EOS MLS cloud ice measurements and cloudy-sky radiative transfer model

A cloud ice retrieval technique is described here using measurements at frequencies near 118, 190, 240, and 640 GHz and 2.5 THz from the Earth Observing System Microwave Limb Sounder on the NASA Aura satellite. Measurement principles, methods for cloud detection, and radiative transfer models for retrieving cloud properties are discussed. The 240-GHz data from high-tangent heights are used to retrieve ice water content at pressures <215 hPa, and the 118-, 190-, 240-, and 640-GHz radiances from low-tangent heights are used to retrieve ice water paths with different penetration depths. Some early Microwave Limb Sounder (MLS) results are highlighted, and the observed cloud signatures are consistent with the expectation from model simulations, in general. The simultaneous measurements from MLS 240 and 640 GHz radiometers contain useful information on particle sizes. There are significant cloud-induced radiances at 2.5 THz, despite strong attenuation from the atmosphere. Cloud-scattering signatures are polarized at 122 GHz, but the polarization differences are typically less than 10% of the total cloud-induced radiance.