Evaluation of MODIS and VIIRS Albedo Products Using Ground and Airborne Measurements and Development of Ceos/Wgcv/Lpv Albedo Ecv Protocols

Zhuosen Wang, University of Maryland, College Park, Earth System Science Interdisciplinary Center, College Park, MD, United States; Oak Ridge Associated Universities Inc., Oak Ridge, TN, United States, Miguel O O Román, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Crystal Schaaf, University of Massachusetts Boston, School for the Environment, Boston, United States, Qingsong Sun, Boston University, Department of Earth and Environment, Boston, MA, United States, Yan Liu, University of Massachusetts Boston, School for the Environment, Boston, MA, United States, Edward Joseph Saenz, University of Massachusetts Boston, Boston, MA, United States and Charles K Gatebe, NASA Ames Research Center, Moffett Field, CA, United States
Abstract:
Surface albedo, defined as the ratio of the hemispheric reflected solar radiation flux to the incident flux upon the surface, is one of the essential climate variables and quantifies the radiation interaction between the atmosphere and the land surface. An absolute accuracy of 0.02-0.05 for global surface albedo is required by climate models. The MODerate resolution Imaging Spectroradiometer (MODIS) standard BRDF/albedo product makes use of a linear “kernel-driven” RossThick-LiSparse Reciprocal (RTLSR) BRDF model to describe the reflectance anisotropy. The surface albedo is calculated by integrating the BRDF over the above ground hemisphere. While MODIS Terra was launched in Dec 1999 and MODIS Aqua in 2002, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite was launched more recently on October 28, 2011. Thus a long term record of BRDF, albedo and Nadir BRDF-Adjusted Reflectance (NBAR) products from VIIRS can be generated through MODIS heritage algorithms. Several investigations have evaluated the MODIS albedo products during the growing season, as well as during dormant and snow covered periods. The Land Product Validation (LPV) sub-group of the Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV) aims to address the challenges associated with the validation of global land products. The validation of global surface radiation/albedo products is one of the LPV subgroup activities. In this research, a reference dataset covering various land surface types and vegetation structure is assembled to assess the accuracy of satellite albedo products. This dataset includes in situ data (Baseline Surface Radiation Network (BSRN), FLUXNET and Long Term Ecological Research network (LTER) etc.) and airborne measurements (e.g. Cloud Absorption Radiometer (CAR)). Spatially representative analysis is applied to each site to establish whether the ground measurements can adequately represent moderate spatial resolution remotely sensed albedo products.
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