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In the same lightning flash, whose usual duration is less than a second, there can be multiple negative cloud-to-ground strokes with different terminations or following a preexisting channel to the ground. In contrast, it is not common to have multiple positive cloud-to-ground (+CG) strokes, and especially multi-stroke +CG flashes sharing the same channel to ground are very rarely observed. This polarity asymmetry is not well understood and many aspects are debated. In this letter, we present for the first time a very high frequency (VHF) radio band observation of a multi-stroke +CG flash along the same channel, observed simultaneously by a VHF broadband interferometer and a Lightning Mapping Array in north-central Colombia. These combined observations have unprecedented temporal and spatial resolution and allowed us to observe in detail the development of the flash and especially to understand the initiation mechanism of the subsequent positive stroke.

Gigantic jets are electric discharges that on rare occasions can be seen at night shooting out of the top of tropical thunderclouds, reaching the ionosphere (90 km). Using sensitive camera systems and detection software, we recorded 70 events over northern Colombia and adjacent seas, most of them captured between 2016 and 2022. This is the first study to compare the meteorological background conditions for thunderstorms that produced gigantic jets in 48 nights against 83 reference cases with monitored thunderstorms that did not produce jets, using vertical profiles from ERA5 reanalysis near the event location. From the vertical profiles, various meteorological parameters are calculated, grouped by metrics of the low level convective parcel, instability, humidity, warm cloud and mixed phase parameters, and vertical wind shear, not limited to default levels. We report statistically significant differences and effect sizes (Cohen's d) for gigantic jet producing environments compared to null environments. Gigantic jets are produced in conditions with reduced low level temperatures in combination with warmer mid levels. This causes a lower cloud base and higher -10 °C isotherm altitude, thus a greater warm cloud depth, as well as reduced updraft and downdraft buoyancy. Over northern Colombia the non-GJ producing storms tend to grow in an environment that supports more vigorous, multicellular convection by enhanced low-level storm-relative winds and stronger downdrafts. Over western Colombia, the non-GJ cases tend to have a lower equilibrium level while having favorable warm cloud parameters. No evidence is found for hypotheses that upper level vertical wind shear enables gigantic jet production, nor are overshooting tops larger. The findings can be used for forecasting gigantic jets and their climatologically optimal regions on Earth. We speculate that the environmental conditions shift the droplet size distribution towards larger drops at the cost of cloud droplets, with enhanced droplet shattering ice multiplication processes as they freeze. Depending on convective evolution, low rime accretion rates could briefly expand the negative charge region downward by inverse polarity charging while the upper positive charge concentration may weaken at the same time, which could lead to a temporary negatively imbalanced electric potential distribution in the cloud needed for gigantic jet emission.

La tempesta Glòria va ser una borrasca extra-tropical que es va intensificar durant diversos dies sobre el mar Mediterrani occidental, aportant pluges i nevades intenses, vents forts i valors record de l'onatge en àrees de al sud d'Europa i nord d'Àfrica. Aquest treball de fi de grau busca avaluar de manera quantitativa els efectes de la tempesta sobre el litoral de la Mediterrània occidental. Es desenvolupen uns índexs numèrics on s'analitzen valoracions físiques, mediambientals i socials per a l'avaluació de l'impacte del temporal. La tormenta Gloria fue una borrasca extra-tropical que se intensificó durante varios días sobre el Mar Mediterráneo occidental, aportando lluvias y nevadas intensas, vientos fuertes y valores record del oleaje en áreas del sur de Europa y norte de África. Este trabajo de fin de grado busca evaluar de manera cuantitativa los efectos de la tormenta sobre el litoral del mediterráneo occidental. Se desarrolan unos índices numéricos donde se analizan valoraciones físicas, mediambientales y sociales para la evaluación del impacto del temporal. Storm Gloria was an extra-tropical storm that intensified over several days over the western Mediterranean Sea, bringing heavy rain and snow, strong winds and record wave values ​​in areas of southern Europe and North Africa. This end-of-degree project seeks to quantitatively evaluate the effects of the storm on the western Mediterranean coast. Numerical indexes are developed where physical, environmental and social evaluations are analyzed for the evaluation of the impact of the storm.

El 20 de enero de 2020, el temporal Gloria provoca el fallo del tramo final de la pasarela que lo unía a la plataforma del pantalán del Pont del Petroli con la playa de Badalona (España). La presente tesis se centra en la recopilación y análisis de datos relacionados con la acción de olas extremas y cargas experimentales relacionadas. Las pruebas de modelos físicos a escala 1:10 se llevaron a cabo en la instalación de canal CIEM de la Universitat Politècnica de Catalunya. Se ha evaluado hasta qué punto estos resultados experimentales concuerdan con las formulaciones existentes propuestas en la literatura. Finalmente, se ha realizado una comparación visual entre el modelado experimental y la poca información de los impactos observados durante la tormenta Gloria. On January 20, 2020, the storm Gloria causes the collapse of the final part of the walkway that connected it to the extremal platform of the Pont del Petroli pier to the beach of Badalona (Spain). The present thesis focuses on the collection and analysis of data relation to the action of extreme waves and experimental related loads. Physical model tests at 1:10 model scale were carried out in the wave flume facility CIEM at Universitat Politècnica de Catalunya. It has been evaluated how much these experimental results agree with the existing formulations proposed in the literature. Finally, a visual comparison between the experimental modelling and the few information of the impacts observed during the Gloria storm has been carried out. Incoming

