scholarly journals Subseasonal Variability of Rossby Wave Breaking and Impacts on Tropical Cyclones during the North Atlantic Warm Season

2018 ◽  
Vol 31 (23) ◽  
pp. 9679-9695 ◽  
Author(s):  
Weiwei Li ◽  
Zhuo Wang ◽  
Gan Zhang ◽  
Melinda S. Peng ◽  
Stanley G. Benjamin ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Warm Season ◽  
Rossby Wave Breaking ◽  
Hit Rate ◽  
The North ◽  
Subseasonal Variability ◽  
The North Atlantic

This study investigates the subseasonal variability of anticyclonic Rossby wave breaking (AWB) and its impacts on atmospheric circulations and tropical cyclones (TCs) over the North Atlantic in the warm season from 1985 to 2013. Significant anomalies in sea level pressure, tropospheric wind, and humidity fields are found over the tropical–subtropical Atlantic within 8 days of an AWB activity peak. Such anomalies may lead to suppressed TC activity on the subseasonal time scale, but a significant negative correlation between the subseasonal variability of AWB and Atlantic basinwide TC activity does not exist every year, likely due to the modulation of TCs by other factors. It is also found that AWB occurrence may be modulated by the Madden–Julian oscillation (MJO). In particular, AWB occurrence over the tropical–subtropical west Atlantic is reduced in phases 2 and 3 and enhanced in phases 6 and 7 based on the Real-Time Multivariate MJO (RMM) index. The impacts of AWB on the predictive skill of Atlantic TCs are examined using the Global Ensemble Forecasting System (GEFS) reforecasts with a forecast lead time up to 2 weeks. The hit rate of tropical cyclogenesis during active AWB episodes is lower than the long-term-mean hit rate, and the GEFS is less skillful in capturing the variations of weekly TC activity during the years of enhanced AWB activity. The lower predictability of TCs is consistent with the lower predictability of environmental variables (such as vertical wind shear, moisture, and low-level vorticity) under the extratropical influence.

Tropical Cyclones in Reduced Rossby Wave Breaking Environments

2021 ◽  
Author(s):  
Bernhard Enz ◽  
David Neubauer ◽  
Michael Sprenger ◽  
Ulrike Lohmann
Keyword(s):  
Boundary Conditions ◽  
Tropical Cyclones ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Tropical Cyclone Activity ◽  
Cyclone Activity ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic

<p><span>Tropical cyclones are a weather phenomenon that can devastate coastlines and cause substantial harm to human life and infrastructure every year. Their seasonal prediction is an effort that has been undertaken for several decades. These predictions are generally useful and have skill. The 2013 season was predicted as above average in activity by all forecasting agencies, but was one of the least active on record. A previously proposed reason for this is the abundance of Rossby wave breaking in the north Atlantic, which dries and cools the tropics by mixing in extratropical air. While the existence of this mechanism is not disputed, other pathways linked to the interactions between tropical and extratropical air masses are suggested and evaluated in this study</span></p><p>The numerical model ICON is used in Limited Area Mode (~13 km horizontal resolution) to simulate the north Atlantic, using ERA5 data for the hurricane season of 2013 to prescribe initial and boundary conditions. To influence Rossby wave breaking, a set of simulations uses 30 day running mean boundary conditions in the northern part of the domain, while a reference set uses regular boundary conditions everywhere along the boundary. Though the results do not falsify the aforementioned hypothesis of the abundance of Rossby wave breaking influencing tropical cyclone activity, they suggest that other mechanisms, such as changes in steering flow, tropopause temperature and wind shear, could also be responsible for changes in tropical cyclone activity. Furthermore, the accumulated cyclone energy seems to be rather closely related to the mean latitude of the 2 potential vorticity unit contour on the 350 K isentropic surface within a small longitudinal window in the western Atlantic.</p>

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.

Supplementary material to "How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region"

2020 ◽  
Author(s):  
Franziska Aemisegger ◽  
Raphaela Vogel ◽  
Pascal Graf ◽  
Fabienne Dahinden ◽  
Leonie Villiger ◽  
...  
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Water Cycle ◽  
Trade Wind ◽  
Rossby Wave Breaking ◽  
Atlantic Trade ◽  
The North ◽  
Supplementary Material ◽  
The North Atlantic

scholarly journals North Atlantic Extratropical Rossby Wave Breaking during the Warm Season: Wave Life Cycle and Role of Diabatic Heating

2018 ◽  
Vol 146 (3) ◽  
pp. 695-712 ◽  
Author(s):  
Gan Zhang ◽  
Zhuo Wang
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Trajectory Analysis ◽  
Diabatic Heating ◽  
Warm Season ◽  
Rossby Wave Breaking ◽  
The North ◽  
Budget Analysis

