Snow Droughts are not Solely Driven by Abnormal Snowfall and Temperature
Lack of snow accumulation, or snow drought, can have detrimental impacts on various aspects of ecosystems and human activities. (Photo by Julia Volk | Pexels.com)
Study finds that many snow droughts are driven by dry and/or warm soil, rather than by high temperatures and/or low snowfall.
The Science
Decreased snow cover observed over the past few decades and projected for the future suggest increasing snow droughts that are threatening water security and management. While various observational data products and model simulations are available to study snow droughts, a comparison between them has been lacking. This study compared different numerical experiments using the Energy Exascale Earth System Model (E3SM) and reference data from the climate dataset ERA5-Land to understand the drivers of snow droughts in 1980–2014. Analysis revealed multiple factors contributing to snow droughts and underscored the need for a more comprehensive understanding of the drivers of snow droughts to reduce uncertainty in projecting their future changes.
The Impact
This study confirmed well-recognized factors like above-normal temperature and low snowfall contribute to the occurrence of snow droughts. However, it also showed other contributors such as low soil moisture, warm soil temperature, and low relative humidity play important roles in the occurrence of snow droughts. The research highlights the exacerbating effect of changing climate patterns, known as El Niño-Southern Oscillation (ENSO) events, on snow drought conditions in various regions. By comparing E3SM simulations and ERA5-Land data, this study identified some model shortcomings and underscored the complexity of predicting and mitigating snow drought and the need for a comprehensive understanding of the factors contributing to snow drought.
Figure 1. Many factors can contribute to snow droughts besides warm air temperature (a) and low snowfall (b). Based on ERA5-Land (blue) and various E3SM simulations (orange, green, red, purple), the probability density functions of snow drought fraction associated with dry soil (d), warm soil (e), dry and warm soil (f) show that 20-30% of snow droughts can be attributed to dry soil and/or warm soil.
Summary
Understanding the threat that snow droughts pose to water security and management is crucial, which is why the study of snow droughts is important. In this study, researchers analyzed snow droughts using offline and coupled land–atmosphere E3SM model results and compared them with reference data derived from ERA5-Land, which fills the gap of limited global and systematic data–model comparisons. The research showed that the occurrences of snow drought are predominantly due to low snowfall, warm temperature, or both. However, about 20–30% of snow droughts in the analysis can occur due to factors such as low soil moisture, warm soil temperature, and low relative humidity (Fig. 1). Due to the lack of consensus on whether ENSO induces or relieves drought in snowpack conditions, the researchers examined snow droughts in ENSO for the years between 1980 and 2014. The study revealed that ENSO events can aggravate snow droughts in various regions. Specifically, El Niño events were found to potentially prolong snow droughts in Russia, whereas La Niña events may contribute to extended snow droughts in Central Asia. Therefore, it is important to consider all the factors that contribute to drought conditions besides temperature and snowfall conditions. It is also important to consider the local conditions and how they interact with larger climate patterns associated with modes of climate variability such as ENSO to fully understand the causes of snow drought.
Publication
- Fang, Y., & Leung, L. R. (2023). Northern Hemisphere snow drought in Earth system model simulations and ERA5-Land data in 1980–2014. Journal of Geophysical Research: Atmospheres, 128, e2023JD039308. https://doi.org/10.1029/2023JD039308
Funding
- This work was supported by the Earth System Model Development program area of the Department of Energy, Office of Science, Biological and Environmental Research program.
Contact
- Yilin Fang, Pacific Northwest National Laboratory
This article is a part of the E3SM “Floating Points” Newsletter, to read the full Newsletter check:
