Iberian summer precipitation modes of variability and extreme events

Ponencia presentada en: VI Congreso Internacional de la Asociación Española de Climatología celebrado en Tarragona del 8 al 11 de octubre de 2008

Assessment of the Record-Breaking 2020 Rainfall in Guinea-Bissau and Impacts of Associated Floods

The impacts of Climate Change are quite visible in Guinea-Bissau. Greater irregularity at the beginning and end of the rainy season, as well as in relation to the interannual variability of precipitation, are evidence that shows these phenomena in West African countries and particularly in Guinea-Bissau, where the agriculture is rain-fed. The year 2020 was characterized as very rainy in comparison to the climatological average of 1981–2020, with positive anomalies throughout the country, despite the late arrival of the wet season, which usually occurs in May. July, August, and September 2020 were the rainiest months, registering above a normal frequency of days with precipitation greater than 50 mm. Bissau, the capital, registered a record-breaking annual rainfall and monthly amounts higher than the 90th and 95th percentiles in July and August, respectively. This heavy rain accompanied by strong winds caused flooding in several urban areas and agricultural fields, and the destruction of roads, houses, and infrastructures in different cities across the country. As a way of mitigating these impacts, the government, through the Ministry of Solidarity, made available 100 million CFA francs (6.5 million euros) to help families that were victims of the floods.info:eu-repo/semantics/publishedVersio

Assessing heatwaves and their association with North African dust intrusions in the Algarve (Portugal)

Heatwaves are an extreme meteorological event in which affected populations may also be exposed to deteriorated air quality conditions due to the increase in air pollutant concentrations, such as PM10 (particulate matter < 10 µg/m3). In order to identify heatwaves (1973–2019) in the region of Faro (Algarve) during the hot season (April–September), the Excess Heat Factor (EHF) index was applied. The Mann–Kendall test revealed an upward trend in three heatwave metrics in Faro, and the trend of accumulated heat load (EHF load) was also positive as would be expected, but its signal was not statistically significant. An inventory of North African dust events (2006–2019) was made, and their simultaneous occurrence with heatwaves was assessed, pointing to only 20% of dust events of the Sahara occurring simultaneously with heatwave days. A cluster analysis was conducted on daily geopotential height fields at 850 hPa level over the 2006–2019 period, and four distinct patterns were identified as the most prominent synoptic circulations promoting both heatwave conditions and North African dust over the Algarveinfo:eu-repo/semantics/publishedVersio

Wind Risk Assessment in Urban Environments: The Case of Falling Trees During Windstorm Events in Lisbon

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 occurrences of fallen trees were selected. It was found that in summer, northerly winds are responsible for 11% of tree falls, with winds from other directions (west, southwest and south) responsible for 5%. From autumn to spring, perturbed weather conditions originating from the west, southwest and south are responsible for 84% of fallen trees. The majority of tree falls occurred when wind speed surpassed 7 m/s in the six hours prior to their fall. Some recommendations to the Civil Protection Agency and the Fire Department are presented to improve the mission of collecting information. This research is a contribution to the assessment of wind risk in Lisbon

Wind risk assessment in urban environments: the case of falling trees during windstorm events in Lisbon

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 occurrences of fallen trees were selected. It was found that in summer, northerly winds are responsible for 11% of tree falls, with winds from other directions (west, southwest and south) responsible for 5%. From autumn to spring, perturbed weather conditions originating from the west, southwest and south are responsible for 84% of fallen trees. The majority of tree falls occurred when wind speed surpassed 7 m/s in the six hours prior to their fall. Some recommendations to the Civil Protection Agency and the Fire Department are presented to improve the mission of collecting information. This research is a contribution to the assessment of wind risk in Lisbon

Heavy rainfall events and mass movements in the Funchal area (Madeira, Portugal): spatial analysis and susceptibility assessment

