DROUGHT DISASTER AND CLIMATIC CHANGE IN YUAN DYNASTY IN GUANZHONG AREA

Based on collecting,arranging and analyzing historic materials in Yuan Dynasty in Guanzhong area, we analyzed ranks,time changes and causes of the drought disasters. Study results indicated that Guanzhong area altogether suffered 33 drought disasters,at the interval of 2.85 years from the early stage (in 1266 AD) to the last stage (in 1359 AD) of the 94 year-long Yuan Dynasty. The drought disasters in Yuan Dynasty in Guanzhong area were mainly mild ones that accounted for 42.4% of the total. Followed were the moderate drought disasters which accounted for 24.2% of the total.Frequency of the severest drought disasters was also high, and they accounted for 21.2% of the total.Frequency of great drought disasters was very low, and they accounted for only 12.1% of the total. Drought disasters were clearly non-uniform at the early,middle and last stages in Yuan Dynasty in Guanzhong area, and increased gradually with time. Temperature and precipitation that were distributed non-uniformly and changed greatly in different years were main causes of the mild and moderate drought disasters. That the climate obviously became drought was main causes of the great and severest drought disasters in the middle stage in Yuan Dynasty in Guanzhong area. The geographical position, climatic background and vegetation damage by human activity intensified the occurrence of drought disasters. There was a drought event in Yuan Dynasty in Guanzhong area that happened during 1296-1332. We determined that mean annual precipitation of great drought disaster was about 400 mm and mean annual precipitation of the severest drought disaster was about 350 mm in main drought disaster areas.