Persistent Anomaly Research Articles

The persistent anomaly of summertime circulation over the Ural Mountains

The tropical heating and transient activity features during the period of the persistent anomaly of summertime circulation over the Ural Mountains are studied, and a possible mechanism responsible for formation and maintenance of persistent anomalies is proposed. The mechanism can be summarized as a kind of self-sustaining through a two-way interaction of stationary wave with transient eddies under the consistent forcing of abnormal heating in the tropics.

A Case of Pure Unroofed Coronary Sinus without Persistent Left Superior Vena Cava

We report a case of 51-year-old woman with pure unroofed coronary sinus without persistent left superior vena cava and other cardiac anomaly. She presented with dyspnea on exertion during several years. Her chest film showed prominent cardiomegaly and dilated hilar vessels. Cardiac rhythm was atrial fibrillation. Transthoracic echocardiography demonstrated the enlar- ged coronary sinus with defect toward left atrium on parasternal long axis view and significant flow from coronary sinus into right atrium on subxyphoid view, and its other findings were dilated right ventricle and right atrium, paradoxical septal motion, moderate tricuspid regurgi- tation and mild mitral regurgitation, which were mimicking of large secundum atrial septal defect. Radion-uclide cardioangiography and cardiac catheterization showed the existence of significant shunt. There was no evidence of persistent left superior vena cava on chest CT. Closure of Coronary sinus opening was done. Thereafter her symptoms of congestive heart failure were much improved. We think that careful examination of 2-D echocardiography can be valuable tool for diagnosis of unroofed coronary sinus in adult patient.

The Dynamics of Large-Scale Cyclogenesis over the North Pacific Ocean

Abstract Earlier studies of persistent large-scale flow anomalies have been extended, with the aim of identifying the primary mechanisms for persistent anomaly development. In this study the focus is on wintertime cases of persistent cyclonic flow anomalies over the North Pacific. These cases are typically manifested by an abnormally intense cyclonic circulation extending over the North Pacific basin, an unusually strong and eastward-extended East Asian jet, and a well-defined Pacific-North American teleconnection pattern. We have conducted extensive diagnostic analyses in order to determine the mechanisms responsible for development. In particular, these diagnostics examine the processes influencing the time evolution of eddy potential enstrophy and potential vorticity anomalies. The cases are preceded by a buildup of anomalously high potential vorticity air at upper levels over eastern Asia. This high potential vorticity air is initially advected eastward in association with synoptic-scale cyclogenesis ...

Barotropic Stationary States and Persistent Anomalies in the Atmosphere

Abstract A robust algorithm, capable of finding nearly stationary solutions of the unforced barotropic vorticity equation near to observed atmospheric streamfunctions, is presented. When applied to observed persistent anomaly patterns, the nearly stationary states (NSSs) produced by the algorithm usually have a distinctive appearance. NSSs produced for observed blocks tend to have even stronger blocks, and NSSs for intense jet anomaly patterns have intense jets. When applied to observed patterns that are not associated with persistent anomalies, the algorithm produces low-amplitude relatively zonal NSSs. The blocking and intense jet anomaly NSSs bear a striking resemblance to previously derived analytic stationary solutions of the vorticity equation. In particular, NSS blocking states are similar to certain types of modons.The algorithm is applied to a number of modified observed flows to better document what features of an observed pattern determine the nature of the resulting NSS. The short-wave compone...

Three-Dimensional Linear Instability of Persistent Anomalous Large-Scale Flows

The linear baroclinic instability of three-dimensional basic flows on the Northern Hemisphere is examined in terms of a simple two-level, quasi-geostrophic model. The basic flows considered comprise an observed six-winter mean flow, as well as anomalous flows which represent episodes where large-scale persistent flow anomalies, such as the Pacific/North American (PNA), East Atlantic (EA), or North Atlantic Oscillation (NAO) patterns exhibit large amplitudes. For the climatological basic state, the fastest-growing normal modes with periods of around 4 days consist of regionally confined, synoptic-scale, baroclinic wave trains. These are considered as cyclogenesis modes, characterizing the linear synoptic-scale eddy activity associated with a given basic flow. This eddy activity has a pronounced maximum over the Pacific, close to the position of the observed Pacific storm track, but the second maximum over the Atlantic, corresponding to the Atlantic storm track, is considerably underestimated. Nevertheless, comparing the structure of the cyclogenesis modes with that of the leading complex EOFs of the observed bandpass-filtered flow, a pattern correlation squared of up to 0.4 is obtained. Truncating the basic state to comprise only the ultralong waves (zonal wavenumber m ≤ 4) results in rather little change in the cyclogenesis modes obtained. Finally, the sensitivity of the cyclogenesis modes to the anomalous basic flows is investigated, using persistent anomaly patterns (PNA, EA, NAO) obtained from a rotated principal component analysis of the observed lowpass-filtered flow. The anomalous basic states are evaluated by adding or subtracting these patterns to/from the winter climatological mean flow. It turns out that the normal-mode wave trains are significantly deflected from their climatological positions, particularly in the EA and NAO cases. This model response is verified against composite maps of observed bandpass variance, obtained for episodes of strong PNA, EA or NAO anomalies respectively. It is found that, although the normal-mode wave trains are still relatively too weak over the Atlantic (compared to the Pacific), the structural differences in the observed bandpass eddy activity between positive and negative anomaly cases are captured quite well by the normal modes.

