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首页> 外文会议>Conference on Ecosystems' Dynamics, Agricultural Remote Sensing and Modeling, and Site-Specific Agriculture; Aug 7, 2003; San Diego, California, USA >Concurrent Measurements of Directional Reflectance and Temperature of a Wintertime Coniferous Forest from Space
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Concurrent Measurements of Directional Reflectance and Temperature of a Wintertime Coniferous Forest from Space

机译：太空针叶林的定向反射率和温度的并发测量

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摘要

We measure directional reflectance and daytime temperature of a wintertime coniferous forest from space using data acquired by the Department of Energy's Multispectral Thermal Imager (MTI). The study site is the Howland experimental forest in central Maine. The data include measurements from all seasons over a one-year period from 2001-2002 but with a concentration in late winter and early spring. The results show variation in both reflectance and temperature with direction and season. The reflectance results compare favorably with previous bidirectional measurements performed at the Howland site. Near-nadir reflectance in the visible bands varies periodically over the year with a high in summer and a low in winter. Near-infrared (NIR) reflectance shows dual variation. The canopy reflectance varies as a function of solar and satellite zenith angle, presumably due to a changing proportion of shadows. Furthermore, a NIR pseudo-BRDF (bidirectional reflectance distribution function) shows that the canopy brightens in the NIR during fall and winter. Retrieved canopy temperatures are consistently warmer in the off-nadir view by about 2℃. with a small seasonal variation. The seasonal canopy temperature trend is well exhibited, and days with snow on the ground are easily distinguished from days with no snow on the ground. The results also show that the retrieved temperatures are consistently warmer than above-canopy air temperature by about 4℃. This difference is greater for off-nadir views and also appears to be larger in the spring and summer than in the fall and winter.
机译：我们使用能源部的多光谱热成像仪（MTI）采集的数据从空间测量冬季针叶林的定向反射率和白天温度。研究地点是缅因州中部的豪兰实验林。数据包括从2001年到2002年的一年中所有季节的测量值，但集中在冬末和初春。结果显示反射率和温度随方向和季节而变化。反射率结果与以前在Howland站点进行的双向测量相比具有优势。可见波段的近天底反射率在一年中有周期性变化，夏季较高，冬季较低。近红外（NIR）反射率显示出双重变化。冠层反射率随太阳和卫星天顶角的变化而变化，这可能是由于阴影比例的变化所致。此外，NIR伪BRDF（双向反射率分布函数）显示，在秋冬季节，NIR中的冠层变亮。在离最低点的视野中，检索到的冠层温度始终较温暖，大约2℃。季节性变化很小。季节性冠层温度趋势表现得很好，并且容易将地面上有雪的日子与地面上没有雪的日子区分开。结果还表明，检索到的温度始终比冠层以上气温高大约4℃。对于离天底的视图，这种差异更大，并且在春季和夏季似乎比秋季和冬季更大。

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