Today we're seeing number stations move off of ham radio and onto protocols like MQTT.
Additionally a lot of "weather stations" around the world are simply number stations. They vary the numbers reported, and wherever they diverge from whatever is determined in advance as the "canonical" source is how information is communicated. This paragraph and the above are just my personal observations please note.
Lastly good examples of weather stations in general (not actual spying things please note) can be found here [1] and here [2].
Additionally a lot of "weather stations" around the world are simply number stations. They vary the numbers reported, and wherever they diverge from whatever is determined in advance as the "canonical" source is how information is communicated. This paragraph and the above are just my personal observations please note.
Lastly good examples of weather stations in general (not actual spying things please note) can be found here [1] and here [2].
[1] - http://weewx.com/stations.html
[2] - https://joesdatacenter.com/hvac/