Quantifying the link between heavy precipitation and Northern Hemisphere blocking—A Lagrangian analysis

Lenggenhager, Sina; Martius, Olivia (2020). Quantifying the link between heavy precipitation and Northern Hemisphere blocking—A Lagrangian analysis. Atmospheric science letters, 21(10), pp. 1-12. Wiley 10.1002/asl.999

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Atmospheric blocks strongly influence surface weather, including extremes such as heat waves and cold spells. Recently, diabatic heating and associated upper‐tropospheric potential vorticity (PV) modification have been identified as important modulators of atmospheric blocking dynamics. Also, robust links between atmospheric blocks and proximate heavy precipitation events have been established. This leads to the question of the extent to which diabatic heating associated with heavy precipitation events influences Northern Hemisphere blocking. This study uses 5 years of 3‐day back trajectories started from objectively identified blocks in the ERA‐Interim dataset to investigate this relationship. A substantial fraction of air parcels in blocks pass through heavy precipitation areas. The exact fraction depends on the choice of heavy precipitation threshold. Roughly 19% of all the trajectories in a block pass a heavy precipitation area (>95th percentile) area while being saturated. Of the air parcels in a block that are heated at least 5 K, 60% pass a heavy precipitation area while saturated. This fraction varies with the season and geographical area. The overall fraction is lowest in summer and highest in winter, higher over oceans than over land, and higher over the Pacific than over the Atlantic. In summer, heating is relevant over the continents and heating over North America influences blocks over the eastern Atlantic. For summer blocks in the North Atlantic and over Scandinavia, heating happens partly over the European continent.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Impact
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography

UniBE Contributor:

Lenggenhager, Sina and Romppainen-Martius, Olivia

Subjects:

900 History > 910 Geography & travel
500 Science > 550 Earth sciences & geology

ISSN:

1530-261X

Publisher:

Wiley

Projects:

[245] Mobiliar Lab für Naturrisiken Official URL

Language:

English

Submitter:

Hélène Christine Louise Barras

Date Deposited:

25 Jun 2020 09:22

Last Modified:

04 Oct 2020 03:14

Publisher DOI:

10.1002/asl.999

Uncontrolled Keywords:

atmospheric blocks, diabatic heating, heavy precipitation, PV modification by latent heating, trajectories

BORIS DOI:

10.7892/boris.144800

URI:

https://boris.unibe.ch/id/eprint/144800

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