Estimating degree-day factors of snow based on energy flux components
<p>Meltwater from mountainous catchments dominated by snow and ice is a valuable source of fresh water in many regions. At mid-latitudes, seasonal snow cover and glaciers act like a natural reservoir by storing precipitation during winter and releasing it in spring and summer. Snowmelt is usua...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-01-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/17/211/2023/tc-17-211-2023.pdf |
| Summary: | <p>Meltwater from mountainous catchments dominated by snow and ice is a valuable source of fresh water in many regions. At mid-latitudes, seasonal snow cover and glaciers act like a natural reservoir by storing precipitation during winter and releasing it in spring and summer. Snowmelt
is usually modelled either by energy balance or by temperature-index
approaches. The energy balance approach is process-based and more
sophisticated but requires extensive input data, while the temperature-index approach uses the degree-day factor (DDF) as a key parameter to estimate melt of
snow and ice merely from air temperature. Despite its simplicity, the
temperature-index approach has proved to be a powerful tool for simulating
the melt process especially in large and data-scarce catchments.</p>
<p>The present study attempts to quantify the effects of spatial, temporal, and climatic conditions on the DDF of snow in order to gain a better understanding of which influencing factors are decisive under which conditions. The analysis is based on the individual energy flux components; however, formulas for estimating the DDF are presented to account for situations where observed data are limited. A detailed comparison between field-derived and estimated DDF values yields a fair agreement with bias <span class="inline-formula">=</span> 0.14 mm <span class="inline-formula"><sup>∘</sup></span>C<span class="inline-formula"><sup>−1</sup></span> d<span class="inline-formula"><sup>−1</sup></span> and root mean square error (RMSE) <span class="inline-formula">=</span> 1.12 mm <span class="inline-formula"><sup>∘</sup></span>C<span class="inline-formula"><sup>−1</sup></span> d<span class="inline-formula"><sup>−1</sup></span>.</p>
<p>The analysis of the energy balance processes controlling snowmelt indicates
that cloud cover and snow albedo under clear sky are the most decisive
factors for estimating the DDF of snow. The results of this study further
underline that the DDF changes as the melt season progresses and thus also with altitude, since melting conditions arrive later at higher elevations. A brief analysis of the DDF under the influence of climate change shows that the DDFs are expected to decrease when comparing periods of similar degree days, as melt will occur earlier in the year when solar radiation is lower, and albedo is then likely to be higher. Therefore, the DDF cannot be treated as a constant
parameter especially when using temperature-index models for forecasting
present or predicting future water availability.</p> |
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| ISSN: | 1994-0416 1994-0424 |