Roles of wave trains and synoptic Rossby waves in creating midlatitude temperature extremes during winter

2021 ◽  
Author(s):  
Irina Rudeva ◽  
Ian Simmonds
Keyword(s):  
Wave Propagation ◽  
Rossby Wave ◽  
Large Scale ◽  
Rossby Waves ◽  
Temperature Anomaly ◽  
Local Temperature ◽  
Temperature Extremes ◽  
Relative Role ◽  
Wide Range ◽  
Wave Trains

<p>Rossby waves, found in the westerly flow at the upper troposphere, transfer energy, moisture, and momentum across large distances, being responsible for atmospheric teleconnections. Large-amplitude waves may contribute to rapid changes in wind and temperature, making them import for creating local temperature or precipitation extremes. Wirth et al (2018) separated Rossby waves into a low-frequency type, referred to as Rossby wave trains, and high-frequency, or synoptic, waves. In this work we explore a relative role of these two types in creating seasonal and synoptic temperature extremes in the midlatitudes.</p><p>We identify wave propagation regions at 300 hPa using ERA-Interim dataset for JFM 1980 – 2017. Our analysis is based on the daily data. This time scale allows identification of waveguides at a wide range of latitudes, suggesting possibility of Rossby wave propagation between midlatitudes and polar regions, as well as tropics. We show that winter temperature extremes in the midlatitudes are associated with anomalies in both high and low latitudes, while the relative importance of these areas differs across midlatitude regions. Furthermore, we demonstrate, that warm Arctic regions can create cold outbreaks in Siberia and North America.</p><p>Analysis of the evolution of midlatitude synoptic extremes reveals the importance of a pre-existing local temperature anomaly, that triggers amplification of large-scale Rossby wave trains and creates a local anomaly in the waveguide. The latter modifies propagation of synoptic scale Rossby waves that further amplify the local temperature anomaly.</p><p>References:</p><p>Wirth, V., M. Riemer, E. K. M. Chang, and O. Martius, 2018: Rossby Wave Packets on the Midlatitude Waveguide—A Review. Mon. Wea. Rev., <strong>146</strong>, 1965–2001. https://doi.org/10.1175/MWR-D-16-0483.1.</p>

Midlatitude Winter Extreme Temperature Events and Connections with Anomalies in the Arctic and Tropics

2021 ◽  
Vol 34 (10) ◽  
pp. 3733-3749 ◽  
Author(s):  
Irina Rudeva ◽  
Ian Simmonds
Keyword(s):  
Wave Propagation ◽  
North America ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Extreme Temperature ◽  
The Arctic ◽  
Temperature Extremes ◽  
Arctic Seas ◽  
Temperature Anomalies ◽  
Wave Trains

AbstractFor the last few decades the Northern Hemisphere midlatitudes have seen an increasing number of temperature extreme events. It has been suggested that some of these extremes are related to planetary wave activity. In this study we identify wave propagation regions at 300 hPa using the ERA-Interim dataset from 1980 to 2017 and link them to temperature extremes in densely populated regions of the Northern Hemisphere. Most studies have used background flow fields at monthly or seasonal scale to investigate wave propagation. For a phenomenon that is influenced by threshold incidents and nonlinear processes, this can distort the net Rossby wave signal. A novel aspect of our investigation lies in the use of daily data to study wave propagation allowing it to be diagnosed for limited but important periods across a wider range of latitudes, including the polar region. We show that winter temperature extremes in the midlatitudes can be associated with circulation anomalies in both the Arctic and the tropics, while the relative importance of these areas differs according to the specific midlatitude region. In particular, wave trains connecting the tropical Pacific and Atlantic may be associated with temperature anomalies in North America and Siberia. Arctic seas are markedly important for Eurasian regions. Analysis of synoptic temperature extremes suggests that pre-existing local temperature anomalies play a key role in the development of those extremes, as well as amplification of large-scale wave trains. We also demonstrate that warm Arctic regions can create cold outbreaks in both Siberia and North America.

scholarly journals Tropical Cyclogenesis in the Western North Pacific as Revealed by the 2008–09 YOTC Data*

2013 ◽  
Vol 28 (4) ◽  
pp. 1038-1056 ◽  
Author(s):  
Yamei Xu ◽  
Tim Li ◽  
Melinda Peng
Keyword(s):  
Rossby Wave ◽  
Wave Energy ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Lower Troposphere ◽  
Energy Dispersion ◽  
Reanalysis Dataset ◽  
Initial Development ◽  
Wave Trains