The north-west (NW) Mediterranean coastal zone is a populous and well-developed area in which the impact of natural hazards like flash floods and coastal storms can result in frequent and significant damages. Although the occurrence and impacts of such hazards have been widely covered, few studies have considered their combined impact on the region, which would result in more damage. Within this context, this study analyses the occurrence and characteristics of compound extreme events of heavy rainfall episodes (as a proxy for flash floods) and coastal storms (using the maximum significant wave height) along the Catalan coast as a paradigm of the NW Mediterranean. Two different types of events are considered: multivariate, in which the two hazards occur at the same location, and spatially compounding, in which they occur within the same limited time window, and their impacts accumulate at distinct and separate locations. The analysis is regionally performed along a coastline extension of about 600¿km by considering seven coastal sectors and their corresponding river catchment basins. Once the compound events are analysed, the synoptic atmospheric pressure fields are analysed to determine the prevailing weather conditions that generated them. Finally, a Bayesian network is used to fully characterize these events over the territory. The obtained results show that the NW Mediterranean, represented by the Catalan coast, has a high probability of experiencing compound extreme events. Despite the relatively small size of the study area, there are significant variations in the event characteristics along the territory, with the most frequent type being spatially compound, except in the northernmost sectors where multivariate events dominate. These northern sectors also present the highest correlation in the intensity of both hazards. Three representative synoptic situations have been identified as dominant for the occurrence of these events, with different relative importance levels of the compounding drivers (rainfall and waves) and different distributions of impacts across coastal basins. Overall, results obtained from specific events indicated that heavy rainfall is related to the most significant impacts despite having a larger spatial reach. This work has been done in the framework of the M-CostAdapt (CTM2017-83655-C2-1&2-R) research project, funded by the Spanish Ministry of Economy and Competitiveness (MINECO/AEI/FEDER, UE). The authors express their gratitude to IH-Cantabria and Puertos del Estado for supplying wave data, and AEMET and SMC for supplying rain data. Our thanks are given to Montserrat Llasat-Botija for her contribution in the identification of the compound events as well as for all the information about the impacts. Peer Reviewed Objectius de Desenvolupament Sostenible::13 - Acció per al Clima

Urban floods repeatedly threaten Barcelona, damaging the city infrastructure and endangering the safety of the population. The urban planning of the city, the socioeconomic distribution, its topography, and the characteristics of precipitation systems translate into these flood events having a heterogeneous effect across the city. It means that the coping capacity has a strong dependence on local factors that must be considered when management plans are developed by the municipality. This work aims to contribute to the better knowledge of precipitation structures associated with heavy rainfall events and floods in Barcelona based on radar data and an urban rain gauge network. Radar data have been provided by the Meteorological Service of Catalonia (SMC), while precipitation data, impact data, and early warnings, have been provided by Barcelona Cicle de l’Aigua S.A. (BCASA), for the period 2013–2018. A new radar-based methodology has been developed to identify convective rainfall structures from radar reflectivity volumes (CAPPI and TOP products) to make the analysis easier. The high computing speed of the procedure allows efficient analysis of a large set of convective cells without scarifying temporal resolution of radar data. Both rainfall fields (radar and rain gauge, respectively) have been compared. Then through the identified rainfall convective structures, thunderstorm hotspots have been identified. Considering an alert indicator from BCASA and the reported incidents, episodes with the highest impact have been analysed in depth. Results show 207 significant rainfall episodes in the ROI for the six years, which are mainly concentrated between September and November. The fact that significant episodes are usually produced by highly convective rain corroborates the advantage of using radar images as a tool to detect any maxima even when no rain gauge is there. In 64 of the episodes, the level of pre-alert was achieved with a maximum frequency between August and September. The proposed algorithm shows more than 8000 centroids of convective cells from 189 cases. Whilst maximum surface reflectivity over 45 dBZ is more prone to occur near the coastline, the centroids of storm cells tend to concentrate more inland. The final objective is to improve the actions taken by the organisation responsible for managing urban floods, which have seen Barcelona recognised as a model city for flood resilience by the United Nations.

