Weather and Climate Dynamics最新文献

{"title":"Increased vertical resolution in the stratosphere reveals role of gravity waves after sudden stratospheric warmings","authors":"W. Wicker, I. Polichtchouk, D. Domeisen","doi":"10.5194/wcd-4-81-2023","DOIUrl":"https://doi.org/10.5194/wcd-4-81-2023","url":null,"abstract":"Abstract. Sudden stratospheric warmings (SSWs) have a long-lasting effect within the stratosphere as well as impacts on the underlying troposphere. However, sub-seasonal forecasts of the winter polar stratosphere fail to use their full potential for predictability as they tend to underestimate the magnitude and persistence of these events already within the stratosphere. The origin of this underestimation is unknown.\u0000Here, we demonstrate that the associated polar stratospheric cold bias following SSW events in sub-seasonal hindcasts can be halved by increasing vertical model resolution, suggesting a potential sensitivity to gravity wave forcing.\u0000While the predictability of the planetary Rossby wave flux into the stratosphere at lead times longer than a week is limited, the existence of a critical layer for gravity waves with a low zonal phase speed caused by the disturbed polar vortex provides predictability to the upper stratosphere. Gravity wave breaking near that critical layer can, therefore, decelerate the zonal flow consistently with anomalous subsidence over the polar cap leading to warmer temperatures in the middle polar stratosphere.\u0000Since the spectrum of gravity waves involves vertical wavelengths of less than 4000 m, as estimated by wavelet analysis, a high vertical model resolution is needed to resolve the positive feedback between gravity wave forcing and the state of the polar vortex. Specifically, we find that at a spectral resolution of TCo639 (approximate horizontal grid spacing of 18 km) at least 198 levels are needed to correctly resolve the spectrum of gravity waves in the ECMWF Integrated Forecasting System. Increasing vertical resolution in operational forecasts will help to mitigate stratospheric temperature biases and improve sub-seasonal predictions of the stratospheric polar vortex.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123786189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of Rossby waves in polar weather and climate","authors":"T. Woollings, Camille Li, M. Drouard, E. Dunn‐Sigouin, Karim A. Elmestekawy, Momme C. Hell, B. Hoskins, C. Mbengue, M. Patterson, T. Spengler","doi":"10.5194/wcd-4-61-2023","DOIUrl":"https://doi.org/10.5194/wcd-4-61-2023","url":null,"abstract":"Abstract. Recent Arctic warming has fuelled interest in the weather and climate of the polar regions and how this interacts with lower latitudes. Several interesting theories of polar-midlatitude linkages involve Rossby wave propagation as a key process even though the meridional gradient in planetary vorticity, crucial for these waves, is weak at high latitudes. Here we review some basic theory and suggest that Rossby waves can indeed explain some features of polar variability, especially when relative vorticity gradients are present. We suggest that large-scale polar flow can be conceptualised as a mix of geostrophic turbulence and Rossby wave propagation, as in the midlatitudes, but with the balance tipped further in favour of turbulent flow. Hence, isolated vortices often dominate but some wavelike features remain. As an example, quasi-stationary or weakly westward-propagating subpolar anomalies emerge from statistical analysis of observed data, and these are consistent with some role for wave propagation. The noted persistence of polar cyclones and anticyclones is attributed in part to the weakened effects of wave dispersion, the mechanism responsible for the decay of midlatitude anomalies in downstream development. We also suggest that the vortex-dominated nature of polar dynamics encourages the emergence of annular mode structures in principal component analyses of extratropical circulation. Finally, we consider how Rossby waves may be triggered from high latitudes. The linear mechanisms known to balance localised heating at lower latitudes are shown to be less efficient in the polar regions. Instead, we suggest the direct response to sea ice loss often manifests as a heat low, with radiative cooling balancing the heating. If the relative vorticity gradient is favourable this does have the potential to trigger a Rossby wave response, although this will often be weak compared to waves forced from lower latitudes.