Periodicities of winter monsoon rainfall over Rayalaseema using Maximum Entropy Method

Periodicities of winter monsoon rainfall over Rayalaseema, Andhra Pradesh, India are studied by using the IITM, PUNE rainfall data for the period 1871-2016 (146years). The mean and standard deviation,  the extreme rainfall events are evualated. If any value of rainfall is greater than or equal to mean + one standard deviation, the corresponding winter monsoon is considered as good winter monsoon. If any value of rainfall is less than or equal to mean - one standard deviation, the corresponding winter monsoon is considered as poor winter monsoon.  The original time series of the winter monsoon rainfall is subjected to 11-year moving averages to examine the variable trends. The composite daily winter monsoon rainfall for good and poor monsoons of Rayalaseema for the four stations, namely; Ananthapur, Cuddapah, Kurnool  and Tirupati are prepared separately. The Rainfall periodicities are calculated using maximum entropy method. The rainfall over  Rayalaseema displays 2.4 years, 3.3 years, 5.0 years and 13.4 years  periodicities. Generally 2.4 – 2.7 years periodicity is attributed to QBO. 3.3 – 8.4 years periodicity is attributed to ENSO. 12.2 – 13.5 years periodicity may be due to sunspot activity.  From the above periodicities, the effect of quasi-biennial oscillation and ENSO is more on the northeast monsoon rainfall activity over Rayalaseema.