Radiative effects of ozone waves on the Northern Hemisphere polar vortex and its modulation by the QBO
The radiative effects induced by the zonally asymmetric part of the ozone field have been shown to significantly change the temperature of the NH winter polar cap, and correspondingly the strength of the polar vortex. In this paper, we aim to understand the physical processes behind these effects...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/6637/2018/acp-18-6637-2018.pdf |
| Summary: | The radiative effects induced by the zonally asymmetric part of the ozone
field have been shown to significantly change the temperature of the NH
winter polar cap, and correspondingly the strength of the polar vortex. In
this paper, we aim to understand the physical processes behind these effects
using the National Center for Atmospheric Research (NCAR)'s Whole Atmosphere
Community Climate Model, run with 1960s ozone-depleting substances and
greenhouse gases. We find a mid-winter polar vortex influence only when
considering the quasi-biennial oscillation (QBO) phases separately, since
ozone waves affect the vortex in an opposite manner. Specifically, the
emergence of a midlatitude QBO signal is delayed by 1–2 months when
radiative ozone-wave effects are removed. The influence of ozone waves on the
winter polar vortex, via their modulation of shortwave heating, is not
obvious, given that shortwave heating is largest during fall, when planetary
stratospheric waves are weakest. Using a novel diagnostic of wave 1
temperature amplitude tendencies and a synoptic analysis of upward planetary
wave pulses, we are able to show the chain of events that lead from a direct
radiative effect on weak early fall upward-propagating planetary waves to a
winter polar vortex modulation. We show that an important stage of this
amplification is the modulation of individual wave life cycles, which
accumulate during fall and early winter, before being amplified by wave–mean
flow feedbacks. We find that the evolution of these early winter upward
planetary wave pulses and their induced stratospheric zonal mean flow
deceleration is qualitatively different between QBO phases, providing a new
mechanistic view of the extratropical QBO signal. We further show how these
differences result in opposite radiative ozone-wave effects between east and
west QBOs. |
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| ISSN: | 1680-7316 1680-7324 |