonde Veranillo: Niger vs Costa Rica August 2006
CFH must be considered an absolute CFH must be considered an absolute reference instrumentreference instrument
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
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