[ES] El objetivo de este trabajo es justificar y diseñar un tanque de tormentas en la zona marítima de la ciudad de Gandía, una de las más afectadas del municipio por inundaciones periódicas. En primer lugar, se corrobora que las inundaciones son el fenómeno climático más habitual y devastador en todo el mundo. Seguidamente, se estudia el riesgo que tiene España y la Comunidad Valenciana de sufrir inundaciones. Además, se presenta el tanque de tormentas como una solución válida para gestionar el exceso de aguas pluviales. A continuación, se procede al análisis hidrológico e hidráulico del barrio de Venecia, en el Grau de Gandía, la zona escogida para emplazar el depósito. Para ello, se hace uso de la metodología propuesta por la Instrucción de Drenaje Superficial 5.2-IC, y de simulaciones con el programa SWMM, para obtener un punto de partida en el volumen del tanque. Posteriormente se diseña el depósito, siguiendo las indicaciones del Manual Nacional de Recomendaciones para el Diseño de Tanques de tormenta, documento elaborado por el Ministerio de Agricultura, Alimentación y Medio Ambiente. Con el fin de evacuar el agua retenida, se ha utilizado el software Epanet para modelar el sistema de bombeo, y el programa SAP2000 para dimensionar los elementos constructivos y realizar un análisis estructural, siguiendo las indicaciones del Documento Básico de Seguridad Estructural y Acciones en la Edificación. Por último, se han elaborado los planos del tanque con el programa Autodesk Inventor, y el presupuesto con el software Arquímedes. De este estudio se concluye que la ejecución real de un proyecto de estas características sería una solución viable para contrarrestar los efectos negativos de las inundaciones en esta zona., [CA] L'objectiu d'aquest treball és justificar i dissenyar un tanc de tempestes a la zona marítima de la ciutat de Gandia, una de les més afectades del municipi per inundacions periòdiques. En primer lloc, es corrobora que les inundacions són el fenomen climàtic més habitual i devastador a tot el món. Seguidament, s'estudia el risc que té Espanya i la Comunitat Valenciana de patir inundacions. A més, es presenta el tanc de tempestes com una solució vàlida per gestionar l'excés d'aigües pluvials. A continuació, es procedeix a l'anàlisi hidrològic i hidràulic del barri de Venècia, al Grau de Gandia, la zona escollida per emplaçar el dipòsit. Per a això, es fa ús de la metodologia proposada per la Instrucció de Drenatge Superficial 5.2-IC, i de simulacions amb el programa SWMM, per obtenir un punt de partida en el volum del tanc. Posteriorment es dissenya el dipòsit, seguint les indicacions del Manual Nacional de Recomanacions per al Disseny de Tancs de tempesta, document elaborat pel Ministeri d'Agricultura, Alimentació i Medi Ambient. Per tal d'evacuar l'aigua retinguda, s'ha utilitzat el programa Epanet per modelar el sistema de bombeig, i el programa SAP2000 per dimensionar els elements constructius i realitzar una anàlisi estructural, seguint les indicacions del Document Bàsic de Seguretat Estructural i Accions en l'Edificació. Finalment, s'han elaborat els plànols del tanc amb el programa Autodesk Inventor, i el pressupost amb el programa Arquímedes. D'aquest estudi es conclou que l'execució real d'un projecte d'aquestes característiques seria una solució viable per contrarestar els efectes negatius de les inundacions en aquesta zona., [EN] The aim of this thesis is to justify and design a storm tank in the maritime area of the city of Gandia, one of the most affected areas of the municipality by periodic flooding. Firstly, it is corroborated that floods are the most common and devastating climatic phenomenon in the world. Next, the risk of flooding in Spain and the Valencian Community is studied. Furthermore, the storm tank is presented as a valid solution for managing excess rainwater. Next, the hydrological and hydraulic analysis of the neighbourhood of Venecia, in the Grau de Gandia, the chosen area to locate the tank, is carried out. To do this, the methodology proposed by the Surface Drainage Instruction 5.2-IC is used, and some simulations with SWMM programme, to obtain a starting point for the volume of the tank. Subsequently, the tank is designed, following the indications of the National Manual of Recommendations for the Design of Storm Tanks, a document produced by the Ministry of Agriculture, Food and Environment. In order to evacuate the retained water, Epanet software is used to model the pumping system, and SAP2000 programme is used to dimension the construction elements and carry out a structural analysis, following the indications of the Basic Document on Structural Safety and Actions in Buildings. Finally, the tank plans were drawn up using Autodesk Inventor program, and the budget was prepared using Archimedes software. From this study it is concluded that the real execution of a project of these characteristics would be a viable solution to counteract the negative effects of flooding in this area.

The Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station (ISS) provides optical radiances and images of lightning flashes in several spectral bands. This work presents a lightning flash simultaneously observed from space by ASIM, the Geostationary Lightning Mapper (GLM) and the Lightning Imaging Sensor on the International Space Station (ISS-LIS); and from ground by the Colombia-Lightning Mapping Array (Colombia-LMA). Volumetric weather radar provides reflectivity data to help to interpret the effects of the cloud particles on the observed optical features. We found that surges in radiance in the band at 777.4 nm appear to be related mostly with lightning processes involving currents as well with branching of lightning leaders with new leader development. In cloud areas with reflectivity 7 km, these have been imaged by ASIM and GLM. But in the region with reflectivity

Els temporals són fenòmens climatològics contra els quals la humanitat hi ha estat lluitant des de sempre. Els efectes d’aquests poden ser molt variats dependent de diferents factors, tal com la direcció d’on provenen, la intensitat o la persistència amb la que actuen, és a dir, la durada. Tot i així, fins que no en succeeix un de ben intens no som realment conscients de les conseqüències que aquests poden provocar. El Gloria va deixar registres sorprenents que van deixar bocabadada a la població. No és el primer cop ni serà l´últim que un esdeveniment d’aquestes característiques impacta contra Catalunya, però no deixa de ser sorprenent la fragilitat de les infraestructures humanes i de l’entorn envers episodis d’aquesta mena. D’aquesta manera, aquest treball conté un anàlisi exhaustiu del temporal Gloria i les seves conseqüències, deixant al descobert els danys i l’empremta que va deixar. Sumant-li a més a més, un estudi en profunditat de la costa catalana i de la morfologia existent. Tractant diferents punts i analitzant diferents dades com els registres d’alçades d’ona significant, la durada o el període de retorn, seria possible caracteritzar aquesta mena d’esdeveniments i estudiar la seva probabilitat d’ocurrència, molt útil sobretot si es mira de cara al futur. En un món com l’actual que va canviant radicalment a una velocitat molt elevada, i que a més a més, es veu amenaçat per l’ombra del canvi climàtic, conèixer a fons i tractar amb temporals d’aquesta mena seria vital, sobretot a l’hora d’implementar millores a les estructures o preparar-se de manera adient per l’arribada de nous esdeveniments tan violents com aquest. Las tormentas son fenómenos climatológicos contra los cuales la humanidad ha estado luchando desde siempre. Los efectos que estos provocan pueden ser muy variados dependiendo de diferentes factores, como por ejemplo la dirección de donde provienen, la intensidad o la persistencia con la que actúan, es decir, la duración. Sin embargo, hasta que no ocurre uno muy intenso no somos realmente conscientes de las consecuencias que estos pueden provocar. El Gloria dejó unos registros sorprendentes que dejaron boquiabierta a la población. No es la primera vez ni será la ultima que un evento de estas características impacta contra Cataluña, pero no deja de ser sorprendente la fragilidad de las infraestructuras humanas y del entorno contra este tipo de episodios. De este modo, este trabajo contiene un análisis exhaustivo sobre el temporal Gloria y sus consecuencias, dejando al descubierto los daños y la huella que dejó. Sumándole, además, un estudio en profundidad de la costa catalana y de la morfología existente. Tratando diferentes puntos y analizando diferentes datos como los registros de altura de ola, la duración o el período de retorno, sería posible caracterizar este tipo de eventos y estudiar su probabilidad de ocurrencia, muy útil principalmente si se mira de cara al futuro. En un mundo como el actual que cambia radicalmente a una velocidad muy elevada, y que, además, se ve amenazado por la sombra del cambio climático, conocer a fondo y tratar con tormentas de este tipo sería vital, principalmente a la hora de implementar mejoras en las estructuras o preparase de manera adecuada para la llegada de nuevos eventos tan violentos como este. Storm are climatological phenomena that mankind has always been fighting against. The effect of these can be very varied depending on different factors, such as the direction where they come from, the intensity or the persistence, in other word, the duration of the event. However, we are not aware of the consequences they can cause until a very intense one occurs. The Gloria registered surprising records that took by surprise all the population. It was not the first time and it won’t be the last, that an event with such characteristics occurs in Catalonia, but the fragility of the human infrastructures and the environment towards phenomena of this kind is still surprising. In this way, this project covers a thorough analysis of the Gloria and its consequences, exposing all the damages and the footprint it left. Adding to this, also a study in depth of the Catalan coast and the existing morphology. By dealing with different data such as the wave height records, the duration or the return period it would be possible to characterize this type of events and study its occurrence probability. In a world that is currently changing radically fast and it’s also being menaced by the climate change, it would be vital to know all about these storms and how to deal with them, especially when refurbishing or implementing improvement to structures or preparing to properly affront these violent events in the future.