The article presents new information on the spatial distribution of intense rainfall and a new map of susceptibility to the formation of mass movements in the mountainous streams of the municipality of Funchal, the capital of the Autonomous Region of Madeira, an archipelago of Portugal. The methodology that was adopted is based on the spatial analysis of weighted overlap of variables, with influence in the occurrence of hydro-geomorphological processes that are at the origin of catastrophic events, marked by the mobilization of solid material towards and along the fluvial channels. Intense precipitations are effectively the main triggering factor of mass movements, which is why their statistical characteristics and local contrasts are analyzed, to integrate this layer of information into the new susceptibility assessment model of mass movements produced in this article. This type of spatialized information is of strategic importance to support the planning of urban expansion, which requires a land use management practice in accordance with the existing risk in the Madeira Island.info:eu-repo/semantics/publishedVersio

Regionalization and susceptibility assessment to daily precipitation extremes in mainland Portugal

The present study aims to identify regions of extreme precipitation in mainland Portugal and to create a single index of extreme precipitation susceptibility (EPSI). For this purpose, twelve extreme precipitation indices were selected from the Expert Team on Climate Change Detection and Indices between 1950 and 2003. By considering only six extreme precipitation indices: R 1day, R 5day, SDII, R20, CWD and R95PTOT for the 10-year return period, between 1950 and 2003, the EPSI was developed to both annual data and meteorological season. The regionalization of extreme precipitation in Portugal were determined using a principal component analysis in T-mode. The results, show three spatial regions obtained from PCA. The three regions were analyzed separate. In the annual EPSI, the highest susceptibility areas are the mountainous regions in northern (e.g. Geres, Peneda, Alv ^ ~ ao, Marao and Montesinho) and central ~ Portugal (e.g. Serra da Estrela), as well as in the Algarve (southern Portugal). Conversely, the lower susceptibility classes are in municipalities of the northeast, Alentejo and along the central-western coast. The results of EPSI show similar results in autumn and winter. In spring, however, the high susceptibility class increases in the Lisbon region and in the Sado Basin. In summer, there is an increase in susceptibility in the northeast, while susceptibility is low over much of Alentejo and Algarve, where precipitation is neglectful. This work presents a first attempt to implement this type of index for mainland Portugal. The first results are very promising, showing a consistent representation of the overall spatial distribution of extreme precipitation susceptibility. The combination of this information by municipalities can be of foremost relevance to civil protection and risk management.info:eu-repo/semantics/publishedVersio

Local weather types by thermal periods: deepening the Knowledge about Lisbon’s Urban Climate

Urbanized hot spots incorporate a great diversity of microclimates dependent, among other factors, on local meteorological conditions. Until today, detailed analysis of the combination of climatic variables at local scale are very scarce in urban areas. Thus, there is an urgent need to produce a LocalWeather Type (LWT) classification that allows to exhaustively distinguish di erent urban thermal patterns. In this study, hourly data from air temperature, wind speed and direction, accumulated precipitation, cloud cover and specific humidity (2009–2018) were integrated in a cluster analysis (K-means) in order to produce a LWT classification for Lisbon’s urban area. This dataset was divided by daytime and nighttime and thermal periods, which were generated considering the annual cycle of air temperatures. Therefore, eight LWT sets were generated. Results show that N and NW LWT are quite frequent throughout the year, with a moderate speed (daily average of 4–6 m/s). In contrast, the frequency of rainy LWT is considerably lower, especially in summer (below 10%). Moreover, during this season the moisture content of the air masses is higher, particularly at night. This methodology will allow deepening the knowledge about the multiple Urban Heat Island (UHI) patterns in Lisbon.info:eu-repo/semantics/publishedVersio

INOVAÇÃO E EXCELÊNCIA NA GEOGRAFIA: JOVENS INVESTIGADORES NAS CIÊNCIAS GEOGRÁFICAS E DO TERRITÓRIO.

A edição do presente número da Finisterra, o 124, assinala dois factos importantes que justificam este editorial. O primeiro facto prende-se com a necessidade de renovação da Finisterra no atual contexto da atividade editorial das revistas científicas; o segundo motivo é de natureza celebrativa, pela associação da revista às comemorações dos 80 anos do Centro de Estudos Geográficos, através do lançamento de uma chamada especial de artigos, intitulada “Inovação e Excelência na geografia: jovens investigadores nas ciências geográficas e do território”, iniciativa que agora se concretiza com a publicação dos documentos selecionados. Os dois factos relevantes que motivam esta nota de abertura suscitam os comentários e reflexões que se partilham em seguida.info:eu-repo/semantics/publishedVersio