Studies on the trend and chaotic behaviour of Tamil Nadu rainfall

Abstract

This study is aimed at in finding the trend or nonlinearity that may exist in the rainfall pattern of the State of Tamil Nadu. Based on the observed rainfall data for a period of 111 years (19012011), a trend analysis with Hurst exponent and non-linearity analysis with Lyapunov exponent is employed. The interpretation of the Hurst exponent of Tamil Nadu rainfall indicates that the Southwest Monsoon rainfall shows a persistent behaviour, whereas the annual rainfall shows an anti-persistence behaviour. The Northeast Monsoon, which is the most important season for the State of Tamil Nadu shows a randomness or non-linearity in its value. The non-linearity in the Northeast Monsoon has been verified through Lyapunov Exponent. The Northeast Monsoon shows a largest positive Lyapunov exponent value than the Southwest and Annual rainfall. This indicates that the Northeast Monsoon of Tamil Nadu is chaotic. The chaotic nature of the Northeast Monsoon is also verified using surrogate data method.