| 03 Feb 2026
Investigation of Saharan dust plumes in Western Europe by remote Sensing, in situ measurements, and transport modelling
Abstract. The radiative forcing of atmospheric dust remains highly uncertain due to the significant spatial and temporal variability of dust particles, as well as their complex interactions with atmospheric constituents, radiation, and clouds. To investigate Saharan dust plumes in Western Europe, we collected comprehensive datasets from remote sensing observations (lidars & photometers), in-situ measurements (aerosol particle size & number), and model claculations (ICON-ART) for 4 different time periods with strong Saharan dust influence in southwest Germany. We determined Saharan dust proprieties and transport pattern employing these comprehensive datasets. Comparison between lidar measurements, sun photometer data, and ICON-ART predictions shows a relative good agreement for dust plume arrival times (± 20 min), dust layer heights and structures (±50 m), backscatter coefficients (± 0.16 Mm−1 sr−1 at 355 nm), aerosol optical depths (± 0.05 at 500 nm), demonstrating the capabilities of ICON-ART in predicting Saharan dust transport. The deviation observed for different meteorological conditions and at different locations are discussed in this paper to substantiate the model validation and to facilitate potential improvement of processes like dust emission, transport, aging, removal, as well as dust properties (size distribution, optics, micro-physics) in transport models like ICON-ART. This study contributes to better understand dust properties in Western Europe and helps to improve model capabilities in predicting Saharan dust plumes as well as their potential impact on clouds and weather.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.
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General comments:
This article presents an observational characterization of four cases of Saharan dust affecting the southwest Germany towards validating a dust transport model ICON-ART. This topic of high relevance to ACP. The in situ observations provide unique capability of characterizing the temporal evolution, vertical distribution, size distribution, and optical properties of dust and their mixture with other aerosol species. However, I feel the current study does not fully take advantage of the observational capability. There are gaps between what the authors aim to do and what they have indeed accomplished. The presentation needs improvement too. Therefore, I recommend returning the manuscript back to the authors for a major revision.
Specific comments:
1. While the authors have claimed, e.g. in the title of the manuscript, that the dust characterized by in situ observation in southwest Germany originated from Sahara, it has not been explicitly shown that these plumes indeed came from Sahara. The supplementary figures show potential connectivity between the dust observed in Germany with antecedent Saharan dust emission from MODIS AOD. But to directly demonstrate the dust source, the authors may need to conduct back trajectory analysis for each of these cases, show the dust trajectory on top of the MODIS AOD maps, and move these maps to the main article.
2. While the authors stated that the major objective of this study was to “assess the performance of dust prediction for ICON-ART, to identify model improvements, and to better understand dust properties during these dust events benefiting from the advanced instruments”, the model assessment is indeed quite qualitative from my reading of the current manuscript:
(i) The model turns off gaseous and other aerosol species, whereas the observations contain a fully mixing scenario. The authors processed the observational data to obtain a dust signal, e.g. by equation (1); this processing may introduce uncertainty for model evaluation per se. I’m not complaining about the use of equation (1) but thinking that it would be optimal if the model turns on full chemistry. Under the full chemistry set up, the authors can truly characterize the ageing and mixing of Saharan dust using their advanced instrumentation.
(ii) If the authors insist using the dust-only set up, they have to clearly state that in the method section. Under this circumstance, the authors have to restrict their goal to validating the meteorology, dust transport pathway, and vertical and size distribution at the observational site. If this is the case, the authors need to expand their validation of the meteorology using three-dimensional data, probably from ERA5, that covers the source to the observation site.
3. The ICON-ART model overestimated wet removal in Case 3, any idea why? Does it relate to the simulated distribution bias in precipitation and cloud? Or the vertical distribution of dust? Can you use real data to demonstrate the reason? I think this is an interesting finding to dive deeper into.
4. The discussion section is overly general, i.e. any model-data comparison work could attribute the discrepancies to these factors. Could you point to your results when discussing about each factor. For example, how did you reach the conclusion that “plume-boundary layer interaction and aerosol mixing play a dominant role”? Do you have evidence from your analysis?
5. The description of each case is overly descriptive and lengthy, with some statements unsupported by any observational evidence. For example, the synoptic weather conditions for Case 2 are extensively discussed without any figure of real data or reference. If the authors decide to take my earlier suggestion and expand the model validation to meteorology, please add quantitative analysis about meteorological condition in all cases. Otherwise, I suggest to reduce such descriptive text about each case.
Technical corrections:
1. Figures 1, 3, 6, 8, 10, 11, 12: missing all or part of the panel index (a, b, …).
2. Contents that better fit the method section:
(i) separation of the total backscatter coefficient into a dust part and a non-dust part.
(ii) definition of the dust layer height.
3. The sentence on lines 255-257: “The volume size distribution ... has the highest concentration…” is confusing.
4. Contents that better fit the corresponding figure caption:
(i) The blue-shaded area … (lines 421-422)
(ii) The boxplots … (lines 429-431)
5. There is a typo of the word “calculation” in the abstract.
6. On line 60, double “also”.
7. On line 83, MODIS is a satellite instrument rather than a satellite.