Spring heat waves drive record western United States snow melt in 2021
Throughout the western US snow melted at an alarming rate in April 2021 and by May 1, hydrologic conditions were severely degraded with declining summer water supply forecasts compared to earlier in the winter. The objectives of this study are to (a) quantify the magnitude and climatological context...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/aca8bd |
| _version_ | 1827869642638491648 |
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| author | Daniel J McEvoy Benjamin J Hatchett |
| author_facet | Daniel J McEvoy Benjamin J Hatchett |
| author_sort | Daniel J McEvoy |
| collection | DOAJ |
| description | Throughout the western US snow melted at an alarming rate in April 2021 and by May 1, hydrologic conditions were severely degraded with declining summer water supply forecasts compared to earlier in the winter. The objectives of this study are to (a) quantify the magnitude and climatological context of observed melt rates of snow water equivalent (SWE) and (b) underpin the hydrometeorological drivers during April 2021 based on atmospheric reanalysis and gridded meteorological data. Peak SWE indicated snow drought conditions were widespread (41% of stations between 5th and 20th percentile) but not necessarily extreme (only 9% of stations less than 5th percentile). Here, using observations from the Snow Telemetry (SNOTEL) network we found record 7 day snow melt rates (median of −99 mm; ±one standard deviation of 61 mm) occurred at 24% of SNOTEL sites and in all 11 Western states. Strong upper atmospheric ridging that began initially in the north Pacific with eastward propagation by mid-April to the Pacific Northwest Coast led to near-surface conditions across the western US conducive to rapid snow loss. One heat wave occurred inland across the Rockies the first week of April and then later in April, a second heat wave impacted the Cascades and northern California. We find that ripening of the snowpack by both record high surface solar radiation and air temperatures were factors in driving the rapid snow melt. Equatorial Pacific sea surface temperatures and the La Niña pattern that peaked in winter along with an eastward propagating and intensifying Madden–Julian Oscillation were likely responsible for driving the placement, strength, and progression of the north Pacific Ridge. This study documents the role of two extreme spring ‘sunny heat wave’ events on snowpack, and the cascading drought impacts which are anticipated to become more frequent in a warming world. |
| first_indexed | 2024-03-12T15:47:57Z |
| format | Article |
| id | doaj.art-6ed66497bcb7490ea9314bb25798ae38 |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T15:47:57Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-6ed66497bcb7490ea9314bb25798ae382023-08-09T15:21:30ZengIOP PublishingEnvironmental Research Letters1748-93262023-01-0118101400710.1088/1748-9326/aca8bdSpring heat waves drive record western United States snow melt in 2021Daniel J McEvoy0Benjamin J Hatchett1Division of Atmospheric Sciences, Desert Research Institute , 2215 Raggio Parkway, Reno, NV 89512, United States of AmericaDivision of Atmospheric Sciences, Desert Research Institute , 2215 Raggio Parkway, Reno, NV 89512, United States of AmericaThroughout the western US snow melted at an alarming rate in April 2021 and by May 1, hydrologic conditions were severely degraded with declining summer water supply forecasts compared to earlier in the winter. The objectives of this study are to (a) quantify the magnitude and climatological context of observed melt rates of snow water equivalent (SWE) and (b) underpin the hydrometeorological drivers during April 2021 based on atmospheric reanalysis and gridded meteorological data. Peak SWE indicated snow drought conditions were widespread (41% of stations between 5th and 20th percentile) but not necessarily extreme (only 9% of stations less than 5th percentile). Here, using observations from the Snow Telemetry (SNOTEL) network we found record 7 day snow melt rates (median of −99 mm; ±one standard deviation of 61 mm) occurred at 24% of SNOTEL sites and in all 11 Western states. Strong upper atmospheric ridging that began initially in the north Pacific with eastward propagation by mid-April to the Pacific Northwest Coast led to near-surface conditions across the western US conducive to rapid snow loss. One heat wave occurred inland across the Rockies the first week of April and then later in April, a second heat wave impacted the Cascades and northern California. We find that ripening of the snowpack by both record high surface solar radiation and air temperatures were factors in driving the rapid snow melt. Equatorial Pacific sea surface temperatures and the La Niña pattern that peaked in winter along with an eastward propagating and intensifying Madden–Julian Oscillation were likely responsible for driving the placement, strength, and progression of the north Pacific Ridge. This study documents the role of two extreme spring ‘sunny heat wave’ events on snowpack, and the cascading drought impacts which are anticipated to become more frequent in a warming world.https://doi.org/10.1088/1748-9326/aca8bdwestern United Statessnow droughtsnow meltheat wavehydroclimate |
| spellingShingle | Daniel J McEvoy Benjamin J Hatchett Spring heat waves drive record western United States snow melt in 2021 Environmental Research Letters western United States snow drought snow melt heat wave hydroclimate |
| title | Spring heat waves drive record western United States snow melt in 2021 |
| title_full | Spring heat waves drive record western United States snow melt in 2021 |
| title_fullStr | Spring heat waves drive record western United States snow melt in 2021 |
| title_full_unstemmed | Spring heat waves drive record western United States snow melt in 2021 |
| title_short | Spring heat waves drive record western United States snow melt in 2021 |
| title_sort | spring heat waves drive record western united states snow melt in 2021 |
| topic | western United States snow drought snow melt heat wave hydroclimate |
| url | https://doi.org/10.1088/1748-9326/aca8bd |
| work_keys_str_mv | AT danieljmcevoy springheatwavesdriverecordwesternunitedstatessnowmeltin2021 AT benjaminjhatchett springheatwavesdriverecordwesternunitedstatessnowmeltin2021 |