Review comments to the paper ”An improved global pressure and ZWD model with optimized vertical correction considering the spatial-temporal variability of multiple height scale factors”, manuscript ID egusphere-2023-2861.

General comments:

In the paper the authors describe a global data base of pressure and zenith wet delay (ZWD) to be used as a priori information in new estimates of ZWD. The authors show that the performance is better than the current existing models which means that this is an important and interesting contribution to the field. The paper however, is hard to read and figures are hard to follow. Major improvements are needed before the paper can be published.

First two minor comments:

1. In the introduction, please give some examples of applications of the this new model. It says that it can improve the positioning precision and enhance convergence speed, but of what and how much? Please mention some potential users of this model.

2. In several places acronyms appear without being defined. Please look through the manuscripts and change this.

Then to the main problems with this paper, which are the figures and the presentation of the results. The panels are too small and provide too much information for the reader to digest. There is no need to display five almost completely blue panels like in figure 4. Another example is that in figure 9 it is not possible to locate Greenland, Andes mountains or the Tibet Plateau which the authors refer to in the text. There are also both maps and bar charts in some of the figures where the bar charts are not explained. It would be beneficial to split these in to separate figures.

My advice is to describe the over all (global) picture in the text and then show figures with some examples where there are big differences or interesting results. For example in figures 8 an 9, it would be more interesting to see full profiles of selected locations than 4 levels globally. This means a complete make over of sections 3 and 4.

No specific or technical comments will be given here since the paper needs such substantial work. This can be given at later stages of the review process.

The authors describe a new model of pressure and zenith wet delay (ZWD) estimations focused on high-altitude areas. This work can be an interesting contribution to the field but the results are not properly represented and the validation is poorly explained. Please consider the following improvements:

* Many acronyms are not defined

* Introduction should include studies about ZTD and its derivates. There are good examples in South America and Europe.

* Figures do not represent the results. If the paper is focused on high-altitude zones, I recommend showing these areas in more detail.

* There are no descriptions of the data sets used for validation beyond their names. 

* Considering radiosonde data: Have you removed outliers? Did you apply a filter to exclude sites with a low amount of registers? 

* Furthermore, radiosondes in South America are few in comparison with North America and Europe, and many of them are located in low-altitude areas. Which criteria are used to describe the good fit of the model there?

If this paper wants to focus on height altitude sites, I recommend to analyze these areas separately.