This study investigates the life cycle of anticyclonic Rossby wave breaking during the extended warm season (July–October) over the North Atlantic basin. It was found that upper-tropospheric breaking waves are coupled with lower-level perturbations and can be traced back to a wave train that extends from the North Pacific. The overturning of potential vorticity (PV) contours during wave breaking is associated with the rapid development of an upper-level ridge, which occurs along the east coast of North America and over a warm and moist airstream. The ridge development is investigated using the PV budget analysis and trajectory analysis. The PV budget analysis suggests that the horizontal advection of PV by the perturbed flow dictates the movement and the later decay of the ridge. The ridge amplification, opposed by the horizontal advection of PV, is driven by the vertical advection and the diabatic production of PV, both of which are connected to diabatic heating. The vital role of diabatic heating in the ridge amplification is corroborated by the trajectory analysis. The analysis suggests that diabatic heating reduces the static stability near the tropopause and contributes to the ridge-related negative PV anomalies. The role of diabatic heating in anticyclonic and cyclonic wave breaking in other regions is also discussed. The findings suggest that moist diabatic processes, which were often excluded from the earlier studies of wave breaking, are crucial for Rossby wave breaking during the warm season. The updated understanding of wave breaking may benefit weather forecasting and climate predictions.

North Atlantic Summertime Anticyclonic Rossby Wave Breaking: Climatology, Impacts, and Connections to the Pacific Decadal Oscillation

2018 ◽  
Vol 32 (2) ◽  
pp. 485-500 ◽  
Author(s):  
Breanna L. Zavadoff ◽  
Ben P. Kirtman
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Pacific Decadal Oscillation ◽  
Wave Breaking ◽  
Reanalysis Data ◽  
Tropical Cyclogenesis ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Anticyclonic Rossby wave breaking (RWB) is characterized by the rapid and irreversible deformation of potential vorticity (PV) contours on isentropic surfaces manifesting as a pair of meridionally elongated high- and low-PV tongues that transport extratropical stratospheric air equatorward and tropical tropospheric air poleward, respectively. Previous studies have noted connections between different types of RWB and the modulation of localized atmospheric phenomena such as the North Atlantic Oscillation (NAO) and tropical cyclogenesis. Despite being the season in which anticyclonic RWB events are most prevalent, no work has focused solely on the frequency, genesis, or variability of the synoptic environment surrounding the equatorward branch of anticyclonic RWB events during the North Atlantic summertime, providing motivation for this study. Using 58 years (1960–2017) of NCEP–NCAR reanalysis data, a comprehensive spatiotemporal climatology of North Atlantic equatorward anticyclonic RWB identified on the 350-K isentropic surface is developed and the synoptic environment surrounding these events from time- and high-PV-tongue centroid-relative perspectives is investigated. Consistent with previous studies, composites suggest that high-PV tongues associated with equatorward anticyclonic RWB introduce anomalously dry, stable extratropical air into the tropical environment, subsequently inhibiting convection there. Additionally, a connection between atmospheric responses to Pacific decadal oscillation (PDO) sea surface temperature (SST) anomalies and the intrabasin frequency of anticyclonic RWB events is uncovered and explored. Results from this study may aid short- to medium-range forecasts of North Atlantic tropical convection, with applications extending into the field of tropical cyclogenesis forecasting.

scholarly journals Links between Rossby Wave Breaking and the North Atlantic Oscillation–Arctic Oscillation in Present-Day and Last Glacial Maximum Climate Simulations

2010 ◽  
Vol 23 (11) ◽  
pp. 2987-3008 ◽  
Author(s):  
Gwendal Rivière ◽  
Alexandre Laîné ◽  
Guillaume Lapeyre ◽  
David Salas-Mélia ◽  
Masa Kageyama
Keyword(s):  
North Atlantic Oscillation ◽  
Last Glacial Maximum ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Arctic Oscillation ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Upper-tropospheric Rossby wave–breaking processes are examined in coupled ocean–atmosphere simulations of the Last Glacial Maximum (LGM) and of the modern era. LGM statistics of the Northern Hemisphere in winter, computed from the Paleoclimate Modeling Intercomparison Project Phase II (PMIP2) dataset, are compared with those from preindustrial simulations and from the 40-yr ECMWF Re-Analysis (ERA-40). Particular attention is given to the role of wave-breaking events in the North Atlantic Oscillation (NAO) for each simulation. Anticyclonic (AWB) and cyclonic (CWB) wave-breaking events during LGM are shown to be less and more frequent, respectively, than in the preindustrial climate, especially in the Pacific. This is consistent with the slight equatorward shift of the eddy-driven jets in the LGM runs. The most remarkable feature of the simulated LGM climate is that it presents much weaker latitudinal fluctuations of the eddy-driven jets. This is accompanied by less dispersion in the wave-breaking events. A physical interpretation is provided in terms of the fluctuations of the low-level baroclinicity at the entrance of the storm tracks. The NAO in the preindustrial simulations and in ERA-40 is characterized by strong latitudinal fluctuations of the Atlantic eddy-driven jet as well as by significant changes in the nature of the wave breaking. During the positive phase, the eddy-driven jet moves to the north with more AWB events than usual and is well separated from the subtropical African jet. The negative phase exhibits a more equatorward Atlantic jet and more CWB events. In contrast, the LGM NAO is less well marked by the latitudinal vacillation of the Atlantic jet and for some models this property disappears entirely. The LGM NAO corresponds more to acceleration–deceleration or extension–retraction of the Atlantic jet. The hemispheric point of view of the Arctic Oscillation exhibits similar changes.

