Assessing information content in MODIS observation on the vertical structure of Marine Boundary Layer clouds using Large-Eddy Simulations and 3D radiative transfer models

In situ observations indicate the existence of significant and highly variable vertical structures in MBL clouds due to various processes, such as adiabatic growth, entrainment and drizzling. However, the vertical structures of MBL clouds, on regional to global scales, remain largely unexplored. MODIS has three shortwave infrared (SWIR) bands centered at 1.6, 2.1 and 3.7 μm. These SWIR bands have different cloud penetration depths, and therefore carry information about different layers in the cloud. Previous studies have shown that the combination of these MODIS bands can be used for studying cloud vertical structure. Unfortunately, several factors, such as 3-D radiative effects, algorithm issues and instrument radiometric accuracy complicate the information contained in these bands. The primary objective of this research is to achieve better understanding of the potentials and limitations of MODIS observations for remote sensing the vertical structure of MBL clouds. To achieve this goal, a comprehensive analysis framework was developed to consist of a LES model, a 3D radiative transfer model and a MODIS simulator. Within this analysis framework, a series of case studies were made to assess the information content in MODIS observation for remote sensing of the vertical structure of MBL clouds. The results from these case studies will be presented. The impact of the uncertainties due to 3D radiative effects, sub-pixel averaging and nonlinearity effect will be discussed.