Fair-Weather Atmospheric Charge Measurements with a Small UAS

Atmospheric electricity measurements made from small unmanned aircraft systems (UAS) are rare but are of increasing interest to the atmospheric science community due to the information that they can provide about aerosol and turbulence characteristics of the atmospheric boundary layer (ABL). Here we present the first analysis of a new data-set of space charge and meteorology measurements made from the small, electric, fixed<wing UAS model MASC<3. Two distinct experiments are discussed: 1) Flights past a 99 m metal tower to test the response of the charge sensor to a fixed dis-tortion of the electric field caused by the geometry of the tower. Excellent agreement is found between the charge sensor response from the MASC<3 and modeled electric field around the tower. 2) Vertical profiles up to an altitude of 2500 m to study the evolution of the ABL with the time of day. These flights demonstrated close agreement between the space charge profiles and temperature, relative humidity, and turbulence parameters, as would be expected on a fair<weather day with summertime convection. Maximum values of space charge measured were of order 70 pC m²³, comparable with other measurements in the literature from balloon platforms. These measurements demonstrate the suitability of small UAS for atmospheric electrical measurements, provided that care is taken over the choice of aircraft platform, sensor placement, minimization of electrical interference, and careful choice of the flight path. Such aircraft are typically more cost<effective than manned aircraft and are being increasingly used for atmospheric science purposes.