the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Feb 2026
Remote sensing of local-dust across the Canadian Arctic
Abstract. We investigated the optical and microphysical characterization of High- and sub-Arctic dust events across the Canadian Arctic Archipelago (CAA). Events from local sources (local dust) were first identified and characterized using a combination of ground-based lidar, two AERONET instruments, and passive (MODIS, Sentinel-2, MISR) imagery in the neighbourhood of the High-Arctic Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut (on Ellesmere Island in the northernmost part of the CAA).
The PEARL findings informed the identification and characterization of local dust events over other parts of the CAA using a suite of satellite instruments whose remote sensing (RS) capabilities were complementary to or an extension of the ground- and satellite-based techniques employed at Eureka. The events included plumes emanating from Axel Heiberg Island, just west of Ellesmere Island, Banks Island in the southwest corner of the CAA, Ellef Ringnes Island in the eastern part of the central CAA and Prince of Wales Island / Victoria Island in the central southern CAA. Plume identification, plume source and CM (coarse mode) aerosol optical depth (AOD) retrievals were investigated using a combination of low to high spatial resolution (MODIS to Sentinel-2) color imagery and the MODIS dark target AOD product over water. Plume thickness, height and speed for most of the events were obtained (depending on orbit availability and lack of cloud contamination) from MISR (Multi-angle Imaging Spectro Radiometer) stereoscopic products.
These RS results support an argument for the ubiquitous presence of pan-Arctic, low altitude dust that is typically (away from any strong sources such as mountainous drainage basins) at the lower levels of detectability offered by ground- and satellite-based RS techniques. The ability to RS airborne, near-source, local dust events and characterize dust properties and dynamics of important regions such as the CAA is critical to understanding local dust impacts such as early snow/ice melt and the nucleation role of local dust in the formation of low-altitude clouds.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-6037', Anonymous Referee #1, 04 Mar 2026
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RC2: 'Comment on egusphere-2025-6037', Anonymous Referee #2, 10 Mar 2026
The topic of remote sensing of high latitude dust (HLD) is of particular interest because dust has direct and indirect radiative effects on the radiation budget and also on surface albedo. As the authors clearly highlight, despite the wide spatial distribution of HLD in the Arctic, its optical properties and abundance do not allow for a clear signature on remotely sensed signals. The use of space-borne observations together with ground-based in situ and remote sensing measurements, which are scarce in the polar regions, can help characterise the properties and effects of HLD.
The manuscript by S.A. Sayedain discusses local HLD in the Canadian Arctic Archipelago (CAA) using both remote sensing and in situ ground-based measurements, as well as satellite observations and products derived from MODIS, MISR, and Sentinel-2 imagery. The authors show how the ground based optical and microphysical measurements at Eureka can be interpreted to detect even weak dust events, and that these events are recognizable in satellite imagery. This supports the detection of other HLD events observed in the pan-CCA only from satellite remote sensing data and wind from CARRA reanalyses.
Although the work is based on rigorous analysis and many details are presented in a very careful manner, the presentation of the work is not very clear in some parts, both in the text and due to the lack of significant figures within it. Although important for following the analysis and describing the results, the figures are included only in the supplementary material in PowerPoint format, while in my opinion they should be presented in the manuscript. More specific comments follow.
About the presentation of the analysed cases, the rather frequent use of footnotes and parenthetical text, combined with reference to supplementary material, does not make the manuscript a completely smooth read. An example is provided in lines 212-216:
“We carried out a purely optical analysis comparing CIMEL and AHSRL data14 in order to demonstrate certain optical dynamics that were consistent with the apparent presence of dust particles at low elevations between 0PAL and the Ridge lab. In a different sequence of events, the 0PAL CIMEL AOD measurements and in situ APS PVSDs shared a common measurement period from July 9 to September 20, 2018. These two periods were an important focus of our ground-based analysis at the PEARL sites”.
The information of the two periods that are taken into account is partially in the text (from July 9 to September 20, 2018) and partially in the footnotes (August 2005 to June 2010). Introducing or re-introducing in the main text the information of the analysed period (in this case) is essential for the reader to understand.
I also believe that parenthesis within another parenthesis should be avoided.
Additionally, some information in the footnotes may be omitted (such as 18 and 21).
It is clear that the complexity of describing what is happening over a large area around Eureka, with a weak footprint especially in remote sensing measurements, requires the use of extensive material, including satellite imagery, reanalysis, etc., hence the use of supplementary material. The result in some cases is that the reader expects some clarifying figures in the main text which are not present and that some text and figures the reader expects in a paragraph are different from what they find. An example is paragraph 4.1.3 Satellite imagery versus ground-based measurements at Eureka: the entire discussion of the evidence for the dust plume over Eureka Sound is based on Sentinel-2 imagery and the CARRA wind field, which however are not found in the text, while the text only contains the wind pattern at Eureka. Furthermore, this paragraph would play a key role in the manuscript because it would link the in situ measurements to the remote sensing ones, on which the case analysis in Section 4.2 is based. However, Section 4.2 seems to me to be practically independent of the previous one.
In my opinion the description of the dust events across the CAA (Section 4.2 and paragraphs therein) should start reporting the date of the event, without leaving this information in footnote 29.