In March 2020 a convective storm erupted at planetographic latitude 76°N in the southern flank of Saturn’s long-lived hexagonal wave. The storm reached a zonal size of 4,500 km and developed a tail extending zonally 33,000 km. Two new short-lived storms erupted in May in the hexagon edge. These storms formed after the convective storms that took place in 2018 in nearby latitudes. There were no noticeable changes in the zonal profile of Saturn's polar winds in 2018-2020. Measurements of the longitude position of the vertices of the hexagon throughout this period yield a value for its period of rotation equal to that of System III of radio-rotation measured at the time of Voyagers. We report changes in the hexagon clouds related to the activity of the storms. Our study reinforces the idea that Saturn’s hexagon is a well rooted structure with a possible direct relationship with the bulk rotation of the planet. This work has been supported by the Spanish project AYA2015-65041-P and PID2019-109467GB444 I00 (MINECO/FEDER, UE) and Grupos Gobierno Vasco IT1366-19. EGM is Serra Hunter Fellow atUPC. This work has used data acquired from the NASA/ESA HST Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These HST observations are associated with program GO/DD 15262. EGM, MS, KAV and ASL thankfully acknowledge the computer resources at Mare Nostrum and the technical support provided by Barcelona Supercomputing Center (AECT-2019-2-0006). We thank all the observers who have contributed with their images to the monitoring of the atmospheric activity on Saturn during the years 2019 and 2020 and whose list and images can be found in the ALPO452 Japan and PVOL databases. Part of the amateur observations analyzed were obtained through a collaboration with Europlanet 2024 RI. Europlanet 2024 RI has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 871149.

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2021, Tutora: Maria del Carmen Llasat, The aim of this article is to study the phenomena associated with strong wind and compound events where this hazard intervenes in the region of North Girona. Of the two blocks in which this work is divided, the first one focuses on the synthesis of the literature about the most common winds in L'Empordà, floods and compound events. The second one focuses on the analysis of the situations that have affected the area based on rainfall (1950-2015), wind (1997-2018) and coastal storm (1973-2013) data provided by the M-CostAdapt project. The compound events that have been taken into account are the combination of two or three of these hazards. In total, 116 compound events took place between 1997 and 2013, mainly in September and October. The most common type was composed by heavy rain and Tramuntana wind, with a maximum wind gust between 45 and 75 Km/h. One of the strongest storms that affected Catalonia in recent years, storm Gloria, has also been analyzed

