scholarly journals Interaction between antecedent planetary-scale envelope soliton blocking anticyclone and synoptic-scale eddies: Observations and theory

2001 ◽  
Vol 106 (D23) ◽  
pp. 31795-31815 ◽  
Author(s):  
Dehai Luo ◽  
Fei Huang ◽  
Yina Diao
Keyword(s):  
Synoptic Scale ◽  
Envelope Soliton ◽  
Planetary Scale ◽  
Blocking Anticyclone

scholarly journals A Barotropic Envelope Rossby Soliton Model for Block–Eddy Interaction. Part II: Role of Westward-Traveling Planetary Waves

2005 ◽  
Vol 62 (1) ◽  
pp. 22-40 ◽  
Author(s):  
Dehai Luo
Keyword(s):  
Surf Zone ◽  
Planetary Waves ◽  
Storm Tracks ◽  
Synoptic Scale ◽  
Zone Structure ◽  
Planetary Scale ◽  
Blocking Anticyclone ◽  
Zonal Wavenumber ◽  
Dipole Soliton

Abstract The role of westward-traveling planetary waves in the block onset and the deformation of eddies during the interaction between synoptic-scale eddies and an incipient block is first examined by constructing an incipient block that consists of a stationary dipole wave for zonal wavenumber 2 and a westward-traveling monopole wave with constant amplitude (C wave) for zonal wavenumber 1 or 2. It is shown that the C-wave can affect the onset and strength of blocking through influencing the preblock (diffluent) flow even though it does not affect the amplification of the dipole wave associated with the synoptic-scale eddies. Whether the storm tracks organized by the deformed eddies deflect northward depends upon the zonal wavenumber, amplitude, and phase of the C wave relative to the stationary dipole wave. A typical retrograde blocking anticyclone can arise through the interaction of an incipient block with synoptic-scale perturbations when the C-wave ridge with zonal wavenumber 1 shifts westward from the east of the dipole wave in an incipient block. In this process, a slight northward deflection of organized storm tracks is also observed, particularly under the condition of a large-amplitude C wave. In addition, the interaction between a diffluent flow, consisting of a coupled dipole and monopole waves, and upstream synoptic-scale eddies is investigated. It is found that the eddy forcing tends to not only periodically amplify the dipole soliton and to retard its eastward movement, but to make the monopole wave break up. The breaking of the traveling monopole wave will suppress the eddy-induced blocking ridge that exhibits a surf zone structure where the negative meridional gradient of planetary-scale potential vorticity exists and cause the planetary-scale blocking field to lose its closed circulation compared to that without coupling.

scholarly journals Dynamics of Eddy-Driven Low-Frequency Dipole Modes. Part I: A Simple Model of North Atlantic Oscillations

2007 ◽  
Vol 64 (1) ◽  
pp. 3-28 ◽  
Author(s):  
Dehai Luo ◽  
Anthony R. Lupo ◽  
Han Wan
Keyword(s):  
Life Cycle ◽  
Theoretical Model ◽  
North Atlantic ◽  
Low Frequency ◽  
Positive Phase ◽  
Negative Phase ◽  
Synoptic Scale ◽  
Planetary Scale ◽  
The North ◽  
The North Atlantic Oscillation

Abstract A simple theoretical model is proposed to clarify how synoptic-scale waves drive the life cycle of the North Atlantic Oscillation (NAO) with a period of nearly two weeks. This model is able to elucidate what determines the phase of the NAO and an analytical solution is presented to indicate a high similarity between the dynamical processes of the NAO and zonal index, which is not derived analytically in previous theoretical studies. It is suggested theoretically that the NAO is indeed a nonlinear initial-value problem, which is forced by both preexisting planetary-scale and synoptic-scale waves. The eddy forcing arising from the preexisting synoptic-scale waves is shown to be crucial for the growth and decay of the NAO, but the preexisting low-over-high (high-over-low) dipole planetary-scale wave must be required to match the preexisting positive-over-negative (negative-over-positive) dipole eddy forcing so as to excite a positive (negative) phase NAO event. The positive and negative feedbacks of the preexisting dipole eddy forcing depending upon the background westerly wind seem to dominate the life cycle of the NAO and its life period. An important finding in the theoretical model is that negative-phase NAO events could be excited repeatedly after the first event has decayed, but for the positive phase downstream isolated dipole blocks could be produced after the first event has decayed. This is supported by observed cases of the NAO events presented in this paper. In addition, a statistical study of the relationship between the phase of the NAO and blocking activity over Europe in terms of the seasonal mean NAO index shows that blocking events over Europe are more frequent and long-lived for strong positive-phase NAO years, indicating that the positive-phase NAO favors the occurrence of European blocking events.

