Innovative Ice Cloud Imager

SEA Ltd

Pathfinder Project (typically 6-12 months duration)

Radiative transfer in the atmosphere is a key climate driver. Radiative transfer in clear air is reasonably well understood – leading to such actions as the global control through UN Treaty of chemicals with major atmospheric effects, such as chlorine-based solvents. Much less well understood is the effect of clouds; low altitude clouds will be studied in detail by the EarthCARE mission, but high altitude cirrus remains a problem. There is anecdotal evidence that the frequency of high altitude cirrus may have been increasing since the development of the jet engine, but systematic global measurements remain for the future. The UK-provided SCR on Nimbus 5 made cirrus measurements during 1973 with 50μm and 130μm channels; a great deal was learned but this did not become an operational system.

More recently, it has been concluded that the preferred approach is to make measurements around the same frequencies, but approached from the microwave side; 300μm corresponds to 1THz, and submm radiometer technology is now becoming available at frequencies in the high 100s of GHz.

The ICI instrument was planned to fly on MetOp 2G, but even though its scientific desirability is not in question, its selection is now in doubt for financial reasons. The UK Met Office is known to have led the arguments for the provision of this data set. In the activity described here it is proposed to study means of providing such cirrus cloud measurements at the lowest possible cost. We propose to compare the submm technology approach with the infrared approach in order to identify the lowest cost instrument which would provide useful data. This will lead to a high value-for-money solution and will enable the disruptive technology developed in the UK to be deployed in a timely manner.

The lead organisation for this project is SEA Limited.