How tropical cyclones drive extreme positive glacier mass balance in the central&ndash;eastern Himalayas

Zhang, Fengying; Gao, Xuelin; Bai, Shihang; Zhang, Ji; Gao, Jing; Lhamo, Rinzin; Zhu, Meilin; Zhao, Huabiao

doi:10.5194/egusphere-2026-3661

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https://doi.org/10.5194/egusphere-2026-3661

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07 Jul 2026

| 07 Jul 2026

How tropical cyclones drive extreme positive glacier mass balance in the central–eastern Himalayas

Fengying Zhang, Xuelin Gao, Shihang Bai, Ji Zhang, Jing Gao, Rinzin Lhamo, Meilin Zhu, and Huabiao Zhao

Abstract. Extreme climate events are increasingly recognized as important drivers of glacier change. Although tropical cyclones (TCs) are a type of extreme weather event, their impacts on glacier mass balance and the associated physical processes remain poorly understood. This study used more than 10 years of in situ observational data and an energy–mass balance model to reconstruct the energy and mass balance of Naimona’nyi Glacier over 2000–2024, and analyzed the impacts of TC Tauktae on glacier mass balance and associated physical mechanisms in May 2021. During May 18–21, 2021, meteorological and energy conditions changed markedly. Precipitation reached its highest level for the same period since 2000 and occurred almost entirely as snowfall, enhancing mass accumulation and surface albedo. Meanwhile, increased cloud cover reduced incoming shortwave radiation, and higher relative humidity decreased latent heat flux. These variations reduced melt energy, suppressed melt and sublimation, and increased mass accumulation, resulting in an extreme positive glacier mass balance for four consecutive days. Regional analysis shows that the associated meteorological and energy anomalies extended across the central and eastern Himalayas. This study reveals the physical mechanisms through which TCs drive glacier change on the Tibetan Plateau from an energy-balance perspective, filling a research gap in this area and providing important insights for regional glacier assessment and future projections.

Received: 22 Jun 2026 – Discussion started: 07 Jul 2026

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Fengying Zhang, Xuelin Gao, Shihang Bai, Ji Zhang, Jing Gao, Rinzin Lhamo, Meilin Zhu, and Huabiao Zhao