A Thesis for applying for the degree of Doctor of Philosophy in Environmental Sciences and Applied Biology. Väitekiri filosoofiadoktori kraadi taotlemiseks rakendusbioloogia erialal. Phytoplankton reflects changes in the environment and plays a vital role in biogeochemical cycles and the climate system. The thesis attempts to link the phytoplankton dynamics with the timing, intensity, and duration of the local forcing factors at different time scales. We highlight the influence of two extremes of the wind gradient – storms and atmospheric stilling, on lake environments and phytoplankton dynamics over short and long periods, several aspects of which are poorly understood. Until recently, atmospheric stilling as a climatic phenomenon has been largely overlooked in lakes studies. To fill this research gap, we focussed on a large shallow polymictic lake (Võrtsjärv, Estonia), that was affected by a 30% decrease in average wind speed since 1996, and for which a long-term (54 years) phytoplankton and hydrometeorological database was available. Further, a contradiction between the continuous decrease in the lake’s nutrient loading and an increasing trend in phytoplankton biomass emerged as a topic of interest for this thesis. We summarise how storms interact with and alter the dynamic of phytoplankton communities. Further, we highlight to what extent this impact can change the ecological processes (e.g., nutrient, carbon, and energy cycling) within lakes and their environmental conditions in the short and long term. Using Nonmetric Multidimensional Scaling ordination of phytoplankton community composition for the years 1964–2017, we revealed three distinct periods with breaking points coinciding with abrupt changes in the wind and/or water level. We introduced a concept of "light niche," a newly discovered mechanism of meteorological control over phytoplankton in light-limited shallow lakes. Combining the monthly phytoplankton data with daily data on hydrometeorological forcing factors — thermal, light, wind, and water-level regimes and using variance partitioning with linear mixed effect modelling (LME), we found that (i) the external forcing factors relevant for each phytoplankton variable could be individualised by having a similar variance partitioning among time scales as the particular phytoplankton variable; (ii) with the largest seasonal variation component, the dominant shade-tolerant filamentous cyanobacteria were most affected by seasonal factors such as solar irradiance and water level; (iii) the LME was proven appropriate for resolving the temporal cross-scale issues. Hüdrometeoroloogiliste ja kliimategurite mõju järvede fütoplanktonile: ajaskaalade olulisus Fütoplankton peegeldab muutusi keskkonnas ja mängib olulist rolli biogeokeemilises aineringes ning kliimasüsteemis. Doktoritöö uurib seoseid fütoplanktoni dünaamika ning erinevates ajaskaalades (päevane, sesoonne, aastatevaheline) toimivate tegurite ajastuse, intensiivsuse ja kestusega. Töös tuuakse esile kahe vastandliku tuulte olukorra – tormide ja tuulevaikuse mõju järvekeskkonnale ja fütoplanktoni dünaamikale, mille mitmed aspektid on seni vähe uuritud. Kuni viimase ajani on järveuuringutes suuresti tähelepanuta jäänud tuulte nõrgenemise kui kliimanähtuse mõju. Selle uurimislünga täitmiseks keskendusime suurele madalale polümiktilisele Võrtsjärvele, mida mõjutavate tuulte keskmine kiirus on alates 1996. aastast vähenenud 30% ning mille kohta on olemas pikaajaline (54 aastat) fütoplanktoni ja hüdrometeoroloogia andmebaas. Tuulte mõju uurimine võimaldas selgitada ka näilist vastuolu järve toiteainete hulga pideva vähenemise ja fütoplanktoni biomassi kasvutrendi vahel. Töö esimene osa võtab kokku teadmised tormide mõju kohta järvede fütoplanktonikoosluste dünaamikale. Tuuakse välja, kuidas tormid mõjutavad ökoloogilisi protsesse järvedes (nt toiteainete kättesaadavust, süsiniku- ja energiaringet) ning nende kaudu fütoplanktoni elutingimusi lühi- ja pikaajalises lõikes. Aastate 1964–2017 Võrtsjärve fütoplanktonikoosluse mitmemõõtmeline analüüs eristas koosluse muutustes kolm perioodi, mille murdepunktid langesid kokku tuule ja/või veetaseme järskude muutustega. Nende seoste põhjal sõnastati nn "valgusniši" kontseptsioon, mis kirjeldab varem tundmatut fütoplanktoni meteoroloogilise kontrolli mehhanismi häguse veega madalates järvedes. Kasutades enam kui poole sajandi vältel kogutud igakuiseid fütoplanktoni andmeid ja kombineerides neid igapäevaste andmetega hüdrometeoroloogiliste tegurite (temperatuur, valgus, tuul ja veetase) kohta uuriti lineaarsete segamudelite abil muutlikkuse jaotumise erinevate ajaskaalade vahel. Leiti, et fütoplanktoni erinevate rühmade jaoks olulisi välistegureid saab kindlaks teha selle järgi, et vastava rühma ja seda mõjutavate tegurite muutlikkus jaotub erinevate ajaskaalade vahel sarnastes proportsioonides. Nii mõjutasid suurima sesoonse muutlikkuse komponendiga tsüanobaktereid enim sesoonsed tegurid, flagellaatide puhul, sarnaselt tuulega, ulatus aga juhusliku ja lühiajalise varieeruvuse komponent 80%-ni. Kokkuvõttes osutusid lineaarsed segamudelid sobivaks tööriistaks erinevates ajaskaalades toimivate tegurite mõju uurimiseks. Publication of this thesis is supported by the Estonian University of Life Sciences.

Convective activity in Catalonia (northeastern Spain) mainly occurs during summer and autumn, with severe weather occurring 33 days per year on average. In some cases, the storms have unexpected propagation characteristics, likely due to a combination of the complex topography and the thunderstorms’ propagation mechanisms. Partly due to the local nature of the events, numerical weather prediction models are not able to accurately nowcast the complex mesoscale mechanisms (i.e., local influence of topography). This directly impacts the retrieved position and motion of the storms, and consequently, the likely associated storm severity. Although a successful warning system based on lightning and radar observations has been developed, there remains a lack of knowledge of storm dynamics that could lead to forecast improvements. The present study explores the capabilities of the radar network at the Meteorological Service of Catalonia to retrieve dual-Doppler wind fields to study the dynamics of Catalan thunderstorms. A severe thunderstorm that splits and a tornado-producing supercell that is channeled through a valley are used to demonstrate the capabilities of an advanced open source technique that retrieves dynamical variables from C-band operational radars in complex terrain. For the first time in the Iberian Peninsula, complete 3D storm-relative winds are obtained, providing information about the internal dynamics of the storms. This aids in the analyses of the interaction between different storm cells within a system and/or the interaction of the cells with the local topography.

