Analysis of drought-flood abrupt alternation in Zhengzhou during summer in 1955-2015

Based on the mo nt hly precipit at ion dat a of Zheng zhou meteor olog ical statio n fr om 1955 to 2015, using lo ng2and sho rt2 cy cle droug ht2f loo d abrupt alter nat ion index, Linear Tendency Estimation, Mann2Kendall test and other mathematical models, we analy zed the annual precipitation and the evolut ion of dr ought2floo d during June to September in Zheng zho u. T he r esults wer e as follow s: T he annual precipitation significantly decreased at a rate of - 71 87 mm/ ( 10a) . T he chang e t rend of the LDFAI in Zheng zhou w as not o bv io us, but the intensit y of LDFAI ex hibited periodic changes, including t wo str ong and tw o w eak peri2 o ds. The intensity of LDFAI g reater than 1 accounted for 371 7% in the r ecent 61 years, w hich meant droug ht2f loo d abrupt alter2 natio n o ccurred f requent ly. The sho rt2cy cle dro ug ht2flo od abrupt alt ernation index bet ween adjacent months had t he most f re2 quent fluctuation from June t o July , the second most from July to Aug ust , and it lev eled off from August to September. In g ener2 al, the intensity of lo ng2cycle flo od2 to2droug ht tr ansit ion w as g ener ally st rong er t han t hat of dr ought2to2flo od tr ansit ion. Bo th long2and sho rt2cy cle dr ought2floo d abrupt alter nat ion phenomena showed a trend o f decline

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