The definition and interpretation of the Arctic oscillation (AO) are examined compared with those North Atlantic (NAO). It is shown that NAO reflects correlations between surface pressure variability at its centers action, whereas this not case for AO. pattern can be identified in a physically consistent way principal component analysis applied to various fields Euro-Atlantic region. A similar identification found Pacific region Pacific–North American (PNA) pattern, but no such here AO does...

Abstract Empirical orthogonal function (EOF) analysis is a powerful tool for data compression and dimensionality reduction used broadly in meteorology oceanography. Often the literature, EOF modes are interpreted individually, independent of other modes. In fact, it can be shown that no such attribution generally made. This review demonstrates general individual (i) will not correspond to dynamical modes, (ii) kinematic degrees freedom, (iii) statistically (iv) strongly influenced by...

Using monthly mean data, daily and theoretical arguments, relationships between surface pressure variations associated with the North Atlantic Oscillation (NAO), tropopause height, strength of stratospheric vortex are established. An increase in NAO index leads to a stronger vortex, about 4 days later, as result increased equatorward refraction upward-propagating Rossby waves. At level effects enhanced polar opposite, resulting lower over Iceland higher Arctic. The raising Arctic stretching...

Abstract The Antarctic Circumpolar Current is the strongest current in ocean and has a pivotal impact on stratification, heat content, carbon content. circumpolar volume transport relatively insensitive to surface wind forcing models that resolve turbulent eddies, process termed “eddy saturation.” Here simple model presented explains physics of eddy saturation with three ingredients: momentum budget, relation between form stress energy, an energy budget. both insensitivity increase stress....

We present an analysis of trace gas correlations in the lowermost stratosphere. In‐situ aircraft measurements CO, N 2 O, NO y and O 3 , obtained during STREAM 1997 winter campaign, have been used to investigate role cross‐tropopause mass exchange on tracer‐tracer relations. At altitudes several kilometers above local tropopause, undisturbed stratospheric air was found with /NO * ratios close unity, /O about 0.003–0.006 CO mixing as low 20 ppbv (NO is a proxy for total reactive nitrogen...

Abstract This paper describes a novel numerical algorithm for simulating the evolution of fine‐scale conservative fields in layer‐wise two‐dimensional flows, most important examples which are earth's atmosphere and oceans. combines two radically different algorithms, one Lagrangian other Eulerian, to achieve an unexpected gain computational efficiency. The is demonstrated multi‐layer quasi‐geostrophic flow, results presented simulation tilted stratospheric polar vortex nearly‐inviscid...

Abstract The North Atlantic eddy-driven jet exhibits latitudinal variability with evidence of three preferred locations: south, middle, and north. Here the authors examine drivers this associated storm track. investigate changes in storm-track characteristics for locations propose a mechanism by which enhanced activity, as measured upstream heat flux, is responsible cyclical downstream shifts jet. This based on nonlinear oscillator relationship between meridional temperature gradient (and...

We construct a two‐variable model that describes the interaction between local baroclinicity and eddy heat flux in order to understand aspects of variance storm tracks. It is heuristic for diabatically forced baroclinic instability close neutrality. The has structure nonlinear oscillator. exhibits some realistic properties observed track variability, most notably intermittent nature activity. This suggests apparent threshold behaviour can be more accurately succinctly described by simple...

Charge affects the activation of cloud droplets by reducing minimum supersaturation at which haze begin to grow. Although droplet charge required enhance is substantial, we show that sufficient charging occurs edges layer clouds because fair-weather current in global atmospheric electrical circuit flows through a discontinuity conductivity. Our theory predicts neutralization will cause transient cooling base. This hypothesis was tested during period extreme solar activity, when detected...

Liquid layer clouds are abundant globally. Lacking strong convection, they do not become electrified by the usual thunderstorm mechanisms of collisional electrification between hydrometeors different phases. Instead, background global circuit current flow in fair weather is largely unaffected cloud's presence, and, if cloud extensive horizontally, vertical conduction passes through cloud. A consequence that, at cloud–air boundary where there a conductivity transition and droplets form or...

