Characterization and Correction of Relative Humidity Measurements from Vaisala RS80-A Radiosondes at Cold Temperatures

Larry M. Miloshevich

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Holger Vömel National Oceanic and Atmospheric Administration, Boulder, Colorado

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Ari Paukkunen Vaisala Oy, Helsinki, Finland

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Andrew J. Heymsfield

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Samuel J. Oltmans National Oceanic and Atmospheric Administration, Boulder, Colorado

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Abstract

Radiosonde relative humidity (RH) measurements are known to be unreliable at cold temperatures. This study characterizes radiosonde RH measurements from Vaisala RS80-A thin-film capacitive sensors in the temperature range 0° to −70°C. Sources of measurement error are identified, and two approaches for correcting the errors are presented. The corrections given in this paper apply only to the Vaisala RS80-A sensor, although the RS80-H sensor is briefly discussed for comparison.

A temperature-dependent correction factor is derived from statistical analysis of simultaneous RH measurements from RS80-A radiosondes and the NOAA cryogenic frostpoint hygrometer. The mean RS80-A measurement error is shown to be a dry bias that increases with decreasing temperature, and the multiplicative correction factor is about 1.3 at −35°C, 1.6 at −50°C, 2.0 at −60°C, and 2.4 at −70°C. The fractional uncertainty in the mean of corrected measurements, when large datasets are considered statistically, increases from 0.06 at 0°C to 0.11 at −70°C. The fractional uncertainty for correcting an individual sounding is about ±0.2, which is larger because this statistical approach considers only the mean value of measurement errors that are not purely temperature dependent. The correction must not be used outside the temperature range 0° to −70°C, because it is a meaningless extrapolation of a polynomial curve fit.

Laboratory measurements of sensor response conducted at Vaisala are used to characterize some of the individual sources of RS80-A measurement error. A correction factor is derived for the dominant RS80-A measurement error at cold temperatures: an inaccurate approximation for the sensor’s temperature dependence in the data processing algorithm. The correction factor for temperature-dependence error is about 1.1 at −35°C, 1.4 at −50°C, 1.8 at −60°C, and 2.5 at −70°C. Dependences and typical magnitudes are given for measurement errors that result from the temperature dependence of the sensor’s time constant, and from several smaller bias errors and random uncertainties.

Corresponding author address: Dr. Larry M. Miloshevich, National Center for Atmospheric Research/MMM, P.O. Box 3000, Boulder, CO 80307-3000.

Email: milo@ucar.edu

Abstract

Radiosonde relative humidity (RH) measurements are known to be unreliable at cold temperatures. This study characterizes radiosonde RH measurements from Vaisala RS80-A thin-film capacitive sensors in the temperature range 0° to −70°C. Sources of measurement error are identified, and two approaches for correcting the errors are presented. The corrections given in this paper apply only to the Vaisala RS80-A sensor, although the RS80-H sensor is briefly discussed for comparison.

A temperature-dependent correction factor is derived from statistical analysis of simultaneous RH measurements from RS80-A radiosondes and the NOAA cryogenic frostpoint hygrometer. The mean RS80-A measurement error is shown to be a dry bias that increases with decreasing temperature, and the multiplicative correction factor is about 1.3 at −35°C, 1.6 at −50°C, 2.0 at −60°C, and 2.4 at −70°C. The fractional uncertainty in the mean of corrected measurements, when large datasets are considered statistically, increases from 0.06 at 0°C to 0.11 at −70°C. The fractional uncertainty for correcting an individual sounding is about ±0.2, which is larger because this statistical approach considers only the mean value of measurement errors that are not purely temperature dependent. The correction must not be used outside the temperature range 0° to −70°C, because it is a meaningless extrapolation of a polynomial curve fit.

Laboratory measurements of sensor response conducted at Vaisala are used to characterize some of the individual sources of RS80-A measurement error. A correction factor is derived for the dominant RS80-A measurement error at cold temperatures: an inaccurate approximation for the sensor’s temperature dependence in the data processing algorithm. The correction factor for temperature-dependence error is about 1.1 at −35°C, 1.4 at −50°C, 1.8 at −60°C, and 2.5 at −70°C. Dependences and typical magnitudes are given for measurement errors that result from the temperature dependence of the sensor’s time constant, and from several smaller bias errors and random uncertainties.

Corresponding author address: Dr. Larry M. Miloshevich, National Center for Atmospheric Research/MMM, P.O. Box 3000, Boulder, CO 80307-3000.

Email: milo@ucar.edu

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  • Antikainen, V., and A. Paukkunen, 1994: Studies on improving humidity measurement in radiosondes: WMO Tech. Conf. on Instruments and Methods of Observation, Geneva, Switzerland, WMO Rep. 57, 1–5.

  • Balagurov, A., A. Kats, and N. Krestyannikova, 1998: Implementation and results of the WMO radiosonde humidity sensors intercomparison (Phase I laboratory test). WMO Tech. Conf. on Meteorological and Environmental Instruments and Methods of Observation, Casablanca, Morocco, WMO Rep. 70, 181–184.

  • Blackmore, W. H., and B. Taubvurtzel, 1999: Environmental chamber tests of NWS radiosonde relative humidity sensors. Preprints, 15th Int. Conf. on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology. Dallas, TX, Amer. Meteor. Soc., 259–262.

  • Elliott, W. P., and D. J. Gaffen, 1991: On the utility of radiosonde humidity archives for climate studies. Bull. Amer. Meteor. Soc.,72, 1507–1520.

    • Crossref
    • Export Citation
  • Gaffen, D. J., 1993: Historical changes in radiosonde instruments and practices. Instruments and observing methods. WMO Rep. 50, 127 pp.