scholarly journals On double Rossby wave breaking in the North Atlantic

2015 ◽  
Vol 120 (21) ◽  
pp. 11,129-11,150 ◽  
Author(s):  
Gabriele Messori ◽  
Rodrigo Caballero
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic

scholarly journals A New Rossby Wave–Breaking Interpretation of the North Atlantic Oscillation

2008 ◽  
Vol 65 (2) ◽  
pp. 609-626 ◽  
Author(s):  
Tim Woollings ◽  
Brian Hoskins ◽  
Mike Blackburn ◽  
Paul Berrisford
Keyword(s):  
North Atlantic Oscillation ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Low Frequency ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
Hemisphere Winter ◽  
The North Atlantic Oscillation

Abstract This paper proposes the hypothesis that the low-frequency variability of the North Atlantic Oscillation (NAO) arises as a result of variations in the occurrence of upper-level Rossby wave–breaking events over the North Atlantic. These events lead to synoptic situations similar to midlatitude blocking that are referred to as high-latitude blocking episodes. A positive NAO is envisaged as being a description of periods in which these episodes are infrequent and can be considered as a basic, unblocked situation. A negative NAO is a description of periods in which episodes occur frequently. A similar, but weaker, relationship exists between wave breaking over the Pacific and the west Pacific pattern. Evidence is given to support this hypothesis by using a two-dimensional potential-vorticity-based index to identify wave breaking at various latitudes. This is applied to Northern Hemisphere winter data from the 40-yr ECMWF Re-Analysis (ERA-40), and the events identified are then related to the NAO. Certain dynamical precursors are identified that appear to increase the likelihood of wave breaking. These suggest mechanisms by which variability in the tropical Pacific, and in the stratosphere, could affect the NAO.

scholarly journals A Feature-Based Approach to Classifying Summertime Potential Vorticity Streamers Linked to Rossby Wave Breaking in the North Atlantic Basin

2020 ◽  
Vol 33 (14) ◽  
pp. 5953-5969 ◽  
Author(s):  
Philippe P. Papin ◽  
Lance F. Bosart ◽  
Ryan D. Torn
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Potential Vorticity ◽  
Wave Breaking ◽  
Activity Index ◽  
Static Stability ◽  
Japan Meteorological Agency ◽  
Average Intensity ◽  
Rossby Wave Breaking ◽  
The North

AbstractThis study examines climatological potential vorticity streamer (PVS) activity associated with Rossby wave breaking (RWB), which can impact TC activity in the subtropical North Atlantic (NATL) basin via moisture and wind anomalies. PVSs are identified along the 2-PVU (1 PVU = 10−6 K kg−1 m2 s−1) contour on the 350-K isentropic surface, using a unique identification technique that combines previous methods. In total, 21 149 individual PVS instances are identified from the ERA-Interim (ERAI) climatology during June–November over 1979–2015 with a peak in July–August. The total number of PVSs identified in this study is more than previous PVS climatologies for this region, since the new technique identifies a wider range of cases. Variations in PVS size and intensity prompt the development of a new PVS activity index (PVSI), which provides an integrated measure of PVS activity that can improve comparisons with TC activity. For instance, PVSI has a stronger negative correlation with seasonal TC activity (r = −0.55) relative to PVS frequency, size, or intensity alone. PVSI in June–July is also positively correlated with PVSI in August–November (r = 0.67), suggesting predictive capability. Compared to the ERAI and Japan Meteorological Agency 55-Year Reanalysis (JRA-55) climatology, there are more PVSs in the Climate Forecast System Reanalysis (CFSR) but these have weaker average intensity overall. While no long-term trend in PVSI is observed in the ERAI or JRA-55 climatologies, a negative trend is observed in CFSR, which could be related to differences in near tropopause static stability early in the climatological period (1979–86) between the CFSR and ERAI datasets.

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