西北地区陆地生态系统植被状态参数业务化遥感研究

植被指数(NDVI)和叶面积指数(LAI)是两个非常重要的陆地生态系统植被状态参数.我们首先利用最大值(MVC)合成方法使用先进遥感数据如MODIS、AVHRR3等得到旬合成植被指数(NDVI),然后利用最新的经验方法针对不同的陆地生态系统类型反演得到叶面积指数,重点研究了我国沙尘暴发生频率较高的我国西北地区植被覆被状态及其变化情况.植被指数能够反映区域,乃至全球范围植被年季状态,用于监测陆地生态系统植物光合作用活动及其变化.植被指数作为一个基础参数能够用于计算反演更高级别的陆地生态系统状态参数.叶面积指数直接影响植被的光合作用,蒸腾作用的变化和陆面过程的能量平衡状态.在沙尘暴预测研究中使用的起沙过程模型需要将叶面积指数作为一个关键输入变量,另外,绝大多数生态过程模型模拟碳、水循环时也都需要将叶面积指数作为一个非常重要的输入变量.我们总结了最新的叶面积指数经验反演方法,针对6钟不同的陆地生态系统类型应用不同经验模型计算得到了叶面积指数.

Operational Retrieval of the Land Ecosystem Vegetation Status Parameters from Remote Sensing Data in Northwest China

The vegetation index (NDVI) and leaf area index (LAI) are two key important land vegetation ecosystem status parameters. This work is concerned with the retrieval of LAI using empirical algorithm through maximum value compositing NDVI from advance remote sensing data, for example Terra/MODIS, NOAA/AVHRR, FY1C/1D-CAVHRR data, and focus on Northwest China land vegetation cover change, where are high frequency dust storm. Vegetation indices (VIs) will provide consistent, spatial and temporal comparisons of large-scale vegetation status that will be used to monitor the Earth's terrestrial photosynthetic vegetation activity for phonological, change detection, and biophysical status parameters derivation of radiometric and structural vegetation parameters. VIs are fundamental parameter for retrieval of high-level land vegetation ecosystem status parameters. As one of the key canopy structural characteristics and biophysical variables, LAI values influence vegetation photosynthesis, transpiration, and energy balance. It is a key input parameter in dust storm forecast model. Most ecosystem process models that simulate the carbon and hydrologic cycles also require LAI as an input variable. It is also an important canopy biophysical variable in understanding the energy budget in the biosphere-atmosphere models. In this work, an empirical method according to different land cover, which utilize relationships between LAI and the NDVI, is used to retrieve LAI. This method is simple, but it is robust and useful. The presented work reviews the newest LAI retrieval method, which is dependent on six land ecosystem types.