  • Heymsfield, A. J., and L. M. Miloshevich, 1993: Homogeneous ice nucleation and supercooled liquid water in orographic wave clouds. J. Atmos. Sci.,50, 2335–2353.

    • Crossref
    • Export Citation
  • ——, and ——, 1995: Relative humidity and temperature influences on cirrus formation and evolution: Observations from wave clouds and FIRE-II. J. Atmos. Sci.,52, 4302–4326.

    • Crossref
    • Export Citation
  • ——, ——, G. Sachse, C. Twohy, and S. Oltmans, 1998: Upper tropospheric relative humidity observations and implications for cirrus ice nucleation. Geophys. Res. Lett.,25, 1343–1346.

    • Crossref
    • Export Citation
  • Hyland, R. W., and A. Wexler, 1983: Formulations for the thermodynamic properties of the saturated phases of H2O from 173.15 K to 473.15 K. ASHRAE Trans.,89(2A), 500–519.

  • Ivanov, A., A. Kats, N. Kurnosenko, J. Nash, and N. Zaitseva, 1991:WMO International Radiosonde Intercomparison—Phase III. WMO Rep. 40, 135 pp.

  • Kitchen, M., 1989: Representativeness errors for radiosonde observations. Quart. J. Roy. Meteor. Soc.,115, 673–700.

    • Crossref
    • Export Citation
  • List, R. J., 1968: Smithsonian Meteorological Tables. 6th ed. Smithsonian Institution Press, 527 pp.

  • Lorenc, A. C., D. Barker, R. S. Bell, B. Macpherson, and A. J. Maycock, 1996: On the use of radiosonde humidity observations in mid-latitude NWP. Meteor. Atmos. Phys.,60, 3–17.

    • Crossref
    • Export Citation
  • Marti, J., and K. Mauersberger, 1993: A survey and new measurements of ice vapor pressure at temperatures between 170 and 250K. Geophys. Res. Lett.,20, 363–366.

    • Crossref
    • Export Citation
  • Mastenbrook, H. J., 1968: Water vapor distribution in the stratosphere and high troposphere. J. Atmos. Sci.,25, 299–311.

    • Crossref
    • Export Citation
  • Matsuguchi, M., S. Umeda, Y. Sadaoka, and Y. Sakai, 1998: Characterization of polymers for a capacitive-type humidity sensor based on water sorption behavior. Sens. Actuators,49, 179–185.

    • Crossref
    • Export Citation
  • Miloshevich, L. M., and A. J. Heymsfield, 1997: A balloon-borne continuous cloud particle replicator for measuring vertical profiles of cloud microphysical properties: Instrument design, performance, and collection efficiency analysis. J. Atmos. Oceanic Technol.,14, 753–768.

    • Crossref
    • Export Citation
  • Oltmans, S. J., and D. J. Hofmann, 1995: Increase in lower stratospheric water vapour at a mid-latitude Northern Hemisphere site from 1981 to 1994. Nature,374, 146–149.

    • Crossref
    • Export Citation
  • Paukkunen, A., 1995: Sensor heating to enhance reliability of radiosonde humidity measurement. Preprints, 11th Int. Conf. on Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Dallas, TX, Amer. Meteor. Soc., 103–106.

  • Ross, R. J., and W. P. Elliott, 1996: Tropospheric water vapor climatology and trends over North America: 1973–93. J. Climate,9, 3561–3574.

    • Crossref
    • Export Citation
  • Sakai, Y., Y. Sadaoka, and M. Matsuguchi, 1996: Humidity sensors based on polymer thin films. Sens. Actuators,35, 85–90.

    • Crossref
    • Export Citation
  • Salasmaa, E., and P. Kostamo, 1975: New thin film humidity sensor. Preprints, Third Symp. on Meteorological Observations and Instrumentation, Washington, DC, Amer. Meteor. Soc., 33–38.

  • Schmidlin, F. J., and A. Ivanov, 1998: Radiosonde relative humidity sensor performance: The WMO intercomparison–Sept 1995. Preprints, 10th Symp. on Meteorological Observations and Instrumentation, Phoenix, AZ, Amer. Meteor. Soc., 68–71.

  • Semerjian, H. G., 1990: Report of calibration on twenty radiosonde humidity sensors (H-Humicap). NIST Rep. TN245604, 12 pp.

  • Soden, B. J., and J. R. Lanzante, 1996: An assessment of satellite and radiosonde climatologies of upper-tropospheric water vapor. J. Climate,9, 1235–1250.

    • Crossref
    • Export Citation
  • ——, S. A. Ackerman, D. O’C. Starr, S. H. Melfi, and R. A. Ferrare, 1994: Comparison of upper tropospheric water vapor from GOES, Raman lidar, and cross-chain loran atmospheric sounding system measurements. J. Geophys. Res.,99, 21 005–21 016.

    • Crossref
    • Export Citation
  • Vömel, H., S. J. Oltmans, D. J. Hofmann, T. Deshler, and J. M. Rosen, 1995: The evolution of the dehydration in the Antarctic stratospheric vortex. J. Geophys. Res.,100, 13 919–13 926.

    • Crossref
    • Export Citation
  • Wade, C. G., 1995: Calibration and data reduction problems affecting national weather service radiosonde humidity measurements. Preprints, Ninth Symp. on Meteorological Observations and Instrumentation, Charlotte, NC, Amer. Meteor. Soc., 37–42.

  • Wexler, A., 1976: Vapor pressure formulation for water in range 0 to 100°C: A revision. J. Res. Nat. Bur. Stand.,80A, 775–785.

  • WMO, 1996: Measurements of upper air temperature, pressure, and humidity. Guide to Meteorological Instruments and Methods of Observation, 6th ed., WMO I.12-1–I.12-32.

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