Abstract: Based on materials collection and analysis, this paper studies grades, frequency and periodicity of the drought disasters and characteristics of the climate in Ordos Plateau region during the Qing Dynasty. The results show that the drought frequency is relatively high in this region during the Qing Dynasty (averaged 0.34 times/ year, and most were mild and moderate drought events. This paper divides the Qing Dynasty into several phases according to the drought frequency in this region. The phases of frequent drought occurrences include 1701-1780, 1821-1845 and 1876-1911. The phases of seldom droughts occurrence includes 1644-1700, 1781-1820 and 1846-1875. About 90% of the drought disaster events were observed in spring and summer or from spring into summer. In different time scales, the cycles of drought disaster occurrences are respectively 7a, 23a, 29a and 54 a. Each grade of droughts has a short quasi-cycle of 5a and the extreme droughts of first principal cycle are 17a. The occurrence of the droughts had two main reasons. One was dry and windy regional climate environment, and the other was human agricultural activities leading to vegetation damage and land desertification. This paper infers that the annual rainfall is 200~250 mm, and that the annual evaporation is 2400~2600 mm in extreme and severe drought years. The Qing dynasty climate in this region can be divided into six stages which are 1644-1700, 1701-1780, 1781-1820, 1821-1845, 1846-1875 and 1876-1911, respectively, and the corresponding annual rainfall is much, little, much, little, much and little, respectively, while the characteristics of evaporation and sandstorm weathers are little, much, little, much, little and much, respectively. What's more, this paper infers that 1762-1766, 1875-1878, 1899-1902 are three dry phases. During the three phases, the annual rainfall was about 230 mm, and the evaporation was about 2500 mm, with frequent windy dust weather and drying trend in the Ordos Plateau region.

Key words: drought, drying trend, grade, Ordos Plateau, wavelet analysis