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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Apr 2019

Research article | 23 Apr 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).

Microwave Radar/radiometer for Arctic Clouds MiRAC: First insights from the ACLOUD campaign

Mario Mech1, Leif-Leonard Kliesch1, Andreas Anhäuser1, Thomas Rose2, Pavlos Kollias1,3, and Susanne Crewell1 Mario Mech et al.
  • 1Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany
  • 2Radiometer-Physics GmbH, Meckenheim, Germany
  • 3School of Marine and Atmospheric Sciences, Stony Brook University, NY, USA

Abstract. The Microwave Radar/radiometer for Arctic Clouds (MiRAC) is a novel instrument package developed to study the vertical structure and characteristics of clouds and precipitation onboard the Polar 5 research aircraft. MiRAC combines a frequency modulated continuous wave (FMCW) radar at 94 GHz including a 89 GHz passive channel (MiRAC-A) and an eight channel radiometer with frequencies between 175 and 340 GHz (MiRAC-P). The radar can be flexibly operated using different chirp sequences to provide measurements of the equivalent radar reflectivity with different vertical resolution down to 5 m. MiRAC is mounted for down-looking geometry on Polar 5 to enable the synergy with lidar and radiation measurements. To mitigate the influence of the strong surface backscatter the radar is mounted with an inclination of about 25° backward in a belly pod under the Polar 5 aircraft. Procedures for filtering ground return and range side-lobes have been developed. MiRAC-P frequencies are especially adopted for low humidity conditions typical for the Arctic to provide information on water vapor and hydrometeor content. MiRAC has been operated on 19 research flights during the ACLOUD campaign in the vicinity of Svalbard in May/June 2017 providing in total 48 hours of measurements from flight altitudes > 2300 m. The radar measurements have been carefully quality controlled and corrected for surface clutter, mounting of the instrument, and aircraft orientation to provide measurements on a unified, geo-referenced vertical grid allowing the combination with the other nadir pointing instruments. An intercomparison with CloudSat shows good agreement in terms of cloud top height of 1.5 km and radar reflectivity up to −5 dBz and demonstrates that MiRAC is able to fill the gap in observing low level clouds with its more than ten times higher vertical resolution down to about 150 m above the surface. This is especially important for the Arctic as about 45 % of the clouds during ACLOUD showed cloud tops below 1200 m, i.e., the blind zone of CloudSat.

Mario Mech et al.
Interactive discussion
Status: open (until 01 Jul 2019)
Status: open (until 01 Jul 2019)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Mario Mech et al.
Data sets

Airborne radar reflectivity and brightness temperature measurements with POLAR 5 during ACLOUD in May and June 2017 L.-L. Kliesch and M. Mech

Mario Mech et al.
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Short summary
An improved understanding of Arctic mixed-phase clouds and their contribution to Arctic warming can be achieved by observations from airborne platforms with remote sensing instruments. Such an instrument is MiRAC combining active and passive techniques to gain information on the distribution of clouds, the occurrence of precipitation and the amount of liquid and ice within the cloud. Operated during a campaign in Arctic summer, it could observe lower clouds often not seen be space-borne radars.
An improved understanding of Arctic mixed-phase clouds and their contribution to Arctic warming...