POWER SPECTRUM ANALYSIS OF THE ANNUAL RAINFALL SERIES FOR MASSACHUSETTS (NE, USA)

Maximum Entropy Spectral Analysis of the annual rainfall series for 1887-1976 (90 years) for Massachusetts (northeastern U.S.A.) shows T = 17.8 (very near the 18.6 year luni-solar signal) as the most prominent periodicity. However, it explains only 12% variance. Also, the next prominent periodicity is T = 2.72 years, i.e. in the QBO (Quasi-Biennial Oscillation, T = 2-3 years) region. Also, regular periodicities account for only 50% variance, leaving 50% as a random component. Hence, predictions are unreliable. Roughly, excess rainfall during 1990-1994 and droughts during 1992-2002 are indicated; but occasional years of opposite behavior cannot be ruled out.