ISMAR (International SubMillimetre Airborne Radiometer) is an airborne radiometer. It measures within the microwave and submillimetre part of the electromagnetic spectra. ISMAR is jointly funded by the UK Met Office and the European Space Agency (ESA). The goal is to develop a retrieval method to estimate, apart from other quantities, the amount of atmospheric ice by ISMAR’s radiometer measurements. Cirrus clouds are a typical example for atmospheric ice.
It is difficult to observe cirrus clouds with typical existing infrared and microwave sensors, because for microwave radiation cirrus clouds are too transparent and for infrared radiation cirrus clouds are too opaque. For submillimetre radiation, cirrus clouds are more opaque than for microwave radiation, but still transparent enough to sense their complete vertical dimensions.
The development of new retrieval methods is especially important in view of ESA’s upcoming next generation polar-orbiting weather satellites (METOP-SG). They will be equipped with the Ice Cloud Imager (ICI)-sensor, which measures at similar frequencies like ISMAR.
- Project lead: Dr. Manfred Brath