Abstract. The importance of vertical wind velocities (in particular positive vertical
wind velocities or updrafts) in atmospheric science has motivated the need to
deploy multi-hole probes developed for manned aircraft in small remotely
piloted aircraft (RPA). In atmospheric research, lightweight RPAs
(< 2.5 kg) are now able to accurately measure atmospheric wind vectors,
even in a cloud, which provides essential observing tools for understanding
aerosol–cloud interactions. The European project BACCHUS (impact of Biogenic
versus Anthropogenic emissions on Clouds and Climate: towards a Holistic
UnderStanding) focuses on these specific interactions. In particular,
vertical wind velocity at cloud base is a key parameter for studying
aerosol–cloud interactions. To measure the three components of wind, a RPA
is equipped with a five-hole probe, pressure sensors, and an inertial
navigation system (INS). The five-hole probe is calibrated on a multi-axis
platform, and the probe–INS system is validated in a wind tunnel. Once
mounted on a RPA, power spectral density (PSD) functions and turbulent
kinetic energy (TKE) derived from the five-hole probe are compared with sonic
anemometers on a meteorological mast. During a BACCHUS field campaign at Mace
Head Atmospheric Research Station (Ireland), a fleet of RPAs was deployed to
profile the atmosphere and complement ground-based and satellite observations
of physical and chemical properties of aerosols, clouds, and meteorological
state parameters. The five-hole probe was flown on straight-and-level legs to
measure vertical wind velocities within clouds. The vertical velocity
measurements from the RPA are validated with vertical velocities derived from
a ground-based cloud radar by showing that both measurements yield
model-simulated cloud droplet number concentrations within 10 %. The
updraft velocity distributions illustrate distinct relationships between
vertical cloud fields in different meteorological conditions.