Electric Field Responses to Airborne Dust in FAAM Aircraft Measurements

Mineral dust influences radiation, clouds, and air quality, and can acquire electric charge through particle interactions and turbulent mixing. Observations of dust electrification at aircraft altitudes remain limited. Aircraft measurements provide a valuable opportunity to investigate how atmospheric electric fields respond to airborne dust under varying thermodynamic and aerosol conditions.

We analyse observations from the FAAM aircraft during flights sampling Saharan dust layers, to investigate electric field mill records associated with airborne dust regions. The electric field mill employed senses the ambient vertical electric field indirectly, but does not directly sample particles. It responds to electric fields induced by charged aerosols, the aircraft, and the surrounding atmosphere. Electric field measurements are analysed alongside co-located thermodynamic, wind, aerosol, and cloud observations, including ascent and descent profiles through dust plumes of varying intensity. In an intense dust case, the electric field signal strengthens as the aircraft approaches and enters the main dust layer at mid-tropospheric altitudes, coincident with decreasing relative humidity and enhanced aerosol loading. These results indicate that the electric field measurements are sensitive to electrically active dust layers aloft, providing new constraints on how dust charging evolves with altitude, humidity, and particle loading.