Arctic climate response to extreme events in synoptic and planetary scale atmospheric energy transport

2020 ◽  
Author(s):  
Johanne H. Rydsaa ◽  
Rune G. Graversen ◽  
Patrick Stoll
Keyword(s):  
Energy Transport ◽  
Winter Season ◽  
Arctic Climate ◽  
The Arctic ◽  
Synoptic Scale ◽  
Near Surface ◽  
Latent Energy ◽  
Atmospheric Energy ◽  
Planetary Scale ◽  
Atmospheric Energy Transport

<p>Atmospheric energy transport into the Arctic (>70° N) has been shown to greatly alter the Arctic temperatures and the development of the Arctic weather and climate. Recent research suggests that latent energy transport into the Arctic by large, planetary-scale atmospheric systems cause a stronger and more long-lasting impact on near surface temperatures, than energy transported by smaller, synoptic scale systems. This implies that Rossby waves impact Arctic climate more than synoptic cyclones. Therefore, shifts in circulation patterns driving atmospheric energy transport into the Arctic on different scales have a potential to change Arctic climate.</p><p>Here, we show that the annual mean impact of latent energy transport on Arctic temperatures is dominated by the winter season transport. Furthermore, by examining the ERA5 dataset for the years 1979-2018, we find that over the past four decades, there has been a shift in the mean winter season latent energy transport, from smaller, synoptic scale systems (-0.03 PW/decade), towards larger, planetary scale systems (+0.05 PW/decade) which as mentioned, have a larger climatic impact. As a consequence, this shift is estimated to have increased the Arctic temperatures. We find that the trends are driven by an increase in the extreme transport events (here we examine the upper 97.5<sup>th</sup> percentile). The upper extremes have increased more than the average on the planetary scale, and decreased more on the synoptic scale. The decrease in extreme synoptic scale transport at 70° N has been confirmed in other analyses of high vorticity weather systems. By examining the extreme transport events on seasonal scales, we reveal differences in the temporal distribution of planetary vs. synoptic scale extreme events, and identify areas of the Arctic that receive the strongest impact with respect to increases in near-surface temperatures.</p>

scholarly journals Prediction skill of tropical synoptic scale transients from ECMWF and NCEP Ensemble Prediction Systems

2016 ◽  
Vol 2 (1) ◽  
Author(s):  
S. Taraphdar ◽  
P. Mukhopadhyay ◽  
L. Ruby Leung ◽  
Kiranmayi Landu
Keyword(s):  
Random Error ◽  
Velocity Potential ◽  
Horizontal Resolution ◽  
Prediction Skill ◽  
Ensemble Prediction ◽  
Boreal Summer ◽  
Lead Times ◽  
Synoptic Scale ◽  
Planetary Scale ◽  
Prediction Systems

AbstractThe prediction skill of tropical synoptic scale transients (SSTR) such as monsoon low and depression during the boreal summer of 2007–2009 are assessed using high resolution ECMWF and NCEP TIGGE forecasts data. By analyzing 246 forecasts for lead times up to 10 days, it is found that the models have good skills in forecasting the planetary scale means but the skills of SSTR remain poor, with the latter showing no skill beyond 2 days for the global tropics and Indian region. Consistent forecast skills among precipitation, velocity potential, and vorticity provide evidence that convection is the primary process responsible for precipitation. The poor skills of SSTR can be attributed to the larger random error in the models as they fail to predict the locations and timings of SSTR. Strong correlation between the random error and synoptic precipitation suggests that the former starts to develop from regions of convection. As the NCEP model has larger biases of synoptic scale precipitation, it has a tendency to generate more random error that ultimately reduces the prediction skill of synoptic systems in that model. The larger biases in NCEP may be attributed to the model moist physics and/or coarser horizontal resolution compared to ECMWF.

scholarly journals A Dynamic Analysis of the Role of the Planetary- and Synoptic-Scale in the Summer of 2010 Blocking Episodes over the European Part of Russia

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Anthony R. Lupo ◽  
Igor I. Mokhov ◽  
Merseid G. Akperov ◽  
Alexander V. Chernokulsky ◽  
H. Athar
Keyword(s):  
Urban Areas ◽  
Warm Season ◽  
Terrestrial Ecosystems ◽  
European Part ◽  
Synoptic Scale ◽  
Excessive Heat ◽  
Planetary Scale ◽  
European Part Of Russia ◽  
Environmental Prediction ◽  
Blocking Event

During the summer of 2010, an unusually persistent blocking episode resulted in anomalously warm dry weather over the European part of Russia. The excessive heat resulted in forest and peat fires, impacted terrestrial ecosystems, greatly increased pollution in urban areas, and increased mortality rates in the region. Using the National Centers for Atmospheric Research (NCAR), National Centers for Environmental Prediction (NCEP) reanalysis datasets, the climatological and dynamic character of blocking events for summer 2010 and a precursor May blocking event were examined. We found that these events were stronger and longer lived than typical warm season events. Using dynamic methods, we demonstrate that the July 2010 event was a synoptic-scale dominant blocking event; unusual in the summer season. An analysis of phase diagrams demonstrated that the planetary-scale did not become stable until almost one week after block onset. For all other blocking events studied here and previously, the planetary-scale became stable around onset. Analysis using area integrated regional enstrophy (IRE) demonstrated that for the July 2010 event, synoptic-scale IRE increased at block onset. This was similar for the May 2010 event, but different from case studies examined previously that demonstrated the planetary-scale IRE was prominent at block onset.

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