Airborne measurements of Arctic sea ice, glacier and snow emissivity at 24-183 GHz

Microwave radiometers were operated on a research aircraft during low-level flights in the Arctic in March 2001. Data from these instruments are used to calculate surface emissivity at millimetre wavelengths. This calculation includes the retrieval of an effective temperature from multiple channels centred at 183 GHz. Emissivity spectra will be presented for a range of surface types, including open water, new ice (nilas), first year, multi-year, and glacial ice. These show that the emissivity of older ice types is lower at 24 GHz, decreases further at higher frequencies, but usually starts to increase by 157 or 183 GHz. These results will help exploit data from satellite instruments, such as AMSU, in the Arctic.