A Study on the Consistency and Trend of the Northeast and Southwest Monsoon Rainfall in Tamil Nadu

Consistency and trend in the Northeast and Southwest monsoon rainfall of Tamil Nadu have been studied utilizing the data for the 60-year period from 1941 to 2000. It is seen that both the Northeast and Southwest monsoon rainfall of Tamil Nadu is consistent in double mass curve analysis method. Frequency distribution of Northeast and Southwest monsoon rainfall of Tamil Nadu is normal. Decreasing mean rainfall (1941-70) of both Northeast and Southwest monsoon is observed for the 30 years and increasing mean rainfall (1971-2000) of both Northeast and Southwest monsoon is observed for the later 30 years. There is no significant increase of the mean rainfall of both Northeast and Southwest monsoon per 30 years. The Northeast and Southwest monsoon rainfall of Tamil Nadu was examined to identify the trends using the statistical techniques such as Randomness test, Mann-Kendall rank statistic method, Students’ t-test, Spearman’s rank correlation test, and WilcoxonMann-Whitney test. Among the various test, all the results conform the existence of trend at 95% significant level of confidence except Spearman rank correlation for the Northeast monsoon rainfall of Tamil Nadu. It agrees with 99% significant confidence level.