Sensor development for in-situ measurements of charge in non-thunderstorm clouds using small UAVs and free balloons

Clouds are some of the least well understood phenomena in atmospheric science. This is in part due to the complexity of microphysical processes involved, but also due to the lack of robust data from in-situ measurements which have a high observational difficulty. Previous research has shown that charge is present in most cloud types, but the location, magnitude and generation mechanisms are not well characterized. Current theory predicts a potentially important role for charge in non-thunderstorm clouds in terms of its effects on cloud droplet interactions, and therefore large scale cloud properties such as height, lifetime and even rainfall. However, lack of in-situ charge and cloud measurements have hampered investigation of this problem so far. This project therefore seeks to investigate the role of charge in non thunderstorm clouds by producing new data sets of charge and cloud microphysical measurements through the development of new observational techniques from novel airborne platforms.

Cloud microphysical observations are currently performed from manned aircraft which are costly, limited in terms of spatial sampling achievable and are limited by human life risk factors. In order to obtain the in-situ cloud and charge measurements, this project will utilise the alternative platforms of UAVs and free balloons, which provide opportunities for much more frequent sampling, which is required in order to fully characterise the variability of non-thunderstorm clouds. Due to the limited size and weight constraints of such platforms, design, integration and testing of new charge and cloud sensors is required, which this project will develop. Due to the current lack of such instrumentation in the atmospheric science community the outcome of the research could revolutionize the availability of in-cloud measurements, particularly in respect to the electrical measurements. The work has potential for strong positive impact on the ability to improve the understanding of cloud microphysical processes and thus to allow for more accurate weather and climate modelling.

The main steps of the research are (a) to investigate the design requirements for a suitable small UAV platform for in-cloud electrical measurements (high altitude flight, high payload capacity, low electric noise injections, long range autonomy). (b) development of payload sensor package (most probably an electric field mill, optical techniques for cloud droplet spectra characterization and temperature and humidity sensors for thermodynamic considerations). (c) investigate the effect of the airborne platforms on the electrical measurements and propose mitigation for sensor interference. (d) produce new data sets of in-situ non-thunderstorm charge and cloud microphysical data using the developed sensors and compare results with previous ground based and airborne measurements.