Analysis of aerosol-cloud interactions and their implications for precipitation formation using aircraft observations over the United Arab Emirates

The majority of scientific flights targeted summertime convection along the eastern Al Hajar Mountains bordering Oman, while one flight sampled non-orographic clouds over the western UAE near the Saudi Arabian border. In this work, we study the evolution of growing cloud turrets from cloud base (9 degrees C) up to the capping inversion level (-12 degrees C) using coincident cloud particle imagery and particle size distributions from cloud cores under different forcing.

Results demonstrate the active role of background dust and pollution as cloud condensation nuclei (CCN) with the onset of their deliquescence in the subcloud region. Subcloud aerosol sizes are shown to extend from submicron to 100 mu m sizes, with higher concentrations of ultra-giant CCN (d > 10 mu m) from local sources closer to the Saudi border, compared with the eastern orographic region where smaller CCN are observed.