Issi working group on atmospheric water vapor 11 feb 2008
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ISSI Working Group on Atmospheric Water Vapor, 11 Feb 2008. Water vapor observations using the CFH. Holger Vömel Cooperative Institute for Research in Environmental Sciences University of Colorado. Overview.

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ISSI Working Group on Atmospheric Water Vapor, 11 Feb 2008

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ISSI Working Group on Atmospheric Water Vapor, 11 Feb 2008

Water vapor observations using the CFH

Holger Vömel

Cooperative Institute for Research in Environmental Sciences

University of Colorado


Overview

  • Science issues:Trend (stratosphere / upper troposphere)SupersaturationUse in forecasting and models

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

  • Logistical issues: World wide coverage Instrument availabilityCostRadiosonde manufacturer interaction


Cryogen

Frost layer

Thermistor

Heater

μ Controller

Detector

Air flow

IR LED

Lens

Mirror

Cryogenic Frostpoint Hygrometer (CFH)

  • Microprocessor control

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

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

  • Phase sensitive detector: electronic sunlight filter

  • No liquid/ice ambiguity

  • Weight: ~ 400 gr

  • Currently interfaced with ECC ozone sonde and Vaisala RS80

  • >300 soundings


Science issue: Trends


Boulder trend

From Scherer et al., ACPD 2007


Boulder trend

From Scherer et al., ACPD 2007


Where to measure trend?

Methane oxidationand PSCs

Processes controllingentry of water into stratosphere

From Holton et al., Rev. Geophys. 1995


Science issue: Supersaturation


Supersaturation from WB-57

From Gao et al., Science, 2003


Harvard Lyman alpha - CFH


RH ice from tropical CFH soundings


Supersaturation in cloud


Measurement issue: Absolute accuracy


1

10

100

1

Pressure (hPa)

10

100

Pressure (hPa)

2 4 6 8 10 12 14

Mixing Ratio (ppmv)

2 4 6 8 10 12 14

Mixing Ratio (ppmv)

Frostpoint vs balloon remote sensing

Aura MLS / FIRS-2 / MkIV / NOAA FP

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


CFH vs ACE-FTS


CFH vs MLS


CFH vs FISH


CFH vs WB-57 instruments

JPL TDL


CFH vs. FLASH

TC4 Costa Rica August 2007


CFH vs. FLASH

AMMA/Ticosonde Veranillo: Niger vs Costa Rica August 2006


CFH vs WB-57 instruments

Harvard Lyman alpha


CFH must be considered an absolute reference instrument


Measurement issue: In (liquid) clouds


Measurement in clouds


Wet bias with liquid phase?


Comparison with groundbased GPS PWV


Comparison with groundbased GPS PWV


Condensate phase

Liquid :

Coarse frost:

Fine frost:


Logistical issues: World wide coverage


CFH Observation sites (campaign based)


Instrument availability

Instrument needs (low estimate):

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

2x per month

144 soundings per year

 Industrial manufacturing


Instrument availability

BUT conflict of

Business interests

  • Profit

  • Trade secrets

    Science interests

  • Economical observations

  • Understanding of instrument

  • Open access policy


Discussion points

  • CFH observations provide highest level of confidence

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

  • Science issues to be addressed need large number of soundings

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


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