scholarly journals Diversity of the Global Teleconnections Associated with the Madden–Julian Oscillation

2021 ◽  
Vol 34 (1) ◽  
pp. 397-414
Author(s):  
Guosen Chen
Keyword(s):  
Rossby Wave ◽  
Potential Vorticity ◽  
Wave Train ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
The Pacific ◽  
Weather And Climate ◽  
Baroclinic Model ◽  
Rossby Wave Train ◽  
Upper Level

AbstractA recent study has revealed that the Madden–Julian oscillation (MJO) during boreal winter exhibits diverse propagation patterns that consist of four archetypes: standing MJO, jumping MJO, slow eastward propagating MJO, and fast eastward propagating MJO. This study has explored the diversity of teleconnection associated with these four MJO groups. The results reveal that each MJO group corresponds to distinct global teleconnections, manifested as diverse upper-tropospheric Rossby wave train patterns. Overall, the teleconnections in the fast and slow MJO are similar to those in the canonical MJO constructed by the real-time multivariate MJO (RMM) indices, while the teleconnections in the jumping and standing MJO generally lose similarities to those in the canonical MJO. The causes of this diversity are investigated using a linearized potential vorticity equation. The various MJO tropical heating patterns in different MJO groups are the main cause of the diverse MJO teleconnections, as they induce assorted upper-level divergent flows that act as Rossby-wave sources through advecting the background potential vorticity. The variation of the Asian jet could affect the teleconnections over the Pacific jet exit region, but it plays an insignificant role in causing the diversity of global teleconnections. The numerical investigation with a linear baroclinic model shows that the teleconnections can be interpreted as linear responses to the MJO’s diabatic heating to various degrees for different MJO groups, with the fast and slow MJO having higher linear skill than the jumping and standing MJO. The results have broad implications in the MJO’s tropical–extratropical interactions and the associated impacts on global weather and climate.

The Global Atmospheric Circulation Response to Tropical Diabatic Heating Associated with the Madden–Julian Oscillation during Northern Winter

2012 ◽  
Vol 69 (1) ◽  
pp. 79-96 ◽  
Author(s):  
Kyong-Hwan Seo ◽  
Seok-Woo Son
Keyword(s):  
Rossby Wave ◽  
Large Scale ◽  
Wave Train ◽  
Large Fraction ◽  
Equation Model ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Background Flow ◽  
Rossby Wave Train ◽  
Circulation Anomalies

Abstract The detailed dynamical mechanisms of the upper-tropospheric circulation response to the Madden–Julian oscillation (MJO) convection are examined by integrating a primitive equation model. A series of initial-value calculations with the climatological boreal winter background flow forced by the MJO-like thermal forcing successfully capture the key aspects of the observed circulation response to the MJO convection. This suggests that a large fraction of MJO-related circulation anomalies are direct responses to tropical heating in both the tropics and extratropics and can be largely explained by linear dynamics. It is found that MJO-like dipole heatings not only intensify tropical upper-tropospheric anomalies but also weaken them at certain regions because of the interaction between equatorial Kelvin and Rossby waves. The Rossby wave train primarily excited by horizontal divergence of upper-level perturbation flow propagates northeastward and then heads back to the equator. In this way, Rossby wave activity once generated over the subtropical Indian Ocean tends to enhance the equatorial upper-tropospheric anomalies over the tropical Atlantic and West Africa that have already been created by the zonally propagating equatorial Rossby and Kelvin waves. A ray path tracing reveals that a successive downstream development of Rossby wave train mostly results from the large-scale waves with zonal wavenumbers 2–3 in the Northern Hemisphere and 3–5 in the Southern Hemisphere. The sensitivity tests show that the overall results are quite robust. It is found, however, that the detailed circulation response to the MJO-like forcing is somewhat sensitive to the background flow. This suggests that MJO-related circulation anomalies may have nonnegligible long-term variability and change as background flow varies.

scholarly journals Mechanisms of Intraseasonal Amplification of the Cold Siberian High

2005 ◽  
Vol 62 (12) ◽  
pp. 4423-4440 ◽  
Author(s):  
Koutarou Takaya ◽  
Hisashi Nakamura
Keyword(s):  
Rossby Wave ◽  
Rossby Waves ◽  
Wave Train ◽  
The Tibetan Plateau ◽  
Cold Air ◽  
Thermal Anomalies ◽  
Siberian High ◽  
Vertical Coupling ◽  
Rossby Wave Train ◽  
Upper Level

