Track Anomalies Research Articles

Using Mean Flow Change as a Proxy to Infer Interdecadal Storm Track Variability

Abstract Several recent studies, based mainly on analyses of reanalysis data, have suggested that the Northern Hemisphere storm tracks have intensified during the second half of the twentieth century. However, comparisons with rawinsonde observations over land areas suggest that eddy variance/covariance statistics may contain spurious jumps that had led to an exaggeration of the storm track secular trend. In this study, storm track variations are inferred from mean flow anomalies using canonical correlation analysis (CCA). A CCA model relating storm track anomalies to mean flow anomalies is derived using recent, more reliable data. The model is then applied to infer storm track anamalies using mean flow anomalies for earlier periods, when storm track analyses are deemed more suspect (or even nonexistent). Results of the CCA analyses suggest that the strong secular trend observed over the Atlantic basin and Europe is consistent with mean flow anomalies, while CCA predictions based on mean flow changes suggest only a much weaker trend in the Pacific storm track activity than that present in the reanalysis data. Over the regions where comparisons with rawinsonde data can be made, the interdecadal trends inferred by the CCA model are quite consistent with rawinsonde data over the Pacific storm track entrance and exit regions, as well as the Atlantic storm track exit regions, but are inconsistent with rawinsonde observations and reanalysis data over northeastern North America, where CCA predictions are generally poor. A CCA hindcast based on Trenberth and Paolino mean sea level pressure data as a predictor shows no indication that the secular increase in storm track intensity extends further back prior to 1960, suggesting that during the entire twentieth century, storm track activity was weakest during the 1960s.

Can biological markers identify endophenotypes predisposing to schizophrenia?

Summary The application of molecular genetic techniques to schizophrenia has so far failed to identify susceptibility genes. This in part may be due to heterogeneity and misclassification of gene carriers. Biological markersanatomical, physiological or biochemical variables that correlate with the main trait of interest and serve to better define that trait or its underlying genetic mechanism-offer a potential solution to these problems. In this article, we review studies that have evaluated the use of the following to identify biological markers of schizophrenia: structural neuroimaging, neuropsychological deficits, neurological signs, eye tracking, eventrelated potentials, and minor physical anomalies. Then we discuss the early reports from the Maudsley Family Study, which is investigating a number of putative biological markers in families multiply affected with schizophrenia.

Organization of Storm Track Anomalies by Recurring Low-Frequency Circulation Anomalies

Abstract From previous studies it is known that anomalous momentum fluxes by bandpass eddies are important in maintaining long-lasting tropospheric flow anomalies. Evidence is presented that suggests that these anomalous fluxes do not occur at random but happen because the structure of storm track activity is modified by the presence of prominent low-frequency, large-scale circulation anomalies. This behavior is noted in an extended integration of a perpetual January simulation with a general circulation model (GCM). Because nonlinear feedbacks between low- and high-frequency variability make it difficult to establish causal relationships between these two ranges of variability, a model is constructed that approximates the storm track activity that would be expected to accompany a given low frequency without including the feedback of the high frequencies onto the low-frequency state. This model is based on the linearized primitive equations and uses a series of short integrations from random initial condi...

A Diagnostic Study of Pacific Basin Circulation Regimes as Determined from Extratropical Cyclone Tracks

Abstract The interannual and intraseasonal track variability of cold season extratropical cyclones in the Pacific basin is examined using an 8 year cyclone track dataset. An EOF technique incorporating VARIMAX rotation in time is used to objectively describe the regime nature of the variations. Based upon this analysis we conclude that the cyclone behavior can be classified into six major regime types, corresponding to the positive and negative amplitude excursions of each of the first three rotated EOFS. Each of these rotated EOFs explains approximately equal fractions of the total variance. A study of the cyclone tracks for individual extreme periods confirms the existence of times where each of these patterns dominate. The average 500 mb height fields for these extreme periods have been examined and are generally consistent with the cyclone track anomalies. The resultant regime description shows strong interannual variability; however, there appears to be little obvious correlation with the ENSO signal...

Sudden Stratospheric Warming and Anomalous U.S. Weather

Severe distortion of tropospheric circulation is associated with major sudden stratospheric warming (SSW) events. This distortion consisting primarily of weakening of smaller-scale synoptic mats and development of strong blocking activity, is reviewed in the context of associated weather anomalies over the United States. Temperature, precipitation and cyclone anomalies of 17 January and February months experiencing SSW are contrasted with months of no stratospheric warming. The SSW is marked by intense cold, dry anomalies centered in the Ohio Valley, with below average temperatures covering the entire United States. In January, slight wet anomalies occur in the lee of the Rockies, and in February the desert southwest becomes quite wet. Cyclone activity decreases by 25% throughout the United States during SSW, most strongly along the West Coast and in association with the disappearance of the Colorado low. Storm track anomalies are documented over the eastern Pacific, the Gulf and Atlantic seaboard, and northeastern Canada. Slight variations of the anomaly patterns in February over the western United States are linked to the temporal evolution of SSW.

Processing of altimetry data

Two methods are discussed for the processing of altimetry data. For the first method it is assumed that the altimetry data, may be analyzed independent of the orbit computation for the satellite that carries the altimeter. Because of the high accuracy of the altimetry data, which can only be fully utilized if it is also introduced into the orbit computations, the second method deals with a simultaneous processing of altimetry data, orbit tracking, and gravity anomalies for the continents. To represent the gravity field, the potential of a simple layer is chosen whose unknown density is assumed to be constant over surface elements into which the surface of the earth is divided. Depending on the accuracy and the amount of the altimetry data, the surface elements for the density values are chosen smaller or larger, so that a very flexible representation of the earth’s gravity field is obtained. Because of the amount and the resolution of the altimetry data a large number of density values have to be determined in a least squares adjustment. To facilitate the computations, buffer zones are introduced so that the large system of normal equations can be broken up into small independent subsystems.