Cloud fraction is a primary product reported in cloud climatologies. However, cloud climatologies derived from satellites always suffer from the view angle effect, whereby cloud fraction increases with the viewing zenith angle. This effect is largely a consequence of (1) an increase in the amount of cloud-sides observed with viewing obliquity and (2) pixel expansion with viewing obliquity. These two effects have traditionally been difficult to decouple; however a new satellite instrument will help solve this problem.

The Multi-angle Imaging SpectroRadiometer (MISR) on-board EOS-Terra is the first high-resolution imager to make global, near-simultaneous, multi-spectral, multi-angle radiometric measurements of the Earth. Nine separate cameras provide viewing zenith angles at the surface that range from ± 70.5°. Each camera is designed to collect data at 275 m resolution over a 360 km swath. With this unique multi-angle viewing capability, MISR, for the first time, accomplishes the examination of the cloud fraction dependence on viewing zenith angle qualitatively and quantitatively. The relationships for the cloud fraction dependence on viewing zenith angle derived from one month of MISR data taken over oceans will be presented, showing that the effect is much larger than previously predicted by other studies. Applications of these statistical relationships in the remote sensing of cloud from satellites will be discussed.