Today it is well accepted that the pollen play an important role in the process of aerosol cloud interaction. Still, the pollen optical properties, as well as the dynamic of their spatio – temporal variations are not studied sufficiently. One of the reasons is that pollen are normally mixed with other types of aerosol, and it is difficult to characterize the properties of “pure” pollen. From this point of view, the study presented is very important. The authors use three remote sensing instruments and provide the particle depolarization ratios at four wavelengths, from UV to IR. It is also important that authors consider numerous measurement cases, accumulated during field campaigns, thus allowing to estimate the depolarization ratio of pure birch and pine pollen. The paper is well and clearly written and is suitable for ACP. I have just several technical notes.

Notes:

Decrease of depolarization at 900 nm looks unexpected. But considering uncertainty of the measurements, may be this decrease is inside the uncertainty interval.

I wonder, why in Fig.2a pollen concentration is shown in logarithmic scale. Probably variations would be better seen in linear scale. But this is up to authors.

Fig.2b. I would change scale of backscattering to 0 - 2 Mm-1sr-1, to see details of profiles. The layer looks to be well mixed and backscattering at 532, 910, 1064 does not change with height, while at 355 nm it increases below 1 km. Can it be effect of overlap? This increase correlates with drop of particle depolarization at 355.

Fig.2c. I would change scale of BAE also: -1 – 2.

Fig.3. If dust contribution increase, it should increase also depolarization at 355 nm. Was it observed?

Line 333. Did authors estimate the EAE value?

The main research content of this paper is the difference in depolarization ratio by wavelength depending on the type of pollen. It is judged to have important value as a paper with high continuity with previously published papers related to pollen. Overall, it is judged to be of excellent quality, but it is judged that it needs some revision.

Please refer to the information below.

Since the PDR value of pollen changes depending on mixing with aerosols other than pollen, such as PM10, it would be good to include this information in the text. In the current thesis, it is indicated in the graph, but it is not separately indicated in the text. It would be better to distinguish the PDR value when it is pure pollen and the value when mixed and indicate the average value in the text.

In line 268~271 and Figure 5, you can see the difference between shang et al (2022), but there is no difference between Bolnmann (2019, 2021) and this study's PDR532, so it would be nice to add it in Figure 5.

line 28, SSPs -> SPPs

line 61, bioaresols -> bioaerosols

line83, Stremline -> Streamline

The authors present both active remote sensing measurements and in situ aerosol observations of birch and pine pollen particles at Vehmasmäki (Kuopio), Finland to analyze the spectral dependence of the particle depolarization ratio (PDR). A special feature of this study is that the concurrent use of three different lidar systems enables measurements of PDR at four different wavelengths. Furthermore, the measurements were conducted at a rural forest site, with typically reduced pollution in the background. This is of great value as it allows the authors to study optical properties of pure pollen which is especially important as pollen have typically low concentrations compared to other atmospheric aerosol types.

Therefore, this study is important and suitable for ACP. Overall, the paper is well written and of good quality. Only some few aspects could be explained further/expressed clearer and several typos should be corrected, which will be addressed in the special comments below.

Special comments:

ll. 60-61: Veselovskii et al. (2021) only used a single broadband fluorescence channel in this study. An approach to obtain spectral fluorescence information by several fluorescence channels has just been presented in Veselovskii et al. (2023, preprint).

ll. 136-137: I don’t understand what is meant with the statement that NS and OPS aerosol size distributions were combined, but NS size distribution was neglected. If only the OPS size distribution was used, then it wasn’t combined with the NS one, was it? Could you please clarify this?

ll. 206-207: The statement ‘For each pollen type … of that specific pollen alone is studied’ has already been stated in the same way in ll. 185-187 and is thus repetitive and could be removed.

ll. 238-240, Fig. 4: Also, the 532 nm PDR seems similarly correlated to pollen concentration and concentration of other aerosols as the two longest wavelengths. Only the PDR at 355 nm seems less influenced. Why? Do you also relate this to the higher sensitivity of longer wavelengths to the comparably large pollen particles? Please explain your conclusion further here.

Figure 6: Why do you have less PDR values at 910 nm (only 2?) for pine concentrations > 4000 m^-3 compared to the other wavelengths? Was there a technical issue with the respective lidar? Maybe you could add a short remark on that, please.

Typos and technical notes:

l. 19: ‘… is closely associated to allergic diseases’  --> is closely associated with allergic diseases

l. 28: ‘SSPs’ --> ‘SPPs’

l. 31: ‘are an effective ice nuclei’ --> are effective ice nuclei (as it is plural)

l. 45: ‘depolarisation’ --> depolarization

l. 60: ‘polarisation’ --> polarization

l. 82: ‘vary from year to another’ --> vary from one year to another

l. 103: ‘can be found at Vakkari et al. (2021)’ --> can be found in Vakkari et al. (2021)

l. 205: ‘Sect.2.6’ --> Sect. 2.6 (missing space)

l. 212, l. 213: don’t forget the point after Fig. …, e. g., ‘Fig 2a’ --> Fig. 2a

l. 213: ‘Fig 2a)’ --> Fig. 2b) (the shaded area is found in panel b)

l. 222: ‘has previously seen’ --> has previously been seen

l. 284: ‘calculations performed’ --> calculations were performed

l. 328: ‘set up’ --> setup (as it is the noun)

References:

Veselovskii, I., Kasianik, N., Korenskii, M., Hu, Q., Goloub, P., Podvin, T., and Liu, D.: Multiwavelength fluorescence lidar observations of fresh smoke plumes, Atmos. Meas. Tech. Discuss. [preprint], https://doi.org/10.5194/amt-2023-5, in review, 2023.