Assessment of VIIRS Aerosol, Albedo and Land Cover Environment Data Records for Climatic Research

Shunlin Liang, Crystal Schaaf, Alan Strahler, Mark Friedl and Feng Gao (BU)

This study has been selected for the NPOESS Preparatory Project (NPP) Science Team membership by assessing a connected suite of atmospheric and land surface Environmental Data Records (EDRs) from VIIRS for their suitability for long-term climate studies. The principal investigator for this project is Dr. Crystal Schaaf at Boston University.

The land aerosol algorithm is the first building block of most of the land EDRs. Utilizing a dark target approach, it retrieves aerosol properties that are, in turn, used to produce the surface reflectances that are the primary input for higher-level products in the land product chain. The land albedo EDR relies on two approaches to obtain daily albedo values for the globe. The heritage algorithm is the MODIS BRDF/Albedo algorithm, which depends on these atmospherically-corrected cloud-free directional surface reflectances for inputs and is used for most land surfaces. An innovative direct estimation approach is utilized for bright backgrounds, such as snow or bright desert, where the atmospheric correction of aerosols can be problematic. The land cover classification algorithm also relies on an annual phenological cycle of high quality surface reflectances to map the world's land cover types.

The investigators on this project are uniquely qualified to evaluate this key land product chain, as they include the authors of both albedo approaches as well as the authors of the heritage MODIS Land Cover algorithm. We have also participated in the international evaluation of the AVHRR-based IGBP DISCover Land Cover product and are currently involved internationally in both albedo and land cover validation under the auspices of the CEOS-LPV activity. Moreover, one investigator has served as the MODIS validation scientist for both the MODIS surface reflectance and the MODIS albedo algorithms, in addition to his role as validation scientist for the NOAA/NASA Pathfinder AVHRR Land Project and the NASA Earth Observer-1 (EO1) Project Team. Thus, our research team is well situated to assess the suitability of the NPP VIIRS implementation of heritage algorithms and the stability of the resulting EDRs for the long term climate data record.