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123607254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robust poleward jet shifts in idealised baroclinic-wave life-cycle experiments with noisy initial conditions","authors":"Felix Jäger, Philip M. Rupp, T. Birner","doi":"10.5194/wcd-4-49-2023","DOIUrl":"https://doi.org/10.5194/wcd-4-49-2023","url":null,"abstract":"Abstract. Idealised baroclinic-wave life-cycle experiments are a widely used tool to study fundamental characteristics of mid-latitude baroclinic instability. A typical life cycle evolves from an initialised baroclinically unstable jet through an exponential growth phase of a particular unstable wave mode, followed by wave breaking during the mature phase and wave–mean flow interaction driving a jet shift during the decay phase. Many authors distinguish between life cycles with predominantly anticyclonic (LC1) and cyclonic (LC2) wave breaking, and the transition between the two flavours is typically controlled via the strength of cyclonic meridional wind shear in the initial conditions. While baroclinic wave growth has traditionally been triggered via a specified initial perturbation with fixed zonal wave number, this study extends the concept of baroclinic-wave life cycles by analysing the influence of random initial perturbations without any preferred zonal dependency on the life-cycle evolution. We find that the growth phase shows a robust LC1–LC2 distinction as a function of initialised meridional shear, while a preference for LC1-like characteristics is observed during the decay phase for all life cycles with non-monochromatic initial perturbations. In particular, the persistent cut-off cyclones that typically form for LC2 initialisations are found to eventually become unstable, with the onset of instability coming sooner for larger noise perturbations. All non-monochromatic life cycles result in a poleward jet shift in their final state, regardless of the strength of the initial shear. Consistently, anticyclonic wave breaking tends to be predominant during the mature and decay phases, even for LC2 initialisations. Equatorward jet shifts associated with cyclonic wave breaking still exist, although purely as a transient interim state. We show that wave–wave interactions resulting from the initialised random wave spectrum play an important role during all phases of the life cycle.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126146991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting the wintertime emergent constraint of the southern hemispheric midlatitude jet response to global warming","authors":"Philippe Breul, P. Ceppi, T. Shepherd","doi":"10.5194/wcd-4-39-2023","DOIUrl":"https://doi.org/10.5194/wcd-4-39-2023","url":null,"abstract":"Abstract. Most climate models show a poleward shift of the southern hemispheric zonal-mean jet in response to climate change, but the inter-model spread is large. In an attempt to constrain future jet responses, past studies have identified an emergent constraint between the climatological jet latitude and the future jet shift in austral winter. However, we show that the emergent constraint only arises in the zonal mean and not in separate halves of the hemisphere, which questions the physicality of the emergent constraint. We further find that the zonal-mean jet latitude does not represent the latitude of a zonally coherent structure, due to the presence of a double-jet structure in the Pacific region during this season. The zonal asymmetry causes the previously noted large spread in the zonal-mean climatology but not in the response, which underlies the emergent constraint. We therefore argue that the emergent constraint on the zonal-mean jet cannot narrow down the spread in future wind responses, and we propose that emergent constraints on the jet response in austral winter should be based on regional rather than zonal-mean circulation features.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114852096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Warm conveyor belts in present-day and future climate simulations – Part 2: Role of potential vorticity production for cyclone intensification","authors":"Hanin Binder, H. Joos, M. Sprenger, H. Wernli","doi":"10.5194/wcd-4-19-2023","DOIUrl":"https://doi.org/10.5194/wcd-4-19-2023","url":null,"abstract":"Abstract. Warm conveyor belts (WCBs) are strongly ascending, cloud- and precipitation-forming airstreams in extratropical cyclones. The intense cloud-diabatic processes produce low-level cyclonic potential vorticity (PV) along the ascending airstreams, which often contribute to the intensification of the associated cyclone. This study investigates how climate change affects the cyclones' WCB strength and the importance of WCB-related diabatic PV production for cyclone intensification, based on present-day (1990–1999) and future (2091–2100) climate simulations of the Community Earth System Model Large Ensemble (CESM-LE). In each period, a large number of cyclones and their associated WCB trajectories have been identified in both hemispheres during the winter season. WCB trajectories are identified as strongly ascending air parcels that rise at least 600 hPa in 48 h. Compared to ERA-Interim reanalyses, the present-day climate simulations are able to capture the cyclone structure and the associated WCBs reasonably well, which gives confidence in future projections with CESM-LE. However, the amplitude of the diabatically produced low-level