Abstract The Year of Tropical Convection (YOTC) high-resolution global reanalysis dataset was analyzed to reveal precursor synoptic-scale disturbances related to tropical cyclone (TC) genesis in the western North Pacific (WNP) during the 2008–09 typhoon seasons. A time filtering is applied to the data to isolate synoptic (3–10 day), quasi-biweekly (10–20 day), and intraseasonal (20–90 day) time-scale components. The results show that four types of precursor synoptic disturbances associated with TC genesis can be identified in the YOTC data. They are 1) Rossby wave trains associated with preexisting TC energy dispersion (TCED) (24%), 2) synoptic wave trains (SWTs) unrelated to TCED (32%), 3) easterly waves (EWs) (16%), and 4) a combination of either TCED-EW or SWT-EW (24%). The percentage of identifiable genesis events is higher than has been found in previous analyses. Most of the genesis events occurred when atmospheric quasi-biweekly and intraseasonal oscillations are in an active phase, suggesting a large-scale control of low-frequency oscillations on TC formation in the WNP. For genesis events associated with SWT and EW, maximum vorticity was confined in the lower troposphere. During the formation of Jangmi (2008), maximum Rossby wave energy dispersion appeared in the middle troposphere. This differs from other TCED cases in which energy dispersion is strongest at low level. As a result, the midlevel vortex from Rossby wave energy dispersion grew faster during the initial development stage of Jangmi.

scholarly journals On the Arrest of Inverse Energy Cascade and the Rhines Scale

2007 ◽  
Vol 64 (9) ◽  
pp. 3312-3327 ◽  
Author(s):  
Semion Sukoriansky ◽  
Nadejda Dikovskaya ◽  
Boris Galperin
Keyword(s):  
Rossby Wave ◽  
Large Scale ◽  
Rossby Waves ◽  
Characteristic Length ◽  
Unsteady Flows ◽  
Energy Propagation ◽  
Dimensional Parameter ◽  
Inverse Energy Cascade ◽  
Energy Sink ◽  
Spectral Ranges

Abstract The notion of the cascade arrest in a β-plane turbulence in the context of continuously forced flows is revised in this paper using both theoretical analysis and numerical simulations. It is demonstrated that the upscale energy propagation cannot be stopped by a β effect and can only be absorbed by friction. A fundamental dimensional parameter in flows with a β effect, the Rhines scale, LR, has traditionally been associated with the cascade arrest or with the scale that separates turbulence and Rossby wave–dominated spectral ranges. It is shown that rather than being a measure of the inverse cascade arrest, LR is a characteristic of different processes in different flow regimes. In unsteady flows, LR can be identified with the moving energy front propagating toward the decreasing wavenumbers. When large-scale energy sink is present, β-plane turbulence may attain several steady-state regimes. Two of these regimes are highlighted: friction-dominated and zonostrophic. In the former, LR does not have any particular significance, while in the latter, the Rhines scale nearly coincides with the characteristic length associated with the large-scale friction. Spectral analysis in the frequency domain demonstrates that Rossby waves coexist with turbulence on scales smaller than LR thus indicating that the Rhines scale cannot be viewed as a crossover between turbulence and Rossby wave ranges.

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.

Teleconnections from Tropics to Northern Extratropics through a Southerly Conveyor

2005 ◽  
Vol 62 (11) ◽  
pp. 4057-4070 ◽  
Author(s):  
Zhuo Wang ◽  
C-P. Chang ◽  
Bin Wang ◽  
Fei-Fei Jin
Keyword(s):  
Wave Propagation ◽  
Rossby Wave ◽  
Rossby Waves ◽  
Propagation Theory ◽  
Wave Source ◽  
Tropical Forcing ◽  
Rossby Wave Source ◽  
Rossby Wave Response ◽  
Rossby Wave Propagation ◽  
The Tropics

Abstract Rossby wave propagation theory predicts that Rossby waves in a tropical easterly flow cannot escape from the Tropics to the extratropics. Here the authors show that a southerly flow component in the basic state (a southerly conveyor) may transfer a Rossby wave source northward; thus, a forcing embedded in the deep tropical easterlies may excite a Rossby wave response in the extratropical westerlies. It is shown that the southerly conveyor determines the location of the effective Rossby wave source and that the extratropical response is relatively insensitive to the location of the tropical forcing, provided that the tropical response can reach the southerly conveyor. A stronger southerly flow favors a stronger extratropical response, and the spatial structure of the extratropical response is determined by the extratropical westerly basic flows.

