Elevation Angular Dependence of Wideband Autocorrelation Radiometric (wibar) Remote Sensing of Dry Snowpack and Lake Icepack

A novel and recently developed microwave radiometric technique, known as wideband autocorrelation radiometry (WiBAR), offers a deterministic method to remotely sense the microwave propagation time ⌧ delay of multi-path microwave emission of low loss terrain covers and other layered surfaces such as dry snowpack and freshwater lake icepack. The microwave propagation time ⌧ delay through the pack yields a measure of its vertical extent; thus, this technique is a direct measurement of depth. We have confirmed the expected simple dependence of the microwave propagation time ⌧ delay on the elevation angle with ground-based WiBAR measurements of the icepack on Douglas Lake in Michigan in early March 2016. The observations are done in the X-band for the icepack. At these frequencies, the volume and surface scattering are small in the pack. This technique is inherently low-power since there is no transmitter as opposed to active remote sensing techniques. In this paper, the system design parameters and physics of operation of the WiBAR is discussed, and it is shown that the microwave propagation time can be readily measured for dry snowpack and lake icepack for observation angles away from nadir to at least 70 .