Figure 5 is very interesting and clear. The reference to Figure S14a doesn't add much, but it makes reading more difficult because of the switch from the manuscript to the Power Point file. On the contrary, Figure S14b with the CARRA wind field could be included in the text instead of in the Power Point file.
To make the manuscript easier to read, I recommend selecting the minimum number of images/maps essential to support the methodology and the results and reporting them in the main text, while leaving non-essential figures and animations in the supplementary material. This is the main aspect to take care of, which in my opinion requires major revisions.
Minor comments
Lines 260-262: this is a repetition
Lines 287-288: I would not say “In the first instance, such weak events would seem to be detectable from a satellite sensor such as MODIS whose nominal precision appears to be significantly smaller” but simply state that the MODIS precision for low AOD is not sufficient to discriminate optically weak dust events
Line 342: if the largest AOD is 0.42, why the legend of figure 5b has a lower value, 0.40, as maximum?
Line 356: same comment as that for line 342.
Citation: https://doi.org/10.5194/egusphere-2025-6037-RC2
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I recommend publication after minor revisions -- specifically, the addition of certain caveats. Here is my full review:
This paper applies a collection of in situ and remote sensing observations to characterize the properties of seven dust events in the Canadian Arctic Archipelago. Surface data focuses on instruments at Eureka: the CIMEL, from which AERONET retrieval products were obtained, the Arctic HSRL, and an APS. Satellite remote sensing data include MODIS, MISR, and Sentinel-2 imagery, aerosol optical depth mapping, and from MISR, also plume heights. Wind data are obtained from MISR and from Reanalysis. The authors have built a cottage industry in studying dust in the Arctic, which is an important topic, as summarized in the paper’s introduction section; this paper aims to provide a useful addition to that literature.
A lot of careful work has gone into analyzing the seven cases presented. The value in this work is that it demonstrates techniques that could to some extent be applied more widely around the Arctic based on remote sensing data alone. Such wider application would be part of follow-on work, which is why the current paper is appropriate for AMT, as the authors indicate. The authors make a considerable effort to justify the interpretation of satellite remote-sensing signals in the seven cases as due to local dust events, and they are each quite convincing, despite very low AOD values. I note that most passive satellite remote-sensing observations in the Arctic remain extremely difficult to interpret. My primary recommendation is that in the Abstract and especially in the Conclusions, caveats might be provided that make clear the seven cases presented here are all distinct, narrow plumes, at least partly over dark water, downwind of likely dust sources, under contemporaneous high-wind conditions, and that interpreting MODIS and MISR data as indicating local dust plumes more generally must be done with similar care. Some further notes are included below.
Notes
Lines 182-184. As this study uses primarily MODIS DT over water, in interpreting the FMF product, one needs to consider that sea spray can also be a “coarse mode” aerosol, especially in the vicinity of the high-wind events that can also be effective in mobilizing local dust. This is not a concern in the seven cases highlighted in the current paper, but caution would be needed when applying the approach more generally.
Figure 2. In itself, this is a tough measurement. All the AODs are below 0.01. I understand that the authors have done a convincing job assembling other indications that this is a dust event. However, I have to ask whether variability in the background AOD produces similar fluctuations in general, especially if the intent is to subsequently apply this technique more widely, specifically in cases lacking the distinct, narrow plumes over dark water surfaces, downwind of regions with the characteristics of likely dust sources represented by the seven cases studied in detail here.
Lines 285-288. I know it is given in the publication cited in the footnote, but this estimate of MOIDS sensitivity to AOD seems *extremely* optimistic, especially when applied in the Arctic. Consider the further, extenuating conditions at high latitudes – low sun angle, very bright snow or ice-covered surfaces that can affect the recorded signal in nearby dark-water areas due to latency, internal reflections, or other instrumental effects, and possible thin cirrus contamination. I guess, for wider application of the approach, it would strengthen the case to show that, in non-dust circumstances (based on verifiable surface measurements where available), such remote-sensing signals are unlikely to occur. I.e., characterize as much as possible the likelihood of false positives.
Figure 4. Another thought, given the challenges involved in applying this technique more widely. Conditions for mobilizing dust would include sufficiently high wind (which is considered for the cases included in the paper), the availability upwind of loose surface dust that is not snow-, ice-, or vegetation-covered (also considered in the paper for the case studies), and usually some surface roughness to mix momentum downward. At least some locations of surface dust deposits have already been mapped across the Arctic, based on the identification of dry river deposits, mountain talus accumulations, etc. in seasons when those surfaces are snow- and ice-free. The exposure of such upwind surfaces at the specific time of dust-plume observation could be verified with contemporaneous satellite imagery. These considerations would be especially important when interpreting possible remote-sensing local dust-plume detections in general, in the absence of ground-truth data. (I agree that the seven specific cases presented in the current paper are convincing.)
Page 18, footnote 34. I’m not sure what “…neither the plume height nor the plume speed sampling trajectories are subject to any objective sampling protocol…” means. As I understand, the MISR MINX retrievals are done on all 1 km pixels within a user-defined aerosol plume region where the spatial contrast relative to surrounding pixels in the multi-angle images is sufficiently above the noise to produce a geometric height retrieval.
Generally, it would be helpful to have a more complete list of Symbols and Abbreviations. I know there is a list in Appendix B, but many are missing, such as, tco, tcp, tcl, VDR, etc. It is a long article, and there are many non-standard abbreviations; searching for the meaning of some abbreviation becomes tedious.