Universität zu Köln

Böck, Tobias ORCID: 0009-0006-0750-9274, Löffler, Moritz ORCID: 0000-0003-0358-6441, Marke, Tobias ORCID: 0000-0001-7804-9056, Pospichal, Bernhard ORCID: 0000-0001-9517-8300, Knist, Christine and Löhnert, Ulrich ORCID: 0000-0002-9023-0269 (2025). Instrument uncertainties of network-suitable ground-based microwave radiometers: overview, quantification, and mitigation strategies. Atmospheric Measurement Techniques, 18 (21). pp. 6251-6270. Copernicus. ISSN 1867-8548

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Abstract

To enhance observations of the atmospheric boundary layer (ABL), the European Meteorological Network (EUMETNET), and the Aerosol, Clouds, and Trace Gases Research Infrastructure (ACTRIS) are currently collaborating to establish networks of microwave radiometers (MWRs). MWRs can be used to derive thermodynamic profiles within the ABL. Understanding and assessing instrument uncertainties of state-of-the-art MWRs are therefore crucial for accurate observations and also data assimilation purposes. Some national weather services are currently exploring the potential of MWR networks to improve short-term weather forecasts. In this paper, we discuss uncertainties inherent to the MWR instrument itself, namely (1) radiometric noise, (2) long-term drifts and jumps, (3) calibration repeatability, (4) biases/systematic differences between instruments, and (5) radome degradation. These uncertainties are expressed in brightness temperatures. For state-of-the-art MWRs (here, the Generation 5 Humidity and Temperature Profiler, HATPRO-Gen5), radiometric noise at ambient temperatures is a maximum of 0.32 K in the V-band but usually lower, especially near cold load temperature ranges in the K-band (≤0.11 K). Long-term drifts or jumps between calibrations, which are at least 2 months apart, are usually below 0.4 K in the K-band and 1.0 K in the V-band but can also be higher. Drifts do not follow a discernable timely pattern and are therefore not easily quantifiable in a meaningful way. Calibrating at least every 6 months is thus advised. Calibration repeatability is shown to be well under 0.16 K. Mean brightness temperature differences between two HATPRO-Gen5 instruments are shown to be as high as 0.15 K in the K-band and 0.58 K in the V-band in the zenith viewing direction. The radome has significantly degraded due to weathering and needs to be replaced if, 10 min after a rain event, residual water on its surface still causes a temperature deviation of more than 2 K, compared with a dry radome.

Item Type:	Article
Creators:	Creators Email ORCID ORCID Put Code Böck, Tobias UNSPECIFIED https://orcid.org/0009-0006-0750-9274 UNSPECIFIED Löffler, Moritz UNSPECIFIED https://orcid.org/0000-0003-0358-6441 UNSPECIFIED Marke, Tobias UNSPECIFIED https://orcid.org/0000-0001-7804-9056 UNSPECIFIED Pospichal, Bernhard UNSPECIFIED https://orcid.org/0000-0001-9517-8300 UNSPECIFIED Knist, Christine UNSPECIFIED UNSPECIFIED UNSPECIFIED Löhnert, Ulrich UNSPECIFIED https://orcid.org/0000-0002-9023-0269 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-812180
Identification Number:	10.5194/amt-18-6251-2025
Journal or Publication Title:	Atmospheric Measurement Techniques
Volume:	18
Number:	21
Page Range:	pp. 6251-6270
Number of Pages:	20
Date:	6 November 2025
Publisher:	Copernicus
ISSN:	1867-8548
Language:	English
Faculty:	External institution Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > Forschungszentrum Jülich Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute for Geophysics and Meteorology
Subjects:	Earth sciences Geography and travel
['eprint_fieldname_oa_funders' not defined]:	Publikationsfonds UzK
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/81218