Picking up your smartphone to check the weather is so easy today that it's easy to forget this was not always the case. Weather sayings of old have given way to modern technologies that follow a long chain: from observations, to simulations with numerical models and analysis. Nowadays, weather forecasts are generated using complex algorithms powered by data from various sources such as weather balloons or aircraft sensors, but satellite observations are the most important ones.
Accurate weather forecasts are only possible thanks to satellites
The accuracy of forecasting the weather from 12-hours to 10-days ahead will be greatly improved thanks to the new MetOp-SG spacecraft' capabilities.
"EUMETSAT operates meteorological satellites and disseminates data to our member states in real time," explains Rosemary Munro, EUMETSAT Polar System-Second Generation (EPS-SG) Programme Scientist. "The national meteorological services rely on accurate and timely operational data flow of the atmosphere, oceans and land that they inject in their own prediction models to build weather forecasts."
Weather forecasting indeed requires a lot of data to continuously improve mathematical modelling. The ability to detect extreme weather events such as storms and heatwaves, depends partly on these models. Philippe Chambon, researcher at Meteo-France, says: "For our numerical weather prediction models, issuing forecasts up to four days ahead, around 90% of our data comes from Earth observation satellites. The MetOp-SG satellites, with their very high performance instruments, will improve our forecasts both at the global and at the regional levels."
The challenges of weather forecasting
A weather forecast is a prediction of the state of the atmosphere at a given time and place, simulated by a numerical model. Imagine the atmosphere divided vertically into several cubes (for example with a size of one-by-one kilometre by a few hundred metres of altitude) where it is possible to evaluate the humidity rate inside, plus the temperature, winds and the amount of cloud and rain. The data is then transformed and analysed using numerical models which enable weather forecasters to provide understandable information for the general public. The sun or cloud icons and temperature readings available instantly on your mobile phone app are all generated via this long chain.
"We never make only one forecast but more than thirty, which are slightly different. The atmosphere behaves in a chaotic way which affects predictability. If the scenarios are quite similar for the next four days the confidence index is high, if we have storms only in some of the scenarios, the index is in general lower because the changes from the starting conditions can lead to different weather outcomes," explains Philippe Chambon of Meteo-France.
Weather forecasts protect human lives and livelihoods
Weather forecasting is also a key way of anticipating violent phenomena such as storms or heat waves so that people likely to be impacted can be warned in advance. This helps to protect lives and livelihoods.
"We can identify dangerous weather phenomena at an early stage that we confirm and clarify over time, updating the predictions several times a day with more recent data and informing citizens and public authorities," says Chambon. "The aim is to draw everyone's attention to the potential dangers and to make people aware of the precautions to take to protect themselves."
Beyond weather forecasting with MetOp-SG
Weather satellites are very useful in our daily life but their benefits are much broader. They provide essential information on the climate and oceans by for example monitoring wildfires and plumes of volcanic ash, the hole in the ozone layer and air pollution.
MetOp-SG's 10 instruments will help scientists improve their understanding of climate changes and their projections. "One of the big game-changers for climate research will be the Infrared Atmospheric Sounding Interferometer (IASI-NG) which is able to monitor a wide range of chemical compounds of the atmosphere such as methane that is a potent greenhouse gas and ammonia that impacts air quality," says Munro.
For Chambon, the Ice Cloud Imager (ICI) instrument will bring a completely new perspective to the study of ice clouds. "We will be able to quantify the amount of small ice crystals in the atmosphere. It is really important because these ice clouds have an impact on the Earth's radiation energy balance. It is one of the sources of uncertainty in climate projections. Thanks to this data, scientists will be able to improve their predictive models and their understanding of global warming."
The planned MetOp-SG A1 and B1 satellite launches in 2025-2026 will ensure continuity with the current MetOp fleet, without a gap. This long term data continuity is essential for weather forecasting and to detect changes in climate monitoring.
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