Coastal risk assessments rely on proper quantification of storm-induced erosion and flooding, and often involve calculations via numerical models. When the real time-series data of a storm are not available as forcing conditions and only bulk information is accessible, synthetic simplified time-evolutions are assumed. The most common approach in coastal studies uses a symmetric triangular storm shape, characterised by the assumptions that the peak of the waves occurs in the middle of the storm, and that the forcing varies linearly. This study aims to investigate this additional source of uncertainty in hazard estimation, using the XBeach-1D model, to assess the differences in simulated erosion and flooding associated with real and synthetic storm definitions. Analysis is performed for real conditions ranging from moderate to extreme at the Northern Adriatic and North-Western Mediterranean coasts, using beach profiles ranging from dissipative to reflective. The storm definitions generate considerable differences in terms of wave power and timing at the peak of the storm. When synthetic storms were applied, coastal hazards were not adequately reproduced in most of the simulated cases. The energy of the storms, profile characteristics, local storm climates, and water levels did not consistently influence the differences between the synthetic- and reality-based outputs. The work of E. Duo was supported by a PhD grant at the Department of Physics and Earth Science of the University of Ferrara, additional funding from the contribution “5 per mille assegnato all’Università di Ferrara - dichiarazione dei redditi dell'anno 2013” assigned through the “Bando Giovani Ricercatori 2016″ of the University of Ferrara, and the EU H2020 ANYWHERE project (GA 700099; www.anywhere-h2020.eu). The work of M. Sanuy and J.A. Jiménez has been done in the framework of the M-CostAdapt (CTM2017-83655-C2-1-R) research project (MINECO/AEI/FEDER, UE). Marc Sanuy was supported by a PhD grant from the Spanish Ministry of Education, Culture and Sport.

Treball d'investigació/Fi de màster. Tutor: Dr. Dídac Pujol. Aquest treball consisteix en una traducció de l’anglès al català del relat “An Honest Woman”, de l’autora nord-americana contemporània Ottessa Moshfegh. Aquesta traducció va dirigida al mateix tipus de destinatari que el text original, és a dir, un públic general adult. Els objectius del treball són: 1) oferir una traducció tan adequada al text original com sigui possible; 2) que el text català tingui el mateix efecte en el lector que el text original; 3) fer un comentari de la traducció, valorant l’adequació de les tècniques de traducció utilitzades per resoldre alguns dels principals obstacles amb què m’he trobat a l’hora de traduir: la cursiva, el gerundi, el vocabulari relacionat amb tempestes i l’ús del guió en els diàlegs. This paper consists of a translation from English into Catalan of the short story “An Honest Woman”, by Ottessa Moshfegh, a contemporary American writer. This translation is directed at the same audience as the source text, a general adult public. The aims of this project are: 1) to present a translation as adequate to the source text as possible; 2) to create the same effects on the target text reader as the original; 3) to write a translation commentary, taking into account the translation strategies used to solve the main translation problems I encountered when translating the source text: italics, gerunds, vocabulary related to thunderstorms, and the use of dashes in dialogue.

Synergistic remote sensing of the atmosphere, combined with adaptive techniques, offers unprecedented opportunities to characterise the evolution of key atmospheric features such as the Atmospheric Boundary Layer (ABL). Using long-duration, high-resolution, profiling observations from active and passive ground-based remote sensing systems during the Verification of the Origins of Rotation in Tornadoes Experiment{Southeast (VORTEX-SE) 2017 field campaign, an attempt is made to characterise ABL development over distinct regions that are well known for their relatively high tornado frequency. In this study, observing systems include an S-band radar, Vaisala CL-31 ceilometer, Doppler Wind lidar (DWL) and radiometric observations from the Collaborative Lower Atmosphere Mobile Profiling System (CLAMPS). In this work, ABL height (ABLH) tracking over the diurnal cycle, and - up to a point - its disambiguation over selected non-precipitating case examples, are attempted. Different observational sets are used, namely, radar reflectivity observations assimilated into a Kalman filter, DWL profiles of the vertical velocity, and virtual potential temperature profiles, as well as radiosoundings and cloudbase reference information collected during Intensive Observation Periods (IOP) carried out in VORTEX-SE, Alabama during 2017. Limitations and advantages of each system are discussed. This work was supported by NOAA grants NA1501R4590232 and NA16OAR4590209, and by the Purdue University Dept. of Earth, Atmospheric, and Planetary Sciences (EAPS). CommSensLab-UPC (Excellence UnitMDM-2016-0600 funded by the Agencia Estatal de Investigación, Spain) collaborated via Spanish Gov.– EURegional Development Funds, ARS project PGC2018-094132-B-I00 and ACTRIS-PPP project GA-739530. The Spanish National Science Foundation (Ministerio de Ciencia, Innovación y Universidades) funded doctoral grant PRE2018-086054 hold by M.P. Araujo da Silva.

Sol·licitant de l'informe: Barcelona Cicle de l'Aigua, S.A.

Africa is one of the most productive lightning regions on Earth, yet it has a lower TGF-to-lightning ratio especially compared with Central America. In this paper we have analyzed the global distribution of different meteorological parameters in order to explain the TGF/lightning ratio asymmetry. We show here that a drier surface and larger CAPE in Africa may produce thunderstorms with intense electric charge regions but elevated in the atmosphere and closer to each other, which allows for higher flash rates and less energetic, shorter and smaller flashes. The results we present here suggest that continental thunderstorms in Africa more rarely fulfill the lightning and thundercloud requirements for TGF production inferred from observations and models.

Charge structure derived from lightning leader development of tropical thunderstorms comprising equatorial latitudes of < ±10° has not been investigated yet. In this work, using a Lightning Mapping Array (LMA) installed in northern Colombia, the charge structure, lightning leader initiations and the cloud-to-ground strokes rates of two thunderstorms have been analyzed. Additionally, radar information is also included. The identification of the charge regions has been obtained by analyzing the propagation of lightning leader developments. Flashes initiate between 4 and 15 km altitude. High initiation rates are different in the two storms. In one case the high rates are found between 8 and 13 km. In the other these are found between 10 and 15 km. The storms show typical tripolar structure where the upper positive charge is present at 10 to ~15 km, the mid-level negative charge is found between 6 and 9 km and the lower positive charge between 4 and 6 km altitude. Intracloud lightning flashes with inverted polarity have been identified for short period. In other periods, screening layer flashes have been detected at 14-15 km. The overall results show that the charge structures in the two Colombian storms are similar to the ones reported in North-Central Florida, but with a significant difference being the more than 2 km higher initiation altitude in Colombia. The vertical configuration of the charge regions and the leader development of these thunderstorms might help to explain the occurrence of Terrestrial Gamma-ray Flashes in tropical thunderstorms

