What it is
A mobile mesonet, or dubbed simply “mesonet,” is a weather station on wheels. You may have seen one before, they’re usually out near severe storms or tornadic supercells during the spring and summer months.
The shapes and designs of these weather stations may look odd, but each one is designed to obtain the truest, most accurate readings of the atmosphere in and around a supercell thunderstorm or tornado.
A mobile mesonet samples the atmosphere at set intervals, usually every second, and records temperature, humidity (dew point, not relative), atmospheric pressure, wind speed and direction. Additionally, they are equipped with GPS devices that plot and track the vehicle’s position and speed for later analysis.
A mesonet is made of an aluminum, or sometimes PVC pipe, rack system mounted to the roof. Each instrument is positioned above the vehicle at specific locations in order to limit or eliminate any influence from the car itself. For example, placing a temperature sensor too close to a vehicle’s roof, especially if it’s a black car, will not give you accurate readings as heat generated from the car’s roof will change the surrounding atmosphere.
Another example is the anemometer, the sensor that records wind speed and direction. If the sensor is placed behind the vehicle’s windshield, the aerodynamics of the car’s shape will increase wind speeds, giving an inaccurate reading of the surrounding air. Therefore, the rack system is designed to place the anemometer above, and forward, of the vehicle’s slipstream at a height of about 5 feet.
Each mesonet has a least one of the following:
- Anemometer – records windspeed and direction
- Temperature probe – samples air temperature
- Humidity probe – samples the dew point
- Atmospheric pressure sensor & port inlet – records the atmospheric pressure.
- GPS Receiver (fluxgate compass)
In addition to the above sensors, some mesonets, particularly those employed by the National Weather Service and other research groups, will use multiple combinations of these sensors using various heights or housings. For example, the National Severe Storms Laboratory used three different temperature/humidity systems so that the readings could be compared after each operation.
You may also see that some mesonets also employ various antennas on the racks, which are either for high frequency radios or radiosonde receivers.
The raw data of these sensors are recorded on a data-logger inside the vehicle. Once operations have ended, the data is pulled onto a laptop or other computer for analysis. Some mesonets also employ computer software onboard that allows the vehicle occupants to monitor the data as it comes in real time.