The electrostatic force between conductive spheres is always attractive at small separations, irrespective of their mean charge, when the charge on constant. In many situations, may not be fixed, such as for water drops in natural atmosphere which vary size and charge. We show that charged increases with increasing variance. importance this unrecognized effect evaluated its potential to enhance rain formation.

A large fraction of papers in the climate literature includes erroneous uses significance tests. Bayesian analysis is presented to highlight meaning tests and why typical misuse occurs. It concluded that a test very rarely provides useful quantitative information. The statistic not measure how confident we can be 'reality' given result.

Abstract The consistency of ensemble forecasts from three global medium‐range prediction systems with the observed transition behaviour a three‐cluster model North Atlantic eddy‐driven jet is examined. clusters consist mid cluster taken to represent an undisturbed and south north representing southward northward shifts jet. span period extended winters (October–February) October 2007–February 2010. mean probabilities transitions between calculated are compared those 23‐extended‐winter...

The North Atlantic eddy‐driven jet is a major component of the large‐scale flow in northern hemisphere. Here we present evidence from reanalysis and ensemble forecast data for systematic flow‐dependent predictability during hemisphere winter (DJF). It found that when weakened or split, it both less persistent predictable. lack manifests itself as onset an anomalously large instantaneous rate spread members becomes weakened. This suggests that, weakens splits, enters into state more sensitive...

Abstract The response of the North Atlantic large‐scale circulation to El Niño–Southern Oscillation (ENSO) exhibits distinct differences between early (November–December) and late (January–February) winter. However, reasons for this are unclear, particularly regarding winter response. Here we examine role storm‐track dynamics in influencing intraseasonal variability ENSO teleconnection Atlantic. During there a broad weakening eddy heat flux upstream storm track during Niño phase, which is...

The observed reduction of Arctic sea ice has drawn a lot interest for its potential impact on midlatitude weather variability. One the outstanding challenges is to achieve deeper understanding dynamical processes involved in this mechanism. To progress area, we have designed and performed an experiment with intermediate complexity atmospheric model. shows transient response surface diabatic heating Barents Kara Seas leading anomalous circulation first locally, then over polar region finally...

The horizontal gradient of potential vorticity (PV) across the tropopause typically declines with lead time in global numerical weather forecasts and tends towards a steady value dependent on model resolution. This paper examines how spreading PV contrast over broader frontal zone affects propagation Rossby waves. approach taken is to analyse waves front finite width simple single-layer model. dispersion relation for linear infinitesimal well known; here, an approximate correction derived...

Using a novel numerical method at unprecedented resolution, we demonstrate that structures of small to intermediate scale in rotating, stratified flows are intrinsically three-dimensional. Such characterized by vortices (spinning volumes fluid), regions large vorticity gradients, and filamentary all scales. It is found such have predominantly three-dimensional dynamics below horizontal L≈12LR, where LR the so-called Rossby radius deformation, equal characteristic vertical fluid H divided...

Cosmic rays modify current flow in the global atmospheric electrical circuit. Charging at horizontal layer cloud edges has been observed to be consistent with circuit vertical through cloud, which can properties of small and pure water droplets. Studies have hampered by absence edge observations, hence base height information is investigated here. Cloud measured Lerwick Observatory, Shetland, UK, analysed using threshold tests spectral analysis. The distributions for low (cloud less than 800...

Rainfall is hypothesized to be influenced by droplet charge, which related the global circuit current flowing through clouds. This tested examining a major increase following release of artificial radioactivity. Significant changes occurred in daily rainfall distribution Shetland Islands, away from pollution. Daily changed 24%, and local clouds optically thickened, within nuclear weapons test period. supports expectations electrically induced microphysical liquid water additional ionization.

The atmosphere's fair weather electric field is a permanent feature, arising from the combination of distant thunderstorms, Earth's conducting surface, charged ionosphere and cosmic ray ionization. Despite its ubiquity, no electricity effect on clouds has been hitherto demonstrated. Here we report surface measurements radiation emitted scattered by extensive thin continental cloud, which, after ~2 min delay, shows changes closely following field. For typical fluctuations in field, about 10%...