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物候是指示气候变化的关键因子,遥感技术的快速发展为物候监测提供了新的途径。遥感叶面积指数(LAI)产品包含了主要的物候信息,并广泛应用于植被物候的监测。了解不同数据产品在提取植被物候信息上的差异是评价遥感产品对物候期监测适用性的重要方面。以东北三省为研究区域,使用非对称性高斯函数拟合法进行数据平滑,利用动态阈值法提取MODIS、CYCLOPES和GLASS叶面积指数(LAI)产品的生长季开始时间(SGS)、生长季结束时间(EGS)和生长季长度(LGS)。研究表明:MODIS和GLASS产品提取的SGS、EGS和LGS比较接近,整体上一致性较好;CYCLOPES产品提取的SGS多数情况下晚于MODIS和GLASS产品而EGS早于MODIS和GLASS产品。通过可利用的实地物候观测数据验证表明:MODIS和GLASS产品提取林地的SGS与物候观测值比较接近,EGS略晚于物候观测值,CYCLOPES产品提取的林地的SGS和EGS更加可靠。
Phenology is a key factor in indicating climate change. The rapid development of remote sensing technology provides a new way for phenological monitoring. Remote sensing leaf area index (LAI) products contain the main phenological information and are widely used in the monitoring of vegetation phenology. Understanding the differences in the extraction of vegetation phenology information for different data products is an important aspect for evaluating the suitability of remote sensing products for monitoring phenology. Taking the three northeastern provinces as the study area, the data were smoothed using the asymmetric Gaussian function fitting method. The growth season start time (SGS), the end of the growth season (MODS, CYCLOPES and GLASS) of the leaf area index (LAI) EGS) and growing season length (LGS). The results show that the SGS, EGS and LGS extracted by MODIS and GLASS products are relatively close and the overall consistency is good. The SGS extracted by CYCLOPES products are later than MODIS and GLASS products and EGS earlier than MODIS and GLASS products. The available field phenological observations verified that the SGS extracted from MODIS and GLASS products was close to phenological observations, EGS was slightly later than phenological observations, and the SGS and EGS extracted from CYCLOPES products were more reliable.