Drones and other small unmanned aerial vehicles (UAVs) have grown in popularity in recent years as a result of their novel uses such as crop monitoring, search and rescue operations, and coast profiling. The potential of SUAVs in atmospheric research and meteorology has also been recognised since drones provide an effective means to install different types of sensors in the lower atmosphere.
Small drones equipped with meteorology sensors, as shown by pioneering experiments performed by Japan’s National Institute of Polar Research, may be beneficial for weather forecasting in areas where weather stations are few or expensive to set up and operate, such as the polar regions. Drones might collect crucial data for creating numerical weather forecasts and upgrading climate models.
However, several practical issues must be handled on this front. One obvious application is wind speed measurement for wind profiling. While a few firms are commercialising drones for measuring wind speed, these drones are often huge and costly. This is because the ultrasonic anemometers they carry are hefty and big. On the other hand, although wind speed may theoretically be estimated from the drone’s internal flight record data, most commercial drones do not provide access to this information. As a result, with no alternate ways for measuring wind speed, the applicability of sUAVs is restricted.
To address this issue, Associate Professor Jun Inoue of the National Institute of Polar Research and Assistant Professor Kazutoshi Sato of the Kitami Institute of Technology in Japan recently conducted a study in which they tested and validated thermal anemometers, a new wind speed measurement device compatible with sUAVs.
Thermal anemometers, commonly known as “hot-wire anemometers,” are tiny electrical devices that may indirectly estimate wind speed based on how quickly a heated wire cools down due to air movement, as stated in their study published in MDPI’s Drones on October 3, 2022. These sensors are perfect for sUAVs since they are incredibly light (one gramme) and affordable (two hundred dollars).
The researchers put their method to the test both in the lab and in the field. They flew a tiny quadcopter drone fitted with a thermal anemometer in front of huge fans in the laboratory trials. They studied how the airflow was affected by the drone as it rose using smoke machines, high-speed cameras, lasers, and image processing tools. Using this information, they developed a bias correction algorithm that allowed the drone to take more accurate wind speed readings.
The researchers conducted field trials by flying their drone over the ice-covered Okhotsk Sea while onboard the Japanese Patrol Vessel Soya to record wind speed. When the researchers compared the data from their drone to that from an ultrasonic anemometer aboard the ship, they discovered that they were in accord, indicating that the drone’s readings were very dependable. “The root-mean-square error was 1.13 m/s, indicating that the suggested correction approach was accurate and well within the requirements for numerical weather forecasts,” Dr Inoue notes.
Overall, this new technique of wind profiling seems to be promising on several fronts. Furthermore, the researchers offered two additional strategies that may be explored in future works: determining both wind direction and speed using two thermal anemometers and sending the collected data in real time.
Wind speed data are useful for more than only climate research and weather forecasting. Drones may benefit from understanding the wind conditions in which they are flying since it allows them to better steady their flight. “Drone flight styles have evolved from flying inside the operator’s visible line of sight to flying outside the operator’s visual line of sight. This is because they are now commonly utilised for long-distance transportation and catastrophe and forest fire inspections “Dr Sato states
“Once we can monitor wind conditions in all types of drones in real-time,” he continues, “operators will be able to concentrate more on their work without having to worry about the drone’s stability and safety.”
