Equatorial Windows and Barriers for Stationary Rossby Wave Propagation

Li, Yanjie; Feng, Jin; Li, Jianping; Hu, Aixue

doi:10.1175/jcli-d-18-0722.1

Cited by 33 publications

(45 citation statements)

References 45 publications

(75 reference statements)

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“…horizontally non-uniform basic flow Li et al, , 2019bZhao et al, 2015Zhao et al, , 2019 to trace the trajectory of the stationary Rossby wave train and characterize the pathway of the impact of the AAMT. The theory is an extension of the classical one by Hoskins and Karoly (1981).…”

Section: Dynamical Diagnosismentioning

confidence: 99%

Influence of the NAO on Wintertime Surface Air Temperature over East Asia: Multidecadal Variability and Decadal Prediction

Xie

Tang

et al. 2021

Adv. Atmos. Sci.

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In this paper, we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature (EASAT) and EASAT decadal prediction. The observational analysis shows that the winter EASAT and East Asian minimum SAT (EAmSAT) display strong in-phase fluctuations and a significant 60–80-year multidecadal variability, apart from a long-term warming trend. The winter EASAT experienced a decreasing trend in the last two decades, which is consistent with the occurrence of extremely cold events in East Asia winters in recent years. The winter NAO leads the detrended winter EASAT by 12–18 years with the greatest significant positive correlation at the lead time of 15 years. Further analysis shows that ENSO may affect winter EASAT interannual variability, but does not affect the robust lead relationship between the winter NAO and EASAT. We present the coupled oceanic-atmospheric bridge (COAB) mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of ∼15 years on the Atlantic Multidecadal Oscillation (AMO) and Africa-Asia multidecadal teleconnection (AAMT) pattern. An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism, with good hindcast performance. The winter EASAT for 2020–34 is predicted to keep on fluctuating downward until ∼2025, implying a high probability of occurrence of extremely cold events in coming winters in East Asia, followed by a sudden turn towards sharp warming. The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.

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Section: Dynamical Diagnosismentioning

confidence: 99%

Influence of the NAO on Wintertime Surface Air Temperature over East Asia: Multidecadal Variability and Decadal Prediction

Xie

Tang

et al. 2021

Adv. Atmos. Sci.

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“…Based on background horizontal winds, the regions with favoured direct meridional movement match results for the energy propagation of stationary waves, with similarities to westerly duct theory (e.g. Webster and Holton, 1982) and the influence of background meridional wind on cross‐equatorial propagation (Li et al ., 2015, 2019; Zhao et al ., 2015, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…Meridional winds favour increased wavelet power in the same direction and disfavour power in the opposite direction. This result is analogous to the finding that stationary waves are able to have cross‐equatorial propagation in regions where the background zonal winds are unsupportive due to meridional winds in the same direction as the energy propagation (Li et al ., 2015, 2019; Zhao et al ., 2015, 2019). Power at 20°N has a negative relationship with the background meridional shear of the zonal wind ( du / dy ) and a positive relationship with the zonal shear of the meridional wind ( dv / dx ), consistent with a positive relationship to vorticity, with the reverse true at 20°S.…”

Section: Discussionmentioning

confidence: 99%

“…For example, under conditions with westerly shear in the meridional direction (positive du/dy) opposed to easterly or no shear, energy from the tropics is more easily transferred to the Northern Hemispheric extratropics (Lau and Lim, 1984). Moreover, adding meridional background winds allows for interhemispheric teleconnection of stationary waves in regions with tropical easterlies (Li et al, 2015(Li et al, , 2019Zhao et al, 2015Zhao et al, , 2019. Specifically, stationary waves may propagate across regions with background easterly winds in the southward direction in regions of background northerlies and in the northward direction in regions of background southerlies.…”

Section: Introductionmentioning

confidence: 99%

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Meridional movement of geopotential height anomalies in the subtropics and the relationship to the base‐state flow

Gahtan

Roundy

2020

Quart J Royal Meteoro Soc

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Qualities of the meridional movements of geopotential height anomalies in the upper troposphere of the subtropics are analysed via wavelet analysis using a meridional–temporal partial Morlet wavelet. Results show that power, which represents increased presence or amplitude of waves with direct meridional movement, is increased in regions where the corresponding equatorial winds in the upper troposphere are westerly or weakly easterly. Furthermore, equatorward power is enhanced near subtropical jet exit regions whereas poleward power is enhanced in jet entrance regions. Regressions of upper‐tropospheric winds, geopotential height, and outgoing long‐wave radiation (OLR) against the wavelet transforms demonstrate that the wavelets are identifying signals with tropical–extratropical interactions that are connected to organized convection in the tropics. The relationship of power with background‐state flow characteristics, including the horizontal winds and shear, are evaluated. Instead of the zonal wind and meridional shear of the zonal wind (du/dy), both the meridional wind and the zonal shear of the meridional wind (dv/dx) appear to have a clearer relationship with the power. Power is favoured for waves whose movement is aligned in the same direction as the meridional wind, and reduced in the opposite direction. Additionally, power increases with increasing zonal shear of the meridional wind in the Northern Hemisphere and with decreasing zonal shear of the meridional wind in the Southern Hemisphere. Power in the equatorward direction is stronger than in the poleward direction and more heavily influenced by background flow characteristics. Furthermore, power for wavelets with smaller meridional and temporal scales tends to have a higher sensitivity to the background horizontal flow as compared to larger meridional and temporal scales.

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“…Li et al [16] further suggested that the large scale monsoonal background flows play a critical role in the interhemispheric teleconnection. Recently, Li et al [19] further explored the windows and barriers for cross-equatorial waves by the wave ray ensemble method.…”

Section: Introductionmentioning

confidence: 99%

Variations in Wave Energy and Amplitudes along the Ray Paths of Barotropic Rossby Waves in Horizontally Non-Uniform Basic Flows

Jiping

Kang

2021

Atmosphere

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A non-divergent barotropic model on a sphere transformed to Mercator coordinates is used to examine the variations in wave energy and amplitude along the energy dispersion paths of barotropic Rossby waves in non-uniform basic flows. Wave energy can be easily solved by specifying the divergence of the group velocity along the corresponding rays. In an analytical non-uniform basic flow that represents the basic features of the observed one at middle latitudes, waves with different periods decay accompanying the decreases in wave energy and amplitude and the increase in the total wavenumber. This implies that the waves are trapped and the energy is eventually absorbed by the basic flow. For the observed non-uniform basic flow that can represent the basic features of the non-divergent wind field at 200 hPa, the situation is more complicated. The significant increase in wave energy can be caused by either the convergence of wave energy or the barotropic energy absorption from the basic flow or both of them. A significant increase in amplitude can also be observed if the total wavenumber varies moderately. This means waves can significantly develop. Waves may decay if both wave energy and amplitude decrease. Waves may propagate without significant developing or decaying to realize a long distance propagation. The propagating waves are mainly caused by oscillating wave energy as well as amplitude.

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Equatorial Windows and Barriers for Stationary Rossby Wave Propagation

Cited by 33 publications

References 45 publications

Influence of the NAO on Wintertime Surface Air Temperature over East Asia: Multidecadal Variability and Decadal Prediction

Influence of the NAO on Wintertime Surface Air Temperature over East Asia: Multidecadal Variability and Decadal Prediction

Meridional movement of geopotential height anomalies in the subtropics and the relationship to the base‐state flow

Variations in Wave Energy and Amplitudes along the Ray Paths of Barotropic Rossby Waves in Horizontally Non-Uniform Basic Flows

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