Airborne measurements of condensation nuclei, cloud condensation nuclei, aerosol sizes and concentrations (PCASP), and cloud droplet spectra (FSSP) were made over the United Arab Emirates (UAE) and the nearby Gulf region during winter and summer months in 2001. A variety of cloud conditions (from convective to mid-level stratiform) as well as clear sky conditions were sampled, both as vertical profiles and through multiple penetrations.

CN aerosol concentrations were found to be highest near local pollution sources, associated with oil production facilities. These aerosols were also effective CCN with enhanced background levels of CCN over most of the UAE and vicinity, but particularly near local pollution sources. Generally, higher cloud droplet concentrations were found in clouds affected by these high aerosol regions, making them more continental in nature. Vertical profiles of the aerosols show that the top of the boundary layer was typically at about 1500 m for the winter experimental period. Concentrations of all aerosols decreased rapidly above the boundary layer, with significant elevated layers of aerosols. Large differences between the CN and PCASP concentrations indicate that regions in the UAE are significant sources of nucleation mode aerosols. Above the boundary layer, it is appears that nucleation mode aerosols are an important source of CCN.

A summary of six months of data collection (January through March, mid-June through mid-September) will be presented, characterizing the aerosol and cloud droplet conditions in the UAE.