Preprints
https://doi.org/10.5194/amt-2021-187
https://doi.org/10.5194/amt-2021-187

  20 Jul 2021

20 Jul 2021

Review status: a revised version of this preprint is currently under review for the journal AMT.

Laboratory characterisation of the radiation temperature error of radiosondes and its application to the GRUAN data processing for the Vaisala RS41

Christoph von Rohden1, Michael Sommer1, Tatjana Naebert1, Vasyl Motuz2, and Ruud J. Dirksen1 Christoph von Rohden et al.
  • 1GRUAN Lead Centre, Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg, Am Observatorium 12, 15848 Tauche/Lindenberg, Germany
  • 2Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology, Cottbus-Senftenberg, Siemens-Halske-Ring 15a, 03046 Cottbus, Germany

Abstract. The paper presents the Simulator for Investigation of Solar Temperature Error of Radiosondes (SISTER), a setup that was developed to quantify the solar heating of the temperature sensor of radiosondes under laboratory conditions by recreating as closely as possible the atmospheric and illumination conditions that are encountered during a daytime radiosounding ascent. SISTER controls the pressure (3 hPa to 1020 hPa) and ventilation speed of the air inside the windtunnel-like setup to simulate the conditions between the surface and 35 km altitude, to determine the dependence of the radiation temperature error on the irradiance and the convective cooling. The radiosonde is mounted inside a quartz tube, while the complete sensor boom is illuminated by an external light source to include the conductive heat transfer between sensor and boom. A special feature of SISTER is that the radiosonde is rotated around its axis to imitate the spinning of the radiosonde in flight. The characterisation of the radiation temperature error is performed for various pressures, ventilation speeds and illumination angles, yielding a 2D-parameterisation of the radiation error for each illumination angle, with an uncertainty smaller than 0.2 K (k = 2) for typical ascend speeds. This parameterisation is applied in the GRUAN processing for radiosonde data, which relies on the extensive characterisation of the sensor properties to produce a traceable reference data product which is free of manufacturer dependent effects. The GRUAN radiation correction model combines the laboratory characterisation with model calculations of the actual radiation field during the sounding to estimate the correction profile. In the second part of this paper it is described how this procedure was applied in the development of the GRUAN data product for the Vaisala RS41 radiosonde (version 1, RS41-GDP.1). The magnitude of the averaged correction profile increases gradually from 0.1 K at the surface to approximately 0.8 K at 35 km altitude. Comparison between sounding data (N = 154) that were GRUAN-processed and Vaisala-processed reveal that the daytime differences are smaller than +0.1 K (GRUAN – Vaisala) in the troposphere and increase above the tropopause steadily with altitude to +0.35 K (GRUAN – Vaisala) at 35 km. These differences are just within the limits of the combined uncertainties (with coverage factor k = 2) of both data products, meaning that the GRUAN processing and the Vaisala processing are in agreement.

Christoph von Rohden et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-187', Anonymous Referee #1, 11 Aug 2021
    • AC1: 'Reply on RC1', Christoph von Rohden, 15 Sep 2021
  • RC2: 'Comment on amt-2021-187', Anonymous Referee #2, 17 Aug 2021
    • AC2: 'Reply on RC2', Christoph von Rohden, 15 Sep 2021

Christoph von Rohden et al.

Data sets

Asset package related to AMT article 'Laboratory characterisation of the radiation temperature error of radiosondes and its application to the GRUAN data processing for the Vaisala RS41' Christoph von Rohden, Michael Sommer, Ruud J. Dirksen https://www.gruan.org/data/data-packages/dpkg-2021-1

Christoph von Rohden et al.

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Short summary
Heating by solar radiation is the dominant error source for daytime temperature measurements by radiosondes. This paper describes a new laboratory setup to characterise this radiation error for pressures and ventilation speeds that are typical for the conditions between the surface and 35 km altitude. This characterisation is the basis for the radiation correction that is applied in the GRUAN data processing for the RS41 radiosonde. The GRUAN data product is compared to that of Vaisala.