关键词: 夏玉米, 夏玉米, 冠层反射光谱, 叶片氮积累量, 监测模型

Abstract: Based on the data of precipitation and the days of precipitation in flood season in Xi’an from 1951 to 2013, the precipitation characteristics in Xi’an in recent 63 years was analyzed with linear regression, Mann- Kendall detection, wavelet analysis and R/S analysis method. The conclusions are as follows: (1) total precipitation, days of total precipitation, light rain, days of light rain all showed a decreasing trend, with a decreasing rate of -1.9 mm/10 a, -0.3 d /10 a, -2.9 mm/10 a and -0.4 d /10 a respectively, and reduced suddenly in the 1960s, and increased suddenly in the 2010s; moderate rain, days of moderate rain, heavy rain and the above, days of heavy rain and the above increased slightly; (2) for the same grade, precipitation and the days of precipitation showed consistent periodic oscillation; as for light rain, heavy rain and the above, and the total rain, precipitation and the days of precipitation all showed 20-25 year decadal periodic oscillation, while moderate rain with 3-4 year inter- annual periodic oscillation; we predict that, precipitation and the days of precipitation of light rain, moderate rain and the total rain will continue decreasing, heavy rain and the above will increase slightly, and begin to decrease after 2015; (3) future trend of precipitation characteristics will be diagnosed and predicted comprehensively with wavelet analysis and Hurst index experiment.