Sol·licitant de l’informe: Gerència de Medi Ambient i Serveis Urbans

Treballs Finals de Grau en Geografia, Facultat de Geografia i Història, Universitat de Barcelona, Curs: 2018-2019, Tutor: Mª Carmen Moreno, El objetivo fundamental de este trabajo es el de establecer la validez de los datos de detección de descargas eléctricas atmosféricas totales (nube/nube y nube/tierra) como fuente fiable de información geofísica Un objetivo secundario será el de establecer la potencial utilización de dicha fuente de información geofísica para la prospección de depósitos subterráneos de agua en regiones áridas y semiáridas. Como hipótesis principal de trabajo se plantea que la recurrencia de las descargas eléctricas sobre una determinada zona geográfica pueda estar relacionada con la estructura geológica del subsuelo.

Meteorological conditions and thunderstorm characteristics related to lightning threats to wind turbines are discussed in this paper. Due to the rotating blades, wind turbines may be regarded peculiar tall objects, more susceptible to lightning strikes than other tall man-made structures. In the present study, Lightning Mapping Array and weather radar observations allowed to draw a clear picture of the thunderstorm characteristics leading to lightning strokes to wind turbines, in a coastal area of the Mediterranean basin. Results showed that lightning threats to wind turbines tend to occur during transitional periods (spring and autumn), although the main thunderstorm activity concentrates in the warm summer months. Thunderstorms with downward strokes to wind turbines presented particular features, like a limited vertical development and a dominant lower positive charge layer. Downward cloud-to-ground strokes hitting wind turbines were mainly of negative polarity and with peak currents above the average. On the other hand, conditions for self-initiated upwards from wind turbines resemble those reported in Japan and the U.S winter thunderstorms, with low-cloud based large electrified stratiform regions. These particular conditions, leading to lightning threats to wind turbines, should be properly included in lightning protection standards.

Aquest article recull el balanç meteorològic del 2017 a l’Alt Empordà, i així es manté la sèrie de resums meteorològics que aquesta revista Annals va iniciar l’any 2014, amb l’objectiu de crear un registre històric de dades i informació meteorològica que amb el pas del temps prendrà un valor climàtic més gran i permetrà conèixer millor l’evolució del clima a la comarca en les darreres dècades. Podrà esdevenir una bona eina analítica per desenvolupar estudis de la comarca dins del context del canvi climàtic. L’article conté un resum meteorològic que té l’objectiu d’explicar i il·lustrar, demanera especialment gràfica, el comportament de lameteorologia el 2017,mostrant tant les dades mitjanes com els valors extrems de temperatura, precipitació i vent a la comarca. Es fa un repàs de les situacions meteorològiques que han presentat més interès atmosfèric, i es mostren les diferències espacials que s’han produït en el territori en el repartiment de les quantitats de pluja i dels valors de temperatura tant mitjans comextrems. Globalment, el 2017 s’ha presentat a la comarca molt càlid i sec, certificant la clara tendència dels darrers anys en les anomalies de la pluja i de la temperatura. La tramuntana va tenir una presència important, sobretot a la tardor i a principis de l’hivern., This article presents a meteorological balance of 2017 in Alt Empordà, and thereby continues the series of meteorological summaries that this journal started in 2014, with the aim of creating a historical record of data and weather information which, in time, will obtain important climatic value and allow us to understand the evolution of climate in the region throughout the last decades. It can become a vital tool for local studies on climate change. This meteorological summary aims to explain and illustrate through graphics the behaviour of meteorology in our region throughout 2017, showing both average data and the extreme values of temperature, precipitation and wind. Meteorological situations of most atmospheric interest are reviewed and as well as spacial differences within the territory of quantities of rain and temperature values, both average and extreme. Overall, 2017 was a warm and dry year in the region, certifying the clear tendency in recent years of unusual rains and temperatures. The tramuntana north wind had an important presence especially in autumn and beginning of winter.