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RC1:
'Comment on egusphere-2026-3661', Anonymous Referee #1, 17 Aug 2026
Review of egusphere-2026-3661: “How tropical cyclones drive extreme positive glacier mass balance in the central-eastern Himalayas” by Zhang et al.
This manuscript assesses the impact of a tropical cyclone on the mass balance of a glacier in the central Himalayas as well as the associated physical processes. The manuscript specifically focuses on the impacts of tropical cyclone Tauktae (May 2021) on the glacier mass balances of Naimona’nyi Glacier, located on the southwestern part of the Tibetan Plateau. First, 10 years of in situ observational data and an energy-mass balance model are used to reconstruct the energy and mass balance of Naimona’nyi Glacier over the period 2000-2024. Then the impact of TC Tauktae on the glacier mass balance and associated physical mechanisms are studied and (partly) extended regionally to the central and eastern Himalayas.
The main findings suggest that due to extreme precipitation (mostly falling in the form of snow) as well as reduced incoming shortwave radiation (due to increased cloud cover) and reduced latent heating (due to increased relative humidity), accumulation increased and melt/sublimation reduced, leading to positive glacier mass balances for four consecutive days on Naimona’nyi Glacier.
The manuscript covers interesting topics that fit in the scope of the journal and provides valuable insights. The manuscript is well written, but the technical quality of the figures is moderate here and there, see my comments. Further I have added some general comments regarding the title and the discussion/design of this study.
General Comments
My first comment is related to the title. When reading the title, the first impression is that this paper is about a study that investigates how tropical cyclones drive extreme positive glacier mass balance in the central-eastern Himalayas. However, while reading the manuscript the impression is that this paper is about a study that investigates the impact of a single tropical cyclone (Tauktae) on a single glacier (Naimona’nyi Glacier) solely as well as the regional atmospheric implications of TC Tauktae. The impacts of TC Tauktae on glacier mass balances in the central and eastern Himalayas have not been addressed and are neither supported by the findings presented in this study. Therefore, in my opinion, the title needs to be changed into something that fits well with the main findings presented in this study, i.e. the impacts of TC Tauktae on the glacier mass balance of Naimona’nyi glacier.
In case the authors want to continue with the title, more evidence is needed to support this title. For example, by looking into the impacts of multiple TCs, such as TC Hudhud, TC Phailin, TC Yaas, and TC Hamoon on multiple glaciers distributed over the central and eastern Himalayas. That raises also the question, whether similar studies exist that looking into the impacts of TCs on other glaciers in the region and beyond? This kind of information could also be useful for the discussion.
This brings me to my second comment that is related to the discussion. The discussion about the regional atmospheric implications of TC Tauktae is interesting to read, but I am doubting about the statement that TC Tauktae had an impact on the eastern Himalayas, as the region fell outside the main track of the TC. In my opinion, the authors need to investigate this more in-depth and revise their findings/statements based on what they find, also see later comments.
Also, I missed a discussion on the limitations and uncertainties of the methods applied in this study. What are the main limitations and uncertainties? What can be said about the significance of the findings presented? Are the findings presented representative for the entire region? Naimona’nyi Glacier is a rather small northward-oriented glacier located at high altitude, which means during TC events or other similar extreme precipitation events I would expect that ablation is limited and accumulation is large as most precipitation will fall in the form of snow, eventually resulting in positive daily glacier mass balances. As the authors claim (based on the title) that TCs drive extreme positive glacier mass balances in the central and eastern Himalayas, I am wondering how the physical mechanisms look like to larger clean ice or debris covered glaciers, such as Rongbuk Glacier or Khumbu Glacier, which have glacier tongues located at a lower altitude than Naimona’nyi Glacier. Also, are there differences in the physical mechanisms between northward-oriented glaciers (generally on the Tibetan Plateau) and southward-oriented glaciers?
Specific Comments
L86-89 and Fig.1: I have a few remarks regarding Figure 1 and the text in the manuscript. For Fig. 1a, could the authors add more geographical information (e.g. Himalayas, Tibetan Plateau) and a grid over the panel to make it easier for the reader to recognize where the Naimona’nyi Glacier is located? Also, what is the source of the background map? If known, please add this information to the caption. As for Fig. 1b, I suggest adding a color bar showing the meaning of the colors in the figure and I recommend adding an additional panel that shows the regional setting of the glacier (more zoomed in compared to Fig 1a. and zoomed out compared to Fig 1b.), including a river network. That helps to guide the reader better through the regional descriptions given by the authors and gives the opportunity to indicate the location of Lake Manasarovar. Further, I suggest adding more information by including the outlines of the glacier branches surrounding the glacier of interest, as the authors describe there is also a southern branch. As for the description of the southern branch, I am wondering whether this is not supposed to be the western branch? Looking at outlines of the glacier from RGI as well as satellite imagery I notice there is only a western branch and not a southern one.

L95: I have some doubts about the correctness of the annual mean air temperature stated by the authors. For a location at almost 6000 m a.s.l. a mean air temperature of 6.0 °C seems to be rather high to me. Is this not supposed to be the annual maximum air temperature? Also looking at Fig. S1 most of the observed temperature data are below 0 °C.

L140: Please add a reference to ERA5 (Hersbach et al., 2020; https://doi.org/10.1002/qj.3803).

L153: Melt and sublimation/evaporation are loss terms but are summed up in equation 1. Does that mean that the model produces negative values of sublimation/evaporation and melt?

L164-166: Why did the authors choose to work with two different temperature lapse rates and precipitation gradients, how did the authors derive these lapse rates/gradients, and do the authors have an explanation for the rather large difference between the higher and lower temperature lapse rates? Is that based (for the lapse rates) on the difference in temperature/elevation between AWS1 and the lowest and highest loggers? Also, if the authors had access to AWS and logger data, why did the authors choose for a fixed lapse rates/gradients over time and not for monthly varying lapse rates/gradients?

Fig. S1: S1a and S1c show the reconstructed vs observed wind speed and air temperature, respectively, but are listed vice versa in the caption. Please check.

Fig. 2: According to the caption and y-axis label, surface temperature (2c) is shown in degrees Celsius, but the values are presented in degrees Kelvin. Please check.

L205 and Fig. S2: Which definition was used for precipitation occurrence? Is it defined similar to wet-day frequency, where an occurrence is counted as 1 when daily precipitation exceeds 1 mm/day? Further I noticed that the y-axis labels of Fig. S2a and S2b are swapped. I guess Fig. S2a shows the cumulative precipitation amount and Fig. S2b shows the cumulative precipitation occurrence. Please check.

