the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Rain-on-snow response to a warmer Pyrenees
Josep Bonsoms
Juan Ignacio López-Moreno
Esteban Alonso-González
César Deschamps-Berger
Marc Oliva
Abstract. Climate warming is changing the magnitude, timing, and spatial patterns of mountain snowpacks. A warmer atmosphere may also lead to precipitation phase shifts, with decreased snowfall fraction (Sf). The combination of Sf and snowpack decreases directly affects the frequency and intensity of rain-on-snow (ROS) events, a common cause of flash-flood events in snow dominated regions. In this work we examine the ROS patterns and sensitivity to temperature and precipitation change (delta-change) in the Pyrenees using a physical-based snow model forced with reanalysis climate data perturbed following 21st century climate projections for this mountain range. ROS patterns are characteritzed by their frequency, rainfall quantity and snow ablation. The highest ROS fr for the baseline climate period (1980–2019) are found in South-West high-elevations sectors of the Pyrenees (17 days/year). Maximum ROS rain is detected in South-East mid-elevations areas (45 mm/day, autumn), whereas the highest ROS ablation is found in North-West high-elevations zones (−10 cm/day, summer). When air temperature is increased from 1 ºC to 4 ºC, ROS rain and frequency increase at a constant rate during winter and early spring for all elevation zones. For the rest of the seasons, non-linear responses of the ROS frequency and ablation to warming are found. Overall, ROS frequency decreases in the shoulders of the season across eastern low-elevated zones due to snow cover depletion. However, ROS increases in cold, high-elevated zones where long-lasting snow cover exists until late spring. Similarly, warming triggers fast ROS ablation (+10 % per ºC) during the coldest months of the season, high-elevations, and northern sectors where the deepest snow depths are found. On the contrary, slow, and non-changes in ROS ablation are expected for warm and marginal snowpacks. These results highlight the different ROS responses to warming across the mountain range, suggest similar ROS sensitivities in near mid-latitude zones, and will help anticipate future ROS impacts in hydrological, environmental, and socioeconomic mountain systems.
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Josep Bonsoms et al.
Status: open (extended)
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RC1: 'Comment on egusphere-2023-178', Anonymous Referee #1, 19 May 2023
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General Comments
The manuscript presents a thorough investigation of the effects of climate warming on rain-on-snow events in the Pyrenees. The manuscript is well-structured, includes a comprehensive state-of-the-art literature review, and an extensive discussion of the results. The methodology is sound, but a bit outdated with regard to the scenario approach used (delta-change method). The results show that an increase of rain-on-snow events has to be expected in mid-winter and at higher altitudes, and a decrease elsewhere. These results are innovative and relevant for various sectors, as discussed in the manuscript. The manuscript is therefore suggested for publication with minor revisions, as indicated below.
Specific Comments
Abstract, line 11: What do you mean with “When air temperature is increased from 1ºC to 4ºC…”? Since your study is based on spatially and temporally varying weather data from reanalysis, there is no fixed 1°C base temperature that you could raise to 4°C. Please reformulate to clarify, that 1°C is not the baseline, but already an additive constant used in the delta change approach.
Section 3.4: Could you please motivate the value of change-factors you selected for the delta change approach? It is important to relate them at least qualitatively to more elaborated climate scenarios. E.g., how do these levels of warming relate to the +2 degree goal? Is +4K a worst case scenario, or an intermediate one? Is +/- 10% precipitation adequately spanning the expected range of change? To answer such questions would strongly increase the general impact of the study, since it could be better related to the general climate change debate going on in our society. There is very limited information on this topic in Section 5, but this needs to be extended and maybe shifted to section 3.4, where the scenario concept of this study is introduced.
Section 3.4: Please clearly discuss the limitations coming along with the delta-change approach. Such a discussion is completely missing so far. E.g. a more realistic simulation of climate change would most probably include a distinct seasonality of precipitation change, which is absent in the delta change approach.
Section 3.5.: The representation of the results in “change per 1K” is great, since it makes the results easily comparable to other regions/seasons/scenarios.
Editorial/Technical
Title: Please consider rephrasing the title. The expression “Rain-on-snow response to a warmer Pyrenees” is semantically very vague (and grammatically incorrect: Pyrenees is in plural). You describe the response of the characteristics of ROS events to warming and precipitation change in the Pyrenees in your manuscript. Something along these lines would be a much clearer title for the article manuscript.
Abstract: Avoid using abbreviations without introducing them in advance (line 8; “ROS fr”).
Line 470: wrong usage of singular/plural (vegetation branches intercepts)
Generally: Some additional proofreading is advisable to remove some remaining minor language mistakes.
Citation: https://doi.org/10.5194/egusphere-2023-178-RC1
Josep Bonsoms et al.
Josep Bonsoms et al.
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