Rime Icing and Hoar Frost Damage to Anemometers and Meteorological Instruments

MeteoWind 1 anemometer with morning hoar frost in central Europe.

QUESTION: What types of icing can a heated MeteoWind anemometer survive?

ANSWER: MeteoWind anemometers can survive and provide data in most all icing conditions found in cold climates.

We differentiate between two types of winter snow conditions for anemometer recommendations:

• Snowy with regular rime/hoar icing events - most winter locations-
  MeteoWind is the best anemometer in the world to deal with snowy conditions, as shown by Boschung Mechatronic from their winter testing in Switzerland, even compared to most ultrasonic anemometers.
  

• Heavy Hoar/Rime Icing - very specific winter locations
  These conditions tend to form large deposits of clear rime or hoar ice that encapsulate anemometers and other meteorological instruments. If over 1kg of clear rime ice forms on the sensor rotor, this, in combination with high winds, can destroy sensors. We have seen these types of ice accumulations bend Ø5 cm stainless steel pipes of snowmaking machines in Slovakia. For this type of extreme climate, we would recommend RM young propeller anemometers or FT Technologies ultrasonic sensors.

How do large accumulations of rime and hoar ice and frost form?

Harsh hoar and rime icing usually occur when fog or drizzle from low-lying regions, accompanied by high winds, is blown uphill into the mountains. As it rises and cools, its airborne water droplets super-cool to sub-zero temperatures without freezing. As the windborne drops impact objects, they immediately freeze and accumulate on each other. Thus the hoar frost and rime ice accumulations usually point into the wind.

Since hoar and rime ice accumulations point into the wind, they act like a very heavy ice sail. Not only is the weight of ice a problem for sensors, but it also acts on a large moment arm that exacerbates wind forces acting on the ice buildup.

MeteoShield Professional with hoar frost buildup during a cold foggy day.

Heater anemometer MeteoWind 2 after a tough, rime ice forming night.

For the most extreme winter icing conditions where accumulations of hoar ice and rime ice can exceed 1kg in combinations with high winds, we recommend using RM Young propeller anemometers or FT Technologies ultrasonic sensors. These sensors while not being able to provide high accuracy, are able to survive in most harsh environments. In such cases where data reliability is more important than precision, these are the sensors of choice.

BARANI DESIGN TECHNOLOGIES IS A MANUFACTURER OF PROFESSIONAL WIND SENSORS, ANEMOMETERS, RAIN GAUGES AND WEATHER STATIONS.

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