rainfall analysis by girma mamo
Research Paper
Trend and variability of rainfall in Tigray, Northern Ethiopia: Analysis of meteorological data and farmers’ perception
Accepted 11th May, 2013
ABSTRACT
Rainfall is the most important but variable climatic parameter in the semiarid tropics. In this study, the trend and variability of rainfall were compared with the perception of farmers in northern Ethiopia. Daily rainfall data obtained from five meteorological stations located in different agroecological zones were used to determine trends in annual and seasonal totals, onset and cessation dates, length of growing period (LGP) and dry spell length. Sen’s estimator and Mann-Kendall's statistical tests were used for trend detection. Two hundred fifty three farmers from three administrative areas (districts) that are close to the meteorological stations were interviewed in order to investigate farmers' perception on rainfall trend and variability in the study area. The results indicate that rainfall in the region is highly variable with a non-significant trend in both annual and seasonal totals for all stations. However, trends of rainfall events such as onset date, cessation date, LGP, and dry spell length were changed significantly in most stations, which agreed with the farmers’ perception. Moreover, most stations experienced drought conditions in the last decade. The results suggest the need for designing appropriate agronomic and water management strategies to offset the negative impacts of rainfall variability in the study area.
Key words: Rainfall, rainfall trend, rainfall variability, onset, length of growing period. INTRODUCTION
Agriculture plays a dominant role in the economy of
Ethiopia, contributing 41% GDP, 80% of the employment and the majority of foreign exchange earnings
(Gebreegziabher et al., 2011). The success of agricultural production has, therefore, large implications, ranging from the state of the countrywide economy to the survival of
Trend and variability of rainfall in Tigray, Northern Ethiopia: Analysis of meteorological data and farmers’ perception
Accepted 11th May, 2013
ABSTRACT
Rainfall is the most important but variable climatic parameter in the semiarid tropics. In this study, the trend and variability of rainfall were compared with the perception of farmers in northern Ethiopia. Daily rainfall data obtained from five meteorological stations located in different agroecological zones were used to determine trends in annual and seasonal totals, onset and cessation dates, length of growing period (LGP) and dry spell length. Sen’s estimator and Mann-Kendall's statistical tests were used for trend detection. Two hundred fifty three farmers from three administrative areas (districts) that are close to the meteorological stations were interviewed in order to investigate farmers' perception on rainfall trend and variability in the study area. The results indicate that rainfall in the region is highly variable with a non-significant trend in both annual and seasonal totals for all stations. However, trends of rainfall events such as onset date, cessation date, LGP, and dry spell length were changed significantly in most stations, which agreed with the farmers’ perception. Moreover, most stations experienced drought conditions in the last decade. The results suggest the need for designing appropriate agronomic and water management strategies to offset the negative impacts of rainfall variability in the study area.
Key words: Rainfall, rainfall trend, rainfall variability, onset, length of growing period. INTRODUCTION
Agriculture plays a dominant role in the economy of
Ethiopia, contributing 41% GDP, 80% of the employment and the majority of foreign exchange earnings
(Gebreegziabher et al., 2011). The success of agricultural production has, therefore, large implications, ranging from the state of the countrywide economy to the survival of