scholarly journals Precursory atmospheric circulations with Rossby wave trains leading to Eurasian extreme cold events

2021 ◽  
Author(s):  
Wenqin zhuo ◽  
Fei Huang ◽  
Ruichang Ding ◽  
Jin Luo
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Train ◽  
Teleconnection Pattern ◽  
Boreal Winter ◽  
Formation Mechanisms ◽  
Baffin Bay ◽  
Atmospheric Circulations ◽  
Westerly Jet ◽  
Wave Trains

Abstract This work examines precursory atmospheric circulations with various wave trains contributing to extreme cooling over central Eurasia in boreal winter from 1979-2016 based on the ERA-Interim dataset. The empirical orthogonal function (EOF) method is used to classify the anomalous sea level pressure field averaged in two weeks prior to extreme cooling. Based on the classification, three types of precursory atmospheric circulation patterns are named according to the origins of wave trains, and their formation mechanisms are revealed as well . Type1: Baffin Bay-origin pattern, which forms in the downstream development of Rossby wave packets generated from the downward stratospheric energy transmission over the Baffin Bay. Type2: Pacific-origin pattern, similar to a Eurasian (EU) teleconnection pattern, arises at the exit area of the westerly jet in the central North Pacific where cyclonic shear exists; then it develops along the northerly westerly jet over the North Atlantic, which may act as a waveguide to the Eurasian continent. Type 3: Atlantic-origin, manifests as the negative phase of type 2, consistent with the Scandinavian (SCAND) pattern, which may results from the air-sea interaction induced by the warm anomaly of sea surface temperature in the middle of North Atlantic. In conclusion, the three types of precursory atmospheric wave train patterns that bring extreme cooling to Eurasia possess diverse disturbing sources and development mechanisms. The results, which are investigated based on a quasi-biweekly time scale , deepen our understanding of the atmospheric genesis of extreme weather and have specific indicative significance to improve the technique of extended forecast.

The Linkage between the Eastern Pacific Teleconnection Pattern and Convective Heating over the Tropical Western Pacific

2015 ◽  
Vol 28 (14) ◽  
pp. 5783-5794 ◽  
Author(s):  
Benkui Tan ◽  
Jiacan Yuan ◽  
Ying Dai ◽  
Steven B. Feldstein ◽  
Sukyoung Lee
Keyword(s):  
Rossby Wave ◽  
Southern China ◽  
Wave Train ◽  
Gulf Of Alaska ◽  
Teleconnection Pattern ◽  
Eastern Pacific ◽  
Late Winter ◽  
Convective Heating ◽  
Central Pacific ◽  
Wave Trains

Abstract The eastern Pacific (EP) pattern is a recently detected atmospheric teleconnection pattern that frequently occurs during late winter. Through analysis of daily ERA-Interim data and outgoing longwave radiation data for the period of 1979–2011, it is shown here that the formation of the EP is preceded by an anomalous tropical convection dipole, with one extremum located over the eastern Indian Ocean–Maritime Continent and the other over the central Pacific. This is followed by the excitation of two quasi-stationary Rossby wave trains. Departing from the subtropics, north of the region of anomalous convection, one Rossby wave train propagates eastward along the East Asian jet from southern China toward the eastern Pacific. The second wave train propagates northward from east of Japan toward eastern Siberia and then turns southeastward to the Gulf of Alaska. Both wave trains are associated with wave activity flux convergence where the EP pattern develops. The results from an examination of the E vector suggest that the EP undergoes further growth with the aid of positive feedback from high-frequency transient eddies. The frequency of occurrence of the dipole convection anomaly increases significantly from early to late winter, a finding that suggests that it is the seasonal change in the convection anomaly that accounts for the EP being more dominant in late winter.

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.

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.

Quasi-Biweekly Oscillation over the tropical western Pacific in boreal winter： Its climate influences on North America

2020 ◽  
Author(s):  
Zizhen Dong ◽  
Lin Wang
Keyword(s):  
North America ◽  
Energy Conversion ◽  
Rossby Wave ◽  
Time Scale ◽  
Wave Train ◽  
Western Pacific ◽  
Boreal Winter ◽  
The South ◽  
Tropical Western Pacific ◽  
South Of Japan

<p><span lang="EN-US">The Quasi-Biweekly Oscillation (QBWO) mode with 10-20-day time scale over the tropical western Pacific (TWP) in boreal winter (December-February), characterized by westward-northwestward propagation from the dateline to the east coast of Philippines (EPH) identified by the first two EEOF modes, is investigated based on the daily mean OLR and ERA-Interim reanalysis datasets from 1979 to 2015. The suppressive (active) QBWO-related convection heating located near EPH at peak day (day 0), results in anomalous divergence (convergence) wind to the south of Japan at upper troposphere due to the heat release. The divergent circulations can advect climatological absolute vorticity, then leads to positive (negative) Rossby wave source, which could propagate eastward. Therefore, a Rossby wave train (RWT) with equivalent barotropical structure over Pacific originated from the south of Japan is observed one/two days later. This wave train propagates northeastward into Alaska and then southeastward into southern North America. The meridional wind associated with the cyclonic/anticyclonic anomalies of RWT advects climatological thermal condition dominating the local temperature tendency over North America. Thus, a significant warming (cooling) over central North America is found at day +4 consistent to the anomalous southerlies (northerlies). In addition, both the barotropical energy conversion (CK) and baroclinic energy conversion (CP) contribute to the RWT on a time scale of 10-20 days maintained against dissipation.</span></p>

scholarly journals Exploring the Tropically Excited Arctic Warming Mechanism with Station Data: Links between Tropical Convection and Arctic Downward Infrared Radiation

2016 ◽  
Vol 73 (3) ◽  
pp. 1143-1158 ◽  
Author(s):  
Matthew D. Flournoy ◽  
Steven B. Feldstein ◽  
Sukyoung Lee ◽  
Eugene E. Clothiaux
Keyword(s):  
Water Vapor ◽  
Rossby Wave ◽  
Infrared Radiation ◽  
Wave Train ◽  
Tropical Convection ◽  
The Arctic ◽  
Water Vapor Flux ◽  
Arctic Warming ◽  
Vapor Flux ◽  
Wave Trains

Abstract The Tropically Excited Arctic Warming (TEAM) mechanism ascribes warming of the Arctic surface to tropical convection, which excites poleward-propagating Rossby wave trains that transport water vapor and heat into the Arctic. A crucial component of the TEAM mechanism is the increase in downward infrared radiation (IR) that precedes the Arctic warming. Previous studies have examined the downward IR associated with the TEAM mechanism using reanalysis data. To corroborate previous findings, this study examines the linkage between tropical convection, Rossby wave trains, and downward IR with Baseline Surface Radiation Network (BSRN) downward IR station data. The physical processes that drive changes in the downward IR are also investigated by regressing 300-hPa geopotential height, outgoing longwave radiation, water vapor flux, ERA-Interim downward IR, and other key variables against the BSRN downward IR at Barrow, Alaska, and Ny-Ålesund, Spitsbergen. Both the Barrow and the Ny-Ålesund station downward IR anomalies are preceded by anomalous tropical convection and poleward-propagating Rossby wave trains. The wave train associated with Barrow resembles the Pacific–North America teleconnection pattern, and that for Ny-Ålesund corresponds to a northwestern Atlantic wave train. It is found that both wave trains promote warm and moist advection from the midlatitudes into the Arctic. The resulting water vapor flux convergence, multiplied by the latent heat of vaporization, closely resembles the regressed ERA-Interim downward IR. These results suggest that the combination of warm advection, latent heat release, and increased cloudiness all contribute toward an increase in downward IR.

scholarly journals Dynamical Evolution of North Atlantic Ridges and Poleward Jet Stream Displacements

2011 ◽  
Vol 68 (5) ◽  
pp. 954-963 ◽  
Author(s):  
Tim Woollings ◽  
Joaquim G. Pinto ◽  
João A. Santos
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Large Scale ◽  
Wave Train ◽  
Jet Stream ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
Circulation Anomalies

Abstract The development of a particular wintertime atmospheric circulation regime over the North Atlantic, comprising a northward shift of the North Atlantic eddy-driven jet stream and an associated strong and persistent ridge in the subtropics, is investigated. Several different methods of analysis are combined to describe the temporal evolution of the events and relate it to shifts in the phase of the North Atlantic Oscillation and East Atlantic pattern. First, the authors identify a close relationship between northward shifts of the eddy-driven jet, the establishment and maintenance of strong and persistent ridges in the subtropics, and the occurrence of upper-tropospheric anticyclonic Rossby wave breaking over Iberia. Clear tropospheric precursors are evident prior to the development of the regime, suggesting a preconditioning of the Atlantic jet stream and an upstream influence via a large-scale Rossby wave train from the North Pacific. Transient (2–6 days) eddy forcing plays a dual role, contributing to both the initiation and then the maintenance of the circulation anomalies. During the regime there is enhanced occurrence of anticyclonic Rossby wave breaking, which may be described as low-latitude blocking-like events over the southeastern North Atlantic. A strong ridge is already established at the time of wave-breaking onset, suggesting that the role of wave-breaking events is to amplify the circulation anomalies rather than to initiate them. Wave breaking also seems to enhance the persistence, since it is unlikely that a persistent ridge event occurs without being also accompanied by wave breaking.

scholarly journals Southern Hemisphere Sensitivity to ENSO Patterns and Intensities: Impacts over Subtropical South America

Atmosphere ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 77 ◽  
Author(s):  
Verónica Martín-Gómez ◽  
Marcelo Barreiro ◽  
Elsa Mohino
Keyword(s):  
South America ◽  
Rossby Wave ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Wave Train ◽  
Circulation Model ◽  
South Pacific ◽  
El Niño Modoki ◽  
Wave Trains

El Niño flavors influence Subtropical South American (SSA) rainfall through the generation of one or two quasi-stationary Rossby waves. However, it is not yet clear whether the induced wave trains depend on the El Niño pattern and/or its intensity. To investigate this, we performed different sensitivity experiments using an Atmospheric General Circulation Model (AGCM) which was forced considering separately the Canonical and the El Niño Modoki patterns with sea surface temperature (SST) maximum anomalies of 1 and 3 °C. Experiments with 3 °C show that the Canonical El Niño induces two Rossby wave trains, a large one emanating from the western subtropical Pacific and a shorter one initiated over the central-eastern subtropical South Pacific. Only the shorter wave plays a role in generating negative outgoing longwave radiation (OLR) anomalies over SSA. On the other hand, 3 °C El Niño Modoki experiments show the generation of a large Rossby wave train that emanates from the subtropical western south Pacific and reaches South America (SA), promoting the development of negative OLR anomalies over SSA. Experiments with 1 °C show no impacts on OLR anomalies over SSA associated with El Niño Modoki. However, for the Canonical El Niño case there is a statistically significant reduction of the OLR anomalies over SSA related to the intensification of the upper level jet stream over the region. Finally, our model results suggest that SSA is more sensitive to the Canonical El Niño, although this result may be model dependent.

scholarly journals Longitude-dependent decadal ozone changes and ozone trends in boreal winter months during 1960–2000

2008 ◽  
Vol 26 (5) ◽  
pp. 1275-1286 ◽  
Author(s):  
D. H. W. Peters ◽  
A. Gabriel ◽  
G. Entzian
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Total Ozone ◽  
Planetary Wave ◽  
Wave Structure ◽  
Boreal Winter ◽  
The North ◽  
The North Atlantic ◽  
Eastern North Atlantic ◽  
The 1960S

Abstract. This study examines the longitude-dependent decadal changes and trends of ozone for the boreal winter months during the period of 1960–2000. These changes are caused primarily by changes in the planetary wave structure in the upper troposphere and lower stratosphere. The decadal changes and trends over 4 decades of geopotential perturbations, defined as a deviation from the zonal mean, are estimated by linear regression with time. The decadal changes in longitude-dependent ozone were calculated with a simple transport model of ozone based on the known planetary wave structure changes and prescribed zonal mean ozone gradients. For December of the 1960s and 1980s a statistically significant Rossby wave track appeared over the North Atlantic and Europe with an anticyclonic disturbance over the Eastern North Atlantic and Western Europe, flanked by cyclonic disturbances. In the 1970s and 1990s statistically significant cyclonic disturbances appeared over the Eastern North Atlantic and Europe, surrounded by anticyclonic anomalies over Northern Africa, Central Asia and Greenland. Similar patterns have been found for January. The Rossby wave track over the North Atlantic and Europe is stronger in the 1980s than in the 1960s. For February, the variability of the regression patterns is higher. For January we found a strong alteration in the modelled decadal changes in total ozone over Central and Northern Europe, showing a decrease of about 15 DU in the 1960s and 1980s and an increase of about 10 DU in the 1970s and 1990s. Over Central Europe the positive geopotential height trend (increase of 2.3 m/yr) over 40 years is of the same order (about 100 m) as the increase in the 1980s alone. This is important to recognize because it implies a total ozone decrease over Europe of the order of 14 DU for the 1960–2000 period, for January, if we use the standard change regression relation that about a 10-m geopotential height increase at 300 hPa is related to about a 1.4-DU total ozone decrease.

