Tropospheric‐stratospheric wave propagation during El Niño‐Southern Oscillation

Weare, Bryan C.

doi:10.1029/2009jd013647

Cited by 9 publications

(14 citation statements)

References 33 publications

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“…Moreover, the MJO is also known to have impacts on the state of the Northern Hemisphere stratospheric polar vortex. These impacts can occur either via vertically propagating Rossby waves directly associated with the MJO convection or indirectly from MJO‐extratropical tropospheric teleconnections that produce preferential wave patterns that excite planetary‐scale waves, which subsequently propagate into the polar stratosphere (e.g., Garfinkel et al, , ; Kang & Tziperman, ; Liu et al, ; Weare, ). Indeed, the MJO has been used as a skillful predictor for Northern Hemisphere sudden stratospheric warming events (Garfinkel & Schwartz, ; Schwartz & Garfinkel, ).…”

Section: Introductionmentioning

confidence: 99%

Tropospheric and Stratospheric Causal Pathways Between the MJO and NAO

et al. 2019

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Previous work has shown that the Madden‐Julian Oscillation (MJO) can influence the North Atlantic Oscillation (NAO) via a Rossby wave teleconnection that propagates through the troposphere (i.e., a tropospheric pathway). In addition, recent work suggests that the MJO can influence the stratospheric polar vortex, which is also known to influence the tropospheric NAO—thus, there likely exists a stratospheric pathway for MJO influence as well. Here, we apply two methods to shed more light on the pathways linking the MJO to the NAO. First, we use a traditional approach in climate science based on analyzing conditional probabilities. Second, we use methods from causal discovery theory based on probabilistic graphical models. Together, these two analysis approaches reveal that the MJO can impact the NAO via both a tropospheric and stratospheric pathway. The stratospheric pathway is shown to come about in two ways: First, both methods show that the MJO itself influences the strength of the stratospheric polar vortex on a timescale of ∼10 days, and then 5 days later the vortex can drive changes in the NAO. Second, the state of the stratospheric polar vortex acts to condition the NAO to be conducive (or not) to MJO influence. When the vortex is in a state that opposes the expected NAO response to the MJO, we find little influence of the MJO on the NAO, however, when the vortex supports the expected NAO response, the NAO is up to 30% more likely to be in a particular state following active MJO periods.

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Section: Introductionmentioning

confidence: 99%

Tropospheric and Stratospheric Causal Pathways Between the MJO and NAO

et al. 2019

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“…Some phenomena introduce longitudinal differences into wind pattern, for example the El Niño-Southern Oscillation -ENSO (e.g. Weare, 2010). The total ozone in the winter higher middle latitudes has a strong longitudinal de- pendence, the maximum-minimum difference being more than 100 Dobson units (D.U.)…”

Section: Introductionmentioning

confidence: 99%

Longitudinal structure of stationary planetary waves in the middle atmosphere – extraordinary years

2018

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Abstract. One important but little studied factor in the middle atmosphere meridional circulation is its longitudinal structure. Kozubek et al. (2015) disclosed the existence of the two-cell longitudinal structure in meridional wind at 10 hPa at higher latitudes in January. This two-cell structure is a consequence of the stratospheric stationary wave SPW1 in geopotential heights. Therefore here the longitudinal structure in geopotential heights and meridional wind is analysed based on MERRA data over 1979-2013 and limited NOGAPS-ALPHA data in order to find its persistence and altitudinal dependence with focus on extraordinary years. The SPW1 in geopotential heights and related two-cell structure in meridional wind covers the middle stratosphere (lower boundary ∼ 50 hPa), upper stratosphere and most of the mesosphere (almost up to about 0.01 hPa). The two-cell longitudinal structure in meridional wind is a relatively persistent feature; only 9 out of 35 winters (Januaries) display more complex structure. Morphologically the deviation of these extraordinary Januaries consists in upward propagation of the second (Euro-Atlantic) peak (i.e. SPW2 structure) to higher altitudes than usually, mostly up to the mesosphere. All these Januaries occurred under the positive phase of PNA (Pacific North American) index but there are also other Januaries under its positive phase, which behave in an ordinary way. The decisive role in the existence of extraordinary years (Januaries) appears to be played by the SPW filtering by the zonal wind pattern. In all ordinary years the mean zonal wind pattern in January allows the upward propagation of SPW1 (Aleutian peak in geopotential heights) up to the mesosphere but it does not allow the upward propagation of the EuroAtlantic SPW2 peak to and above the 10 hPa level. On the other hand, the mean zonal wind filtering pattern in extraordinary Januaries is consistent with the observed pattern of geopotential heights at higher altitudes.

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“…Some phenomena introduce longitudinal differences into wind pattern, for example the El Niño-Southern Oscillation -ENSO (e.g. Weare, 2010). The total ozone in the winter higher middle latitudes has a strong longitudinal dependence, with the maximum-minimum difference being more than 100 Dobson Units (DU) (e.g.…”

Section: Introductionmentioning

confidence: 99%