Abstract Mechanisms of intraseasonal amplification of the Siberian high are investigated on the basis of composite anomaly evolution for its strongest events at each of the grid points over Siberia. At each location, the amplification of the surface high is associated with formation of a blocking ridge in the upper troposphere. Over central and western Siberia, what may be called “wave-train (Atlantic-origin)” type is common, where a blocking ridge forms as a component of a quasi-stationary Rossby wave train propagating across the Eurasian continent. A cold air outbreak follows once anomalous surface cold air reaches the northeastern slope of the Tibetan Plateau. It is found through the potential vorticity (PV) inversion technique that interaction between the upper-level stationary Rossby wave train and preexisting surface cold anomalies is essential for the strong amplification of the surface high. Upper-level PV anomalies associated with the wave train reinforce the cold anticyclonic anomalies at the surface by inducing anomalous cold advection that counteracts the tendency of the thermal anomalies themselves to migrate eastward as surface thermal Rossby waves. The surface cold anomalies thus intensified, in turn, act to induce anomalous vorticity advection aloft that reinforces the blocking ridge and cyclonic anomalies downstream of it that constitute the propagating wave train. The baroclinic development of the anomalies through this vertical coupling is manifested as a significant upward flux of wave activity emanating from the surface cold anomalies, which may be interpreted as dissipative destabilization of the incoming external Rossby waves.

scholarly journals The Southwest China Flood of July 2018 and Its Causes

Atmosphere ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 247 ◽  
Author(s):  
Lijuan Wang ◽  
Lin Wang ◽  
Yuyun Liu ◽  
Wei Gu ◽  
Peiqiang Xu ◽  
...  
Keyword(s):  
Rossby Wave ◽  
North Pacific ◽  
Western North Pacific ◽  
Southwest China ◽  
Wave Train ◽  
Western Pacific Subtropical High ◽  
Water Vapor Transport ◽  
Dynamical Condition ◽  
The Pacific ◽  
Rossby Wave Train

Excessive rainfall was observed over Southwest China in July 2018, leading to floods in several major tributaries of the Yangtze River and landslide and debris flow in the neighboring provinces. The rainfall during 7–11 July was unusually heavy and broke the record that can be traced back to 1961. The occurrence of the excessive rain can be attributed to the anomalous convection over the western North Pacific and the presence of a mid-latitude Rossby wave train. On one hand, the convection over the western North Pacific was anomalously strong in July 2018, and it could have excited the negative phase of the Pacific–Japan pattern and led to a northwestward shift of the western Pacific subtropical high. Hence, the water vapor transport toward inland China including Southwest China was enhanced, providing a favorable moisture environment for precipitation. On the other hand, a mid-latitude Rossby wave train was observed to propagate from Northern Europe towards East Asia, which was conducive to anomalous ascending motion over Southwest China via warm advection and differential vorticity advection, creating a favorable dynamical condition for precipitation. As a result, the combination of the two effects mentioned above led to the occurrence of the flood over Southwest China in July 2018.

The Intraseasonal Oscillation of Eastern Tibetan Plateau Precipitation in Response to the Summer Eurasian Wave Train

2016 ◽  
Vol 29 (20) ◽  
pp. 7215-7230 ◽  
Author(s):  
Wenting Hu ◽  
Anmin Duan ◽  
Yun Li ◽  
Bian He
Keyword(s):  
Tibetan Plateau ◽  
Rossby Wave ◽  
Geopotential Height ◽  
General Circulation ◽  
Wave Train ◽  
Intraseasonal Oscillation ◽  
Eastern Tibetan Plateau ◽  
Energy Propagation ◽  
Rossby Wave Train ◽  
Upper Level

Abstract This study examines the characteristics and mechanisms associated with the dominant intraseasonal oscillation (ISO) that controlled eastern Tibetan Plateau summer rainfall (ETPSR) over the period 1979–2011. The results of both power and wavelet spectrum analysis reveal that ETPSR follows a significant 7–20-day oscillation during most summers. The vertical structure of the ETPSR ISO in the dry phase is characterized by a vertical dipole pattern of geopotential height with a positive center on the eastern Tibetan Plateau (TP) and a negative center on the western TP. The wet phase shows the opposite characteristics to the dry phase. The transitions between the dry and wet phases during an ETPSR ISO cycle are related to a Rossby wave train that presents as large anomalous anticyclonic and cyclonic centers that alternate along the pathway from the eastern Atlantic to southern China via the TP. It corresponds to the evolution of the phase-independent wave-activity W, which implies an eastward/southeastward energy propagation of the ISO. The dominant modes of the daily 200-hPa geopotential height as identified by the rotated empirical orthogonal function (REOF) demonstrate that the different phases of the Rossby wave train influence the upper-level circulation over the eastern TP, which then impacts precipitation in the region. Furthermore, fluctuations in the eastern Atlantic may be the key factor for the propagation of the Rossby wave train that influences the upper-level circulation and rainfall variability over the eastern TP. Results from numerical experiments using an atmospheric general circulation model support the conclusion that the fluctuations over the eastern Atlantic contribute to the ISO of ETPSR.

