李青寰博士——遥感科学国家重点实验室2019年系列学术讲座之三十四

主要内容：

Forest cover significantly attenuates natural upwelling ground microwave emission from seasonal terrestrial snow. This presents a major challenge for the accurate retrieval of snow from airborne or spaceborne passive microwave (PM) observations. Forest transmissivity is a key parameter describing tree emission because not only does it influence the proportion of sub-canopy upwelling microwave emission penetrating through the forest canopy, it also controls the forest thermal emission. Hence, it is a very important parameter for correcting the influence of forests on spaceborne or airborne observations of the Earth’s land surface. Under sub-zero temperatures, vegetation water content can be frozen influencing the microwave transmissivity of trees. Yet this phenomenon has not been verified through experimentation leaving significant uncertainty in tree emission modelling and spaceborne microwave observations. Therefore, a season-long experiment was designed to study this phenomenon. Ground-based radiometer observations of tree emission, spaceborne observations of forest emission, and model simulations of canopy emission were conducted during this experiment. In this presentation, we will discuss: 1) the influence of physical temperature on tree transmissivity; 2) the influence of the temperature-transmissivity relationship on the tree emission; 3) how the temperature-transmissivity relationship on the tree emission could influence the PM snow retrieval, and how to reduce its influence.