Abstract

This study analyses the regional climate variability, especially La Niña or El Nino Southern Oscillation events and their impact on rainfall variability and vegetation coverage. The temporal and spatial distributions of temperature, precipitation, and vegetation coverage have been investigated for the two agricultural productive seasons from (2000–2008), using data from 11 meteorological station and MODIS satellite data in Gojjam, Ethiopia. The normalized difference vegetation index (NDVI) is widely accepted as a good indicator for providing vegetation properties and associated changes for large spatial scale. The analyses indicated that climate variability is quite common particularly in the small rainy season, Belg and continues to affect the vegetation condition in the region. The statistical correlation analysis indicated that there is a strong positive correlation between NDVI and the seasonal rainfall in most years, whereas, the temperature increase decreases the vegetation coverage in both seasons. The effect of ENSO, climate variability has been high to the regional rainfall variability in mostly of the months or years. In the fully strong El Nino or La Nina episode years like 2000 and 2002 the SST and rainfall showed positive correlation with r2 values 0.75 and 0.63, respectively. The NDVI anomaly pattern is almost similar to that of the main documented precipitation and temperature anomaly pattern associated with ENSO. The spatial and temporal analyses of basic climate elements and NDVI values for the growing season showed that NDVI and rainfall are highly variable during the 9 years period. The ENSO analyses showed an increase in seasonal vegetation coverage during El Nino episodes contrasting to La Niña episodes. However, there has been a rainfall delay during El Niño episodes in the first one or two months of Kiremt season.

Keywords: Climate variability; La Niña or El Niño Southern Oscillation; Normalize different vegetation indices; Remote sensing; Spatial and temporal