Drought Monitoring with Estimates of the Fraction of Absorbed Photosynthetically-Active Radiation (fAPAR) Derived from MERIS

The Fraction of Absorbed Photosynthetically Active Radiation (fAPAR) is a biophysical parameter referring to the state and photosynthetic activity of the plant canopy, and it is directly correlated with the primary productivity of the vegetation. fAPAR is recognized among the Essential Climate Variables of the UN Global Climate Observing System (GCOS) and is a key quantity in carbon cycle models. fAPAR is currently estimated from satellite data using different approaches. This indicator is potentially sensitive to droughts, since it relates to the interception of solar radiation in the canopy of the vegetation, which is reduced under conditions of water stress. The European Commission Joint Research Centre (JRC) is developing the prototype of the European Drought Observatory (EDO) for drought monitoring and forecasting at the European level. Among the other indicators, EDO employs fAPAR as an additional operational parameter for drought monitoring and detection. In this work, the methodology adopted within EDO and the fAPAR data used are presented. EDO employs 10-day composites of fAPAR estimates produced by the European Space Agency (ESA) from MERIS (Medium Resolution Imaging Spectroradiometer) data by means of the MERIS Global Vegetation Index (MGVI) algorithm developed at the European Commission Joint Research Centre (JRC). In order to produce fAPAR anomalies, the MERIS fAPAR time series have been extended with fAPAR estimates obtained from the NASA SeaWiFS (Sea-viewing Wide Field-of-view Sensor) sensor with an algorithm fully compatible with the MGVI. Our results show that MERIS-derived fAPAR anomalies have the capacity to detect droughts on an operational basis, and that the indicator has a correlation with other drought indicators such as the Standardized Precipitation Index (SPI). In particular, MERIS-derived fAPAR offers an enhanced performance compared to the MODIS (Moderate-resolution Imaging Spectroradiometer) fAPAR product and to NDVI anomalies and seems to be correlated with drought conditions in a wider range of geophysical scenarios, highlighting the significant advantage of using advanced algorithms in concrete applications.

ROSSI Simone;  NIEMEYER Stefan; 

2012-09-12

Taylor & Francis Group

JRC67114

978-1-4398-3557-9,