Power Spectrum Analysis of Pre-Monsoon Season Rainfall over Andhra Pradesh and Telangana

Maximum rainfall events and periodicities of pre-monsoon rainfall over Rayalaseema, Telangana and coastal Andhra Pradesh, India were studied by using the IITM, PUNE rainfall data for the period 1871-2016 (146years). The data has exposed to 11-years running averages and the periods of decreasing and increasing changes are calculated. The time series of the monthly rainfall were disseminated through a high-pass filter to climate periods above 21-years and then subjected to rangesscrutinypending maximum entropy method to obtain province periodicities. These substantial periodicitiesover coastal Andhra Pradesh at 5.4 years, 3.84 years, 2.8 years and 2.2 years are observed. In Rayalseema at 5.21 years, 3.8 years, 3.17 years, 2.7 years and 2.3 years periodicities identified over Telangana at 10.4 years, 6.4 years, 2.8 years, 3.74 years, 2.8years and 2.2 years periodicities observed. From this periodicity, we can understand that the impact of 2.4 to 2.7 years periodicity is attributed to quasi-biennial oscillation, 3.3-8.4 years periodicity is attributed to ENSO and 12.2-13.5 years periodicity may be due to sunspot activity. From the above periodicities, the effect of QBO and ENSO is more on the pre-monsoon rainfall activity over Coastal Andhra Pradesh, Rayalaseema and Telangana.