Progress in Passive Microwave Remote Sensing of the Cryosphere


      Dr. Ludovic Brucker, NASA Goddard Space Flight Center


The different elements of the cryosphere at high latitudes, like the Greenland and Antarctic ice sheets, sea ice in both hemispheres, frozen soil, and seasonal snow covers on land are both actors in the Earth's climate system and indicators of its evolution. Therefore, it is important to monitor the current state and changes of these elements. Such monitoring from in-situ measurements is very challenging due to the remote and harsh environments. In contrast, space-based sensors are appealing tools, especially microwave radiometers, which provide daily observations of the high latitudes with a weak sensitivity to the atmospheric properties and the solar illumination.


Algorithms are developed to convert the electromagnetic measurements in geophysical and climate variables (e.g. snow accumulation, sea ice concentration, melt event, snow depth). This is never straightforward. For instance, passive microwave observations depend mostly on snow temperature and snow emissivity, i.e., the vertical evolution of the snow properties (such as grain size and density). To retrieve geophysical and climate variables, a good knowledge of emissivities and, thus, of snow properties is required. To that end, in-situ and remote measurements of the Polar Regions are collected and analyzed to develop satellite algorithms.