Global variability of terrestrial surface properties derived from MODIS visible to thermal-infrared measurements

Abstract

There are now over five years of MODIS Global Land Data Products that have been applied to global terrestrial land cover, carbon, and water science. There is a suite of land products for Land Cover Characteristics, such as Land Cover, Vegetative Cover Conversion, Continuous Fields, and Fire. The Radiation Budget Variables include Surface Reflectance Products, Land Surface Temperature, Snow and Ice Cover, BRDF and Albedo, and Ecosystem Variables are characterized by Vegetation Indices (NDVI/ EVI), LAI and FPAR, Gross Primary Production and Net Primary Production (GPP/NPP). The land cover products are being used in assessing global change in the biosphere by quantifying land cover type and detecting changes resulting from climatic forcings and human-induced and natural disturbances. The MODIS fire product includes daily mapping of active fires, burned area estimates, and analyses of large-scale wildfire disturbances. The MODIS NDVI and EVI are used for global vegetation analyses at 250 m resolution, adding to the historical AVHRR-NDVI time series data record. There are also advanced biophysical variables generated, such as the leaf area index (LAI) and fraction of absorbed photosynthetically active radiation (FPAR) products which are needed for advanced modeling of climate, carbon cycles, and water balance of the land surface. The daily gross primary production and annual net primary production (GPP/NPP) are components of the land carbon cycle and provide a first step in CO2 source/ sink analysis. Recent results of using this product with the historical AVHRR NDVI data record show a 6% increase in terrestrial NPP over the last 18 years. Two new experimental products are also of utility in land surface science, a canopy water content index and an evaporation index based on surface energy partitioning principles, and have potential value for regional drought analysis, water management and wildfire risk assessments. The radiometric quality of MODIS has proven to be excellent for land science. These high quality, consistent and well-calibrated satellite measurements are becoming invaluable in detection and monitor changes and trends of the biosphere. I. INTRODUCTION The assessment and monitoring of spatial and temporal patterns of terrestrial vegetation activity are important in ecosystem variability studies and in understanding linkages between ecosystem structure and function and climate variability including changes in ecosystem processes associated with land conversions. The Moderate Resolution Imaging Spectroradiometer (MODIS) is a key instrument onboard the Terra and Aqua satellite platforms. Terra's orbit around the Earth is timed so that it passes from north to south across the equator in the morning, while Aqua passes south to north over the equator in the afternoon(1). Terra MODIS and Aqua MODIS are viewing the entire Earth's surface every 1 to 2 days, acquiring data in 36 spectral bands. These data are being used to improve our understanding of land surface global dynamics and processes. MODIS is playing an important role in the development of validated, global data products useful to interactive Earth system models able to predict environmental change accurately enough to assist policy makers in making sound decisions concerning the protection of the planet (2).