14 Nov 2022
14 Nov 2022
Status: this preprint is currently under review for the journal AMT.

A new airborne broadband radiometer system and an efficient method to correct thermal offsets

André Ehrlich1,, Martin Zöger2,, Andreas Giez2, Vladyslav Nenakhov2, Christian Mallaun2, Rolf Maser3, Timo Röschenthaler3, Anna E. Luebke1, Kevin Wolf1,a, Bjorn Stevens4, and Manfred Wendisch1 André Ehrlich et al.
  • 1Leipzig Institute for Meteorology, Leipzig University , Germany
  • 2German Aerospace Center, Flight Experiments, Oberpfaffenhofen, Germany
  • 3enviscope GmbH, Frankfurt am Main, Germany
  • 4Max Planck Institute for Meteorology, Hamburg, Germany
  • anow at: Institute Pierre-Simon Laplace, Sorbonne Université, Paris, France
  • These authors contributed equally to this work.

Abstract. The instrumentation of the High Altitude and Long Range (HALO) research aircraft is extended by the new Broadband AirCrAft RaDiometer Instrumentation (BACARDI) to quantify the radiative energy budget. Two sets of pyranometers and pyrgeometers are mounted to measure upward and downward solar (0.3–3 μm) and thermal-infrared (3–100 μm) irradiances. The radiometers are installed in a passively ventilated fairing to reduce the effects of the dynamic environment, e.g., fast changes of altitude and temperature. The remaining thermal effects range up to 20 W m-2 for the pyranometers and 10 W m-2 for the pyrgeometers; they are corrected using an new efficient method that is introduced in this paper. Using data collected by BACARDI during a night flight, the thermal offsets are parameterized by the rate of change of the radiometer sensor temperatures. Applying the sensor temperatures instead of ambient air temperature for the parameterization provides a linear correction function (200–600 W m-2 K-1 s), that depends on the mounting position of the radiometer on HALO. Furthermore, BACARDI measurements from the EUREC4A (Elucidating the role of clouds-circulation coupling in climate) field campaign are analyzed to characterize the performance of the radiometers and to evaluate all corrections applied in the data processing. Vertical profiles of irradiance measurements up to 10 km altitude show that the thermal offset correction limits the bias due to temperature changes to values below 10 W m-2. Measurements with BACARDI during horizontal, circular flight patterns in cloud-free conditions demonstrate that the common geometric attitude correction of the solar downward irradiance provides reliable measurements in this typical flight sections of EUREC4A, even without active stabilization of the radiometer.

André Ehrlich et al.

Status: open (until 22 Dec 2022)

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André Ehrlich et al.

André Ehrlich et al.


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Short summary
Measurements of the broadband radiative energy budget from aircraft are needed to study the effect of clouds, aerosol particles, and surface conditions on the Earth's energy budget. However, the moving aircraft introduces challenges to the instrument performance and post processing of the data. This study introduces a new radiometer package, outlines an efficient method to correct thermal offsets, and provides exemplary measurements of solar and thermal-infrared irradiance.