the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Sep 2026
EarthCARE Commissioning Calibration and Validation Campaign in Ottawa (ECALOT): An Integrated Approach to Multi-level EarthCARE Validation
Abstract. The EarthCARE Commissioning Calibration and Validation Campaign in Ottawa (ECALOT) was a dedicated airborne and surface-based campaign designed to support the calibration and validation of Level 1 and Level 2 products from the EarthCARE satellite mission. The campaign was conducted between October 2024 and March 2025 in eastern Canada, primarily in the regions surrounding Ottawa and Montreal. Airborne observations were carried out using the National Research Council Canada (NRC) Convair-580 research aircraft, equipped with remote sensing instruments analogous to those flown on EarthCARE, including a nadir/zenith/side-looking 94 GHz cloud radar system with Doppler capability and zenith/nadir-pointing 355 nm elastic lidars, together with a comprehensive suite of in situ cloud and aerosol probes. Complementary surface-based observations were obtained at a primary site at the Ottawa Macdonald-Cartier International Airport and two additional climate sentinel stations in the Montreal region, providing continuous ground-based reference measurements of surface radiation, atmospheric thermodynamic profiles, precipitation, and other meteorological variables.
A total of seven research flights were conducted, sampling a range of mid-latitude continental cloud conditions, including stratocumulus, multilayer cloud systems, and nimbostratus associated with liquid- or solid-phase precipitation. The ECALOT sampling strategy was designed to integrate airborne and surface-based in situ and remote-sensing observations collected along and offset from EarthCARE’s ground track, while accounting for temporal offsets relative to the satellite overpass. Together, the ECALOT campaign provides coordinated multi-platform observations that enable evaluation of active sensor measurements, radar-lidar-imager synergy, representation of liquid, ice and mixed-phase clouds, three-dimensional scene construction, and radiative closure across EarthCARE’s data processing chain, while also providing observational constraints for improving the representation of mixed-phase clouds and their radiative effects in numerical models.
Competing interests: Robin J. Hogan (robin.hogan@ecmwf.int) is one of the editors of the special issue to which this manuscript is submitted.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 24 Oct 2026)
- RC1: 'Comment on egusphere-2026-5347', Anonymous Referee #1, 19 Oct 2026 reply
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RC2: 'Comment on egusphere-2026-5347', Anonymous Referee #2, 19 Oct 2026
reply
Review of ‘EarthCARE commissioning Calibration and Validation Campaign in Ottawa (ECALOT): An Integrated Approach to Multi-level EarthCARE Validation’ by Qu et al.
General Comments
The manuscript provides an overview of the ECALOT campaign, conducted between October 2024 and March 2025 to support the calibration and validation of Level 1 and Level 2 products of the EarthCARE mission. The campaign combined coordinated research flights with continuous ground-based measurements.
To my feeling, the current state of the manuscript reads heavily like an introductory ‘whitepaper’ than a real scientific publication. The manuscript spends significant space describing general concepts and planned analyses while referencing ‘in-preparation’ manuscripts for quantitative results. Before publication, the authors should make the effort to restructure the manuscript; to streamline redundancies; provide more concrete information on measurements, instrument calibration and uncertainties, and on the matchup quality. Furthermore, the authors should work on better highlighting the value of the measurements for EarthCARE validation by showing conclusive studies.
The manuscript is well within the scope of the journal and presents a valuable contribution. However, to my opinion, major revisions are required before publication.
Main points:
- The manuscript suffers from repetitions across Section 1, 2, and 3. I recommend to consolidate Section 2 and 3 into a single, streamlined campaign overview and design section, and to avoid repeatedly detailing the general EarthCARE processing chain and Level1/Level2 product definitions.
- Throughout Section 6 the manuscript fails to provide concrete conclusions but refers to upcoming papers. If this paper is strictly intended as a campaign overview paper, this should be clearly stated in the title and abstract. However, even as an overview paper, it should present synthesized results and/or statistical summaries rather than pointing only to future publications.
- The text emphasizes the flight sampling strategies but lacks explicit quantitative details on how well the satellite and aircraft matched in practice across the 7 flights. What were the offsets in km and seconds/minutes for each flight? I recommend to include a summary table.
- The manuscript comes short in describing the instrument calibration and quality control. E.g. the description of the airborne elastic cloud lidar (AECL) mentions signal merging and deadtime corrections, but fails to explain how absolute calibration was performed or how the depolarization ratio was calibrated and corrected. The description of quality control of the surface measurements relies mostly on standard flags. More detailed quantified uncertainties and statements on instrument stability across the 6-month deployment are required.
- The detailed discussion of GEOMS template creation is too technical for a scientific article and adds little value to the scientific massage. It should be removed or significantly shortened.
Minor points:
- Table 1: The instrument table is extensive, but the text lacks operational details (e.g. flight altitudes, range limits of the airborne lidar/radar under typical campaign conditions). This should be changed, to include all relevant information.
- Table 5 and Table 7: There is significant overlap between Table 5 (mapping ECALOT datasets) and Table 7 (EarthCARE products). These two tables should be merged to avoid duplications.
Citation: https://doi.org/10.5194/egusphere-2026-5347-RC2
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see attached pdf