Publications

Endsley, KA; Zhao, MS; Kimball, JS; Devadiga, S (2023). Continuity of Global MODIS Terrestrial Primary Productivity Estimates in the VIIRS Era Using Model-Data Fusion. JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES, 128(9), e2023JG007457.

Abstract
The NASA Terra and Aqua satellites have been successfully operating for over two decades, exceeding their original design life. However, the era of NASA's Earth Observing System may be coming to a close as early as 2023. Similarities between the Moderate Resolution Imaging Spectroradiometer (MODIS), aboard Aqua and Terra, and the Visible Infrared Imaging Radiometer Suite (VIIRS) sensors aboard the Suomi NPP, NOAA-20 and NOAA-21 satellites enable potential continuity of long-term earth observational records in the VIIRS era. We conducted a comprehensive calibration and validation of the MODIS MOD17 product, which provided the first global, continuous, weekly estimates of ecosystem gross primary productivity (GPP) and annual estimates of net primary productivity (NPP). Using Bayesian model-data fusion, we combined 18 years of tower fluxes with prior data on plant traits and hundreds of field measurements of NPP to benchmark MOD17 and to develop the first terrestrial productivity estimates from VIIRS. The updated mean global GPP (NPP) flux from the future MOD17 Collection 7 product and new VNP17 product for 2012-2018 is 127 & PLUSMN; 2.8 Pg C year-1 (58 & PLUSMN; 1.1 Pg C year-1), which compares well with independent top-down and bottom-up estimates. MOD17 and VNP17 depict upward productivity trends over recent decades, with 2000-2018 MOD17 GPP (NPP) rising by 0.47 (0.25) Pg C year-2 but slowing to 0.35-0.44 (0.11-0.13) Pg C year-2 over 2012-2021, with a greater reduction in the NPP growth rate. The new VIIRS VNP17 product has the potential to extend these estimates of global, terrestrial primary productivity beyond 2030. The NASA Terra and Aqua satellites have been successfully operating for over two decades, far longer than their original 5-year design life. However, both satellites may be unable to maintain their original orbits as early as 2023. These satellites carry the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, which are very similar to the Visible Infrared Imaging Radiometer Suite (VIIRS) sensors aboard newer satellites. The long record of MODIS data collected so far may therefore be extended by the VIIRS sensors, particularly the global estimates of the amount of carbon in the atmosphere taken up and stored by plants. We used multiple independent data sets to figure out if and how the MODIS MOD17 computer model should be changed to improve its accuracy and to use data from VIIRS. The new VIIRS VNP17 data could extend our record of plant-atmosphere carbon exchange beyond the year 2030. Over two decades of global productivity estimates from Moderate Resolution Imaging Spectroradiometer (MODIS) cannot be continued without use of Visible Infrared Imaging Radiometer Suite (VIIRS) dataWe performed a comprehensive calibration and validation, and sensitivity and uncertainty analyses of MODIS MOD17 and new VIIRS VNP17Both MOD17 and new VNP17 depict upward productivity trends and mean and interannual variability consistent with independent data

DOI:
10.1029/2023JG007457

ISSN:
2169-8961