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Convergence Lines (convergence + line)

Distribution by Scientific Domains
Earth and Environmental Science100%

Selected Abstracts

A numerical study of the effect of sea breeze circulation on photochemical pollution over a highly industrialized peninsula

METEOROLOGICAL APPLICATIONS, Issue 1 2010
Cristina Mangia
Abstract Numerical simulations compared with measurements are used to investigate the effect of sea breeze circulation on the ozone accumulation over a highly industrialized peninsula in southern Italy, where high levels of ozone concentration are often registered. A frequent meteorological phenomenon in this region during weak summer synoptic conditions is the development of complex sea breeze systems from the coastlines, with convergence areas within the peninsula. A case study characterized by strong winds alternating with sea breeze circulations was selected. The simulations show that during weak synoptic conditions, sea breezes transport ozone and its precursors over land from the sea, as well as from the coastlines where the largest industrialized districts are localized. The overlapping breezes lead to ozone accumulation in the area where sea breeze convergence occurs. This may explain the high values of ozone registered close to the sea breeze convergence lines. The comparison between predictions and experimental data indicates that the numerical system successfully reproduces both weather and ground level ozone concentration in different meteorological conditions, resulting in a fundamental tool for both scientific comprehension of the evolution of air contaminants and interpretation of the monitoring data. Copyright © 2009 Royal Meteorological Society [source]

Numerical prediction of severe convection: comparison with operational forecasts

METEOROLOGICAL APPLICATIONS, Issue 1 2003
Milton S. Speer
The prediction of severe convection is a major forecasting problem in Australia during the summer months. In particular, severe convection in the Sydney basin frequently produces heavy rain or hail, flash flooding, and destructive winds. Convective activity is a forecasting challenge for the Sydney basin, mainly from October to April. Currently, there is a need for improved numerical model guidance to supplement the official probabilistic convective outlooks, issued by the operational forecasters. In this study we assess the performance of a very high resolution (2 km) numerical weather prediction (NWP) model in terms of how well it performed in providing guidance on heavy rainfall and hail, as well as other mesoscale features such as low level convergence lines. Two cases are described in which the operational forecasts were incorrect on both occasions. Non-severe thunderstorms were predicted on 1 December 2000 but severe convection occurred. Severe convection was predicted on 8 December 2000, but no convection was reported. In contrast, the numerical model performed well, accurately predicting severe convection on 1 December and no convection on 8 December. These results have encouraged a program aimed at providing an enhanced numerical modelling capability to the operational forecasters for the Sydney basin. Copyright © 2003 Royal Meteorological Society [source]

Simulations of low-level convergence lines over north-eastern Australia

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 616 2006
Gerald L. Thomsen
Abstract We describe high-resolution numerical model simulations of low-level convergence lines over north-eastern Australia using the Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5). The simulations are for selected events that were documented during the Gulf Lines Experiment, held in September,October 2002. The calculations provide further insights into the dynamics of the convergence lines and the mechanisms involved in their formation. In particular they show two clearly distinct convergence lines, one that corresponds to the morning glory and one which corresponds to the North Australian Cloud Line; the former originates from the east-coast sea breeze over Cape York Peninsula south of about 14°S, while the latter originates from the east-coast sea breeze north of this latitude. They support also a recently proposed conceptual model for the generation of southerly morning glories and show for the first time the separation of a bore-like disturbance following the collision of a nocturnal cold front to the south of the inland trough with a sea-breeze front to the north of the trough. Moreover, they show the progressive transition of the east-coast sea-breeze front and the inland cold front from gravity-current-like flows to bore-like disturbances overnight to form north-easterly and southerly morning glories, respectively. Copyright © 2006 Royal Meteorological Society. [source]