Statistics and Dynamics of Persistent Anomalies

Persistent anomalies with recurrent spatial patterns play an important role in the atmosphere's low-frequency variability. A connection between statistical and dynamical methods of description and prediction of persistent anomalies is established by computing and analyzing the empirical orthogonal functions (EOFs) in a simple deterministic model, on the one hand, and in Southern Hemisphere geopotential heights, on the other. The dynamical model is governed by the fully nonlinear, equivalent-barotropic vorticity equation on the sphere, with simplified forcing, dissipation and topography. The Southern Hemisphere data consist in gridded daily maps of 500 mb heights from June 1972 to July 1983. Two types of persistent anomalies appear in this time series, both having a strong wavenumber-three component; they differ by the value of the constant phase of this wave and by the strength of the wavenumber-one component. The first two EOFs bear a striking resemblance to these two patterns. It is concluded that the dynamical interpretation of EOFs is their pointing from the time mean to the most populated regions of the system's phase space. Pursuing this interpretation, a Markov-chain formulation of transitions from one persistent anomaly regime to another is introduced, and the implications for long-range forecasting are discussed.

The superallowed decay of 35Ar: A persistent anomaly

Abstract The branching ratio for the decay of 35 Ar to the first excited state in 35 Cl has been measured to be (1.34±0.08)% with the ISOLDE on-line isotope separator. Combining this result with previous data leads to the value (98.28±0.06)% for the branching ratio of the ground state (superallowed) transitions. This does not resolve the apparent anomalousness of the derived Cabibbo angle for this transition, which now stands at θ v

Magnetic Data on the Structure of the Central Arctic Region

A study of 23,000 miles of total intensity aeromagnetic profiles in the central Arctic has been made by the U. S. Geological Survey and the U. S. Coast and Geodetic Survey. The profiles were flown at 20,000 feet above sea level and cover approximately 1,350,000 square miles of the Arctic Ocean between the North Pole and the North American continent. When the profiles are smoothed to remove crustal anomalies, the resulting contoured values differ from the U. S. Hydrographic Office Chart 1703 N for 1955 corrected to 1951 by as much as 2000 gammas in the northern part of the Arctic Archipelago. A nondipole regional focus east of Greenland has decreased in amplitude but has changed very little in position since 1907.5. There is a profound difference in the magnetic characteristics of the rocks on either side of the underwater Lomonosov Ridge across the Arctic Ocean. In the Eurasian Basin the high-altitude profiles are relatively smooth or show only minor anomalies, but on the North American side of the ridge there is a large area of closely spaced, high-amplitude anomalies which has been designated the Central Magnetic Zone. Although the anomaly trends parallel the Alpha Rise, this zone is far more extensive, including nearly half of the Canadian Basin on one side and probably all the Central Arctic Basin on the other side of the rise. The Lomonosov Ridge is marked by a persistent anomaly of moderate size that indicates the presence of magnetic material in the ridge. Probable block-fault structures along the flanks of the Alpha Rise are associated with blocklike magnetic anomalies of comparable widths. A characteristic magnetic pattern occurs over an area of jagged bottom topography in the Eurasian Basin. A similar magnetic pattern over part of the Lena Trough may indicate another area of jagged topography. The belt of epicenters associated with the Mid-Atlantic Ridge continues through this rugged part of the Eurasian Basin, but the absence of the typical high magnetic anomaly makes it doubtful that the mid-oceanic ridge extends through this part of the Arctic. Magnetic data indicate that the thick sections of sedimentary rocks in the Paleozoic geosynclinal belts of northern Ellesmere Island and northern Greenland continue out under the adjacent continental shelves north of Greenland, west of the Arctic Archipelago, north of the part of Alaska east of Barrow, and under part of the Chukchi Shelf, and that they make up the bulk of the Nansen Swell off Spitsbergen. Thick sedimentary fill is indicated in the magnetically flat areas of the Eurasian Basin next to the Lomonosov Ridge and in the southern part of the Canadian Basin. The magnetic profiles on the Eurasian side of the Lomonosov Ridge closely resemble typical magnetic profiles over both Atlantic and Pacific oceans, where as the profiles of the Central Magnetic Zone on the North American side of the Lomonosov Ridge are completely unlike the oceanic data and show a striking similarity to typical profiles over the Precambrian rocks of the Canadian Shield and its buried equivalent under the Central Stable Region of the United States. Therefore, it is concluded that the Arctic region consists of a probable oceanic area on the Eurasian side and a basin formed by downdropped continental rocks, presumably a Precambrian complex similar to that of the Canadian Shield, on the North American side of the ridge.