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首页> 外文期刊>Hydrology and Earth System Sciences >Phenological response of vegetation to upstream river flow in the Heihe Rive basin by time series analysis of MODIS data
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Phenological response of vegetation to upstream river flow in the Heihe Rive basin by time series analysis of MODIS data

机译：基于MODIS数据的黑河流域植被对上游径流的物候响应。

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Liquid and solid precipitation is abundant in the high elevation, upperreach of the Heihe River basin in northwestern China. The development ofmodern irrigation schemes in the middle reach of the basin is taking up anincreasing share of fresh water resources, endangering the oasis andtraditional irrigation systems in the lower reach. In this study, theresponse of vegetation in the Ejina Oasis in the lower reach of the HeiheRiver to the water yield of the upper catchment was analyzed by time seriesanalysis of monthly observations of precipitation in the upper and lowercatchment, river streamflow downstream of the modern irrigation schemes andsatellite observations of vegetation index. Firstly, remotely sensed NDVIdata acquired by Terra-MODIS are used to monitor the vegetation dynamic fora seven years period between 2000 and 2006. Due to cloud-contamination,atmospheric influence and different solar and viewing angles, however, thequality and consistence of time series of remotely sensed NDVI data aredegraded. A Fourier Transform method – the Harmonic Analysis of Time Series(HANTS) algorithm – is used to reconstruct cloud- and noise-free NDVI timeseries data from the Terra-MODIS NDVI dataset. Modification is made on HANTSby adding additional parameters to deal with large data gaps in yearly timeseries in combination with a Temporal-Similarity-Statistics (TSS) methoddeveloped in this study to seek for initial values for the large gapperiods. Secondly, the same Fourier Transform method is used to model timeseries of the vegetation phenology. The reconstructed cloud-free NDVI timeseries data are used to study the relationship between the wateravailability (i.e. the local precipitation and upstream water yield) and theevolution of vegetation conditions in Ejina Oasis from 2000 to 2006.Anomalies in precipitation, streamflow, and vegetation index are detected bycomparing each year with the average year. The results showed that: theprevious year total runoff had a significant relationship with thevegetation growth in Ejina Oasis and that anomalies in the spring monthlyrunoff of the Heihe River influenced the phenology of vegetation in theentire oasis. Warmer climate expressed by the degree-days showed positiveinfluence on the vegetation phenology in particular during drier years. Thetime of maximum green-up is uniform throughout the oasis during wetteryears, but showed a clear S-N gradient (downstream) during drier years.
机译：在中国西北黑河流域的高海拔，上游地区，液体和固体降水丰富。流域中游的现代灌溉计划的发展正在占用越来越多的淡水资源，危及下游的绿洲和传统灌溉系统。在这项研究中，通过时间序列分析上流域和下流域的降水，现代灌溉计划下游的河流流量，对黑河流域下游的额济纳绿洲的植被对上游集水区的水产的响应进行了分析。卫星指数的卫星观测。首先，利用Terra-MODIS采集的遥感NDVI数据监测了2000年至2006年这7年间的植被动态。由于云污染，大气影响以及不同的太阳角度和视角，但是时间序列的质量和一致性遥感NDVI数据被降级。傅立叶变换方法-时间序列谐波分析（HANTS）算法-用于从Terra-MODIS NDVI数据集中重建无云和无噪声的NDVI时间序列数据。通过添加附加参数来处理年度时间序列中的大量数据缺口，并结合本研究中开发的时间相似度统计（TSS）方法来寻找较大缺口周期的初始值，对HANTS进行了修改。其次，使用相同的傅里叶变换方法对植被物候的时间序列进行建模。重建的无云NDVI时间序列数据用于研究额济纳绿洲2000年至2006年的水分利用度（即局部降水和上游水产量）与植被状况演变之间的关系。降水，溪流和植被指数的异常是通过将每年与平均年份进行比较来检测。结果表明：上年总径流量与额济纳绿洲的植被生长密切相关，黑河春季月径流量的异常影响了整个绿洲的植被物候。以天数表示的较暖气候对植被物候具有积极影响，尤其是在较干燥的年份。在较湿的年中，整个绿洲的最大绿化时间是一致的，但在较干燥的年中，显示出明显的S-N梯度（下游）。

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