羊草草原不同生长时期反射波谱日变化特性的分析

对不同生长时期的羊草草原反射日变化特征的测试与分析结果：１）羊草群落反射日变化特征在７月初表现为时间的单峰曲线，在８，９月中旬为时间的直线型曲线，在一天中的不同时段，各波段反射率与太阳高度角和时间的变化分别存在极显的相关关系；（２）同各个波段反射率的日变化特征相比，ＲＶＩ和ＮＤＶＩ都能有效地减少太阳高度角变化的影响，其中以ＮＤＶＩ的作用最好；３）８月中旬对太阳辐射的利用强度最大，各个波段的反射率

An Analysis of Spectral Reflectance Diurnal Change for Leymus chinensis Steppe in Different Seasons

The result of spectral reflectance diurnal change for Leymus chinensis community in different seasonal showed:1)the diurnal change curves of spectral reflectance trend to sing peak type in July,but to linear type in August and Spetember correlated to time change.There were remakable correlation between reflectance of vegetation and sun angel or time in morning and in afternoon,resectively;2)compared with the viation of reflectance,RVI and NDVI,especially was the latter,can decreased the influence of sun angel on spectral reflectance of vegetation,effectively;3)the intensity that made use of radiation for vegetation was highest and the diurnal change range,both of reflectance in each band and vegetation indices,were lowest in August,but more great fluctuations would appeared in other monthes,it is necessary to rectify the reflectance (or spectral vegetation index) measured at different moment during a day.