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
来源: 魏静
被阅读 301 次
2019-11-15
  报告题目:The influence of winter time boreal forest tree transmissivity on tree emission and passive microwave snow observations
    
  报告人:李青寰  博士
 
  邀请人:蒋玲梅  副教授
       
  时 间:2019年11月18日(周一)9:00
         
  地 点:北京师范大学生地楼180
           
  报告人简介:
 
  李青寰博士于2019年5月毕业于加拿大滑铁卢大学地理与环境管理学院,现任滑铁卢大学地理与环境管理学院博士后。其主要研究方向为地表参数遥感反演以及植被、积雪和土壤的辐射传输过程。具体研究课题为森林地区相关地物的辐射传输过程以及森林地区积雪厚度和水雪当量反演。李青寰在博士期间参与日本航天局AMSR2地表积雪反演项目,主要研究森林地区的积雪反演以及AMSR2积雪产品的验证工作;参与设计了位于芬兰气象局Sodankylä Geophysical Observatory的植被亮温观测实验。实验结果表明在低温状况下,植物水分含量会因为结冰而降低,从而影响植被的辐射传输过程,并阐述了该现象对森林地区积雪反演的影响。。
 
  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.