Climate Oscillation of the Summer Rainfall Anomaly Pattern for the Flood Season of 1991

The distribution of summer rainfall anomalies in 1991 consists with the EOF expanded third eigenvector from the 《Yearly charts of dryness/wetness in China for the last 500-year period》. By analyzing the time coefficient of the third eigenvector it is found that the dryness/wetness pattern index in 1991 appears a Bruckner cycle with 37 years and is related to the SOI with the cycle of 36.7 years. It is also found that it has relation to the globe temperature change (the correlation coefficient between them is 0.41) and to the correlation distribution of SST in North Pacific, which is similar to the sea surface temperature anomalies pattern during the E1 Nino period. Therefore, the appearance of drought/flood pattern in 1991 may be related to the inherent climatic oscillation, such as the long-term variation for itself in the dryness/wetness pattern, the globe climate warming, and particularly, the intensification phase of the ENSO events.