[cat] Catalunya, i en concret el Pla de Lleida, són zones sovint afectades per les pedregades. En general, els episodis més severs i freqüents es produeixen des de finals de la primavera fins a principis de la tardor. Aquest període coincideix amb el moment en què determinats cultius de la zona són altament vulnerables, degut al seu cicle vegetatiu. La importància a nivell econòmic i social que tenen les pedregades al territori català, com també la complexitat del fenomen, ha comportat que nombrosos científics hagin estudiat el tema des de diferents punts de vista. En aquesta tesi s'ha aprofundit en temes de diagnosi i predicció, amb una fase preliminar d'anàlisi per conèixer la distribució espacial i estacional de les pedregades a la zona. En temes de diagnosi, i amb l'objectiu de conèixer el diàmetre de la pedra obtinguda en indrets sense possibilitat d'observació directa, s'ha aplicat un mètode d'estimació de la mida de la pedra. Els resultats més òptims s'han aconseguit a partir del mètode cokriging universal, combinant poques dades puntuals, les observacions en superfície, amb una variable contínua secundària, que en aquest cas es tracta d'informació radar. Els valors estimats més propers a la realitat s'han aconseguit utilitzant el producte vertically integrated liquid (VIL) de la imatge no corregida del radar de la Panadella (CDV). Pel que fa al camp de la predicció, s'ha aplicat l'algorisme lightning jump (LJ), amb importants modificacions respecte a la metodologia original i adaptant-lo a les necessitats operatives del Servei Meteorològic de Catalunya (SMC), amb l'objectiu de pronosticar temps sever a curt termini al nostre país. El percentatge d'encert d'aquesta eina davant aquests fenòmens és molt elevat. A més, un altre fet important és que el percentatge d'error és molt baix. La distància de temps en què s'alerta de possible temps sever, coneguda com a lead time, inicialment, s'ha mogut entre 15 i 45 minuts amb un pic als 20 minuts. Posteriorment, a partir de la incorporació del paràmetre de la multiplicitat en l'algorisme, aquesta distància temporal s'ha incrementat fins a 120 minuts. L'anàlisi de la predicció segons la severitat de la tempesta o, altrament dit, segons el diàmetre de la pedra ha estat costosa i se n'han extret poques conclusions discriminatòries, a partir dels casos estudiats. En conjunt, l'activitat elèctrica i el comportament d'alguns paràmetres radar no han mostrat diferències significatives per arribar a determinar si una tempesta va acompanyada de pedra grossa o petita, en el moment que salta una alerta de LJ. Només el perfil de reflectivitat seria considerat una característica determinant que pot facilitar aquest tipus de pronòstic. Durant les campanyes més recents, l'eina de LJ ha estat aplicada en l'operativa de l'Equip de Predicció i Vigilància (EPV) de l’SMC. Inicialment, es va posar en mode de prova, i va passar, vistos els bons resultats, a l'operativa en temps real. Aquest seguiment ha permès portar un control diari de l'eina i trobar millores en l'algorisme. Per tant, es demostra l'aplicabilitat de la present tesi en tasques del dia a dia. La multiplicitat, esmentada prèviament, ha estat una característica afegida recentment, la qual ha permès pronosticar pedregades de mida inferior als 2 cm, precipitacions intenses, com també millora la predicció de temps sever. Finalment, per cobrir la manca d'observacions en determinades situacions de severitat, s'ha dut a terme la campanya de ciència ciutadana Plega/Caça la pedra. S'han obtingut uns resultats satisfactoris triplicant quasi el nombre d'observacions respecte d'anys anteriors. Aquesta quantitat d'observacions ha permès fer un millor control i validació de l'eina de LJ., [eng] The hail is a common severe weather phenomenon in Catalonia, producing important damages in different society environments. Nowadays, there are a lot of doubts about its forecast and, although, on respect the diagnosis of size hail. Both uncertainties are due to the high variability of hailstorms. This PhD is based on the analysis of thunderstorms associated to severe weather (large hail, tornados or waterspout, downburst and strong wind gust). The PhD has been focus on answering some of the existent doubts. On one hand, a diagnosis forecast tool has been applied to obtain information about hail diameter recorded after that one thunderstorm had affected an area without any direct measure instrument. On the other hand, a severe forecast tool named “Lightning jump” has been studied, adapted and put in operational. This algorithm permits to do a nowcasting forecast about severe weather phenomena in one hour in advance. It is an innovation PhD considering the incorporation of diagnosis and forecast new tools. Moreover, some of them are used currently in the Servei de Meteorològic de Catalunya for severe weather forecasting purposes.

Extreme events, such as wave-storms, need to be characterized for coastal infrastructure design purposes. Such description should contain information on both the univariate behaviour and the joint-dependence of storm-variables. These two aspects have been here addressed through generalized Pareto distributions and hierarchical Archimedean copulas. A non-stationary model has been used to highlight the relationship between these extreme events and non-stationary climate. It has been applied to a Representative Concentration Pathway 8.5 Climate-Change scenario, for a fetch-limited environment (Catalan Coast). In the non-stationary model, all considered variables decrease in time, except for storm-duration at the northern part of the Catalan Coast. The joint distribution of storm variables presents cyclical fluctuations, with a stronger influence of climate dynamics than of climate itself.

In this work we study the belief in the existence of tempestarii or inmissores tempestatum in Hispania in Late Antiquity. Despite the scarcity of sources on this subject, those that do exist suggest that, in the Iberian Peninsula, people believed individuals to be capable of causing storms with their own will. The sources in question include two Chindaswinth laws, which express the authorities’ concerns over “storm-makers” capable of ruining the crops of others. In addition, two epigraphic testimonies, reproducing magic formulae engraved on slate (with an imprecise date between the 8th and 10th centuries) suggest the presence in Hispania of the defensores mentioned by Agobard of Lyon in the Frankish Kingdom, magicians who claimed to know how to move storms away from the fields. These scarce sources can be complemented by information from Frankish Gaul sources, and particularly the aforementioned Agobard. Finally, we consider how the Church sought to combat these beliefs, appropriating and adapting them to its own thought, and replacing the evil spirits that caused storms with Satan and his demons, and the divinities that protected the fields with Christian saints and angels., En el presente trabajo estudiamos la creencia en la existencia de tempestarii o inmissores tempestatum en la Hispania tardoantigua. A pesar de la escasez de fuentes para dicho tema, éstas nos permiten aseverar que en la península Ibérica la gente reconocía como reales los individuos capaces de provocar tormentas con su sola voluntad. Estas fuentes corresponden a dos leyes de Chindasvinto, que manifiestan la preocupación de las autoridades por los «hacedores de tormentas» que arruinaban las cosechas de terceros. Además, dos testimonios epigráficos, que reproducen fórmulas mágicas grabadas sobre pizarra (con una cronología imprecisa que corre entre los siglos VIII y X), sugieren la presencia en Hispania de los defensores mencionados en el reino franco por Agobardo de Lyon, magos que presumían de alejar las tempestades de los campos de cultivo. La pobreza de estas fuentes puede completarse con la información proporcionada por fuentes de la Galia franca, entre las que destaca el mencionado Agobardo. Finalmente, vemos cómo la Iglesia combatió estas creencias apropiándose de ellas y adaptándolas a su pensamiento, sustituyendo los malos espíritus que provocaban tormentas por Satán y sus demonios, y las divinidades que protegían los campos por los ángeles y los santos cristianos.