Waves

Jet Stream ◽  
2019 ◽  
pp. 47-60
Author(s):  
Tim Woollings
Keyword(s):  
Rossby Wave ◽  
Rossby Waves ◽  
Severe Weather ◽  
Jet Stream ◽  
Atmospheric Physics ◽  
Weather Events ◽  
Basic Understanding ◽  
North And South

The chapter opens with a description of severe weather events which occurred across Asia in the summer of 2010. These events were linked in atmospheric physics by a Rossby wave, which causes the jet stream to meander north and south. The concept of vorticity is introduced in order to give a basic understanding of Rossby waves. Some characteristics of the jet stream over Asia are also discussed, such as how it changes with the seasons.

scholarly journals Spatial variations in the warming trend and the transition to more severe weather in midlatitudes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Francisco Estrada ◽  
Dukpa Kim ◽  
Pierre Perron
Keyword(s):  
Radiative Forcing ◽  
Warming Trend ◽  
Severe Weather ◽  
Montreal Protocol ◽  
The Arctic ◽  
Extreme Weather Events ◽  
Jet Stream ◽  
Atmospheric Blocking ◽  
Regional Warming ◽  
Weather Events

AbstractDue to various feedback processes called Arctic amplification, the high-latitudes’ response to increases in radiative forcing is much larger than elsewhere in the world, with a warming more than twice the global average. Since the 1990’s, this rapid warming of the Arctic was accompanied by no-warming or cooling over midlatitudes in the Northern Hemisphere in winter (the hiatus). The decrease in the thermal contrast between Arctic and midlatitudes has been connected to extreme weather events in midlatitudes via, e.g., shifts in the jet stream towards the equator and increases in the probability of high-latitude atmospheric blocking. Here we present an observational attribution study showing the spatial structure of the response to changes in radiative forcing. The results also connect the hiatus with diminished contrast between temperatures over regions in the Arctic and midlatitudes. Recent changes in these regional warming trends are linked to international actions such as the Montreal Protocol, and illustrate how changes in radiative forcing can trigger unexpected responses from the climate system. The lesson for climate policy is that human intervention with the climate is already large enough that even if stabilization was attained, impacts from an adjusting climate are to be expected.

scholarly journals How the Speed and Latitude of the Jet Stream Affect the Downstream Response to Recurving Tropical Cyclones

2019 ◽  
Vol 147 (9) ◽  
pp. 3261-3281 ◽  
Author(s):  
Peter M. Finocchio ◽  
James D. Doyle
Keyword(s):  
Tropical Cyclones ◽  
Rossby Wave ◽  
Rossby Waves ◽  
Jet Stream ◽  
Low Latitude ◽  
Low Latitudes ◽  
Diabatic Processes ◽  
Jet Interactions ◽  
Downstream Flow ◽  
Jet Streak

Abstract Recurving tropical cyclones (TCs) that interact with the jet stream can trigger Rossby wave packets that amplify the flow far downstream, but the extent to which the jet stream modulates TC–jet interactions and the development of the downstream response remains unclear. This study uses 25 idealized simulations from the COAMPS-TC model to examine how the latitude and maximum wind speed of an initially zonal jet stream affect the downstream response to recurving TCs. During the first 5 days of the simulations, the formation of a jet streak and a ridge immediately downstream of the TC occurs earlier on low-latitude jets than on high-latitude jets. This is due to weaker TC inertial stability at low latitudes, which promotes negative potential vorticity advection by the irrotational outflow along the jet. Increasing the speed of the jet locally reduces inertial stability poleward of the TC, but does not profoundly affect the ability of the TC to perturb the jet. Beyond 5 days, the highest-latitude and fastest jets, which have the largest baroclinic growth rates, exhibit the highest-amplitude Rossby waves and the most rapidly intensifying surface cyclones farther downstream of the TCs. Both measures of the downstream response are more sensitive to changing the speed than the latitude of the jet. Deactivating condensational heating, shortly after TCs trigger a Rossby wave packet, decreases the amplitude and variability of the downstream flow by up to 3 times relative to the fully moist simulations. This result emphasizes the importance of moist diabatic processes for generating an amplified downstream response to recurving TCs within 7–10 days.

A Climatology of the Extratropical Flow Response to Recurving Atlantic Tropical Cyclones

2020 ◽  
Vol 148 (2) ◽  
pp. 541-558
Author(s):  
Allison Lynn Brannan ◽  
Jeffrey M. Chagnon
Keyword(s):  
Tropical Cyclones ◽  
Rossby Wave ◽  
Wavelet Decomposition ◽  
Rossby Waves ◽  
Extreme Weather Events ◽  
Translation Speed ◽  
Flow Modification ◽  
Flow Response ◽  
Weather Events ◽  
Isentropic Potential Vorticity

