On the time-scales of the downward propagation and of the tropospheric planetary wave response to the stratospheric circulation

Nikulin, Grigory; Lott, François

doi:10.5194/angeo-28-339-2010

Cited by 7 publications

(2 citation statements)

References 44 publications

(65 reference statements)

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“…Still, the presence of such a time lag alone is not sufficient to say that the signal originated in the stratosphere [ Plumb and Semeniuk , 2003]. Moreover, Nikulin and Lott [2010] recently found that the downward propagation of stratospheric anomalies occurs only at periods longer than 50 days. This suggests that the signals in response to the 11 year SC that we find formed within the troposphere itself.…”

Section: Discussionmentioning

confidence: 99%

The vertical connection of the quasi-biennial oscillation-modulated 11 year solar cycle signature in geopotential height and planetary waves during Northern Hemisphere early winter

Cnossen¹,

Lu²

2011

J. Geophys. Res.

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[1] We analyzed observational geopotential height data to provide some new insights on the 11 year solar cycle signal in the Northern Hemisphere early winter and its modulation by the quasi-biennial oscillation (QBO). The signals are strongest in the upper stratosphere. When the QBO is in its easterly phase (QBOe), it appears to move gradually eastward and poleward, resulting in a predominantly positive signal over the pole, with a weaker vertically connected negative signal over the Icelandic Low. When the QBO is in its westerly phase (QBOw), the polar stratospheric signal is mainly negative and appears connected to a negative anomaly in the troposphere over the Aleutian Low. A spectral analysis of the stratospheric response in planetary waves showed a reduction of wave number 2 power under QBOe and an enhancement of wave number 3 under QBOw. These responses are characterized by an overall increase/decrease in wave activity at middle to high latitudes rather than a latitudinal shift of wave activity. There is no clear stratospheretroposphere connection under QBOe, but under QBOw, there is a vertically coherent increase in wave power at wave numbers 1-3 with a period of 5.6-6.9 days. We suggest that the differences in response under QBOe and QBOw can be explained through differences in initial vortex strength, resulting in either a stronger influence from the low-latitude upper stratosphere (QBOe) or from the troposphere (QBOw) on the polar stratosphere.Citation: Cnossen, I., and H. Lu (2011), The vertical connection of the quasi-biennial oscillation-modulated 11 year solar cycle signature in geopotential height and planetary waves during Northern Hemisphere early winter,

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Section: Discussionmentioning

confidence: 99%

The vertical connection of the quasi-biennial oscillation-modulated 11 year solar cycle signature in geopotential height and planetary waves during Northern Hemisphere early winter

Cnossen¹,

Lu²

2011

J. Geophys. Res.

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“…This influence is related to radiative and chemical effects, but also to dynamical effects: some modes of stratospheric variability propagate downward, like the Quasi-Biennial Oscillation (QBO, Baldwin et al 2001) in the tropics, and the Arctic Oscillation (AO, Baldwin and Dunkerton 1999) in the mid latitudes. When the stratospheric anomalies reach the tropopause, they can potentially influence the surface climate, at least in the mid-latitudes (for the AO effect in the LMDZ mid-latitudes see for instance Lott et al 2005;Nikulin and Lott 2010). In order to take into account the impact of the stratospheric dynamics and chemistry in the coupled climate simulations, the LMDZ vertical grid was extended in the stratosphere, with a resolution close to a previous stratospheric version of LMDZ4 described by Lott et al (2005).…”

Section: Introductionmentioning

confidence: 99%

Impact of the LMDZ atmospheric grid configuration on the climate and sensitivity of the IPSL-CM5A coupled model

et al. 2012

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The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m 2 which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m 2 when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged.

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Tropical variability and stratospheric equatorial waves in the IPSLCM5 model

et al. 2011

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International audienceThe atmospheric variability in the equatorial regions is analysed in the Earth System Model pre-industrial simulation done at IPSL in the framework of CMIP5. We find that the model has an interannual variability of about the right amplitude and temporal scale, when compared to the El-Niño Southern Oscillation (ENSO), but that is too confined to the western Pacific. At the intra-seasonal periods, the model variability lacks of large-scale organisation, and only produces one characteristic Madden-Julian Oscillation every 10 winters typically. At shorter time-scales and in the troposphere, the model has Rossby and Kelvin Convectively Coupled Equatorial Waves (CCEWs), but underestimates the Kelvin CCEWs signal on OLR. In the model stratosphere, a composite analysis shows that the Temperature and velocities fluctuations due to the Kelvin waves are quite realistic. In the model nevertheless, the stratospheric waves are less related to the convection than in the observations, suggesting that their forcing by the midlatitudes plays a larger role. Still in the model, the Kelvin waves are not predominantly occurring during the life cycle of the tropospheric Kelvin CCEWs, a behaviour that we find to be dominant in the observations. The composite analysis is also used to illustrate how the waves modify the zonal mean-flow, and to show that the model Kelvin waves are too weak in this respect. This illustrates how a model can have a reasonable Kelvin waves signal on the velocities and temperature, but can at the same time underestimate their amplitude to modify the mean flow. We also use this very long simulation to establish that in the model, the stratospheric equatorial waves are significantly affected by ENSO, hence supporting the idea that the ENSO can have an influence on the Quasi-Biennial Oscillation. © 2011 Springer-Verlag

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On the time-scales of the downward propagation and of the tropospheric planetary wave response to the stratospheric circulation

Cited by 7 publications

References 44 publications

The vertical connection of the quasi-biennial oscillation-modulated 11 year solar cycle signature in geopotential height and planetary waves during Northern Hemisphere early winter

The vertical connection of the quasi-biennial oscillation-modulated 11 year solar cycle signature in geopotential height and planetary waves during Northern Hemisphere early winter

Impact of the LMDZ atmospheric grid configuration on the climate and sensitivity of the IPSL-CM5A coupled model

Tropical variability and stratospheric equatorial waves in the IPSLCM5 model

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