See attached document for detailed comments. The paper is suitable for publication in ACP but its presentation needs a bit of work.

Overall

This paper reports on stratospheric ozone trends in the tropical

region and is motivated by the recent claim by Lu (2022a, 2002b) that

a tropical ozone hole exists. A rebuttal to the paper by Lu was

published by Chipperfield et al. (2022) that argued that this claim is

not substantiated by observations and that the interpretation of galactic

cosmic rays (GCR) being a cause for this severe loss is highly unlikely.

This paper confirms that there are only small tropical ozone changes

observed in the tropics over the last decades supporting the arguments

given in the rebuttal by Chipperfield et al. So far so good. My issue

with the paper is that it is not clear to me what new insights are

provided here. The small trends in the tropics have been reported

before (WMO 2022, Weber et al. 2022, Godin-Beekmann et al. 2022). I

also do not see what new arguments are delivered here with resepct to

what has been already reported by Chipperfield et al. in response to

Lu (2022).

The authors need to state clearly what new aspects are brought in here

that justifies publication of this paper. A major revision is required.

Other major issues

* Various ozone and reanalysis data are used in this study and trends

  calculated from them. Apparently not all datasets have been updated

  to end of 2022. MERRA-2, ERA5, GSG, and SBUV/OMPS MOD data are

  available up to end of 2022. Stratospheric ozone trends from

  GOZCARDS, SWOOSH, and reanalysis data are only shown up to 2018, why

  not up to end of 2022?

* To make the paper more concise (and probably shorter), the authors

  should try to focus on trends in the tropical region (see paper

  title), rather than global and extratropical regions, which are

  extensively discussed here.

* The regression model used is poorly described. It is pretty much

  standard that ozone trends are derived using multiple linear

  regression (MLR) that contain additional terms (proxies) describing

  ozone variability (e.g. WMO 2022, Weber et al. 2022, Godin-Beekmann

  et al. 2022). What is the justification for not using MLR? A

  comparison between MLR (previous work) and simple linear regression

  results (this work) may become difficult.

Minor issues

There are many rather minor issues, but are not summarised here. They

may be reviewed after a major revision.

References

Lu, Q.-B., Response to “Comment on ‘Observation of large and

all-season ozone losses over the tropics’” AIP Adv., 12, 075006

(2022)], doi: 10.1063/5.0129344, 2022b.