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

Período: de 07/10/2011 à 07/10/2011

Horário: Dia 7 de outubro de 2011, às 10h30min

Local: Embrapa Informática Agropecuária

Arnon Karnieli

The Remote Sensing Laboratory, Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Israel.

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 60º N) during the summer growing season (April – September). Information on LST and NDVI was obtained from long-term (21-year) datasets acquired with the Advanced Very High Resolution Radiometer (AVHRR). It was found that when water is the limiting factor for vegetation growth (typical situation for low latitudes of the study area and during the mid-season), 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, while other biophysical variables play a lesser role. Air temperature is the primary factor in mid summer. 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.

Fonte: http://www.cpa.unicamp.br/alcscens/Karnieli_abstract.pdf