Misestimation of Growing Season Length Due to Inaccurate Construction of Satellite Vegetation Index Time Series
Misestimation of Growing Season Length Due to Inaccurate Construction of Satellite Vegetation Index Time Series
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DOI：
10.1109/lgrs.2019.2895805
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发表时间：
2019-02
影响因子：
4.8
通讯作者：
Cong Wang;K. Zhu
中科院分区：
文献类型：
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作者：
Cong Wang;K. Zhu
基于卫星的植被指数（VI）广泛用于监测地表物候（LSP）。目前，成熟的VI产品利用最大值复合（MVC）算法来生成复合VI时间序列（TS）。然而，许多此类产品缺乏 VI 值的实际获取日期 (AD)。作为替代方案，使用复合周期的中值或平均日期来重建 VI TS，这可能会导致 LSP 检测出现偏差。这封信通过使用 MVC 方法从陆地长期数据记录每日 NDVI 产品生成 15 天复合归一化植被指数 (NDVI) TS，量化了北半球的 LSP 偏差。结果表明，NDVI值的AD通常晚于春季合成周期的平均日期，秋季早于，有效导致北半球（北纬30°以北）生长季长度平均高估5.91天。这种偏差具有显着的空间格局，在中国东北、北美中部和高纬度地区观察到较高值。但总体来看，时间趋势并未受到太大影响。因此，我们建议研究界尽可能使用准确的时间信息从 VI TS 中提取 LSP。
Satellite-based vegetation index (VI) is widely used in monitoring land surface phenology (LSP). Currently, well-developed VI products utilize the maximum value composite (MVC) algorithm to produce a composite VI time series (TS). Many of these products, however, lack the actual acquisition date (AD) of the VI value. As an alternative, the median or mean date of a composite period is used to reconstruct the VI TS, which might lead to bias on LSP detection. This letter quantifies the LSP bias in the Northern Hemisphere by generating a 15-day composited normalized difference vegetation index (NDVI) TS from the land long-term data record daily NDVI products using the MVC method. The results show that the AD of the NDVI value is usually later than the mean date of a composite period in spring and earlier in fall, effectively leading to a total overestimation of the growing season length of 5.91 days on average across the Northern Hemisphere (north of 30° N). This bias has a significant spatial pattern with high values observed in Northeastern China, Central North America, and high-latitude areas. However, the temporal trend is not largely influenced overall. Accordingly, we suggest the research community using accurate temporal information, whenever possible, in extracting LSP from VI TS.