Fig. S3 (here and throughout the manuscript where this applies): The units of daily precipitation are supposed to be (mm/day) instead of (mm)?

L244-245: In my opinion it is better to phrase the sentence as “…anomalous low snowfall frequency and amount…” instead of “…anomalous snowfall frequency and amount…”.

Fig. 4: The dashed black line representing the mean of the baseline period is missing here.

Section 4.2: Are the mass balance and flux values presented here area-averages over the glacier?

L322: Please check, as Fig. S4a does not show glacier mass balance values but precipitation.

L329-334, Fig. 6: I recommend exchanging the panels a) and b), which means the glacier mass balance for the baseline period is presented first, followed by the glacier mass balance for the TC period.

Figs.8-10, and Figs. S8-S13: These figures are hard to read/interpret due to dark or light blobs that are present, which is basically caused by the scaling and the color schemes implemented in these figures. I strongly recommend that the authors check all these figures, change the color schemes and/or change the scaling. For example, for Figs 8 and 9 and other similar figures I recommend 1) to change the colormap (Blues) to a colormap with multiple colors such as BrBG (Matplotlib colormap), MPL_BrBG (NCL color table) or a color scheme comparable with the one used in Fig. S9 instead, and 2) change the scaling by applying less color classes, changing the levels used for plotting data, e.g. [0,1,2,5,10,15,20,30,40,50] or increasing the max. value that can be displayed. Also, I recommend increasing the size of the red diamond marker and to include the black dashed and green solid lines in Figure 1 as well.

Further I suggest adding the track of TC Tauktae to these figures. By adding the track, it is better to see whether precipitation falling in a certain area is associated with the TC or another synoptic system. Also, I am wondering (counts for here and previous figures 8 and 9) why the authors show the fields for the entire TP region and not zoom in on the region of interest, i.e. the Himalayas?

L436-437: I notice that looking at the precipitation fields in Fig. 8, the TC comes from the southwest on May 17 and arrives in the central Himalayas at May 18/19. It looks like that the TC had a significant impact in this area, but that the eastern Himalayas was barely affected.

L445-446: I think that the absence of the increase in albedo in the eastern Himalayas is related to the absence of snowfall and therefore already hints that what happens in the eastern Himalayas, during May 17-21, 2021, is not related to TC Tauktae.

L470-471: Could the authors elaborate more on how the moisture transport by large-scale circulation is related to the limited snow cover in the eastern Himalayas? What do the isotope-based studies show?

L471-473: Based on the outcomes presented in this study, evidence that the meteorological and energy perturbations associated with TC Tauktae has affected the eastern Himalayas is lacking in my opinion. Optionally, the authors could perform moisture tracking analyses to trace moisture sources associated with precipitation falling in the central or eastern Himalayas during the May 18-19, 2021 period?

Fig. 10: This figure is hard to read as the (tick) labels are quite small and 6 separate figures seems to have merged into one, which is suboptimal. Therefore, I recommend splitting up Fig. 10 into 6 separate figures (Fig. 10- Fig. 15), and to address these one by one.
Citation: https://doi.org/10.5194/egusphere-2026-3661-RC1
RC2:
'Comment on egusphere-2026-3661', Anonymous Referee #2, 25 Aug 2026
Review egusphere-2026-3661
The authors combine regional reanalysis data with in-situ climate data on and around a glacier on the Tibetan Plateau to characterize the impacts of a tropical cyclone that hit Western India in 2021 on glacier mass balance. The idea for the study is interesting and worthwhile pursuing and could be an important contribution to understand cryosphere response in a time of changing extremes. The methods are generally also adequate. Unfortunately, the authors have missed to provide crucial details in Methods, Results and Discussion and many statements are not backed up by data, hence making this study not yet ready for publication. I detail the biggest concerns below, followed by a line by line review. Due to the largely missing Discussion I have not further addressed the Conclusion.

The authors repeatedly leave it unclear where data they show is coming from (which station or ERA5).

The specific TC investigated never really reached the TP and based on the data shown I am wondering if this is even a signal from the cyclone or simply an above average precipitation event. It is definitely not extreme in terms of volume or duration and since the authors provide no context on how often this happens in the location (or how it may change) there is no way for the reader to eventually judge whether TCs as such are now important or irrelevant for mass balance. Since the event is short (3 days) any effect on mass balance is anyway taken with a lot of caution, considering that the ‘balance’ part is not an instantaneous process.

