The study of precipitation stable isotopes is of great significance for tracing the water vapor source and studying the water cycle, and it is also of great importance for reconstructing past climatic and environmental changes. This paper investigated the characteristics and mechanisms of multi-scale variability in precipitation stable isotopes in the southern and western Tibetan Plateau. It is worth noting that this paper demonstrates that Indian Summer Monsoon (ISM) circulation homogenizes isotopic signatures across the southern and western Tibetan Plateau, while westerly dominance amplifies regional differences through distinct moisture pathways, and ENSO significantly influences the interannual variability of precipitation stable isotopes in the study area. However, the paper has some issues that require further improvement and clarification.

General comments:

1. About positive values of δ18O and δD in precipitation at the study sites. Figure 2 shows that there are a large number of positive values of δ18O and δD at the two study sites, especially at Yadong. It is necessary to analyze and explain the reasons for the occurrence of these positive values and their indicative significance.
2. Regarding the selection of altitudes/heights at which the air parcels reach the study sites in backward trajectory analysis. It was pointed out in lines 200-204 that “to assess the influence of moisture sources on precipitation stable isotopes, to calculate 120 h backward trajectories for air masses arriving 200 m above ground level at Yadong and Ali stations.” Another thing is that the heights used for calculating water vapor flux are from 500 hPa to 200 hPa in this study. These analyses are all intended to explain the sources and paths of water vapor, but there is inconsistency in the selection of the levels. Since this study focuses on the stable isotopes of precipitation, why not choose the condensation levels instead of 200 m above ground level to calculate the trajectory of the air parcels reaching the study sites? If the condensation levels or 500 hPa or other heights are chosen, will the backward trajectories be significantly different from the current ones? These should be analyzed and explained.

Specific comments:

1. The variation of precipitation throughout the year at Yadong is bimodal, with two peaks in April and October. What is the impact of this pattern of precipitation variation on precipitation stable isotopes? Or what characteristics of precipitation isotopes can indicate the peak precipitation information? If there is currently sufficient data available for the issues, please discuss and explain them.
2. Lines 219-220, where g is gravitational acceleration, while Ps and Pt are surface pressure and top pressure, respectively. The expression of Pt is inaccurate.
3. In Figure 2(f), (g), (h), (i), (j), especially in (j), the units of their vertical coordinates should be displayed.
4. According to the definition of seasonal division in lines 232-236, the “late monsoon (October)” should be the “post-monsoon”? And pay attention to the expression of “late monsoon” in the following text.
5. Line 434, “ISM dominated the moisture transport during pre-monsoon of 2021”. In this sentence, the first part is about the monsoon (ISM), but the second part mentions “during pre-monsoon”. It seems that the logic or expression is not accurate literally. Similar expressions can also be found in other parts of the text. Please make corrections and/or clarifications. If possible, the seasons can be divided based on the specific dates of the onset and withdrawal of the Indian monsoon each year during the study period in this paper. This seasonal division might be more meaningful for the study of precipitation stable isotopes.