陕西MODIS／NDVI的区域分布和季节变化

Regional Distribution and Seasonal Variation of MODIS/NDVI over Shaanxi Area

利用MODIS数据研究植被指数的时空变化特征，可以较详细地反映不同类型植被在其生长周期内的长势情况，以及各类植被生长状况在空间上的过渡和差异性。利用2004年全年的MODIS资料，采用NDVI多时相最大值合成法（MVC），生成了一年的月合成NDVI数据集产品，分析表明：①陕西MODIS／NDVI年平均值为0．39，变化范围在-0．54～0．85之间。NDVI的年内频率分布只有在冬季（1月）呈现单峰型，其他季节均表现为双峰型。②冬季陕西NDVI的分布南北差异较小；春季延安以北和延安以南差异明显；夏季和秋季NDVI值的分布体现了陕北北部长城沿线风沙区、黄土高原丘陵沟壑区稀疏植被、陕北南部子午岭和黄龙山林区森林植被、关中农田植被、秦巴山地森林植被和农田植被以及它们的地表差异特征。③不同植被类型的NDVI季节变化差别显著，这种NDVI时间序列曲线如实地反映了各种类型植被的生长规律，并能区分它们在生长规律上的细微差别，这又为植被区划、农作物种植面积的遥感监测提供了理论和实践基础。

The growing status of different vegetation types in their developing periods and their spatial difference can be understood in detail by analyzing the spatial and temporal variation of MODIS/NDVI. Research on Monthly NDVI data set over Shaanxi, which has been composed by the method MVC using 2004 MODIS data. shows： ①the yearly average of MODIS/NDVI over Shannxi is 0.39, changing between 0.54～0.85. The monthly distribution of NDVI appears a single peak in winter, but double peaks in the other seasons. ②The difference of NDVI distribution between the north and the south of Shaanxi is smaller in winter, but larger in the other seasons. The distribution of NDVI in summer and.autumn reflects the regional characters of the sand-blown region along the Great Wall in the north of northern Shaanxi, the hill and ravine region on loess plateau, the forest region in Ziwuling and Huanglong mountains, the farmland region in Guanzhong, the forest and farmland region in Qinba mountain. ③There are remarkable differentiation of seasonal NDVI among different types of vegetation.