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Radiosonde Temperature Measurements in Strong Inversions: Correction for Thermal Lag Based on an Experiment at the South Pole

Radiosonde Temperature Measurements in Strong Inversions: Correction for Thermal Lag Based on an Experiment at the South Pole,10.1175/1520-0426(1997)0

Radiosonde Temperature Measurements in Strong Inversions: Correction for Thermal Lag Based on an Experiment at the South Pole   (Citations: 25)
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Very steep shallow temperature inversions occur during most of the year in the near-surface layer on the Antarctic Plateau. A radiosonde carried by a balloon rising at a few meters per second does not measure such inversions accurately because the response time of the thermistor is several seconds. To quantify this error, the authors flew a radiosonde on a tethered kite on several occasions in winter at South Pole Station immediately prior to the routine launch of the same sonde on a weather balloon. In all cases, the equilibrated temperatures measured by the tethered sonde at a given pressure level were higher than those from the balloon-borne sonde throughout most of the inversion layer. Assuming that the tethered sonde data represent the true atmospheric temperature profile, a procedure can be developed to correct the temperature data from routine radiosonde soundings for the finite response time of the thermistor. The authors devise an accurate deconvolution method to retrieve the true atmospheric temperature profile from the radiosonde data when the thermistor response time is known. However, a simple technique of shifting the profile a few seconds back in time gives results that are nearly equivalent to the deconvolution. Additional temperature errors result at the South Pole because the radiosonde is launched immediately after being brought out of a warm room, making it necessary to further adjust data from the lowest few tens of meters. It is found that the temperature errors cause a 0.3 W m22 error in the computed downward longwave radiation flux in winter at the South Pole, most of which is in spectral regions dominated by emission from water vapor and carbon dioxide. This is similar to the 0.5 W m22 change induced by the increase in carbon dioxide concentration from preindustrial to present values. The thermal lag is shown to be significant also for winter profiles in Alaska. A correction for thermal lag is recommended for all situations where radiosondes are used to measure steep temperature gradients in the boundary layer: in polar regions throughout the year, at midlatitude continental stations in winter, and at the tops of subtropical marine stratocumulus clouds.
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    • ...Vertical profiles of temperature and pressure measured by radiosondes and output from NWAs often fail to miss the extreme temperature changes near the tops of the boundarylayer inversions [48]–[51]...

    Patrick Minniset al. CERES Edition2 Cloud Property Retrievals Using TRMM VIRS and Terra and...

    • ...Mahesh et al. [1997] compared radiosonde temperature measurements at South Pole with those made by thermistors onboard a tethered balloon, finding that marked thermal lag errors usually affect the radiosonde measurements up to an altitude of about 250 m above the surface, i.e., up to 40 s after launch...
    • ...At Dome C, all the radiosondes were routinely prepared in an appropriate room and then left in the external ambient air for at least 5 min before launch, thus avoiding errors such as those evidenced by Mahesh et al. [1997]...

    Claudio Tomasiet al. Analysis of a 4 year radiosonde data set at Dome C for characterizing ...

    • ...It may be partly explained by a temperature difference between the sounder and the air outside when the sounder is launched (Mahesh et al. 1997)...

    Hubert Galléeet al. Validation of a limited area model over Dome C, Antarctic Plateau, dur...

    • ...[5] Before use, whether for operational or research purposes, historical radiosonde profiles often require corrections for temporal lags [e.g., Mahesh et al., 1997; Hudson et al., 2004; Miloshevich et al., 2004] and biases due to solar radiation and contamination [Wang et al., 2002; Miloshevich et al., 2004; Rowe et al., 2008; Miloshevich et al., 2009]...
    • ...Lag corrections to RS temperature profiles [Mahesh et al., 1997] are no longer necessary for the newer RS92 sondes [Rowe et al., 2008]...

    Christophe Genthonet al. Meteorological atmospheric boundary layer measurements and ECMWF analy...

    • ...However, when a cloud forms underneath an inversion, the measured vertical profile often misses the coldest temperature under the inversion, likely as a result of the sharpness of the inversion and the relatively slow thermal response of the instrument [e.g., Mahesh et al., 1997]...
    • ...The lack of colder temperatures in the soundings at cloud top could be due to radiosonde lag effect noted earlier [Mahesh et al., 1997] or to the cloud being Figure 6. (a–f) Same as Figure 5 except for daytime Aqua results...

    Xiquan Donget al. Comparison of CERES-MODIS stratus cloud properties with ground-based m...

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