Sentences with phrase «zonal wave»

The first principal component is significantly correlated with the SAM index (the first principal component of sea - level - pressure or 500 - hPa geopotential heights for 20u S — 90u S), and the second principal component reflects the zonal wave - 3 pattern, which contributes to the Antarctic dipole pattern of sea - ice anomalies in the Ross Sea and Weddell Sea sectors.

However, using National Centers for Environmental Prediction − National Center for Atmospheric Research (NCEP - NCAR) reanalysis data (41), Petoukhov et al. (34) showed that, during a number of recent NH extremes in July and August, certain persistent high - amplitude atmospheric wave patterns with barotropic vertical structure evolved, to which the quasistationary component of midlatitude barotropic free waves with zonal wave numbers k ≈ 6 − 8 made an exceptionally large contribution.

Time series of the observed amplitudes (in meters per second) of zonal wave numbers m = 6 (black), m = 7 (red), and m = 8 (blue) for the 15 - d running means of the meridional wind velocity at 300 hPa averaged over 37.5 ° N − 57.5 ° N for May − September 2012 and 2013, based on daily reanalysis data (41).

1a designates the amplitude of the 15 - d running means of the external thermal + orographic barotropic forcing with zonal wave number m at the EBL, averaged over the midlatitude belt Δ = 37.5 ° − 57.5 ° N.

(B) Nondimensional stationary wave number squared (the curve, left y axis) and resonance zonal wave number k (the straight line, right y axis) at the QRA event.

The indicated variation in the values of A˜m, max are determined basically by changes in the values of zonal wind within the waveguide, the meridional and zonal wave numbers of the resonance waves, and the width of the waveguide's interior, ΔQRAint.

These waves with zonal wave numbers k ≈ 6 − 8 (they can be noninteger; we will call these waves k waves) usually experience strong meridional dispersion, and, for that reason, their energy disperses rapidly.

A strong snowmelt in late April / early May and torrential rains in late May / early June could have been caused by the occurrence of persistent quasibarotropic high - amplitude QRA structures with zonal wave numbers m = 6 and m = 7 in the field of the NH midlatitude meridional velocity.

The dimensional meridional wave number l of the quasistationary barotropic midlatitude free waves with nondimensional zonal wave number k ≈ 6 − 8 (the k wave) is calculated from the equation (see equation S5 in ref.

Unlike the one considered in Branstator (26) for zonal wave number 5, the formation of these waveguides is based on a specific change in the latitudinal shape (and not the magnitude) of the quasizonal extratropical winds at the equivalent barotropic level (EBL).

All of the necessary conditions for the QRA event were met for the free wave with zonal wave number k ≈ 7.05 within the midlatitude waveguide whose boundaries are marked by the vertical solid lines in B.

All of the necessary conditions for the QRA event were met for the free wave with zonal wave number k ≈ 6.8 within the midlatitude waveguide whose boundaries are shown by the vertical solid lines in B.

Our study shows that, in boreal spring - to - autumn 2012 and 2013, a majority of the weather extremes in the Northern Hemisphere midlatitudes were accompanied by highly magnified planetary waves with zonal wave numbers m = 6, 7, and 8.

34 can favor an onset of midlatitude quasiresonant amplification (QRA) of these waves, causing a strong increase in the atmosphere's dynamical response to quasistationary midtroposphere external forcing with zonal wave numbers m = 6, 7, and 8 (Calculation of the Meridional Wave Number).

Here we show that a considerable part of these extremes were accompanied by highly magnified quasistationary midlatitude planetary waves with zonal wave numbers m = 6, 7, and 8.

The necessary conditions for QRA were met for the quasistationary free wave with zonal wave number k ≈ 6.8 within the midlatitude waveguide (see Fig. 3B).

40, the barotropic orographic and thermal forcing with zonal wave numbers m is the major extratropical source for forced quasistationary barotropic dynamical waves with these zonal wave numbers.

Free extratropical Rossby waves with zonal wave numbers about 6 to 8 mostly occur as high - amplitude, fast traveling waves (the so - called synoptic transients responsible for much of the weather variability in the extratropics); once established, they can freely propagate predominantly to the east with a phase speed c ≈ 6 − 12 m ⋅ s − 1 without maintenance from external forcing.

Petoukhov et al. (34) proposed a common mechanism for generating persistent high - amplitude quasibarotropic planetary - scale wave patterns of the NH midlatitude atmospheric circulation with zonal wave numbers m = 6, 7, and 8 that can explain a number of the major NH summer extremes over the 1980 — 2011 period (34, 35).

