Cold surge episodes over southeastern Brazil - a potential vorticity perspective

Sprenger, Michael; Martius, Olivia; Arnold, Julian (2013). Cold surge episodes over southeastern Brazil - a potential vorticity perspective. International journal of climatology, 33(12), pp. 2758-2767. Wiley 10.1002/joc.3618

[img]
Preview
Text
joc3618.pdf - Published Version
Available under License Publisher holds Copyright.

Download (2MB) | Preview

Most intense cold surges and associated frost events in southern and southeastern Brazil are characterized by a large amplitude trough over South America extending toward tropical latitudes and a ridge to the west of it over the Pacific Ocean. In this study, potential vorticity (PV) streamers serve to examine the flow condition leading to cold surges. Case studies suggest that several PV anomalies are related to cold surge episodes: (1) the potential vorticity unit (2-PVU) isoline upstream of South America becomes progressively more distorted prior and during the cold surge episode, indicating a flow situation which is conducive for Rossby wave breaking and hence a flow which strongly deviates from zonality; (2) the initial stage of a cold surge episode is characterized by a northward bulging of high-PV air to the east of the Andes, resulting in a PV streamer whose northern end reaches Uruguay and southeastern Brazil; the strong PV gradient on its western flank constitutes a flow configuration that induces and maintains the transport of sub-Antarctic air toward the subtropics; (3) a distinct negative PV anomaly, a blocking, originates over the eastern South Pacific, upstream of the South America sector. A composite analysis of 27 cold surges is performed for stratospheric PV streamer frequency on several isentropic surfaces. It reveals that equatorward wave breaking over South America and the western South Atlantic represents an important potential component of the dynamics of intense cold surges. The indications are most pronounced around the isentropic levels of 320 K and immediately before the day with largest temperature drops over subtropical Brazil.

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

UniBE Contributor:

Romppainen-Martius, Olivia

Subjects:

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

ISSN:

0899-8418

Publisher:

Wiley

Language:

English

Submitter:

Monika Wälti-Stampfli

Date Deposited:

15 Jan 2014 17:11

Last Modified:

13 Apr 2016 10:55

Publisher DOI:

10.1002/joc.3618

Uncontrolled Keywords:

cold surge; potential vorticity; Rossby wave breaking

BORIS DOI:

10.7892/boris.39674

URI:

https://boris.unibe.ch/id/eprint/39674

Actions (login required)

Edit item Edit item
Provide Feedback