USE OF SATELLITE SOLAR-INDUCED CHLOROPHYLL FLUORESCENCE FOR METEOROLOGICAL DROUGHT ASSESSING: MERITS AND LIMITATIONS

Solar-induced chlorophyll fluorescence (SIF) could provide information on plant physiological response to water stress (e.g., drought). There are growing interests to study the effect of drought on SIF. However, to what extent SIF responds to climate variables such as precipitation, temperature and potential evapotranspiration is not clear. In this regard, we evaluated the relationship between two satellite-based SIF products of different spatial resolutions and three commonly used meteorological drought indices (Standardized Precipitation-Evapotranspiration Index, SPEI; Standardized Precipitation Index, SPI and Palmer Drought Severity Index, PDSI) under diverse climate regions in the continental United States. Results showed satellite SIF responded to prolonged meteorological drought but it appeared to be less correlated to 1-month SPEI and SPI. Compared with coarse spatial resolution SIF, fine resolution SIF slightly improved the correlations with long-term meteorological drought indices. More importantly, we found the relationship between SIF and meteorological drought varied spatially with high sensitivity occurring in dry areas with high mean annual temperature and low vegetation productivity. Temperature, vegetation properties and precipitation are the major factors affecting the relationships between SIF and meteorological drought indices. Taken together, satellite SIF is highly sensitive to meteorological drought especially the long-term meteorological drought but the high sensitivity is constrained to dry regions.