Submillimeter/far-infrared channel selection simulations for a cirrus radiometer

We report on the progress of a far-infrared/submillimeter radiometer being developed in Cardiff for the measurement of cirrus clouds. Remote sensing of cirrus clouds is known to be of great importance to the long-term accuracy of current General Circulation Models (GCM) and climate prediction but with greater measurement coverage needed. The instrument reported here is an aircraft deployed, 5 channel fixed band radiometer capable of retrieving cirrus Ice Water Path (IWP) and mean particle diameter (Dme) using a spectral range of between 10 cm-1 and 55 cm-1. The radiometer will capitalise on ongoing measurements from the Fourier transform interferometer based, Far-infrared Sensor for Cirrus (FIRSC), an instrument for which Cardiff has been closely associated. Initial results of channel selection simulations are presented here with comparisons between different combinations of channel frequency and bandwidths, along with the number of channels used and cloud particle shape. Also demonstrated is the effect of instrument noise on retrieval performance which is shown to be the dominant source of retrieval error