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3 Research Findings
3.1 Interannual Rainfall Variability
Application of the different statistical tools on rainfall records in the 96-year study
period resulted in findings that differed among the four countries.
Rainfall in Ivory Coast showed two break years in the study period: 1981 for the
Standardized Precipitation Index and Pettitt’s test, and 1982 for Lee and Heghinian’s
test (Figs. 2, 3, and 4). Compared to the former, the latter two have periods of unequal
duration with different characteristics. The wet period, which extends from 1921 to
1981, shows an average rainfall of 1538 mm, while the dry period, from 1982 to 2016,
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
1921
1924
1927
1930
1933
1936
1939
1942
1945
1948
1951
1954
1957
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
1999
2002
2005
2008
2011
2014
SPI
1981
Fig. 2 Evolution of the Standardized Precipitation Index in Ivory Coast from 1921 to 2016
Fig. 3 Evolution of Pettitt’s
test results in Ivory Coast
from 1921 to 2016