Project Funding: 2011 - 2014

NRA: 2010 NASA: NPP Science Team for Climate Data Records   

Funded by NASA

Abstract:
"Surface albedo (and reflectance anisotropy) has been recognized by GTOS as an essential climate variable (ECV) crucial for accurate modeling and monitoring of the Earth's radiative and biophysical regimes (Schaaf et al., 2009). As such, albedo is one of the primary VIIRS Environmental Data Records required by the NPOESS Preparatory Project (NPP). Unfortunately the VIIRS specification only calls for a single broadband value, retrieved on a daily basis under cloud-free conditions at the time of overpass, whereas most numerical prediction models (and global climate and biogeochemical models) nowadays call for a representation of the surface radiation in terms of both the photosynthetically active radiation (shortwave radiation less than 0.7μm) and the near and midwave radiation (0.7- 4.0 μm). Many applications are relying on even more than two multispectral bands. Two VIIRS algorithms have been implemented to fulfill this operational requirement for a single broadband albedo. The first (roughly based on a MODIS heritage) relies on periodic multi-day retrievals of narrowband anisotropy models to estimate the Bidirectional Reflectance Distribution Function (BRDF) of each pixel (Schaaf et al., 2002; Lucht et al., 2000) and then couples these with the surface reflectance retrieved on any single day to obtain an estimate of the daily shortwave albedo at the overpass time. The second approach relies on single-day top-of-atmosphere radiances and precomputed radiative transfer model information to estimate daily broadband surface albedos (Liang et al., 2003; 2005), particularly over highly reflective surfaces. While both approaches can provide spectral albedos, these are not currently planned for archive and dissemination. Furthermore, in the case of the MODIS heritage algorithm, the operational user will have no access to the underlying spectral anisotropy models (the BRDF Intermediate Process or IP) for each location and therefore they are precluded from computing spectral albedos for themselves as well as computing albedo under other illumination conditions, specifying the surface boundary conditions, or correcting surface reflectances to a common view-angle. Note that reflectances corrected to a common nadir view, Nadir BRDF-Adjusted Reflectances (NBAR) are the primary input for the MODIS land cover and phenology products and a number of receiving facilities have implemented the daily MODIS Direct Broadcast BRDF anisotropy model retrieval code so that they can generate not only daily albedo, but also daily view-angle-corrected reflectances and view-angle-corrected vegetation indices to monitor local landcover change, assess rangeland capacity and estimate agricultural productivity. Therefore this proposal seeks continued participation in the NPP Science Team and focuses on further evaluation of the contractor implemented daily albedo quantities and preservation of the long term record of climate-quality albedo, BRDFs, and NBAR quantities that has been so successfully initiated under MODIS.

2015 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)

• Utilizing Highly Portable Terrestrial Lidar to Improve Spatial and Temporal Resolution of Ecological Monitoring Efforts   --   (Ian Paynter, Edward Saenz, Francesco Peri, Crystal Schaaf, Angela Erb, Robert Chen, Jennifer Bowen, Alan Strahler, Zhan Li, Jan van Aardt, Jasmine Muir, Lola Fatoyinbo, Bruce Cook, Miguel Román, David Clark, Deborah Clark, Leo Campos, William Miranda)   [abstract]
• Evaluation of the VIIRS daily BRDF, NBAR, and Albedo product as compared to the MODIS V006 daily BRDF, NBAR, and Albedo product and in situ measurements   --   (Yan Liu, Zhuosen Wang, Qingsong Sun, Crystal Schaaf, Miguel O. Román, Angela Erb)   [abstract]

2013 NASA Terrestrial Ecology Science Team Meeting Poster(s)

• Monitoring Seasonal Albedo and Vegetation Phenology with the V006 Daily MODIS BRDF/albedo Product   --   (Zhuosen Wang, Crystal Schaaf, Alan Strahler, Xiaoyang Zhang, Yanmin Shuai, Yan Liu, Qingsong Sun)   [abstract]

More details may be found in the following project profile(s):

• NASA Terrestrial Ecology (TE) Project Profile