Update b1-radio-sounding.md

docs/b-data-atmosphere/b1-radio-sounding.md

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-# Radio soundings
-
-MeteoSwiss performs [soundings](https://www.meteoswiss.admin.ch/weather/measurement-systems/atmosphere/radio-soundings.html) twice a day (`00:00 UTC` and `12:00 UTC`) from the sounding station in Payerne (station identifier `PAY`) using weather balloon radiosondes.
+# Radiosounding Data (Payerne Aerological Station)
 
+MeteoSwiss operates one of the world’s longest, continuously measured upper‑air time series at the aerological station in Payerne (WIGOS ID: 0‑20000‑0‑06610). Radiosoundings provide vertical profiles of key atmospheric state variables and are essential for weather forecasting, climate monitoring, numerical model assimilation, and satellite validation.
+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 sounding are published  either as graphs ([emagrams](https://www.meteoswiss.admin.ch/services-and-publications/applications/radio-soundings.html#tab=radio-soundings-emagram)) or as [decoded data](https://www.meteoswiss.admin.ch/services-and-publications/applications/radio-soundings.html#tab=radio-soundings-decoded) files. 
 The radiosondes measure temperature and humidity as well as its position and altitude using [GNSS](https://www.swisstopo.admin.ch/en/global-navigation-satellite-systems). Attached to a [weather balloon](https://www.meteoswiss.admin.ch/weather/weather-and-climate-from-a-to-z/weather-balloon.html) and carried high into the atmosphere, wind speed and direction as well as atmospheric pressure can further be derived. 
 
-The data obtained in this way are of great importance for weather forecasts and climate research. 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 sounding are published  either as graphs ([emagrams](https://www.meteoswiss.admin.ch/services-and-publications/applications/radio-soundings.html#tab=radio-soundings-emagram)) or as [decoded data](https://www.meteoswiss.admin.ch/services-and-publications/applications/radio-soundings.html#tab=radio-soundings-decoded) files. 
+## Measurement Programme
+The operational radiosounding system delivers complete vertical profiles of:
+
+Pressure (P)
+Temperature (T)
+Relative Humidity (RH)
+Wind (speed and direction) from GPS tracking
+Geopotential height
+Derived parameters, e.g.
+
+Tropopause height
+0 °C isotherm height
+Stability indices (CAPE, CIN, Lifted Index, etc.)
+Various atmospheric layer means and thicknesses
+
+## Launch schedule
+MeteoSwiss performs two soundings per day, launched at:
+
+23 UTC (nominal time 00 UTC)
+11 UTC (nominal time 12 UTC)
+
+Additional soundings may be performed during special events, campaigns, or severe weather episodes.
+
+## Instrumentation
+Since 2018, MeteoSwiss operates Vaisala RS41 radiosondes.
+Historical sondes include:
+
+SRS‑400
+SRS‑C34
+SRS‑C50
+
+A full homogenization of the Payerne PTU data (FC21*) is available for climate applications.
 
-## Data download {#data-download}
+## Data Structure
+Files per sounding
+Each file contains:
+
+-Full vertical profile from ground to ~35 km
+-All measured and derived parameters
+-Metadata such as launch time, sonde type, ascent rate, and processing flags
+
+## Data granularity
+
+-Level‑by‑level ascent data (typically ~800–1200 levels per profile)
+-Standard pressure levels
+-Significant levels
+-Derived levels (tropopause, isotherms, etc.)
+
+## Data periods
+
+-Historical data since the 1940s
+-Homogenized PTU series available from 1959–2025
+-Operational RS41 data from 2018–present
+
+## Data updates
+
+-New soundings appear shortly after each ascent
+-Historical archives are static; homogenized series updated occasionally
+ ## Data download {#data-download}
 
 The file contains the data from the most recent sounding. The update frequency depends on the two soundings per day (at `00:00 UTC` and `12:00 UTC`).
 
@@ -21,7 +77,6 @@ The following **example data file** is available for download: [`ogd-radiosoundi
 [`CSV`](https://opendatadocs.meteoswiss.ch/general/download#column-separators-and-decimal-dividers) with an estimated volume of 0.02 MB per file.
 
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