Combined active and passive Ultra-wide band remote sensing of Polar ice sheet temperature profiles
Abstract
The cryosphere is a critical component of the Earth system that continues to experience rapid change. Recent studies have shown the important impact of ice sheet internal temperatures, providing new impetus for the development of methods to remotely sense internal ice temperatures.
The Ultra-Wideband Software-Defined Microwave Radiometer (UWBRAD) was developed for sensing internal ice sheet temperature profiles using 0.5-2GHz microwave radiometry. Reliable and accurate retrievals based on the coherent model from UWBRAD require density profile measurements from borehole sites "bracketing" the flight path in order to infer the required density fluctuation parameters of variances and correlation lengths. This dependence has limited expansion of the method into regions without borehole sites. An Ultra-Wideband Microwave Active/ Passive Sensor was proposed to reduce or eliminate the dependence on borehole information. It can be shown that the primary impact of density fluctuations is through only the "upper cap" layer of the firn where density fluctuations are largest. It is also assumed that the upper ~50-100m of the firn has a uniform temperature. Then using Maxwell equations with the dyadic Green's function of layered media for the cap and the WKB approximation for the inhomogeneous lower half space of the ice sheet below the cap layer, the brightness temperatures can be reduced to an equation expressing the brightness temperatures in terns of the cap layer reflections and absorption and the emission from the lower half space of ice sheet. In this case, the multiple parameters of the density fluctuations can be condensed into the reflections and absorption that are a function only of frequency. Thus temperature profile retrieval can be performed using the above from passive brightness temperatures assuming reflections and absorption can be obtained by active radar reflections. This model is termed the "coherent reflectivity model". Simulation results have shown a good agreement between this model and the previous passive only coherent model. The results indicate the potential of using combined active and passive remote sensing of temperature profiles of polar ice sheets that is betetr than the previous method of passive only.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C31C1559T
- Keywords:
-
- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0750 Sea ice;
- CRYOSPHERE;
- 4556 Sea level: variations and mean;
- OCEANOGRAPHY: PHYSICAL