These waves are solutions to the full wave equation, including forcing, for integer values of the zonal wave number m (we will refer to them as m waves).

In contrast to these fast traveling waves, the quasistationary extratropical barotropic free waves with zonal wave numbers 6 to 8 are normally weak, with a magnitude of the meridional wind velocity less than 1.5 — 2.5 m ⋅ s − 1 (25, 34, 35, 39, 40).

It is essentially a zonally symmetric structure, but with a zonal wave three pattern superimposed.

In the parlance of statistical climatology, the «zonal wave 3 pattern» has increased (see Raphael, GRL 2004).

Not exact matches

We found that brown dwarfs are similar to the gas giants in the Solar System (in that they have zonal circulation), but that they are more like Neptune and less like Jupiter (their brightness variations are driven by large - scale waves in zones rather than Great Red Spot - like storms as in Jupiter).

Performing a hybrid, finite - amplitude wave activity budget analysis they elucidated the nonlinear and irreversible aspects of wave interactions while the zonal wind adjusted toward a poleward - shifted state.

Abstract: «Persistent episodes of extreme weather in the Northern Hemisphere summer have been shown to be associated with the presence of high - amplitude quasi-stationary atmospheric Rossby waves within a particular wavelength range (zonal wavenumber 6 — 8).

Westerlies don't reverse, but shift from Zonal Flow with few low amplitude Rossby Waves to Meridional Flow with more and higher amplitude Waves (Figure 3).

MD wave fades moving deeper into SH due to lack of land mass & land impediment to antarctic circumpolar (southern ocean) flow --(need midlatitude zonal land - sea contrast for meridional deflection of westerlies = differential land - sea equator - pole column - integrated - temperature gradient response to solar forcing, easily measured using a simple wavelet tachometer, which detects externally governed universal constraint)

As in the zonal wind animation, Rossby wave packets are clearly recognizable, as are a host of smaller coherent vortices.

It now appears clear that when the sun is active the jets are more zonal (east to west) with short lines of air mass mixing and less clouds whilst when the sun is less active the jets are more meridional (waving north and south) with longer lines of air mass mixing and more clouds.

And there is good evidence that the annular modes would not exist in the absence of positive feedbacks between the induced changes in the zonal wind and the wave fluxes.

The equations for Rossby waves (Calculation of the Meridional Wave Number, Physics of the Parameter, and Calculation of the Amplitudes) show that this can occur if a set of necessary conditions are met: u ¯ > 0 in the midlatitude region; the highest value of l within the waveguide is in the range of the meridional wave numbers lm dominantly contributing to the external forcing with a given m, which provides closeness of the k waves to respective m waves not only in terms of the zonal but also the meridional wave numbers, favoring the QRA of the m waves; the total latitudinal width of the waveguide is no less than the characteristic spatial scale of the relevant Airy function (25), which is used as the boundary condition at its southern and northern boundaries; and latitudinal distribution of l is sufficiently smooth in the waveguide, and both TPs lie within a midlatitude region of ∼ 25 ° N — 30 ° N and ∼ 65 ° N − 70 ° N, as the necessary condition for the application of quasilinear Wentzel − Kramers − Brillouin (WKB) method (25) when solving the equations for Rossby waves.

The resulting temperature gradients lead to changes in the zonal wind, which, in turn, changes planetary wave — mean flow interactions.

Whether a waveguide develops for a particular wave number k depends on the latitudinal shape of the zonal mean midtroposphere zonal winds u ¯ in the extratropical atmosphere.

In our paper, we have dealt with the zonally averaged zonal winds as the mean flow and excluded from our consideration packets of quasistationary planetary waves trapped in predominantly meridional elongated waveguides, specifically those originating in the tropics.

This is important because climate change is reflected most in these latitudes as the Circumpolar vortex shifts between Zonal and Meridional flow and the amplitude of the Rossby Waves vary.

Because the longwave atmospheric weather patterns (Rossby waves) have a scale of several thousand kilometers, it is not unusual for the temperature of a region the size of the United States to be substantially warmer or co lder during a single season than the zonal mean temperature.

Two effects are identified that each contribute to a slower eastward progression of Rossby waves in the upper - level flow: 1) weakened zonal winds, and 2) increased wave amplitude.

Persistence of waves can not only occur with high pressure, but also e.g. with low pressure systems (potentially leading to flooding) or with persistent zonal flow (supporting the occurrence of extreme cyclones).

This change in zonal flow reduces the zonal drive pushing Rossby waves within the zone, resulting in increases in Blocking / Cut - Off conditions.