Extreme wind climate of Uruguay
Uruguay belongs to the second most prone region of the world to the occurrence of severe convective storms, and to the region of South America that presents the highest frequency of occurrence of intense cyclogenesis events. Both meteorological processes produce high winds in the country, which repr...
Salvato in:
| Autore principale: | |
|---|---|
| Natura: | doctoralThesis |
| Lingua: | inglese |
| Pubblicazione: |
2015
|
| Soggetti: | |
| Accesso online: | http://hdl.handle.net/20.500.12008/8394 |
| Tags: |
Nessun Tag, puoi essere il primo ad aggiungerne!!
|
| Riassunto: | Uruguay belongs to the second most prone region of the world to the occurrence of severe convective storms, and to the region of South America that presents the highest frequency of occurrence of intense cyclogenesis events. Both meteorological processes produce high winds in the country, which represent a risk for the physical integrity and lives of the population, produce losses and damage to their properties and to critical infrastructure; impact the agronomic, energy, insurance and construction sectors. In particular, wind loading is the dominant environmental loading for buildings and structures in Uruguay. Extra-tropical cyclones can produce extensive wind damage and sustain high winds speeds in large parts of the country over several hours; however, research carried out for specific sectors of the country showed that intense convective activity had been responsible for most of the wind damage and incidences reported in their cases. The analysis of 4 years of meteorological data from 25 automatic weather stations distributed across the country also showed the significance of intense convective activity in the extreme wind climate of Uruguay: the highest wind gusts, as well as the highest 10min mean wind speeds, presented distinctive non-synoptic and transient characteristics, and usually occurred under intense convection. On the other hand, the geographic behaviour of high winds found differed from the geographic distribution presented in the official national extreme wind map, established by the national code UNIT 50-84 Wind actions on structures: the highest wind gusts would not occur along the South Atlantic and Río de la Plata coastlines and along the border with Argentina. Instead, more high wind events with higher wind speeds would be registered toward the northwest of the country. In this area, wind gusts of 40m/s were measured several times at 10m height at fixed locations in open terrain in just 4 years. In addition, a clear seasonal trend was found in wind gust speeds as well as in 10min mean wind speeds, with the highest wind speeds mainly occurring from October to March, and especially in November and February, in accordance with the behaviour of severe convective activity in the region. It could also be verified that intense convective activity as well as synoptic high wind events generate their highest wind speeds mainly from the southwest quadrant. A similar seasonal trend was found in the 10min mean wind speeds annual maxima measured along 35 years at the official meteorological station at Carrasco airport in Montevideo, capital city of Uruguay, implying that convective activity, apart from producing the highest wind gusts across all the country, would also dominate the maxima 10min mean wind speeds measured at 10m height for longer return periods. In addition, it could be observed that the extreme value distribution of 10min mean wind speeds annual maxima for Montevideo may be adequately modelled by a Gumbel distribution, while the UNIT 50-84 wind code proposes a Frechet distribution for wind gust speeds extreme statistics. The characteristics of non-synoptic high wind events, generally related to the occurrence of intense convective activity, should be considered in national and regional wind codes. In particular, extreme wind maps should be directly based in measurements of wind gust speeds, as there is not a direct relation between mean and wind gust speeds during severe convection. For these studies, the wind gust averaging period, the time response of the wind measuring system, as well as the quality of the wind data should be considered and carefully analysed. In order to recommend adequate models for the flow structure of strong convective outflows for national and regional wind codes, calculations, and physical and numerical simulations, additional research and full-scale measurements would be needed. Besides the international recognition of the necessity of more full-scale measurements, these models may need to consider regional characteristics. Other aspects of the Uruguayan wind code for actions on structures are also discussed, and the necessity of their review and update is emphasised. |
|---|