Use of NDVI and Land Surface Temperature for Drought Assessment: Merits and Limitations

Abstract

A large number of water- and climate-related applications, such as drought monitoring, are based on spaceborne-derived relationships between land surface temperature (LST) and the normalized difference vegetation index (NDVI). The majority of these applications rely on the existence of a negative slope between the two variables, as identified in site- and time-specific studies. The current paper investigates the generality of the LST–NDVI relationship over a wide range of moisture and climatic/radiation regimes encountered over the North American continent (up to 60°N) during the summer growing season (April–September). Information on LST and NDVI was obtained from long-term (21 years) datasets acquired with the Advanced Very High Resolution Radiometer (AVHRR). It was found that when water is the limiting factor for vegetation growth (the typical situation for low latitudes of the study area and during the midseason), the LST–NDVI correlation is negative. However, when energy is the limiting factor for vegetation growth (in higher latitudes and elevations, especially at the beginning of the growing season), a positive correlation exists between LST and NDVI. Multiple regression analysis revealed that during the beginning and the end of the growing season, solar radiation is the predominant factor driving the correlation between LST and NDVI, whereas other biophysical variables play a lesser role. Air temperature is the primary factor in midsummer. It is concluded that there is a need to use empirical LST–NDVI relationships with caution and to restrict their application to drought monitoring to areas and periods where negative correlations are observed, namely, to conditions when water—not energy—is the primary factor limiting vegetation growth.

A Two-Source Model for Estimating Evaporative Fraction (TMEF) Coupling Priestley-Taylor Formula and Two-Stage Trapezoid

“…Some previous studies indicated that when water is the limiting factor for vegetation growth, the LST has a negative correlation with NDVI. However, a positive LST-NDVI correlation exists when energy is the limiting factor for vegetation growth [40][41][42]. Therefore, the TMEF model is suggested to the areas and periods where water is the limiting factor for vegetation growth, such as in arid and semi-arid areas and during the midseason.…”

Evaluation of Drought Indices Based on Thermal Remote Sensing of Evapotranspiration over the Continental United States

“…The strongest correlations between the ESI and the USDM are observed over the Great Plains and in the southeastern United States. These are areas identified by Karnieli et al (2010) where LST and NDVI tend to be anticorrelated, indicating moisture-limiting (as opposed to energy limiting) vegetation growth conditions. ET will be most sensitive to changing subsurface moisture conditions in these areas, and therefore anomalies should be indicative of drought.…”

Differences in resource management affects drought vulnerability across the borders between Iraq, Syria, and Turkey

“…Much research is focused on the meteorological aspects of drought (i.e., reduction in precipitation); however, an agricultural perspective that focuses on soil moisture and crop production can provide more indepth insight into the socioeconomic impacts of drought (Eklund and Seaquist 2015). This can be carried out using satellite images to assess the vegetation quality as an indicator of soil moisture (Gouveia et al 2009, Karnieli et al 2010. Drought by itself is not a natural disaster; it becomes one when the lived effects of the drought are extremely detrimental to local populations.…”