scholarly journals Modulation of the Westerly and Easterly Quasi-Biennial Oscillation Phases on the Connection between the Madden–Julian Oscillation and the Arctic Oscillation

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 175 ◽  
Author(s):  
Lei Song ◽  
Renguang Wu
Keyword(s):  
Rossby Wave ◽  
Arctic Oscillation ◽  
Wave Train ◽  
The Arctic ◽  
Madden Julian Oscillation ◽  
Quasi Biennial Oscillation ◽  
Rossby Wave Train ◽  
Asian Pacific ◽  
The Arctic Oscillation ◽  
Biennial Oscillation

Previous studies have revealed the relationship between the Madden–Julian oscillation (MJO) and the Arctic Oscillation (AO). The MJO phase 2/3 is followed by the positive AO phase, and the MJO phase 6/7 is followed by the negative AO phase. This study reveals that the MJO phase 6/7–AO connection is modulated by the Quasi-Biennial Oscillation (QBO) through both tropospheric and stratospheric pathways during boreal winter. The MJO 2/3 phase and AO relationship is favored in both QBO easterly (QBOE) and westerly (QBOW) years because of the MJO-triggered tropospheric Rossby wave train from the tropics toward the polar region. The AO following the MJO 6/7 phase shifts to negative in QBOW years, but the MJO–AO connection diminishes in QBOE years. In QBOW years, the Asian-Pacific jet is enhanced, leading to more evident poleward propagation of tropospheric Rossby wave train, which contributes to the tropospheric pathway of the AO–MJO 6/7 connection. Besides, the enhanced Asian-Pacific jet in QBOW years is favorable for vertical propagation of planetary waves into the stratosphere in MJO phase 6/7, leading to negative AO, which indicates the stratospheric pathway of the AO–MJO 6/7 connection.

scholarly journals The Influence of the Madden–Julian Oscillation on Canadian Wintertime Surface Air Temperature

2009 ◽  
Vol 137 (7) ◽  
pp. 2250-2262 ◽  
Author(s):  
Hai Lin ◽  
Gilbert Brunet
Keyword(s):  
Air Temperature ◽  
Wave Train ◽  
Winter Season ◽  
Surface Air Temperature ◽  
Madden Julian Oscillation ◽  
Eastern Canada ◽  
Central Pacific ◽  
Sea Level Pressure ◽  
The Indian Ocean ◽  
Rossby Wave Train

Using the homogenized Canadian historical daily surface air temperature (SAT) for 210 relatively evenly distributed stations across Canada, the lagged composites and probability of the above- and below-normal SAT in Canada for different phases of the Madden–Julian oscillation (MJO) in the winter season are analyzed. Significant positive SAT anomalies and high probability of above-normal events in the central and eastern Canada are found 5–15 days following MJO phase 3, which corresponds to an enhanced precipitation over the Indian Ocean and Maritime Continent and a reduced convective activity near the tropical central Pacific. On the other hand, a positive SAT anomaly appears over a large part of northern and northeastern Canada about 5–15 days after the MJO is detected in phase 7. An analysis of the evolution of the 500-hPa geopotential height and sea level pressure anomalies indicates that the Canadian SAT anomaly is a result of a Rossby wave train associated with the tropical convection anomaly of the MJO. Hence, the MJO phase provides useful information for the extended-range forecast of Canadian winter surface air temperature. This result also provides an important reference for numerical model verifications.

scholarly journals Stratospheric Influences on the MJO-Induced Rossby Wave Train: Effects on Intraseasonal Climate

2020 ◽  
Vol 33 (1) ◽  
pp. 365-389 ◽  
Author(s):  
Lon L. Hood ◽  
Malori A. Redman ◽  
Wes L. Johnson ◽  
Thomas J. Galarneau
Keyword(s):  
Solar Cycle ◽  
Rossby Wave ◽  
Southern Oscillation ◽  
Wave Train ◽  
Winter Season ◽  
Surface Air Temperature ◽  
Quasi Biennial Oscillation ◽  
Sea Level Pressure ◽  
The North ◽  
Rossby Wave Train

