The energetic particle precipitation (EPP) indirect effect (IE) refers to the downward transport of reactive odd nitrogen (NOx = NO + NO2) produced by EPP (EPP‐NOx) from the polar winter mesosphere and lower thermosphere to the stratosphere where it can destroy ozone. Previous studies of the EPP IE examined NOxdescent averaged over the polar region, but the work presented here considers longitudinal variations. We report that the January 2009 split Arctic vortex in the stratosphere left an imprint on the distribution of NO near the mesopause, and that the magnitude of EPP‐NOxdescent in the upper mesosphere depends strongly on the planetary wave (PW) phase. We focus on an 11‐day case study in late January immediately following the 2009 sudden stratospheric warming during which regional‐scale Lagrangian coherent structures (LCSs) formed atop the strengthening mesospheric vortex. The LCSs emerged over the north Atlantic in the vicinity of the trough of a 10‐day westward traveling planetary wave. Over the next week, the LCSs acted to confine NO‐rich air to polar latitudes, effectively prolonging its lifetime as it descended into the top of the polar vortex. Both a whole atmosphere data assimilation model and satellite observations show that the PW trough remained coincident in space and time with the NO‐rich air as both migrated westward over the Canadian Arctic. Estimates of descent rates indicate five times stronger descent inside the PW trough compared to other longitudes. This case serves to set the stage for future climatological analysis of NO transport via LCSs.
The present study examines the northern stratosphere during April 2020, when the polar vortex split into two cyclonic vortices during a winter‐early spring period with the strongest ozone depletion on record. We investigate the dynamical evolution leading to the split at middle stratospheric levels, including the fate of fluid parcels on the vortex boundary during its rupture and the distribution of ozone between the vortices resulting from the split. We also illustrate the vertical structure of the vortices after the split. The findings obtained with Lagrangian methods confirm the key role for the split played by a flow with a special configuration of barriers to the motion of parcels. A trajectory analysis clarifies how the ozone distribution between vortices was such that ozone poorest air remained in the main vortex. The offspring vortex had a deep structure from the troposphere and later decayed to vanish by the end of April.
more » « less- Award ID(s):
- 1832842
- NSF-PAR ID:
- 10362063
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 48
- Issue:
- 16
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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