The effect of cloud forward scattering on the ICESat surface altimetry measurements

To accurately measure the topographic changes of sea ice and ice sheets, we need to understand the effect of clouds and blowing snow on photon path length. Forward scattering of the laser light from clouds increases the photon path length and the surface appear farther from the satellite. This is especially true for blowing snow because of its low altitude. This effect is referred to as atmospheric range delay.

In the presentation we discuss biases in surface elevation measurements caused by undetected thin clouds. We present a simple radiative transfer model that accounts for the first-order scattering contribution and estimates range delay as a function of the telescope field of view and optical properties of cloud and blowing snow. Range delay examples will be shown using ICESat observations. Finally, we discuss the possibility of correcting surface altimetry data for biases due to cloud and blowing snow forward scattering.