AbstractThe tropical Madden–Julian oscillation (MJO) excites a northward propagating Rossby wave train that largely determines the extratropical surface weather consequences of the MJO. Previous work has demonstrated a significant influence of the tropospheric El Niño–Southern Oscillation (ENSO) on the characteristics of this wave train. Here, composite analyses of ERA-Interim sea level pressure (SLP) and surface air temperature (SAT) data during the extended northern winter season are performed to investigate the additional role of stratospheric forcings [the quasi-biennial oscillation (QBO) and the 11-yr solar cycle] in modifying the wave train and its consequences. MJO phase composites of 20–100-day filtered data for the two QBO phases show that, similar to the cool phase of ENSO, the easterly phase of the QBO (QBOE) produces a stronger wave train and associated modulation of SLP and SAT anomalies. In particular, during MJO phases 5–7, positive SLP and negative SAT anomalies in the North Atlantic/Eurasian sector are enhanced during QBOE relative to the westerly phase of the QBO (QBOW). The opposite occurs during the earliest MJO phases. SAT anomalies over eastern North America are also more strongly modulated during QBOE. Although less certain because of the short data record, there is some evidence that the minimum phase of the solar cycle (SMIN) produces a similar increased modulation of SLP and SAT anomalies. The strongest modulations of SLP and SAT anomalies are produced when two or more of the forcings are superposed (e.g., QBOE/cool ENSO, SMIN/QBOE, etc.).

scholarly journals Rossby Wave Propagation from the Arctic into the Midlatitudes: Does It Arise from In Situ Latent Heating or a Trans-Arctic Wave Train?

2020 ◽  
Vol 33 (9) ◽  
pp. 3619-3633 ◽  
Author(s):  
Tingting Gong ◽  
Steven B. Feldstein ◽  
Sukyoung Lee
Keyword(s):  
Wave Propagation ◽  
Rossby Wave ◽  
Wave Train ◽  
The Arctic ◽  
Latent Heating ◽  
Latent Heat Release ◽  
Rossby Wave Propagation ◽  
Rossby Wave Train ◽  
In Situ Generation

AbstractThe relationship between latent heating over the Greenland, Barents, and Kara Seas (GBKS hereafter) and Rossby wave propagation between the Arctic and midlatitudes is investigated using global reanalysis data. Latent heating is the focus because it is the most likely source of Rossby wave activity over the Arctic Ocean. Given that the Rossby wave time scale is on the order of several days, the analysis is carried out using a daily latent heating index that resembles the interdecadal latent heating trend during the winter season. The results from regression calculations find a trans-Arctic Rossby wave train that propagates from the subtropics, through the midlatitudes, into the Arctic, and then back into midlatitudes over a period of about 10 days. Upon entering the GBKS, this wave train transports moisture into the region, resulting in anomalous latent heat release. At high latitudes, the overlapping of a negative latent heating anomaly with an anomalous high is consistent with anomalous latent heat release fueling the Rossby wave train before it propagates back into the midlatitudes. This implies that the Rossby wave propagation from the Arctic into the midlatitudes arises from trans-Arctic wave propagation rather than from in situ generation. The method used indicates the variance of the trans-Arctic wave train, but not in situ generation, and implies that the variance of the former is greater than that of latter. Furthermore, GBKS sea ice concentration regression against the latent heating index shows the largest negative value six days afterward, indicating that sea ice loss contributes little to the latent heating.

scholarly journals Tropical Cyclogenesis Associated with Rossby Wave Energy Dispersion of a Preexisting Typhoon. Part I: Satellite Data Analyses*

2006 ◽  
Vol 63 (5) ◽  
pp. 1377-1389 ◽  
Author(s):  
Tim Li ◽  
Bing Fu
Keyword(s):  
Rossby Wave ◽  
Satellite Data ◽  
Wave Energy ◽  
Large Scale ◽  
Wave Train ◽  
Vertical Shear ◽  
Energy Dispersion ◽  
Data Analyses ◽  
Wave Trains ◽  
Rossby Wave Train

Abstract The structure and evolution characteristics of Rossby wave trains induced by tropical cyclone (TC) energy dispersion are revealed based on the Quick Scatterometer (QuikSCAT) and Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) data. Among 34 cyclogenesis cases analyzed in the western North Pacific during 2000–01 typhoon seasons, six cases are associated with the Rossby wave energy dispersion of a preexisting TC. The wave trains are oriented in a northwest–southeast direction, with alternating cyclonic and anticyclonic vorticity circulation. A typical wavelength of the wave train is about 2500 km. The TC genesis is observed in the cyclonic circulation region of the wave train, possibly through a scale contraction process. The satellite data analyses reveal that not all TCs have a Rossby wave train in their wakes. The occurrence of the Rossby wave train depends to a certain extent on the TC intensity and the background flow. Whether or not a Rossby wave train can finally lead to cyclogenesis depends on large-scale dynamic and thermodynamic conditions related to both the change of the seasonal mean state and the phase of the tropical intraseasonal oscillation. Stronger low-level convergence and cyclonic vorticity, weaker vertical shear, and greater midtropospheric moisture are among the favorable large-scale conditions. The rebuilding process of a conditional unstable stratification is important in regulating the frequency of TC genesis.

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