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THE USE OF STABILITY INDICES IN THE STUDY OF CONVECTIVE SITUATIONS: THE CASE OF 1997 AUTUMN STORMS, IN LISBON - The autumn of 1997 in Portugal was remarkable for the occurance of several situations of storms, some of them with tragic consequences, as they caused floods with casualties and enormous damages. In Lisbon, four heavy rainfall events accurred from the 18th October to 3rd November and we want to investigate the thermodynamic condtions of these severe storms to deepen our knowledge of these situations with regard to climate. For this purpose, several stability indices communly used in thunderstorm forecasting were calculated. We concluded that they are useful to measure the degree of instability of certain atmospheric situations, bur more applications must be made in order to define some significative thresholds for the indices...
WEATHER RADAR IMAGE IN CLIMATOLOGY - After a brief overview about weather radar as a remote sensing instrument, some problems concerning the use of radar images are discussed. The great interest of radar images as a tool in Climatology is pointed out. Finally, a case study about two rainfall events in Nancy (France) in April 1995 is presented.
Jump-type Fleming-Viot process Selection Stationary distribution Coupling
The subject matter of this paper is the analysis of some fine properties (some path properties) of a jump-type Fleming-Viot process. It is shown that such processes exhibit sample paths contained in the set of atomic measures, when the mutation operator is bounded.
Jump-type Fleming-Viot process Selection Girsanov transformation Duality
Trees bring many benefits to the urban environment. However, they may also cause hazards to human population, being the major causes of injuries and infrastructural damage during strong wind events. In the city of Lisbon, strong winds rather frequently result in tree falls, depending on the season and meteorological conditions. This paper presents a methodology to analyse tree damage due to strong wind events in urban environments. Each occurrence has been recorded by the Lisbon Fire Brigade and Rescue Services (Regimento de Sapadores Bombeiros de Lisboa - RSBL). Information provided by RSBL relating to the period of 1990-2005 was considered along with hourly wind speed and direction, species, fitossanitary conditions and urban parameters. To ensure that the fallen trees were caused by strong winds, only days with three or more occurre...
Trees bring many benefits to the urban environment. However, they may also cause hazards to human population, being the major causes of injuries and infrastructural damage during strong wind events. In the city of Lisbon, strong winds rather frequently result in tree falls, depending on the season and meteorological conditions. This paper presents a methodology to analyse tree damage due to strong wind events in urban environments. Each occurrence has been recorded by the Lisbon Fire Brigade and Rescue Services (Regimento de Sapadores Bombeiros de Lisboa - RSBL). Information provided by RSBL relating to the period of 1990-2005 was considered along with hourly wind speed and direction, species, fitossanitary conditions and urban parameters. To ensure that the fallen trees were caused by strong winds, only days with three or more occurre...
SUMMARY In this paper some results of a preliminary study on the influence of surface features on convective precipitation and thunderstorm activity in the region of Lisbon are discussed. The present work is focused on the strong thunderstorms affecting Lisbon on the 9th September 2009. The spatial distributions of precipitation and cloud-to-ground electrical discharges are investigated in relation to land surface characteristics, such as fraction of urbanised area, relief features and other geographical factors. The spatial distribution of thunderstorm activity is also compared with the surface fields of temperature and turbulent heat fluxes, derived from satellite data. The data analysis indicates a more intense thunderstorm activity over the Lisbon region than on the surrounding areas during this episode. The results suggest that t...
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