Table 2 reveals that there are eight years with
extreme negative SOI (values less than or equal to
mean minus one standard deviation) and another
eight years with extreme positive values (values
greater than or equal to mean plus one standard
deviation). The Mann-Whitney rank test (De and
Mukhopadhyaya 1999) is performed for the rainfall
associated with the extreme positive and extreme
negative SOI episodes during the above 16 years.
The test statistic value is 2.1, which is signifi-
cant at 5% level. The inverse relation is clearly
seen in 12 years out of 16 years. Coastal Andhra
Pradesh received an average amount of 300.9 mm
rainfall (22% deficit) during positive SOI episodes
and an average amount of 494.7 mm rainfall (28%
excess) during negative SOI episodes. This indicates
a shift towards wetter (drought) conditions in
relation to the extreme negative (positive) SOI in
September.
the 4 decades is −0.48, which is significant at 1%
levelrainfall is dominant in the recent four
decades (1958 onwards) (figure 1 an