A Storyline Approach to the June 2021 Northwestern North American Heatwave

Article Geosciences, Multidisciplinary

The 2021 Western North American Heatwave and Its Subseasonal Predictions

Hai Lin et al.

Summary: This study evaluates the ability of 10 Subseasonal-to-Seasonal prediction models to predict above-normal temperatures in western North America 2-3 weeks in advance. It is found that most models were able to predict the high temperatures in Western Canada during June 28-July 4 as early as June 10. However, for forecasts initialized earlier than June 17, none of the models could accurately capture the magnitude of the observed temperature anomaly. The study identifies the importance of two processes: an upper tropospheric wave train associated with the boreal summer intraseasonal oscillation in Southeast Asia, and an anomalous North Pacific atmospheric river leading to high moisture conditions. Most models were able to predict the wave train across the North Pacific, but a realistic representation of moisture transport and its pattern appears crucial for the extended-range forecast of this heatwave.

GEOPHYSICAL RESEARCH LETTERS (2022)

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Article Geosciences, Multidisciplinary

The 2021 Pacific Northwest Heat Wave and Associated Blocking: Meteorology and the Role of an Upstream Cyclone as a Diabatic Source of Wave Activity

Emily Neal et al.

Summary: The study investigates the meteorological and dynamical conditions that led to extreme heat in the Pacific Northwest from late June to early July 2021. It finds that an upper-level atmospheric blocking and surface cyclogenesis off the coast of Alaska contributed to the extreme heat event. The study also highlights the critical role of a localized non-diabatic source in the formation and strength of the blocking.

GEOPHYSICAL RESEARCH LETTERS (2022)

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Article Environmental Sciences

Drivers and Mechanisms of the 2021 Pacific Northwest Heatwave

D. L. Schumacher et al.

Summary: In late June 2021, a heatwave with unusually high temperatures occurred in western North America, particularly in the Pacific Northwest. The study finds that the physical drivers of this event are the anticyclonic circulation aloft, which converts potential energy into sensible heat, and the establishment of deep atmospheric boundary layers facilitated by mountainous terrain and dry soils. Anomalous soil moisture also contributes to the temperature rise. The research suggests that similar large-scale atmospheric circulation driven by enhanced thermodynamic drivers could result in even more extreme temperatures, particularly in a warmer climate.

EARTHS FUTURE (2022)

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Article Geosciences, Multidisciplinary

Rapid attribution analysis of the extraordinary heat wave on the Pacific coast of the US and Canada in June 2021

Sjoukje Y. Philip et al.

Summary: In late June 2021, record-breaking temperatures in the US and Canada's Pacific Northwest resulted in increased deaths and health issues. Through a multi-model, multi-method analysis, it was found that human-induced climate change significantly influenced the probability and intensity of these extreme heat waves. The study emphasizes the urgent need for adaptation and mitigation strategies to address the significant consequences of our rapidly warming climate.

EARTH SYSTEM DYNAMICS (2022)

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Article Meteorology & Atmospheric Sciences

An Updated Assessment of Near-Surface Temperature Change From 1850: The HadCRUT5 Data Set

C. P. Morice et al.

Summary: HadCRUT5 is a new version of a global surface temperature data set, incorporating sea-surface temperature and land near-surface air temperature measurements. Two variants are produced for different applications, with the combination of revised input data sets and statistical analysis resulting in greater warming of the global average over the entire record period.

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES (2021)

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Article Meteorology & Atmospheric Sciences

The ERA5 global reanalysis: Preliminary extension to 1950

Bill Bell et al.

Summary: The extension of the ERA5 reanalysis back to 1950 improves the previously published segment covering 1979 to the present by assimilating more traditional observations and utilizing early satellite data. The global surface temperature anomalies and precipitation variability show high correlations with observations, despite significant differences in representing specific regions. Areas for improvement include assimilating tropical cyclone data and enhancing the representation of surface temperatures over Australia.

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY (2021)

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Article Environmental Sciences

Causes of the Record-Breaking Pacific Northwest Heatwave, Late June 2021

James E. Overland

Summary: The extreme heat event that hit the Pacific Northwest in late June 2021 caused hundreds of deaths, loss of marine life, and forests. The event was triggered by the split of the polar vortex in the Arctic, accompanied by warming, which may represent a critical state in large-scale atmospheric circulation variability.

ATMOSPHERE (2021)

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Article Geosciences, Multidisciplinary

Ubiquity of human-induced changes in climate variability

Keith B. Rodgers et al.

Summary: Climate variability plays a crucial role in climate adaptation efforts, and greenhouse warming alters variance spectra of Earth system variables, leading to a wide range of changes. The modeling results have important implications for climate adaptation, resource management, seasonal predictions, and assessing stressors on terrestrial and marine ecosystems.

EARTH SYSTEM DYNAMICS (2021)

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Article Multidisciplinary Sciences