Abstract Previous case studies have noted a significant extratropical flow response to recurving Atlantic tropical cyclones (TCs), which is often linked to extreme weather events downstream. This study examines the modification of Rossby waves on the extratropical jet in response to recurving Atlantic TCs from a climatological perspective. Changes in amplitude and location of Rossby waves are identified using a wavelet decomposition technique on isentropic potential vorticity. The climatology demonstrates that recurving Atlantic TC events are capable of modifying the amplitude of the extratropical flow. Though the majority of TCs did not produce a significant, systematic modification of the extratropical flow amplitude, a subset of events were associated with a period of significant Rossby wave deamplification occurring from the time of recurvature to 48 h after recurvature, followed by a return of the Rossby wave power beginning around 96 h after recurvature. The characteristics of the TCs were not significantly associated with the resulting extratropical flow modification—a result consistent with previous western North Pacific climatologies. The nature of the extratropical flow response is most strongly tied to the average translation speed of the TC relative to the Rossby wave over the 72 h following recurvature. This study highlights the importance of investigating the extratropical flow response to recurving Atlantic TCs with regards to predictability.

Some aspects of Rossby waves and non-linear dynamics

2021 ◽  
Author(s):  
Brian Hoskins
Keyword(s):  
Rossby Wave ◽  
Rossby Waves ◽  
Tropical Convection ◽  
Jet Streams ◽  
Linear Dynamics ◽  
Middle Latitudes ◽  
Weather Events ◽  
Wave Trains ◽  
The Impact ◽  
Weather Anomalies

<p>Rossby waves are able to communicate weather anomalies in one region to other regions. There anomalous weather events can follow if the wave is persistent and large amplitude. They can also be caused by breaking of the wave leading to blocking. The impact on the middle latitudes via stationary Rossby wave trains triggered by tropical convection anomalies has been of interest for many years. However, tropical convective events can also interact with higher latitude jet streams and the weather systems on them through a very different mechanism. In this talk, some examples will be given that indicate the flaring of tropical convection can lead to strong upper tropospheric outflows in which filaments of air with near equatorial values of PV interact with higher latitude jet streams and the weather systems on them.</p>

Understanding Severe Weather Events at Airport Spatial Scale

2020 ◽  
Author(s):  
Enrico Solazzo ◽  
Pierre-Yves Tournigand ◽  
Stefano Barindelli ◽  
Valerio Guglieri ◽  
Eugenio Realini ◽  
...  
Keyword(s):  
Spatial Scale ◽  
Severe Weather ◽  
Weather Events

scholarly journals A Total Lightning Trending Algorithm to Identify Severe Thunderstorms

2010 ◽  
Vol 27 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Patrick N. Gatlin ◽  
Steven J. Goodman
Keyword(s):  
Severe Weather ◽  
Lightning Flash ◽  
Severe Thunderstorm ◽  
Critical Success ◽  
Severe Thunderstorms ◽  
Weather Events ◽  
Total Lightning ◽  
Jump Algorithm ◽  
Early Indication ◽  
Critical Success Index

Abstract An algorithm that provides an early indication of impending severe weather from observed trends in thunderstorm total lightning flash rates has been developed. The algorithm framework has been tested on 20 thunderstorms, including 1 nonsevere storm, which occurred over the course of six separate days during the spring months of 2002 and 2003. The identified surges in lightning rate (or jumps) are compared against 110 documented severe weather events produced by these thunderstorms as they moved across portions of northern Alabama and southern Tennessee. Lightning jumps precede 90% of these severe weather events, with as much as a 27-min advance notification of impending severe weather on the ground. However, 37% of lightning jumps are not followed by severe weather reports. Various configurations of the algorithm are tested, and the highest critical success index attained is 0.49. Results suggest that this lightning jump algorithm may be a useful operational diagnostic tool for severe thunderstorm potential.

The role of the Pacific Decadal Oscillation and ocean-atmosphere interactions in driving United States heatwaves

2021 ◽  
Author(s):  
Sem Vijverberg ◽  
Dim Coumou
Keyword(s):  
Rossby Wave ◽  
Rossby Waves ◽  
Low Frequency ◽  
Causal Link ◽  
Causal Mechanism ◽  
Temperature Forecast ◽  
The Pacific ◽  
Ocean Atmosphere ◽  
The Waves

<p>Heatwaves can have devastating impact on society and reliable early warnings at several weeks lead time are needed. Heatwaves are often associated with quasi-stationary Rossby waves, which interact with sea surface temperature (SST). Previous studies showed that north-Pacific SST can provide long-lead predictability for eastern U.S. temperature, moderated by an atmospheric Rossby wave. The exact mechanisms, however, are not well understood. Here we analyze Rossby waves associated with heatwaves in western and eastern US. Causal inference analyses reveal that both waves are characterized by positive ocean-atmosphere feedbacks at synoptic timescales, amplifying the waves. However, this positive feedback on short timescales is not the causal mechanism that leads to a long-lead SST signal. Only the eastern US shows a long-lead causal link from SSTs to the Rossby wave. We show that the long-lead SST signal derives from low-frequency PDO variability, providing the source of eastern US temperature predictability. We use this improved physical understanding to identify more reliable long-lead predictions. When, at the onset of summer, the Pacific is in a pronounced PDO phase, the SST signal is expected to persist throughout summer. These summers are characterized by a stronger ocean-boundary forcing, thereby more than doubling the eastern US temperature forecast skill, providing a temporary window of enhanced predictability.</p>

A novel identification and tracking method of weather-relevant 3D Potential vorticity streamers

2021 ◽  
Author(s):  
Christoph Fischer ◽  
Elmar Schömer ◽  
Andreas H. Fink ◽  
Michael Riemer ◽  
Michael Maier-Gerber
Keyword(s):  
Rossby Wave ◽  
Potential Vorticity ◽  
Wave Breaking ◽  
Extreme Weather ◽  
Individual Characteristics ◽  
Distance Functions ◽  
Extreme Weather Events ◽  
Rossby Wave Breaking ◽  
Feature Vectors ◽  
Weather Events

<p>Potential vorticity streamers (PVSs) are elongated quasi-horizontal filaments of stratospheric air in the upper troposphere related to, for example, Rossby wave breaking events. They are known to be related to partly extreme weather events in the midlatitudes and subtropics and can also be involved in (sub-)tropical cyclogenesis. While several algorithms have been developed to identify and track PVSs on planar isentropic surfaces, less is known about the evolution of these streamers in 3D, both climatologically but also for a better understanding of individual weather events. Furthermore, characteristics of their 3D shape have barely been considered as a predictor for high impact weather events like (sub-)tropical cyclones.</p><p>We introduce a novel algorithm for detection and identification of PVSs based on image processing techniques which can be applied to 2D and 3D gridded datasets. The potential vorticity was taken from high resolution isentropic analyses based on the ERA5 dataset. The algorithm uses the 2 PVU (Potential Vorticity Unit) threshold to identify and extract anomalies in the PV field using signed distance functions. This is accomplished by using a stereographic projection to eliminate singularities and keeping track of the reduced distortions by storing precomputed distance maps. This approach is computationally efficient and detects more interesting structures that exhibit the general behavior of PVSs compared to existing 2D techniques.</p><p>For each identified object a feature vector is computed, containing the individual characteristics of the streamers. In the 3D case, the algorithm looks at the structure en bloc instead of operating individually on multiple 2D levels. This also makes the identification stable regarding the seasonal cycle. Feature vectors contain parameters about quality, intensity and shape. In the case of 2D datasets, best-fitting ellipses computed from the statistical moments are regarded as a description of their shape. For 3D datasets, recent visualizations show that the boundary of these structures could be approximated by quadric surfaces . The feature vectors are also amended by tracking information, for example splitting and merging events. This low-dimensional representation serves as base for ERA5 climatologies. The data will be correlated with (sub-)tropical cyclone occurrence to spot useful and novel predictors for cyclone activity and preceding Rossby Wave Breaking events.</p><p>Overall, this new type of PVS identification algorithm, applicable in 2D or 3D, allows to diagnose the role of PVS in extreme weather events, including their predictability in ensemble forecasts.</p>

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 Contributions of equatorial planetary waves and small-scale convective gravity waves to the 2019/20 QBO disruption

2021 ◽  
Author(s):  
Min-Jee Kang ◽  
Hye-Yeong Chun
Keyword(s):  
Gravity Waves ◽  
Rossby Wave ◽  
Rossby Waves ◽  
Reanalysis Data ◽  
Small Scale ◽  
Negative Wave ◽  
Quasi Biennial Oscillation ◽  
Wave Forcing ◽  
Equatorial Wave ◽  
Convective Gravity Waves

Abstract. In January 2020, unexpected easterly winds developed in the downward-propagating westerly quasi-biennial oscillation (QBO) phase. This event corresponds to the second QBO disruption in history, and it occurred four years after the first disruption that occurred in 2015/16. According to several previous studies, strong midlatitude Rossby waves propagating from the Southern Hemisphere (SH) during the SH winter likely initiated the disruption; nevertheless, the wave forcing that finally led to the disruption has not been investigated. In this study, we examine the role of equatorial waves and small-scale convective gravity waves (CGWs) in the 2019/20 QBO disruption using MERRA-2 global reanalysis data. In June–September 2019, unusually strong Rossby wave forcing originating from the SH decelerated the westerly QBO at 0°–5° N at ~50 hPa. In October–November 2019, vertically (horizontally) propagating Rossby waves and mixed Rossby–gravity (MRG) waves began to increase (decrease). From December 2019, contribution of the MRG wave forcing to the zonal wind deceleration was the largest, followed by the Rossby wave forcing originating from the Northern Hemisphere and the equatorial troposphere. In January 2020, CGWs provided 11 % of the total negative wave forcing at ~43 hPa. Inertia–gravity (IG) waves exhibited a moderate contribution to the negative forcing throughout. Although the zonal-mean precipitation was not significantly larger than the climatology, convectively coupled equatorial wave activities were increased during the 2019/20 disruption. As in the 2015/16 QBO disruption, the increased barotropic instability at the QBO edges generated more MRG waves at 70–90 hPa, and westerly anomalies in the upper troposphere allowed more westward IG waves and CGWs to propagate to the stratosphere. Combining the 2015/16 and 2019/20 disruption cases, Rossby waves and MRG waves can be considered the key factors inducing QBO disruption.

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