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首页> 外文会议>Asian conference on remote sensing;ACRS >IMPACT OF BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTION ON MODIS VEGETATION INDICES IN SOUTHEAST ASIA TROPICAL FORESTS
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IMPACT OF BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTION ON MODIS VEGETATION INDICES IN SOUTHEAST ASIA TROPICAL FORESTS

机译：双向反射分布函数对东南亚热带森林MODIS植被指数的影响

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Tropical forests play important roles on global climate and biodiversity. The Moderate Resolution Imaging Spectroradiometer (MODIS), with high temporal resolution, provide a useful tool to study tropical forest dynamics, including seasonality and inter-annual variation. However, optical satellite data have cloud, aerosol and bidirectional reflectance distribution function (BRDF) effects, that create uncertainty in tropical forest studies. In the Amazon, some researchers demonstrated the difficulties in separating true forest dynamics from BRDF artefacts and seasonal cloud and aerosol influences. Lastly, optical reflectance saturation in dense tropical forests may restrict the retrieval of phenology information. In this study, we investigated the impact of BRDF effects on MODIS vegetation indices (VI) in Southeast Asia (SEA) tropical forests, the least studied area compared to other major tropical forests (South America and Central Africa). Moreover, unlike Amazon tropical forests, VI seasonality in SEA forests is not synchronous with sun-sensor geometries. We used 10-year data of daily MODIS BRDF (MCD43A1) collection 6 product, a kernel-driven model product that allows us to retrieve VI values for a range of fixed solar zenith angles (SZA). We compared these with the standard VI products (MOD13A1, MYD13A1) to analyse BRDF influences. The results show significant BRDF effects in all forest sites. Generally, smaller SZA yielded higher VI signals in forests. We found tradeoff's between VI robustness to BRDF effects and saturation that impacted upon the retrievals of phenology parameters.
机译：热带森林在全球气候和生物多样性方面发挥着重要作用。具有高时间分辨率的中分辨率成像光谱仪（MODIS）为研究热带森林动态（包括季节性和年际变化）提供了有用的工具。但是，光学卫星数据具有云，气溶胶和双向反射分布函数（BRDF）的作用，这在热带森林研究中造成了不确定性。在亚马逊地区，一些研究人员证明了将真正的森林动态与BRDF人工产物以及季节性云雾和气溶胶影响区分开来的困难。最后，茂密的热带森林中的光反射饱和可能会限制物候信息的检索。在这项研究中，我们调查了BRDF效应对东南亚（SEA）热带森林中MODIS植被指数（VI）的影响，该区域是与其他主要热带森林（南美和中非）相比研究最少的区域。此外，与亚马逊热带森林不同，东南亚森林中的VI季节变化与太阳传感器的几何形状不同步。我们使用了每日MODIS BRDF（MCD43A1）集合6产品的10年数据，这是一种由内核驱动的模型产品，可让我们检索一系列固定太阳天顶角（SZA）的VI值。我们将它们与标准VI产品（MOD13A1，MYD13A1）进行了比较，以分析BRDF的影响。结果表明，BRDF在所有森林地点均具有显着效果。通常，较小的SZA在森林中产生较高的VI信号。我们发现，VI对BRDF的鲁棒性与饱和度之间存在折衷，后者影响了物候参数的检索。

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