Characteristics and comparative analysis of the reconstructed drought/flood grade sequence of eastern Northwest China from 1470 to 1912

Abstract

The eastern Northwest Chinese drought/flood grade sequence was reconstructed according to historical data on drought and flood disasters for the period from 1470 to 1912. The changing characteristics of drought/flood disasters over 443 years in eastern Northwest China were analyzed by employing methods such as the moving average, accumulative anomaly, moving t test, and wavelet analysis. To verify the reliability of this sequence, long-term trends were analyzed and compared using precipitation sequences reconstructed for Huashan and the drought/flood index for Longxi. The drought/flood grade curve and stalagmite oxygen isotopic records of two provinces were also compared. The results show that: (1) drought disasters were severe and frequent in eastern Northwest China. An alternating pattern between drought and flood occurrences was observed, which can be divided into four stages: 1470–1540, 1541–1615, 1616–1796, and 1797–1912. We further classified the four stages into 12 partial drought or partial flood periods. (2) Twelve abrupt changes were observed on the decadal scale and five abrupt changes were detected on the half-century scale. (3) The reconstructed sequences display a periodic variability on multiple scales; notable variability was detected on the following timescales: 130–110 years, 70–80 years, 50–52 years, 28 years, 10–15 years, and 5 years. The first four primary periods were 28 years, 15 years, 73 years, and 5 years; 28 years shows the strongest oscillation. (4) Based on the comparison and analysis, the reconstructed drought/flood grade sequence is highly consistent with other precipitation sequences. It corresponds to stalagmite oxygen isotopes records of the same period. All these findings indirectly confirm the reliability of the recovered historical flood and drought grade sequence based on historical data.