Data assimilationData assimilation is a mathematical discipline that seeks to optimally combine theory (usually in the form of a numerical model) with observations. There may be a number of different goals sought – for example, to determine the optimal state estimate of a system, to determine initial conditions for a numerical forecast model, to interpolate sparse observation data using (e.g. physical) knowledge of the system being observed, to set numerical parameters based on training a model from observed data.
Lake GenevaLake Geneva (le Léman lə lemɑ̃, lac Léman lak lemɑ̃, rarely lac de Genève lak də ʒ(ə)nɛv; Lago Lemano; Genfersee ˈɡɛnfərˌzeː; Lai da Genevra) is a deep lake on the north side of the Alps, shared between Switzerland and France. It is one of the largest lakes in Western Europe and the largest on the course of the Rhône. Sixty per cent () of the lake belongs to Switzerland (the cantons of Vaud, Geneva and Valais) and forty per cent () to France (the department of Haute-Savoie).
RhôneThe Rhône (rəʊn , ʁon) is a major river in France and Switzerland, rising in the Alps and flowing west and south through Lake Geneva and southeastern France before discharging into the Mediterranean Sea. At Arles, near its mouth, the river divides into the Great Rhône (le Grand Rhône) and the Little Rhône (le Petit Rhône). The resulting delta forms the Camargue region. The river's source is the Rhône Glacier, at the east edge of the Swiss canton of Valais.
GenevaGeneva (dʒəˈniːvə ; Genève ʒənɛv) is the second-most populous city in Switzerland (after Zürich) and the most populous city of Romandy, the French-speaking part of Switzerland. Situated in the south west of the country, where the Rhône exits Lake Geneva, it is the capital of the Republic and Canton of Geneva, and a center for international diplomacy. The city of Geneva (ville de Genève) had a population of 203,951 in 2020 (Jan. estimate) within its small municipal territory of , but the Canton of Geneva (the city and its closest Swiss suburbs and exurbs) had a population of 504,128 (Jan.
Hydrological transport modelAn hydrological transport model is a mathematical model used to simulate the flow of rivers, streams, groundwater movement or drainage front displacement, and calculate water quality parameters. These models generally came into use in the 1960s and 1970s when demand for numerical forecasting of water quality and drainage was driven by environmental legislation, and at a similar time widespread access to significant computer power became available.
Atmospheric reanalysisAn atmospheric reanalysis (also: meteorological reanalysis and climate reanalysis) is a meteorological and climate data assimilation project which aims to assimilate historical atmospheric observational data spanning an extended period, using a single consistent assimilation (or "analysis") scheme throughout. In operational numerical weather prediction, forecast models are used to predict future states of the atmosphere, based on how the climate system evolves with time from an initial state.
SaôneThe Saône (soʊn , son; Sona; Arar) is a river in eastern France. It is a right tributary of the Rhône, rising at Vioménil in the Vosges department and joining the Rhône in Lyon, at the southern end of the Presqu'île. The name Saône derives from that of the Gallic river goddess Souconna, which has also been connected with a local Celtic tribe, the Sequanes. Monastic copyists progressively transformed Souconna to Saoconna, which ultimately gave rise to Saône. The other recorded ancient names for the river were Brigoulus and Arar.
RhineThe Rhine (raɪn ) is one of the major European rivers. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps. It forms part of the Swiss-Liechtenstein, Swiss-Austrian, and Swiss-German borders. After that the Rhine defines much of the Franco-German border, after which it flows in a mostly northerly direction through the German Rhineland. Finally in Germany, the Rhine turns into a predominantly westerly direction and flows into the Netherlands where it eventually empties into the North Sea.
Canton of GenevaThe Canton of Geneva, officially the Republic and Canton of Geneva, is one of the 26 cantons forming the Swiss Confederation. It is composed of forty-five municipalities, and the seat of the government and parliament is in the City of Geneva. Geneva is the French-speaking westernmost canton of Switzerland. It lies at the western end of Lake Geneva and on both sides of the Rhone, its main river. Within the country, the canton shares borders with Vaud to the east, the only adjacent canton.
Reuss (river)The Reuss (Swiss German: Rüüss) is a river in Switzerland. With a length of and a drainage basin of , it is the fourth largest river in Switzerland (after the Rhine, Aare and Rhône). The upper Reuss forms the main valley of the canton of Uri. The course of the lower Reuss runs from Lake Lucerne to the confluence with the Aare at Brugg and Windisch. The Reuss is one of the four major rivers taking their source in the Gotthard region, along with the Rhine, Ticino and Rhône.
River engineeringRiver engineering is a discipline of civil engineering which studies human intervention in the course, characteristics, or flow of a river with the intention of producing some defined benefit. People have intervened in the natural course and behaviour of rivers since before recorded history—to manage the water resources, to protect against flooding, or to make passage along or across rivers easier. Since the Yuan Dynasty and Ancient Roman times, rivers have been used as a source of hydropower.
SimulationA simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the simulation represents the evolution of the model over time. Often, computers are used to execute the simulation. Simulation is used in many contexts, such as simulation of technology for performance tuning or optimizing, safety engineering, testing, training, education, and video games.
FloodA flood is an overflow of water (or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrology and are of significant concern in agriculture, civil engineering and public health. Human changes to the environment often increase the intensity and frequency of flooding, for example land use changes such as deforestation and removal of wetlands, changes in waterway course or flood controls such as with levees, and larger environmental issues such as climate change and sea level rise.
Kalman filterFor statistics and control theory, Kalman filtering, also known as linear quadratic estimation (LQE), is an algorithm that uses a series of measurements observed over time, including statistical noise and other inaccuracies, and produces estimates of unknown variables that tend to be more accurate than those based on a single measurement alone, by estimating a joint probability distribution over the variables for each timeframe. The filter is named after Rudolf E. Kálmán, who was one of the primary developers of its theory.
Ensemble Kalman filterThe ensemble Kalman filter (EnKF) is a recursive filter suitable for problems with a large number of variables, such as discretizations of partial differential equations in geophysical models. The EnKF originated as a version of the Kalman filter for large problems (essentially, the covariance matrix is replaced by the sample covariance), and it is now an important data assimilation component of ensemble forecasting.
RainRain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water for hydroelectric power plants, crop irrigation, and suitable conditions for many types of ecosystems. The major cause of rain production is moisture moving along three-dimensional zones of temperature and moisture contrasts known as weather fronts.
Drainage basinA drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the drainage divide, made up of a succession of elevated features, such as ridges and hills. A basin may consist of smaller basins that merge at river confluences, forming a hierarchical pattern. Other terms for a drainage basin are catchment area, catchment basin, drainage area, river basin, water basin, and impluvium.
Po (river)The Po (poʊ , ˈpɔ) is the longest river in Italy. It flows eastward across northern Italy starting from the Cottian Alps. The river's length is either or , if the Maira, a right bank tributary, is included. The headwaters of the Po are a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face of Monviso. The Po then extends along the 45th parallel north before ending at a delta projecting into the Adriatic Sea near Venice.
PrecipitationIn meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor (reaching 100% relative humidity), so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation but colloids, because the water vapor does not condense sufficiently to precipitate.
River deltaA river delta is a landform shaped like a triangle, created by the deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs when a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment. It is so named because its triangle shape resembles the Greek letter Delta. The size and shape of a delta are controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment.
