Drought and Flooding Over Ming and Qing Dynasties in Weinan of Shaanxi Province and Their Determinants

Abstract

【Background】 Drought and flooding are two extreme weathers facing agriculture production in the world. They happen regionally, but the global warming over the past century has substantially increased their frequency in all regions. Understanding their underlying mechanisms is important for risk management and mitigating their detrimental impact. 【Objective】 This paper is to analyze the flooding and droughts occurring over Ming and Qing dynasties in Weinan of Shaanxi province, as well as their underlying determinants. 【Method】 The analysis was based on the archive - Chinese meteorological records over the last 3 000 years. Their multiscale features were calculated using the ensemble empirical mode decomposition (EEMD). 【Result】 Over the two dynasties, the frequency of droughts and flooding showed a pattern of increasing first followed by a decline before stabilizing. Temporally, drought and flooding were hierarchically periodic, with nested periods of 2~5 years, 10 years, 18 years, 27 years, 52 years, 84 years and 100 years. Such a hierarchy was associated well with the 2~5 year period of the El Niño, 10-year period of solar activity, 50-year period of centennial cycle, and 20~30 year period of the Pacific Decadal Oscillation (PDO), respectively. The wavelet of cross and condensate spectrums showed that drought and flooding in this region was closely related to solar activity, El Niño and Pacific interdecadal oscillation. The inter-annual and inter-decadal variation of the quasi-4a and quasi-38a explained 59.5% and 20.1% of the variance of drought and flooding respectively, indicating that the oscillation of drought and flooding was impacted by inter-annual period more than by the inter-decadal period. 【Conclusion】 The occurrence of drought and flooding over the Ming and Qing dynasties in Weinan of Shaanxi province showed hierarchical periods, which were closely related to the solar activity, El Niño and the decadal oscillation of Pacific Ocean.

Keywords

• weinan
• ming and qing dynasties
• drought and flooding
• climate change
• interannual-centennial scale