Synoptic Circulation Patterns Research Articles

Regional apportionment of sulfate and tracer elements in Rhode Island precipitation

Regional receptor modeling methods have been used to estimate the relative contributions of northeastern and midwestern source regions to sulfate wet deposition in southern Rhode Island. Three years' precipitation samples were collected and analyzed for the tracer elements As, Sb, Se, and noncrustal IV, which were used in a ‘chemical element balance’ procedure to determine the relative regional contributions. Careful considerations is given to the possibility of fractionation processes altering the relative proportions of the tracers during precipitation scavenging, with the conclusion that such processes are unlikely. The Midwest is the major source for sulfate in precipitation (75% annually). By contrast, aerosol sulfate is about 50% midwestern, suggesting that distant midwestern sources are more important at cloud level than at the surface. Winter rain is slightly more northeastern than summer rain, while snow is markedly so. Comparison of individual event apportionments with synoptic circulation patterns during those events indicates that the apportionments are reasonable.

Variations in boundary layer properties associated with clouds and transient weather disturbances at the South Pole during winter

Both the increasing concentrations of greenhouse gases and potential changes in cloud distributions are likely to affect the surface energy budget of the polar regions. Changes in the polar atmosphere are linked to dynamical processes that control the transport of mass, heat, and moisture from lower latitudes and in turn, feed back into the global circulation. Radiation and meteorological data collected at the South Pole during the 1986 austral winter are analyzed to gain a better understanding of the relationships between cloud radiative effects, transport processes and the vertical distribution of temperature and wind. An algorithm is developed to characterize the quasi‐permanent surface‐based temperature inversion and the “warm” radiatively active layer above it. Mean winter temperature and wind profiles for clear and overcast conditions are combined with surface radiation measurements and synoptic circulation patterns to study the mechanisms that cause periodic weakening of the inversion. Results support previous studies that ascribe this weakening to (1) warm air advection, (2) downward vertical mixing of sensible and latent heat, and (3) longwave cloud radiative heating. The integrity of the inversion depends on the combined effects of all three mechanisms. Parameters representing the intensity of the inversion and the bulk wind shear through the lower troposphere are suggested as appropriate indices for the detection of climate change in the region of the Antarctic Plateau.

On the evidence of a general whirling action in the Providence Tornado

The results of a systematic investigation and recording of tornado and waterspout occurrence in Greece for the 10-year period 2000–2009 are presented. This is the first database developed in Greece in an attempt to collect and record comprehensive information about tornadoes, waterspouts, funnel clouds, dust devils and other whirlwind phenomena. The primary research purpose of this database is to search, diagnose and record tornado and waterspout occurrences and identify their morphological and climatological features. Based on the 10-year data, a mean annual number of 1.1 tornadoes per unit area of 104 km2, is depicted for Greece. The seasonality appears differently for various parts, with winter most active tornado season for western Greece and summer for northern Greece. Spatial distribution showed that tornadoes are more frequent over western Greece and the Ionian coasts with a local maximum over northwest Peloponnese. Waterspouts occur in both the Aegean and the Ionian Sea mostly in summer and autumn, with a peak in September, while a considerable geographical maximum is located over north off the shore of Iraklion, Crete Island. A preliminary estimate of probability of tornado occurrence for each of the 51 Greek prefectures plus the Mount Athos area, showed highest values for Kerkyra Island and Elias prefectures, western Greece. Analysis based on intensities as assessed by damage data, indicated that the majority of tornadoes reached T4 of the T-scale or F2 of the F-scale. Short wave trough is found as the most relevant synoptic circulation pattern to tornadic activity. Thermodynamic and wind parameters showed a wide range of values, suggesting that threat levels should be adjusted for various areas since tornadoes and waterspouts can occur in different environments.