Rainfall analysis on slope land of wind-water erosion crisscross region in northern Loess Plateau

In order to clarify rainfall characteristics, and to provide scientific basis for researches on soil erosion, development and utility on rainfall and surface runoff of the wind－water erosion crisscross region in the northern Loess Plateau, rainfall analysis were performed on the slope land of the Liudaogou Basin in the rainy season in the five years (2006－2010). The observed rainfall data was separated on the time axis by different time intervals of 3 min, 5 min, 10?min and 1 h using Box Car Pro 4.3 software. Rain intensity, distribution of rain duration and rainfall were analyzed. The results showed that the maximum rain intensity of 3 min, 5 min, 10 min and 1 h were 2.2, 2.08, 1.68 and 0.70 mm/min, respectively; average rain intensity of the total rain duration in the rainy season of the five years (2006－2010) were 0.12, 0.09, 0.06 and 0.03 mm/min, respectively; with increasing of the time interval the rain intensity decreased; the event probability of the low rain intensity was much higher than that of the high rain intensity for all series of time intervals; the event probability for 3 min rain intensity > 1 mm/min, 5 min rain intensity >1 mm/min, 10 min rain intensity >0.8 mm/min and 1 h rain intensity > 0.4 mm/min were 0.4%, 0.2%, 0.2% and 0.1%, respectively. The number of rainfall events whose rain duration was less than 30 min accounted for approximately 50% of the total rainfall events, and the number of rain duration > 2 h accounted for approximately 23% of the total; the number of rain duration > 12 h only accounted for 2.6% of the total rainfall events. The number of rainfall events whose rainfall was no more than 1 mm accounted for approximately 50% of the annual mean whereas their total rainfall only accounted for less than 7% of average annual precipitation; annual mean of the rainfall events whose rainfall was more than 20 mm was 5, and the total rainfall of such rainfall events exceeded 20% of average annual precipitation. The rainfall characteristics on the slope land of the wind-water erosion crisscross region in the northern Loess Plateau were clarified to a certain degree.