中国黄土高原地区干旱特征

利用黄土高原51站40年气象观测资料及修正palmer干旱指数,主要采用EEOF(扩展经验正交分解函数)等分解方法,研究黄土高原土壤干旱演变。结果表明:40年来干旱趋于加重;1973年、1989年为Petitt变点,1973年之前旱年相对较少,1989年之后干旱年份明显增多干旱加重;干旱最敏感区(变化大值区)在高原腹地,高原周边地区干旱变幅较小;干旱变化振荡周期以2~4年为主;干旱准2年振荡的空间演变清晰,干旱移动方向和强度变化比较明显,在5个月之内强度、范围加大,大值区数值增大并向周围扩展旱情加重,再经过5个月后干旱大值区的数值下降快于周围,从敏感区向高原四周扩散;干旱变化强度、位相等具有区域差异,主要存在高原西部、晋中盆地、高原东北部、关中平原、渭河上游区等5个次区域。

Characteristics of soil drought at Loess Plateau of China

By investigating the meteorological data of 51 stations during recent 40 years,the whole and regional distribution of soil drought variation at the Loess Plateau of China was studied.The results show that the main spatial-temporal variability of abnormal soil drought has the same trend in whole of the plateau that the soil drought has gradually aggravated in recent years.In soil drought calculation,1973 and 1989 was Petitt change points.The drought years were less than rainy ones before 1973 and more than rainy ones after 1989 in the region.The sensitivity area of soil-drought was in the center of the Loess Plateau.Range of drought change in peripheral area of the plateau was less than other areas.In wavelet analysis,soil drought has a remarkable 2-4 year period and a clear spatial evolution of 2 year sub-oscillation.The variation of soil drought spread from center to periphery of the plateau within 5 months.The soil drought varied slower in the edge part than that in the center of the plateau in the next 5 months.Spatiotemporal change and intensity of soil drought have regional difference,which mainly distributed at the 5 sub-regions of the Loess Plateau: the west part of the plateau,the middle Shanxi basin,the north-east part of the plateau,the central Shaanxi Plain and the upper reaches of the Weihe River.