PV anomaly in the cyclone centre is underestimated in the climate simulations, most likely because of reduced vertical resolution compared to ERA-Interim. The comparison of the simulations for the two climates reveals an increase in the WCB strength and the cyclone intensification rate in the Southern Hemisphere (SH) in the future climate. The WCB strength also increases in the Northern Hemisphere (NH) but to a smaller degree, and the cyclone intensification rate is not projected to change considerably. Hence, in the two hemispheres cyclone intensification responds differently to an increase in WCB strength. Cyclone deepening correlates positively with the intensity of the associated WCB, with a Spearman correlation coefficient of 0.68 (0.66) in the NH in the present-day (future) simulations and a coefficient of 0.51 (0.55) in the SH. The number of explosive cyclones with strong WCBs, referred to as C1 cyclones, is projected to increase in both hemispheres, while the number of explosive cyclones with weak WCBs (C3 cyclones) is projected to decrease. A composite analysis reveals that in the future climate C1 cyclones will be associated with even stronger WCBs, more WCB-related diabatic PV production, the formation of a more intense PV tower, and an increase in precipitation. They will become warmer, moister, and slightly more intense. The findings indicate that (i) latent heating associated with WCBs (as identified with our method) will increase, (ii) WCB-related PV production will be even more important for explosive cyclone intensification than in the present-day climate, and (iii) the interplay between dry and moist dynamics is crucial to understand how climate change affects cyclone intensification.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129761081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The global atmospheric energy transport analysed by a wavelength-based scale separation","authors":"P. Stoll, R. Graversen, G. Messori","doi":"10.5194/wcd-4-1-2023","DOIUrl":"https://doi.org/10.5194/wcd-4-1-2023","url":null,"abstract":"Abstract. The atmosphere transports energy polewards by circulation cells and eddies. To the present day, there has been a knowledge gap regarding the preferred spatial scales and physical mechanisms of eddy energy transport. To fill the gap, we separate the meridional atmospheric energy transport in the ERA5 reanalysis by spatial scales and into quasi-stationary and transient flow patterns and latent and dry components. Baroclinic instability is the major instability mechanism in the transient synoptic scales and is responsible for forming cyclones, anticyclones, and small-scale Rossby waves. At the planetary scales, circulation patterns are often induced by other mechanisms such as flow interaction with orography and land–sea heating contrasts. However, a separation between circulation patterns at the synoptic and planetary scales has yet to be established.\u0000We find that both baroclinically induced and transient energy transport is predominantly associated with eddies at wavelengths between 2000 and 8000 km.\u0000The maxima in both types of transport occur at wavelengths around 5000 km, in good agreement with linear baroclinic theory. Since these results are independent of latitude, we adapt the scale separation of the energy transport to be based on the wavelength instead of the previously used wavenumber. We define the synoptic transport by the wavelength band between 2000 and 8000 km. We analyse the annual and seasonal mean in the energy transport components and their inter-annual variability. The scale-separated transport components are fairly similar in both hemispheres.\u0000Transport by synoptic waves is the largest contributor to extra-tropical energy and moisture transport, mainly of a transient character, and is influenced little by seasonality. In contrast, transport by planetary waves depends highly on the season and has two distinct characteristics. (1) In the extra-tropical winter, planetary waves are important due to a large transport of dry energy. This planetary transport features the largest inter-annual variability of all components and is mainly quasi-stationary in the Northern Hemisphere but transient in its southern counterpart. (2) In the sub-tropical summer, quasi-stationary planetary waves are the most important transport component, mainly due to moisture transport, presumably associated with monsoons.\u0000In contrast to transport by planetary and synoptic waves, only a negligible amount of energy is transported by mesoscale eddies (< 2000 km).