Identification

Title

An ERA5 climatology of synoptic-scale negative potential vorticity–jet interactions over the western North Atlantic

Abstract

Abstract. Recent numerical modeling and theoretical work deduce that potential vorticity (PV) can turn negative in the Northern Hemisphere as a result of localized convective heating embedded in vertical wind shear. It has been further postulated that negative potential vorticity (NPV) may be relevant for the large-scale circulation, as it has been observed to grow in scale into elongated mesoscale bands when in close proximity to the jet stream, accelerating jet stream winds and degrading numerical weather prediction skill. However, these findings are largely confined to case studies. Here, we use a climatological and composite perspective to evaluate the occurrence of elongated bands of NPV over the northwest Atlantic and its implications for jet stream dynamics. This research focuses on synoptic-scale bands (>1650 km) of NPV that are in close proximity (< 100 km) to the jet stream (termed NPV–jet interactions) using ERA5 data from January 2000 to December 2021. Climatological characteristics show that NPV–jet interactions occur most frequently over the coastal western Atlantic during boreal winter along 40° N. This latitude band has also seen an 11 % increase (relative change) in NPV–jet interactions over the 22-year time period. Separating NPV–jet interactions into three distinct large-scale flow patterns using k-means clustering conceptually illustrates the evolution of NPV features from their initial formation along the westward flank of the ridge to the eastern flank of the ridge. The large-scale environment of NPV–jet interactions is characterized by a trough–ridge couplet adjacent to positive integrated vapor transport (IVT) anomalies, conducive to warm conveyor belts and mesoscale convective systems. Even when NPV is positioned in a more adiabatic environment (far away from regions of strong IVT anomalies), robust positive-PV gradient and wind speed anomalies exist along the jet stream. Inspecting three detailed case studies that serve as archetypes of the three clusters, we showed that the presence of NPV near the jet stream adiabatically enhances wave activity flux due to NPV mutually strengthening momentum transport and the ageostrophic flux of the geopotential. The results show that the close proximity of synoptic-scale NPV to the jet stream is conducive to the occurrence of wind speed maxima and could be dynamically relevant in enhancing downstream development despite NPV's theorized origin from submesoscales.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.net/ark:/85065/d7q81jh4

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2025-04-11T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

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name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact