scholarly journals How Does Indian Monsoon Regulate the Northern Hemisphere Stationary Wave Pattern?

2021 ◽  
Vol 8 ◽  
Author(s):  
Jun-Hyeok Son ◽  
Kyong-Hwan Seo ◽  
Seok-Woo Son ◽  
Dong-Hyun Cha
Keyword(s):  
Northern Hemisphere ◽  
Diabatic Heating ◽  
Wave Train ◽  
Stationary Wave ◽  
Wave Pattern ◽  
The North ◽  
Baroclinic Model ◽  
Rossby Wave Train ◽  
Vorticity Anomaly ◽  
Central North Pacific

The Northern Hemisphere summer climate isstrongly affected by a circumglobal stationary Rossby wave train, which can be manifested by the first EOF mode of the geopotential height at 200 hPa. Interannual variation of this Northern Hemisphere wave (NHW) pattern has a significant impact on remarkably warm surface temperature anomalies over the North Atlantic, Northeast Europe, East Asia to Central-North Pacific, and America, particularly in 2018 and 2010. The NHW pattern is likely generated by atmospheric diabatic heating and vorticity forcing: diabatic heating is mainly confined in the Indian summer monsoon (ISM) precipitation region, whereas the anti-cyclonic vorticity forcing is distributed in the globe. The ISM is a well-known diabatic heat source; however, the main source of vorticity forcing has not been established. In general, the tropical vorticity anomaly comes from diabatic heating-induced atmospheric waves and randomly generated inherent internal waves. The linear baroclinic model experiment reveals that the NHW pattern can be generated by the westward propagating tropical waves generated by the ISM diabatic heat forcing.

Cluster Analysis of Northern Hemisphere Wintertime 500-hPa Flow Regimes during 1920–2014*

2015 ◽  
Vol 72 (9) ◽  
pp. 3597-3608 ◽  
Author(s):  
Ming Bao ◽  
John M. Wallace
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Wave Train ◽  
Stationary Wave ◽  
Negative Polarity ◽  
Wave Pattern ◽  
Western Hemisphere ◽  
The North ◽  
The North Atlantic

Abstract Clusters in the Northern Hemisphere wintertime, 10-day low-pass-filtered 500-hPa height field are identified using the method of self-organizing maps (SOMs). Results are based on 1) a 57-winter record of ERA and 2) a 93-winter record of the NOAA Twentieth-Century Reanalysis (20CR). The clusters derived from SOMs appear to be more robust and more linearly independent than their counterparts derived from Ward’s method, and clusters with comparable numbers of member days are more distinctive in terms of the standardized Euclidean distances of their centroids from the centroid of the dataset. The reproducible SOM clusters in the hemispheric domain are 1) the negative polarity of the North Atlantic Oscillation (NAO), 2) a pattern suggestive of Alaska blocking with a downstream wave train extending over North America and the North Atlantic, 3) an enhancement of the climatological-mean stationary wave pattern in the Western Hemisphere that projects positively upon the Pacific–North America (PNA) pattern, and 4) a pattern that projects upon the negative polarity of the PNA pattern. The first three patterns have important impacts on the wintertime climate in North America and Europe. In particular, they are helpful in interpreting prevailing flow patterns during the exceptional winters of 1930–31, 2009–10, and 2013–14. Because of the very limited number of independent samples in a single winter, the number of days per winter in which the circulation resides within individual clusters varies erratically from winter to winter, rendering attribution difficult.

scholarly journals Dynamical mechanisms linking Indian monsoon precipitation and the circumglobal teleconnection

2021 ◽  
Author(s):  
Jonathan D. Beverley ◽  
Steven J. Woolnough ◽  
Laura H. Baker ◽  
Stephanie J. Johnson ◽  
Antje Weisheimer ◽  
...  
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Rossby Waves ◽  
Wave Train ◽  
Forecast Model ◽  
Seasonal Forecast ◽  
The North ◽  
Circumglobal Teleconnection ◽  
Rossby Wave Train ◽  
Ecmwf Model

AbstractThe circumglobal teleconnection (CGT) is an important mode of circulation variability, with an influence across many parts of the northern hemisphere. Here, we examine the excitation mechanisms of the CGT in the ECMWF seasonal forecast model, and the relationship between the Indian summer monsoon (ISM), the CGT and the extratropical northern hemisphere circulation. Results from relaxation experiments, in which the model is corrected to reanalysis in specific regions, suggest that errors over northwest Europe are more important in inhibiting the model skill at representing the CGT, in addition to northern hemisphere skill more widely, than west-central Asia and the ISM region, although the link between ISM precipitation and the extratropical circulation is weak in all experiments. Thermal forcing experiments in the ECMWF model, in which a heating is applied over India, suggest that the ISM does force an extratropical Rossby wave train, with upper tropospheric anticyclonic anomalies over east Asia, the North Pacific and North America associated with increased ISM heating. However, this eastward-propagating branch of the wave train does not project into Europe, and the response there occurs largely through westward-propagating Rossby waves. Results from barotropic model experiments show a response that is highly consistent with the seasonal forecast model, with similar eastward- and westward-propagating Rossby waves. This westward-propagating response is shown to be important in the downstream reinforcement of the wave train between Asia and North America.

scholarly journals Dynamical Processes Related to the Appearance of Quasi-Stationary Waves on the Subtropical Jet in the Midsummer Northern Hemisphere

2006 ◽  
Vol 19 (8) ◽  
pp. 1531-1544 ◽  
Author(s):  
Naoki Sato ◽  
Masaaki Takahashi
Keyword(s):  
Middle East ◽  
Northern Hemisphere ◽  
Wave Train ◽  
Stationary Wave ◽  
Stationary Waves ◽  
Statistical Features ◽  
Basic Field ◽  
Subtropical Jet ◽  
Anomaly Pattern ◽  
Highly Correlated

Abstract Statistical features of quasi-stationary planetary waves were examined on the subtropical jet in the midsummer Northern Hemisphere by using objectively analyzed data and satellite data. As a result, a quasi-stationary wave train that is highly correlated with the midsummer climate over Japan was identified. A clear phase dependency of the appearance of waves was also confirmed. An analysis of temporal evolution and wave activity flux revealed that the eastward propagation of the wave packet starts in the Middle East, passes over East Asia, and reaches North America. The anomaly pattern is strengthened through kinetic energy conversion near the entrance of the Asian jet over the Middle East. The interaction between the anomaly pattern and the basic field contributes to the appearance of the anomalous wavelike pattern. Although the wave train is correlated with the anomaly of convective activity over the western North Pacific and the Indian Ocean, it is implied that internal dynamics are important in determining the statistical features of the appearance of anomalous quasi-stationary waves on the subtropical jet.

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 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.).

On submarine sand-waves and tidal lee-waves

1959 ◽  
Vol 253 (1273) ◽  
pp. 218-241 ◽  
Keyword(s):  
Wave Train ◽  
Tidal Flow ◽  
Stationary Wave ◽  
Slow Phase ◽  
Density Gradients ◽  
Sand Waves ◽  
The North ◽  
Lee Waves ◽  
The North Sea ◽  
The Stability

A simplified analysis is made of the stability of long waves in a sand bed under deep, slow, and steady (or slowly varying) water flow. Allowing for vertical variation in density and shear, the linearized hydrodynamical equations yield a symmetrical flow whose only action is to impart a slow phase velocity to existing sand-waves without altering their amplitude. The only mechanism found under which sand-waves could grow under the assumed conditions is that of a stationary wave train in the lee of a permanent obstacle. The lee-waves require density gradients greater than a certain minimum, independently of any stability due to shear. Application of this model to tidal flow in the Summer thermocline over the Continental Shelf west of Brittany yields a spectrum of wave-building increments which agrees in general wavelength and shape with that of sand-waves measured on La Chapelle Bank (47° 41' N, 7° 13' W). Changes in amplitude of a few sand-grain diameters per year would be expected. Thermal stratification would be insufficient for the same mechanism to generate waves in the North Sea, but the possibility of density gradients due to suspended sediment is suggested as a likely factor of importance.

scholarly journals Predictability of Recurrent Weather Regimes over North America during Winter from Submonthly Reforecasts

2018 ◽  
Vol 146 (8) ◽  
pp. 2559-2577 ◽  
Author(s):  
N. Vigaud ◽  
A.W. Robertson ◽  
M. K. Tippett
Keyword(s):  
North America ◽  
North Atlantic ◽  
Large Scale ◽  
Wave Train ◽  
Spatial Structures ◽  
Weather Regimes ◽  
The North ◽  
Sst Variability ◽  
Cluster Partition ◽  
Rossby Wave Train

Abstract Four recurrent weather regimes are identified over North America from October to March through a k-means clustering applied to MERRA daily 500-hPa geopotential heights over the 1982–2014 period. Three regimes resemble Rossby wave train patterns with some baroclinicity, while one is related to an NAO-like meridional pressure gradient between eastern North America and western regions of the North Atlantic. All regimes are associated with distinct rainfall and surface temperature anomalies over North America. The four-cluster partition is well reproduced by ECMWF week-1 reforecasts over the 1995–2014 period in terms of spatial structures, daily regime occurrences, and seasonal regime counts. The skill in forecasting daily regime sequences and weekly regime counts is largely limited to 2 weeks. However, skill relationships with the MJO, ENSO, and SST variability in the Atlantic and Indian Oceans suggest further potential for subseasonal predictability based on wintertime large-scale weather regimes.

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>

The Role of Linear Interference in Northern Annular Mode Variability Associated with Eurasian Snow Cover Extent

2011 ◽  
Vol 24 (23) ◽  
pp. 6185-6202 ◽  
Author(s):  
Karen L. Smith ◽  
Paul J. Kushner ◽  
Judah Cohen
Keyword(s):  
Snow Cover ◽  
Rossby Wave ◽  
Wave Train ◽  
Stationary Wave ◽  
Wave Activity ◽  
Northern Annular Mode ◽  
Eurasian Snow Cover ◽  
Eurasian Snow ◽  
Rossby Wave Train ◽  
Wave Activity Flux

Abstract One of the outstanding questions regarding the observed relationship between October Eurasian snow cover anomalies and the boreal winter northern annular mode (NAM) is what causes the multiple-week lag between positive Eurasian snow cover anomalies in October and the associated peak in Rossby wave activity flux from the troposphere to the stratosphere in December. This study explores the following hypothesis about this lag: in order to achieve amplification of the wave activity, the vertically propagating Rossby wave train associated with the snow cover anomaly must reinforce the climatological stationary wave, which corresponds to constructive linear interference between the anomalous wave and the climatological wave. It is shown that the lag in peak wave activity flux arises because the Rossby wave train associated with the snow cover is in quadrature or out of phase with the climatological stationary wave from October to mid-November. Beginning in mid-November the associated wave anomaly migrates into a position that is in phase with the climatological wave, leading to constructive interference and anomalously positive upward wave activity fluxes until mid-January. Climate models from the Coupled Model Intercomparison Project 3 (CMIP3) do not capture this behavior. This linear interference effect is not only associated with stratospheric variability related to Eurasian snow cover anomalies but is a general feature of Northern Hemisphere troposphere–stratosphere interactions and, in particular, dominated the negative NAM events of the fall–winter of 2009/10.

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