\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129652420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"European heatwaves in present and future climate simulations: a Lagrangian analysis","authors":"L. Schielicke, S. Pfahl","doi":"10.5194/wcd-3-1439-2022","DOIUrl":"https://doi.org/10.5194/wcd-3-1439-2022","url":null,"abstract":"Abstract. Heatwaves are prolonged periods of anomalously high temperatures that can have devastating impacts on the environment, society and economy. In recent history, heatwaves have become more intense and more numerous over most continental areas, and it is expected that this trend will continue due to the ongoing global temperature rise. This general intensification may be modified by changes also in the underlying thermodynamical and dynamical processes. In order to study potential changes in heatwave characteristics and dynamics, we compare Lagrangian backward trajectories of airstreams associated with historic (1991–2000) and future (2091–2100) heatwaves in six different European regions. We use a percentile-based method (Heat Wave Magnitude Index daily) to identify heatwaves in a large ensemble of climate simulations (Community Earth System Model Large Ensemble (CESM-LE) with 35 members). The simulations have been forced by historical representative concentration pathways (RCPs) up to 2005 and by the RCP8.5 scenario afterwards. In general, we find that air parcels associated with heatwaves are located to the east or inside the respective regions 3 d prior to the events. For future heatwaves, the model projects a north-/northeastward shift of the origin of the air masses in most study regions. Compared to climatological values, airstreams associated with heatwaves show a larger temperature increase along their trajectory, which is connected to stronger descent and/or stronger diabatic heating when the air parcels enter the boundary layer. We find stronger descent associated with adiabatic warming in the northern, more continental regions and increased diabatic heating in all regions (except of the British Isles) in the simulated future climate. The enhanced diabatic heating is even more pronounced for heatwaves over continental regions. Diabatic temperature changes of near-surface air are driven by sensible heat fluxes, which are stronger over dry soils. The amplified diabatic heating associated with future heatwaves may thus be explained by an additional drying of the land surface.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"68 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121014427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reanalysis representation of low-level winds in the Antarctic near-coastal region","authors":"T. Harrison, Stavroula Biri, T. Bracegirdle, J. King, Elizabeth C. Kent, É. Vignon, J. Turner","doi":"10.5194/wcd-3-1415-2022","DOIUrl":"https://doi.org/10.5194/wcd-3-1415-2022","url":null,"abstract":"Abstract. Low-level easterly winds encircling Antarctica help drive coastal currents which modify transport of circumpolar deep water to ice shelves, and the formation and distribution of sea ice. Reanalysis datasets are especially important at high southern latitudes where observations are few. Here, we investigate the representation of the mean state and short-term variability of coastal easterlies in three recent reanalyses, ERA5, MERRA-2 and JRA-55. Reanalysed winds are compared with summertime marine near-surface wind observations from the Advanced Scatterometer (ASCAT) and surface and upper air measurements from coastal stations. Reanalysis coastal easterlies correlate highly with ASCAT (r= 0.91, 0.89 and 0.85 for ERA5, MERRA-2 and JRA-55, respectively) but notable wind speed biases are found close to the coastal margins, especially near complex orography and at high wind speeds. To characterise short-term variability, 12-hourly reanalysis and coastal station winds are composited using self-organising maps (SOMs), which cluster timesteps under similar synoptic and mesoscale influences. Reanalysis performance is sensitive to the flow configuration at stations near steep coastal slopes, where they fail to capture the magnitude of near-surface wind speed variability when synoptic forcing is weak and conditions favour katabatic forcing. ERA5 exhibits the best overall performance, has more realistic orography, and a more realistic jet structure and temperature profile. These results demonstrate the regime behaviour of Antarctica's coastal winds and indicate important features of the coastal winds which are not well characterised by reanalysis datasets.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"120 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123307212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Signatures of Eurasian heat waves in global Rossby wave spectra","authors":"Iana Strigunova, R. Blender, F. Lunkeit, N. Žagar","doi":"10.5194/wcd-3-1399-2022","DOIUrl":"https://doi.org/10.5194/wcd-3-1399-2022","url":null,"abstract":"Abstract. This paper investigates systematic changes in the global atmospheric circulation statistics during Eurasian heat waves (HWs). The investigation of Rossby wave energy anomalies during HWs is based on the time series of Hough expansion coefficients representing Rossby waves with the troposphere–barotropic structures through the extended boreal summer in the European ERA5, ERA-Interim, Japanese 55-year Reanalysis (JRA-55) and Modern-Era Retrospective analysis for Research and Applications (MERRA). The climatological Rossby wave energy distribution is shown to follow a χ2 distribution with skewness dependent on the zonal scale. The applied multivariate decomposition reveals signatures of the Eurasian HWs in the probability density functions (PDFs) of the Rossby wave energy across scales. Changes in the PDFs are consistent with changes in the intramonthly variance during HWs. For the zonal-mean state (the zonal wavenumber k=0), a decrease in skewness is found, although it is not statistically significant. A reduction in skewness hints to an increase in the number of active degrees of freedom, indicating more independent modes involved in the circulation. A shift in the spectral distribution of the k=0 intramonthly variance is shown to describe a weakening of the mean westerlies near their core at 45∘ N and their strengthening at high latitudes. At planetary scales (k= 1–3), the skewness in the troposphere–barotropic Rossby wave energy significantly increases during HWs. This coincides with a reduction of intramonthly variance, in particular at k=3, and persistent large-scale circulation anomalies. Based on the χ2 skewness, we estimate a reduction of the active degrees of freedom for the planetary-scale Rossby waves of about 25 % compared to climatology. At synoptic scales (k= 4–10), no change in skewness is detected for the Eurasian HWs. However, synoptic waves k= 7–8 are characterised by a statistically significant increase in intramonthly variance of about 5 % with respect to the climatology. In addition, a shift of the entire Rossby wave energy distribution at synoptic scales, along with amplification, is observed during HWs.","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128667736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decadal variability and trends in extratropical Rossby wave packet amplitude, phase, and phase speed","authors":"G. Fragkoulidis","doi":"10.5194/wcd-3-1381-2022","DOIUrl":"https://doi.org/10.5194/wcd-3-1381-2022","url":null,"abstract":"Abstract. The ongoing global yet spatially inhomogeneous warming prompts the inspection of decadal variability in the extratropical upper-tropospheric circulation properties. This study provides observational evidence in this regard by utilizing reanalysis data to examine the past interannual-to-decadal variability and unveil trends in the probability distribution of Rossby wave packet (RWP) amplitude (E), phase (Φ), and phase speed (cp). First, a comparison between the NE Pacific and N Atlantic regions indicates that the 300 hPa E probability distribution exhibits a seasonally and regionally varying decadal variability. No apparent discrepancy arises between different reanalysis datasets, except from the JJA season where two historical reanalyses systematically underestimate E compared to three modern-era reanalyses. Further exploiting the local-in-space and local-in-time character of the employed diagnostics in ERA5 reveals that, while many areas experience pronounced RWP property variations at interannual and/or decadal timescales, patterns of statistically significant trends in the 1979–2019 period do emerge. Notably, the Northern Hemisphere E field exhibits positive trends in the N Pacific, the NE Atlantic, and S Asia in DJF, whereas negative trends are found in a substantial portion of the extratropics in JJA. In terms of cp, distinct patterns characterize MAM, with positive trends in parts of the N Atlantic and most of Europe and negative trends to the north of these regions and parts of the N Pacific. The Southern Hemisphere features a poleward shift in the band of climatologically maximum E values in DJF, widespread positive E trends in MAM, and positive cp trends in large parts of the extratropics in DJF and MAM. Assessing the decadal variability of RWP phase reveals zonally extended patterns of alternating trends in the trough–ridge occurrence ratio for MAM in the Northern Hemisphere and JJA in both hemispheres. Furthermore, no covariance is observed between area-averaged daily-mean E and cp at decadal timescales, as revealed by the bivariate probability distribution trends in the E–cp domains for the different regions and seasons. Finally, it is shown that many parts of the N Pacific and N America experience a shift to increasing occurrence of large-amplitude and/or quasi-stationary RWPs in DJF during 1999–2019, which is a manifestation of the pronounced interannual-to-decadal variability that characterizes the E and cp seasonal distributions in some areas and seasons. Overall, this study underscores that substantial seasonal and regional variations characterize the past decadal variability and trends that emerge in the seasonal probability distributions of key RWP properties.\u0000","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":"273 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114566169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}