NDVI response to rainfall in different ecological zones in Jordan

Abstract

The response of NDVI to rainfall was analyzed using NOAA/AVHRR satellite imagery acquired over a time period of ten growing seasons (1981 to 1992) and rainfall data from 16 weather stations in four ecological zones in Jordan. Results of linear regression analysis showed better response of NDVI to cumulative rainfall than to 10-day rainfall with best correlation in the Mediterranean zone. Significant relationships were found between seasonal rainfall and NDVI range (Δ_NDVI) with better correlations for logarithmic and power relationships than for linear relationship. A strong linear relationship occurred between the annual rainfall and end-of-season NDVI in the Mediterranean zone and weak or no correlation in other zones. The correlations were improved when the rainfall data were averaged, summed and correlated with the average NDVI. More agreement, however, was observed between the maximum NDVI image and rainfall than for the average NDVI image and rainfall. Results also showed that stratification of the data according to soil type and/or land cover would not necessarily improve the correlation. However, stratification of the data according to ecological zone demonstrated obvious differences between the NDVI-rainfall in the different zones.

Keywords:

• NDVI
• AVHRR
• Vegetation
• Jordan
• Mediterranean
• arid
• semiarid

Acknowledgment

The authors would like to thank the Distributed Active Archive Center (Code 902) at the Goddard Space Flight Center, Greenbelt, MD, USA and its staff for producing and distributing the Pathfinder AVHRR Land dataset in its present form. Also, they appreciate the enriching comments of the anonymous reviewers and Kimberly Bandy.