Abstract
In this work, sensible heat flux estimated using a bulk transfer method was validated with a three-dimensional ultrasonic anemometer or surface layer scintillometer at various sites. Results indicate that it remains challenging to obtain temperature and wind speed at an appropriate reference height. To overcome this, alternative observations using an unmanned aerial vehicle (UAV) were considered. UAV-based wind speed and sensible heat flux were indirectly estimated and atmospheric boundary layer (ABL) height was then derived using the sensible heat flux data. UAV-observed air temperature was measured by attaching a temperature sensor 40 cm above the rotary-wing of the UAV, and UAV-based wind speed was estimated using attitude data (pitch, roll, and yaw angles) recorded using the UAV’s inertial measurement unit. UAV-based wind speed was close to the automatic weather system-observed wind speed, within an error range of approximately 10%. UAV-based sensible heat flux estimated from the bulk transfer method corresponded with sensible heat flux determined using the eddy correlation method, within an error of approximately 20%. A linear relationship was observed between the normalized UAV-based sensible heat flux and radiosonde-based normalized ABL height.
Highlights
Indirect methods of estimating sensible heat flux from measurable mean wind speed and temperature in the surface layer or the whole atmospheric boundary layer (ABL) are based on appropriate flux–profile relationships
We suggest an indirect approach to estimate wind speed, sensible heat flux, and ABL height by applying unmanned aerial vehicle (UAV)-based inertial measurement unit (IMU) data observed from flight, UAV-observed temperature, and surface measurement, which is more economic and less labor-intensive compared to methods of earlier studies
We show that these profiles, and estimates of wind speed, heat flux, and ABL height can be achieved using a rotary-wing UAV equipped with a temperature/humidity sensor approximately 40 cm above the UAV
Summary
Indirect methods of estimating sensible heat flux from measurable mean wind speed and temperature in the surface layer or the whole atmospheric boundary layer (ABL) are based on appropriate flux–profile relationships. The ABL height is usually determined using vertical profiles of specific humidity, potential temperature, and CO2 mixing ratios from atmospheric soundings [2,3]. New data sources (e.g., radiometers, wind profilers, lidars, sodars, tethered balloons, and aircraft) have resulted in the development of additional methods to understand ABL structure and processes [4,5]. While these data sources can acquire stable vertical profiles of temperature and wind speed, there are challenges regarding their widespread application
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