The 3-Week-Long Transport History and Deep Tropical Origin of the 2021 Extreme Heat Wave in the Pacific Northwest

Katharina Baier, Marcus Rubel, Andreas Stohl

Publications: Contribution to journalArticlePeer Reviewed


The heat wave in late June of 2021 (PNW21) set new temperature records in the Pacific Northwest (PNW). In Lytton the highest temperature ever recorded in Canada was measured. Several studies have already explored this extreme event in detail, however, here we compare the atmospheric air mass transport and heating processes associated with this heat wave with the 34 other most extreme heat events in the same region during the period 1960–2021, using a long backtracking time of 25 days. We found significant differences in the heat waves. During PNW21 most of the air was coming from the Philippine Sea, with more than 40% of the air located south of 15°N, and anomalous advection of sensible and latent heat from the Tropics was the dominant cause of PNW21. The latent heat was efficiently converted into sensible heat by precipitation, which was unique, as most other extremes experienced net diabatic cooling.

Original languageEnglish
Article numbere2023GL105865
JournalGeophysical Research Letters
Issue number24
Publication statusPublished - 28 Dec 2023

Austrian Fields of Science 2012

  • 105206 Meteorology


  • atmospheric transport
  • extreme event
  • heat wave
  • Northwest Pacific

Cite this