Global snow drought hot spots and characteristics - PubMed (original) (raw)

Global snow drought hot spots and characteristics

Laurie S Huning et al. Proc Natl Acad Sci U S A. 2020.

Abstract

Snow plays a fundamental role in global water resources, climate, and biogeochemical processes; however, no global snow drought assessments currently exist. Changes in the duration and intensity of droughts can significantly impact ecosystems, food and water security, agriculture, hydropower, and the socioeconomics of a region. We characterize the duration and intensity of snow droughts (snow water equivalent deficits) worldwide and differences in their distributions over 1980 to 2018. We find that snow droughts became more prevalent, intensified, and lengthened across the western United States (WUS). Eastern Russia, Europe, and the WUS emerged as hot spots for snow droughts, experiencing ∼2, 16, and 28% longer snow drought durations, respectively, in the latter half of 1980 to 2018. In this second half of the record, these regions exhibited a higher probability (relative to the first half of the record) of having a snow drought exceed the average intensity from the first period by 3, 4, and 15%. The Hindu Kush and Central Asia, extratropical Andes, greater Himalayas, and Patagonia, however, experienced decreases (percent changes) in the average snow drought duration (-4, -7, -8, and -16%, respectively). Although we do not attempt to separate natural and human influences with a detailed attribution analysis, we discuss some relevant physical processes (e.g., Arctic amplification and polar vortex movement) that likely contribute to observed changes in snow drought characteristics. We also demonstrate how our framework can facilitate drought monitoring and assessment by examining two snow deficits that posed large socioeconomic challenges in the WUS (2014/2015) and Afghanistan (2017/2018).

Keywords: climate; drought; hydrology; snow; water resources.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.

Fig. 1.

(Top) Relative change in snow drought characteristics around the world from 1980 through 2018. A positive (negative) change indicates that an increase (decrease) in the respective variable occurred during the latter half of years. Percent changes are presented for the total and average durations (difference normalized by the variable value from the first period). The exceedance probability refers to the chance that the drought intensity (I) is greater than the average intensity from the first period (I ave). Changes in probabilities are displayed as differences. (Bottom) The sample global SWEI classification map shows the seven study regions (regions A through G).

Fig. 2.

Fig. 2.

Three-month SWEI classification for CONUS during (A_–_E) December 2014 to April 2015 and (F_–_I) December 2016 to March 2017. Dashed line in A defines the eastern boundary of the WUS (105°W). Classifications used here and hereafter: D0/W0, abnormally dry/wet; D1/W1, moderate drought/wet spell; D2/W2, severe drought/wet spell; D3/W3, extreme drought/wet spell; D4/W4, exceptional drought/wet spell; NN, near normal (

SI Appendix, Table S1

).

Fig. 3.

Fig. 3.

Three-month SWEI classification during the December 2017 to March 2018 snow drought in Afghanistan: (Left) Northern Hemisphere and (Right) Afghanistan and surrounding area.

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