インド域の循環パターンによるエルニーニョ期間中の赤道東太平洋

Abstract

This study investigates the relationship between circulation anomalies over India during the month of April, and sea surface temperature (SST) anomalies of the eastern Pacific Ocean (Niño 3 region). It is found that rain over northern parts of India and position of 500hPa ridge at 75°E, respectively, have significant correlation coefficients with subsequent SST anomalies of eastern Pacific Ocean (Niño 3 region). Moreover, these relationships are stronger during El Niño years. Since, during El Niño years, peak warming in SST occurs during October-December months, it could well be assessed with the help of these two parameters with the lead time of six months, once occurrence of an El Niño event is indicated by already existing dynamical models. To predict the peak warming during the El Niño years, data of April rain and position of 500hPa April ridge for eleven El Niño years, (1951, 1953, 1957, 1965, 1969, 1972, 1976, 1982, 1987, 1992, 1997) were subjected to the principal component analysis. First principal component was used to predict the average SST anomalies of October-December months through a simple regression equation using cross validation method. The standard deviation of average SST anomalies of October-December months for these eleven years is 0.96, while the root mean square error of the predicted value is 0.52, which is indicative of the good skill of prediction.