the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Seasonal updraft speeds change cloud droplet number concentrations in low level clouds over the Western North Atlantic
- 1Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany
- 2Institut für Physik der Atmosphäre, Johannes Gutenberg-Universität, Mainz, Germany
- 3NASA Langley Research Center, Hampton, VA, USA
- 4Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
- 5Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona, USA
- 6Experimental Aerosol and Cloud Microphysics Department, Leibniz Institute for Tropospheric Research, Leipzig, Germany
- 7Faculty of Physics and Earth Sciences, Leipzig Institute for Meteorology, University of Leipzig, Leipzig, Germany
- 8Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, Arizona, USA
- 1Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany
- 2Institut für Physik der Atmosphäre, Johannes Gutenberg-Universität, Mainz, Germany
- 3NASA Langley Research Center, Hampton, VA, USA
- 4Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
- 5Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona, USA
- 6Experimental Aerosol and Cloud Microphysics Department, Leibniz Institute for Tropospheric Research, Leipzig, Germany
- 7Faculty of Physics and Earth Sciences, Leipzig Institute for Meteorology, University of Leipzig, Leipzig, Germany
- 8Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, Arizona, USA
Abstract. Low level clouds over the Western North Atlantic show a seasonal cycle in cloud properties which anticorrelates to aerosol concentrations. To determinate the impact of dynamic and aerosol processes within marine low clouds we examine the seasonal impact of updraft speed w and cloud condensation nuclei concentration at 0.43 % supersaturation (NCCN0.43 %) on the cloud droplet number concentration (NC) of low level clouds over the Western North Atlantic Ocean. Aerosol and cloud properties were measured with instruments on board the NASA LaRC Falcon HU-25 during the ACTIVATE (Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment) mission in summer (August) and winter (February-March) 2020. The data are grouped in different NCCN0.43 % loadings and the density functions of NC and w near the cloud bases are compared. For low updrafts (w < 1.3 m s-1), NC in winter are mainly limited by the updraft speed and in summer additionally by aerosols. At larger updrafts (w > 3 m s-1), NC are impacted by the aerosol population, while at clean marine conditions cloud nucleation is aerosol limited and for high pollution it is influenced by aerosols and updraft. The aerosol size distribution in winter shows a bimodal distribution in clean marine environments, which transforms to a unimodal distribution in high pollution levels due to altering processes, whereas unimodal distributions prevail in summer with a significant difference in their aerosol concentration and composition. The increase in pollution level is accompanied with an increase of organic aerosol and sulfate compounds in both seasons. We demonstrate that NC can be explained by cloud condensation nuclei activation through upwards processed air masses with varying fractions of activated aerosols. The activation highly depends on w and thus supersaturation between the different seasons, while the aerosol size distribution additionally affects NC within a season. Our results quantify the seasonal influence of w and NCCN0.43 % on NC and can be used to improve the representation of low marine clouds in models.
Simon Kirschler et al.
Status: final response (author comments only)
-
RC1: 'Comment on acp-2022-171', Anonymous Referee #1, 11 Apr 2022
-
AC1: 'Reply on RC1', Simon Kirschler, 22 Apr 2022
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-171/acp-2022-171-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Simon Kirschler, 22 Apr 2022
-
CC1: 'Publisher's comment on acp-2022-171', Copernicus Publications, 29 Apr 2022
Due to a mistake during the posting of the preprint, page 2 of the preprint had been deleted. Therefore, we have now exchanged the preprint with its complete version.
We would like to apologize to the authors and readers for this mistake and for any inconvenience caused.
Copernicus Publications
editorial@copernicus.org -
RC2: 'Comment on acp-2022-171', Anonymous Referee #2, 10 May 2022
This manuscript investigates the influences of vertical updraft speeds and CCN concentration of cloud droplet number concentrations using air craft measurements. The conducted measurements and analytical methods (while not fully explained, see my comment below) appear scientifically sound. The paper is not particularly original, but can still be considered as a useful contribution to the scientific community. There are a few issues that need to be addressed better before I can recommend accepting this paper for publication.
Major comments
The authors define three pollution levels, or regimes, based on measured CCN concentrations. There are a few issues related to this approach requiring better justifications, or some revisions. First, although it makes sense to use CCN as a measure of pollutions for the purposes of this paper, this wording is problematic considering that for air quality community pollution levels are usually defined based on concentrations of a selected chemical compounds, or simply PM mass concentration. This causes also confusing statements, such as that on lines 398-400: for air quality people it sound strange to claim that the mass concentrations of the most typical particulate air pollutants increased only moderately as the pollution levels increased in winter. I would encourage the authors to reconsider what to call the different CCN regimes used in this paper. Second, what is bases for the grouping of the different CCN regimes? The borders between the different groups given on lines 214-215 seem rather arbitrary to me. Third, if strict limits for different CCN groups are given (lines 215-215) how is it then possible that CCN concentration in different groups can overlap each other (Figure 4a and text on lines 278-380)? Finally, do the authors have any idea on why the medium CCN regime was absent during the winter?
The description of the methodology used to determine w and Smax needs to be expanded (lines 218-223). How is Smax determined in practice? It is unclear whether w or weff is really used later in the paper, as weff appear only in equation 2. If this methodology has been described in more detail in earlier literature, the relevant studies should, at the very least, cited here properly.
I have a hard time to understand how the values of Smax given on lines 350-351 have been obtained, and how they are related to the lines in figure 6c. This problem is, at least partly, related to the lack description how Smax has been determined in this study.
I would appreciate if the authors had listed concrete scientific goals for this paper. Written like it is now (lines 59-61), a reader might get an impression that the purpose of this paper is solely to produce data for other researchers for e.g model evaluation.
Minor/technical comments
line 255: … between 208 and 1367 …
line 293: please separate Ngt85 from the rest of the text using commas (i.e. …, Ngt85, …).
lines 305 and 315: the term altering processes sounds odd to me. I suppose the authors mean a combination of chemical and physical (aerosol) processes that convert sub-CCN size (nucleation and Aitken mode particles) into largest ones that then contribute to the CCN population.
lines 338-341: while I agree on that the HP regime shows the strongest increases with increasing w at w < 1.6 m s-1 and at w > 3 m s-1, it is hard to see from figure 6 that there would be such border for LP or MP, or that they would clearly saturate at high values of w.
The units of quantities are usually written using normal text, not in italics. Furthermore, different parts of the units should be separated from each other using spaces (i.e. m s-1, not ms-1).
The title of Section 4 should be reconsidered (Summary and Conclusions), as most of this section is simply summary of the results with only few conclusions provided.
Simon Kirschler et al.
Data sets
Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment Data Armin Sorooshian http://doi.org/10.5067/SUBORBITAL/ACTIVATE/DATA001
Simon Kirschler et al.
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 323 | 139 | 17 | 479 | 6 | 8 |
- HTML: 323
- PDF: 139
- XML: 17
- Total: 479
- BibTeX: 6
- EndNote: 8
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1