The AMV phase-dependence of the connection between February NAO and March surface air temperature over the Tibetan Plateau

2021 ◽  
Author(s):  
Jingyi Li ◽  
Fei Li ◽  
Shengping He ◽  
Huijun Wang ◽  
Yvan J Orsolini
Keyword(s):  
Tibetan Plateau ◽  
Air Temperature ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Train ◽  
Surface Air Temperature ◽  
The Tibetan Plateau ◽  
The North ◽  
Rossby Wave Train ◽  
The North Atlantic

<p>The Tibetan Plateau (TP), referred to as the “Asian water tower”, contains one of the largest land ice masses on Earth. The local glacier shrinkage and frozen-water storage are strongly affected by variations in surface air temperature over the TP (TPSAT), especially in springtime. This study reveals a distinct out-of-phase connection between the February North Atlantic Oscillation (NAO) and March TPSAT, which is non-stationary and regulated by the warm phase of the Atlantic Multidecadal Variability (AMV+). The results show that during the AMV+, the negative phase of the NAO persists from February to March, and is accompanied by a quasi-stationary Rossby wave train trapped along a northward-shifted subtropical westerly jet stream across Eurasia, inducing an anomalous adiabatic descent that warms the TP. However, during the cold phase of the AMV, the negative NAO does not persist into March. The Rossby wave train propagates along the well-separated polar and subtropical westerly jets, and the NAO−TPSAT connection is broken. Further investigation suggests that the enhanced synoptic eddy and low-frequency flow (SELF) interaction over the North Atlantic in February and March during the AMV+, caused by the enhanced and southward-shifted storm track, help maintain the NAO anomaly pattern via positive eddy feedback. This study provides a new detailed perspective on the decadal variability of the North Atlantic−TP connections in late winter−early spring.</p>

Multidecadal variations in the East Asian winter monsoon and their relationship with the Atlantic Multidecadal Oscillation since 1850

2021 ◽  
pp. 1-39
Author(s):  
Jiapeng Miao ◽  
Dabang Jiang
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Train ◽  
East Asian ◽  
Northeast Asia ◽  
Atlantic Multidecadal Oscillation ◽  
Phase Shifting ◽  
Positive Phase ◽  
Eurasian Continent ◽  
Rossby Wave Train

AbstractThis study investigates the characteristics and physical mechanisms of the multidecadal variations in the East Asian winter (December–January–February) monsoon (EAWM) since 1850 based on multiple observational and reanalysis datasets. The results indicate that the EAWM undergoes multidecadal weakening during the periods of 1869–1919 and 1986–2004 but strengthening during the period of 1920–1985. Similar evolutions can be observed in the time series of the area-averaged winter surface air temperature over East Asia. Associated with the EAWM multidecadal variations, a quasi-barotropic Rossby wave train originating from the subtropical North Atlantic propagating across the Eurasian continent to Northeast Asia also experiences phase shifting at the same time. In its positive phase, the low-level anticyclonic anomaly over the northern Eurasian continent causes a stronger Siberian high; the mid- and high-level cyclonic anomalies over Northeast Asia deepen the East Asian trough and strengthen the East Asian jet stream, respectively. Thus, the positive phase of the wave train is conducive to stronger EAWMs and vice versa. The diagnostic analysis of the Rossby wave source indicates that the upper-tropospheric divergence anomalies over the North Atlantic can favor the excitation of this wave train, and the feedback forcing of high-frequency eddies plays important roles in its maintenance. In addition, the phase shifting of the Atlantic Multidecadal Oscillation (AMO) can induce a similar Rossby wave train across the Eurasian continent, through which it further modulates the multidecadal variations in the EAWM. Warm phases of the AMO are favorable for a stronger EAWM and colder mid-latitude Eurasian continent and vice versa.

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