Abstract/Summary

Severe financial losses are caused annually due to low visibility weather conditions such as fog. Accurate forecasting of fog onset and dissipation, along with attempts to suppress fog are essential to mitigate these societal impacts. To enhance the understanding of fog, a broad description of its properties is required. This thesis presents some of the first measurements of the electrical and microphysical properties of fog in the United Arab Emirates (UAE) and is the first to investigate the effects of artificial charge emission during fog in this region. The analysis indicates that the Potential Gradient (PG) values observed during fog in the UAE were substantially higher than those previously reported in the literature (ranging from − 1247 V/m to 1400 V/m). Furthermore, the PG during fog was often negative, with 93% of cases showing negative PG values (with a median PG value of − 397 V/m), particularly during latter stages of the wintertime fog events. This unusual polarity of PG is hypothesized to result from the deposition of fog droplets, where positive charges are transported from the top of the fog layer downwards towards the surface, thus altering the PG. Additionally, the results demonstrated a bimodal droplet size distribution during natural fog conditions, with peaks at less than 1 μm and around 10 μm in two events, and between 20–23 μm in other events. Beyond natural fog dynamics, artificial negative charge was emitted into the fog through four corona ionisers, demostrating an effective change in PG, with a decrease of approximately 40 to 60 V/m. In addition, these experiments showed modifications in the droplet size distribution, including an increase in the concentration of small particles (0.2–0.5 μm) and a decrease in the larger particles (>5 μm), resulting in a visibility improvement of 5–6%. These findings align with the theoretical considerations that charge can promote the formation of small droplets, stabilise them against evaporation and enhance the collision and coalescence of the larger droplets, offering valuable insights into potential weather modification methods that avoid the use of chemicals. Such methods could be particularly beneficial for regions with high fog frequency, like the UAE.