Temporal-spatial variability in correlations of drought and flood during recent 500years in Inner Mongolia, China

Drought and flood are two frequent natural disasters in the world. Identification of temporal-spatial variability and its scale-dependence for drought-flood correlation can help to predict, hence to alleviate the losses. The correlations of drought with flood at 1, 3, 5, 10, 50 and 100-year scales at moving window of 30years during recent 500years were analyzed by spatial statistics based on geographical information system in Inner Mongolia, China. The results demonstrated that the frequency and intensity of two disasters increased generally during last 500years. The drought-flood correlations indicated a rhythm of alternate positive and negative relation with unspecific timescale, enlarged by prolonging of time scale from 1year to 5years, for either frequency or intensity. A lag effect, flood always occurred at the 4 or 5year following drought was observed. Located in the climatic marginal zone, eastern study region was strongly affected by the East Asia monsoon, showed a weak drought-flood correlation; western study region was controlled by continental climate, showed a significant drought-flood correlation. These correlations were also affected by periodic ENSO disturbance and mountain terrains. With the climatic changes, the drought-flood correlations also change in recent decades. These long-range correlations at various temporal-spatial scales provide a theoretical basis for the scientific prediction of drought and flood outbreaks, for a long term as well as a short wavelet.