Present weather sensor

It works on a principle similar to a bistatic radar, noting the passage of droplets, or flakes, between a transmitter and a sensor.

Thus, if the detector identifies the falling speed for the dual snow/drizzle at an ambient dew point greater than 1 °C (34 °F) it will classify it as drizzle, and below −1 °C (30 °F), it will be snow.

When these additional data still do not make it possible to differentiate (e.g. if the dew point of the previous example is between −1 and 1 °C), the type is then reported as "unknown".

However, they will issue a special report if one or more of their sensors detects a significant change in weather conditions.

Scatterometers and transmissometers, where the extinction of a visual signal through air from a source to a receiver is noted, will give the horizontal visibility.