Automated temporal NDVI analysis over the Middle East for the period 1982 - 2010

Sammanfattning: The NDVI time-series consist of trend, season and noise. Changes in the season component are related to climate factors and they happen gradually over long period of time. The changes in the trend component are often due to human activities, fires and etc. This paper implements two algorithms (PolyTrend and DBEST) in R language, in order to examine the vegetation changes in the Middle East and to give more possibilities in the hands of the remote sensing communities. DBEST can analyse the gradual and the abrupt changes by decomposing the data, while PolyTrend classifies the inter-annual change between the picks of the green season. PolyTrend and DBEST were adapted for R language environment. Two additional algorithms were developed to apply both algorithms over NDVI3g data set of the Middle East. A third algorithm discovered the affected land-cover through an overlay analysis by the use of the UMD land-cover classification data set. PolyTrend showed linear (4%), quadratic (2%) and cubic (3%) trends. The different trend types were often found to be grouped in clusters. The largest clusters of trends were found near the south-eastern corner of the Arabian Peninsula and in the central regions of Saudi Arabia. More than 10% of all mixed forests were affected by these trends, most of which were in negative direction. DBEST showed that 1% of the vegetation experienced a higher magnitude of change. Clusters of these changes were mainly located in the south-eastern and the western part of Turkey, the northern regions of Iraq and Syria, as well as along the coastlines of the Black Sea and the Caspian Sea. The changes were mainly related to the cropland and the grassland and were more in positive directions. The study demonstrated the potential of PolyTrend and DBEST in R language for the remote sensing. It concludes that probably climatic factors affected the forests in Turkey and Iran. The high magnitude of changes of the cropland and grassland indicates that in some regions the agriculture expanded, while in others it declined.