There is little to no scrutiny of the magnitude of the specific event versus the general precipitation situation in the location. While the authors mention percentiles in the text, they never show them in any figure and hence its impossible to say whether this event was in any way out of the ordinary.

The Discussion rather than discussing the Results introduces completely new results (spatial analysis) and provides no discussion of the results, hence resulting in a big crucial part missing from this research.

Line by line comments:
L46f: I think this is somewhat awkward phrasing – positive mass balance is associated to all parts of the balance, it just means there is more of input than output. Consider revising to ‘Positive mass balance is often driven by positive anomalies in snowfall combined with low temperature regimes …’
L68f: I believe the impacts were much larger (see for example https://rrp.unescap.org/knowledge-products/4891) and ‘traffic jams’ should be removed, as its not a relevant impact. Also more precisely ‘it was one of the more severe TCs in the Arabian Sea in recent years’.

L72f: I am somewhat surprised that you find that snowfall increases were perceptible on the TP for this TC. Tauktae subsided already before the lower Himalayan foothills in India/Pakistan and while I understand that additional moisture has likely reached much higher, there should be some evidence of increased snowfall. As you have access to station data it would be prudent to show this increase or alternatively refer to studies that have shown the same. This then relates to a next comment for L273f. Here you then refer to Fig S.4, which in my view would need to be in the main manuscript. But it requires more context – you should show more days before and after the event to show the relative scale of this additional precipitation impact. Does it really qualify as especially high for this location and season? You compare to the mean baseline, but I am not sure how that is computed – if you include 0 values there it’s not surprising it quickly gets much lower on average. You should also show quantiles for that baseline. Especially as in the text you refer to the 9^th percentile as well. Figure S2 suggests that this specific month was nowhere out of the ordinary, and with so little added volume of snowfall, I wonder if we can speak of a particularly heavy event at this location. I now see that you do introduce some of this in Figure 4 in the manuscript but as for Figure S4 there is no specification from which station these data are taken and again no context with respect to percentiles are givene even though you do refer to those in the text.
L86: Provide exact coordinates, possibly also the RGI/GLIMS ID.
Figure 1: In Panel (a) it would be prudent to show general glacier extents/regions (RGI or other glacier inventories). In Panel (b) more context is needed. I advise to have an ortho photo as background for topographic context and extend the contour lines beyond the glacier. What is the colour scale? Elevation? Legens is missing!
L190f: It’s crucial that you note how many gaps were filled/how much data were missing and how the quality of filling was assessed. I assume that for the TC event in-situ data was available for all variables.
L215f: The model comparison should go into results, not the Data section.
L273f and Fig S4. From which station are these data taken? Also how do you know about the rainfall/snowfall fraction as stated in L289 when you only measure precipitation?

L284f: Regarding the comparison to the baseline period see above – comparing to the mean of precipitation over so few days is problematic if you include dry days. Percentiles are required!
L289f: This precision falls I believe well within the range of uncertainty and either it is all snowfall in any case or the numbers are too high.
L294f: You do not provide evidence for this statement, required.
L296f: I don’t think that a difference between 3 and 4 days is significant to warrant a statement of marked distinctiveness of this event.
L405ff and Figure 8, 9 and 10: This drops as something completely new in the Discussion and should be introduced in the Results first!
L482f: This section is material for the Introduction.
Citation: https://doi.org/10.5194/egusphere-2026-3661-RC2

Fengying Zhang, Xuelin Gao, Shihang Bai, Ji Zhang, Jing Gao, Rinzin Lhamo, Meilin Zhu, and Huabiao Zhao

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https://doi.org/10.5194/egusphere-2026-3661-supplement

Fengying Zhang, Xuelin Gao, Shihang Bai, Ji Zhang, Jing Gao, Rinzin Lhamo, Meilin Zhu, and Huabiao Zhao

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Short summary

Extreme weather events can influence glacier change, but the role of tropical cyclones remains poorly understood. This study investigates the impact of a tropical cyclone in May 2021 on Naimona’nyi Glacier. The event brought heavy snowfall, increased cloud cover, and reduced incoming shortwave radiation, which suppressed melting and enhanced snow accumulation. As a result, the glacier experienced an extremely positive mass balance.


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