Finite-amplitude deep-water waves on currents

1979 ◽  
Vol 292 (1392) ◽  
pp. 371-390 ◽  
Keyword(s):  
Wave Propagation ◽  
Deep Water ◽  
Water Waves ◽  
Large Scale ◽  
Finite Amplitude ◽  
The Other ◽  
Wave Trains ◽  
Deep Water Waves

Accurate integral properties of plane periodic deep-water waves of amplitudes up to the steepest are tabulated by Longuet-Higgins (1975). These are used to define an averaged Lagrangian which, following Whitham, is used to describe the properties of slowly varying wave trains. Two examples of waves on large-scale currents are examined in detail. One flow is that of a shearing current, V ( x ) j , which causes waves to be refracted. The other flow, U ( x ) i , varies in the direction of wave propagation and causes waves to either steepen or become more gentle. Some surprising features are found.

Signatures of midlatitude heat waves in Rossby wave variability spectra 

2021 ◽  
Author(s):  
Iana Strigunova ◽  
Richard Blender ◽  
Frank Lunkeit ◽  
Nedjeljka Žagar
Keyword(s):  
Rossby Wave ◽  
Large Scale ◽  
Rossby Waves ◽  
Heat Waves ◽  
Probability Distributions ◽  
Physical Space ◽  
Mean Flow ◽  
Single Wave ◽  
Fourier Decomposition ◽  
Latitude Belt

<p>This work aims at identifying extreme circulation conditions such as heat waves in modal space which is defined by eigensolutions of the linearized primitive equations. Here, the Rossby waves are represented in terms of Hough harmonics that are an orthogonal and complete expansion set allowing Rossby wave diagnostics in terms of their total (kinetic and available potential) energies. We expect that this diagnostic provides a more clear picture of the Rossby wave variability spectra compared to the common Fourier decomposition along a latitude belt. </p> <p>The probability distributions of Rossby wave energies are analysed separately for the zonal mean flow, for the planetary and synoptic zonal wavenumbers. The robustness is ensured by considering the four reanalyses ERA5, ERA-Interim, JRA-55 and MERRA. A single wave is characterized by Gaussianity in the complex Hough amplitudes and by a chi-square distribution for the energies. We find that the distributions of the energy anomalies in the wavenumber space are non-Gaussian with almost the same positive skewness in the four reanalyses.  The skewness increases during persistent heat waves for all energy anomaly distributions, in agreement with the recent trend of increased subseasonal variance in large-scale Rossby waves and decreased variance at synoptic scales. The new approach offers a selective filtering to physical space. The reconstructed circulation during heat waves is dominated by large-scale anticyclonic systems in northeastern Europe with zonal wavenumbers 2 and 3, in agreement with previous studies, thereby demonstrating physical meaningfulness of the skewness. </p> <p> </p>

The impact of ENSO and the Atlantic Multidecadal Variability (AMV) on the upper tropospheric large scale flow in the PRIMAVERA models.

2020 ◽  
Author(s):  
Paolo Ghinassi ◽  
Federico Fabiano ◽  
Virna L. Meccia ◽  
Susanna Corti
Keyword(s):  
Rossby Wave ◽  
Large Scale ◽  
Rossby Waves ◽  
Wave Activity ◽  
Transient Wave ◽  
Weather Regime ◽  
Weather Regimes ◽  
The Pacific ◽  
Large Scale Flow ◽  
The Impact

<p>Rossby waves play a fundamental role for both climate and weather. They are in fact associated with heat, momentum and moisture transport across large distances and with different types of weather at the surface. Assessing how they are represented in climate models is thus of primary importance to understand both predictability and the present and future climate. In this study we investigate how ENSO and the AMV affect the large scale flow pattern in the upper troposphere of the Northern Hemisphere, using reanalysis data and data from the PRIMAVERA simulations.</p><p>The upper tropospheric large scale flow is investigated in terms of the Rossby wave activity associated with persistent and recurrent patterns over the Pacific-North American and Euro-Atlantic regions during winter, the so called weather regimes. In order to quantify the vigour of Rossby wave activity associated with each weather regime we make use of a recently developed diagnostic based on Finite Amplitude Local Wave Activity in isentropic coordinates, partitioning the total wave activity into the stationary and transient components. The former is associated with quasi-stationary, planetary Rossby waves, whereas the latter is associated with synoptic scale Rossby wave packets. This allows one to quantify the contribution from stationary versus transient eddies in the total Rossby wave activity linked to each weather regime.</p><p>In this study we explore how ENSO and the AMV affect both the weather regimes frequencies and the upper tropospheric waviness in the Pacific and Atlantic storm tracks, respectively. Furthermore we analyse how both the stationary and transient wave activity component modulate the onset and transition between different regimes.</p>

scholarly journals An Adiabatic Mechanism for the Reduction of Jet Meander Amplitude by Potential Vorticity Filamentation

2018 ◽  
Vol 75 (12) ◽  
pp. 4091-4106 ◽  
Author(s):  
Ben Harvey ◽  
John Methven ◽  
Maarten H. P. Ambaum
Keyword(s):  
Decay Rate ◽  
Rossby Wave ◽  
Potential Vorticity ◽  
Large Scale ◽  
Rossby Waves ◽  
Weather Forecasting ◽  
Single Layer ◽  
Jet Streams ◽  
Rapid Reduction ◽  
Simple Method

Abstract The amplitude of ridges in large-amplitude Rossby waves has been shown to decrease systematically with lead time during the first 1–5 days of operational global numerical weather forecasts. These models also exhibit a rapid reduction in the isentropic gradient of potential vorticity (PV) at the tropopause during the first 1–2 days of forecasts. This paper identifies a mechanism linking the reduction in large-scale meander amplitude on jet streams to declining PV gradients. The mechanism proposed is that a smoother isentropic transition of PV across the tropopause leads to excessive PV filamentation on the jet flanks and a more lossy waveguide. The approach taken is to analyze Rossby wave dynamics in a single-layer quasigeostrophic model. Numerical simulations show that the amplitude of a Rossby wave propagating along a narrow but smooth PV front does indeed decay transiently with time. This process is explained in terms of the filamentation of PV from the jet core and associated absorption of wave activity by the critical layers on the jet flanks, and a simple method for quantitatively predicting the magnitude of the amplitude reduction without simulation is presented. Explicitly diffusive simulations are then used to show that the combined impact of diffusion and the adiabatic rearrangement of PV can result in a decay rate of Rossby waves that is 2–4 times as fast as could be expected from diffusion acting alone. This predicted decay rate is sufficient to explain the decay observed in operational weather forecasting models.

Planetary Wave Propagation off California and Its Effect on Zooplankton

2008 ◽  
Vol 38 (3) ◽  
pp. 702-714 ◽  
Author(s):  
Allan J. Clarke ◽  
Marcelo Dottori
Keyword(s):  
Wave Propagation ◽  
Sea Level ◽  
Rossby Wave ◽  
Nutrient Concentration ◽  
Large Scale ◽  
Time Derivative ◽  
Sea Level Anomalies ◽  
Zooplankton Population ◽  
Coastal Sea ◽  
Rossby Wave Propagation

Abstract Lagged correlation of dynamic height from the gappy California Cooperative Oceanic Fisheries Investigation (CalCOFI) with monthly San Diego sea level for the period 1949–2001 shows that the dynamic height propagates westward at 4.10 cm s−1, about double the speed of the large-scale low-frequency Rossby wave (2.2 cm s−1). Ocean Topography Experiment (TOPEX)/Poseidon/Jason-1’s along-track sea level height estimates since January 1993, filtered interannually, propagate westward at 4.3 cm s−1, verifying that observed westward propagation is about double that expected. Including the effect of the mean California Current on the Rossby wave propagation does not explain the discrepancy but rather slightly increases it. If variations in the ocean depth in the CalCOFI region are also taken into account, the westward propagation is still only about one-half that observed. Standard theory therefore does not explain the observations. Because of the westward propagation, interannual variations in alongshore geostrophic surface current are proportional to the time derivative of sea level. This means that such large-scale interannual current variability can be monitored with appropriate lag by the time derivative of coastal sea level. The anomalous alongshore flow advects particles, the anomalous alongshore particle displacement being proportional to sea level. Since nutrient concentration is lower in the south, the anomalous alongshore displacement results in a lower nutrient concentration when sea level is anomalously high and a higher nutrient concentration when the sea level is anomalously low. Vertical displacement also results in a similar relationship between nutrients and sea level, so it is not surprising that sea level anomalies are strongly related to fluctuations in zooplankton population. In fact, consistent with the westward Rossby wave propagation, the logarithm of the zooplankton population averaged over the CalCOFI region is well correlated with coastal sea level anomalies and lags it by about 2 months. By this result monthly anomalous San Diego sea level can be used to monitor and predict interannual changes in the zooplankton population.

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