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The radiosondes measure air pressure, temperature and humidity. Attached to a weather balloon and carried high into the atmosphere, the radiosonde also records the exact position, allowing altitude, wind speed and direction to be determined. The data obtained in this way are of great importance for weather forecasts and climate research.
MeteoSwiss launches a weather balloon twice a day from the sounding station in Payerne. Special soundings are also carried out to determine other parameters such as ozone or aerosol concentrations. In addition, MeteoSwiss operators launch research flights, for which several radiosondes are attached to the same balloon. This allows the readings to be compared with each other, checked for quality and verified.
Radiosonde data from MeteoSwiss
The data collected during the radiosonde’s ascent are transmitted by radio to the receiving station in Payerne, where they are logged in the MeteoSwiss database. The results of the latest soundings are published here either as graphs (emagrams) or as decoded data files. Combined views with soundings from neighbouring countries are also available.
High-resolution radio soundings can be obtained for professional and scientific use. Emagrams for aviation purposes can be purchased in the MeteoSwiss App.
Emagrams illustrate the various processes in the troposphere. The term “emagram” is a combination of the words energy, mass and diagram. The diagram consists of altitude-dependent data for temperature, humidity, air pressure and wind.
Global sounding station network
There are over 600 stations worldwide that carry out aerological soundings. Soundings are performed simultaneously at these stations every twelve hours. The information obtained from this process is made available to all national weather services, where it is plotted in the upper-level weather maps and analysed, as well as being used as the basis for weather forecasting models. Around 170 of these stations fulfil more stringent requirements and are used for long-term climate monitoring. The aerological station in Payerne is part of a global network of reference stations for climate monitoring (GRUAN-GCOS Reference Upper-Air Network).
Radiosondes contain a range of measurement instruments and act as both a transmitter and a receiver:
- Measurement instruments: The temperature and humidity sensors are optimised to achieve the highest possible measurement quality. The altitude and position of the radiosonde are ascertained by means of a GPS sensor. The atmospheric pressure is calculated on the basis of geopotential altitude. Readings are taken every second from the sensors deployed, with the vertical distance between two measurement points being approximately five metres.
- Radio transmitter: In addition to the measurement instruments, a radio transmitter and a battery for powering the electronics are located in the radiosonde’s housing.
- Receiver: A frequency band of 401 - 406 MHz, which is reserved for meteorological use, is used to receive the signals transmitted from the radiosondes. The GPS information from the radiosonde allows the receiving antenna to be optimally aligned relative to the position of the radiosonde.
Anyone who discovers a radiosonde outdoors is asked to take it home with them. A label on the radiosonde shows a website URL with instructions for returning the device to MeteoSwiss, where its components will be recycled.
These instructions are also available as a leaflet: