Ice in Clouds Experiment – Dust: a field campaign to study aerosol-cloud interactions

The Ice in Clouds Experiment - Dust (ICE-D) field campaign will take place during July and August 2015, based at Praia, Cape Verde Islands. The primary objective of the campaign is to study the properties of Saharan desert dust primaily as ice nuclei (IN), but also as cloud condensation nuclei (CCN), and the impact of these dust particles on cloud microphysical processes and precipitation formation in both convective and stratiform clouds.

The UK FAAM BAe-146 research aircraft will carry out in-situ measurements of the dust aerosol and cloud properties. On the ground at Praia, there will be extensive suite of aerosol measurements. In addition, a dual-polarisation Doppler X-band radar will be operated to identify suitable cloud regions for aircraft sampling and to provide coordinated observations of the expected vertical columns of supercooled raindrops and development of precipitation within about 100km of the island.

The measurements of mineral dust and their influence on the clouds are fundamental. The uncertainty in the aerosol-cloud interactions causes uncertainty in the radiative properties of clouds and consequently can contribute significantly to the overall uncertainty in climate change predictions. The plan is to make measurements in clouds with and without dust and with varying concentrations. The Sahara is a primary source of mineral dust particles, transported in the atmosphere westwards across the Atlantic. Mineral dust with sources from the Saharan region have been identified as efficient ice nuclei in laboratory and field studies, but the effect on cloud evolution has not been measured. The Cape Verde area is near the source region where dust concentrations are large, and both dust events and cumulus congestus clouds are frequently observed. The large gradients in dust concentration enable aircraft sampling over a wide range of conditions in a single flight.