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首页> 外文期刊>Remote Sensing of Environment: An Interdisciplinary Journal >Comparison of active and passive water vapor remote sensing from space: An analysis based on the simulated performance of IASI and space borne differential absorption lidar
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Comparison of active and passive water vapor remote sensing from space: An analysis based on the simulated performance of IASI and space borne differential absorption lidar

机译：太空主动和被动水蒸气遥感的比较：基于IASI和星载差分吸收激光雷达模拟性能的分析

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摘要

Two remote sensing systems, which are considered to be operated in space, the Infrared Atmospheric Sounding Interferometer (IASI) and the Water Vapour Lidar Experiment in Space (WALES) are compared with respect to their measurement methodologies and their performance. The focus is the retrieval of water vapor, which is determined by the inversion of the radiative transfer equation in case of IASI and by the differential absorption lidar (DIAL) technique in case of WALES. It is realized that different techniques and definitions for the specification of errors exist which are subject of confusion in the remote sensing community. After a clarification of this issue, a comparison of IASI and WALES water vapor retrievals is performed using the same water vapor climatologies and the same 2-d water vapor fields provided by a global numerical weather prediction (NWP) model.The methodologies and the capabilities of each instrument are compared in regions without clouds. Using end-to-end simulations for both instruments, which are to our knowledge performed for the first time, systematic errors are compared up to 16 km. It is found that the dependence of IASI retrievals on a variety of atmospheric parameters leads to compensating effects. Due to the multiwavelength retrieval, errors in the water vapor spectroscopy can partly cancel. The residual error is quantified by inversion of the radiative transfer equation in dependence of several atmospheric variables. In contrast, errors in water vapor DIAL are very sensitive to laser spectral properties as well as to the accuracy of water vapor spectroscopy, as single water vapor absorption lines are used for each vertical segment of the retrieval. As laser transmitters with excellent spectral specifications are feasible, this can still lead to very low systematic errors under all atmospheric conditions.Noise errors are determined using analytical models and are compared up to 16 km. At the same vertical (1-2 km) and horizontal (100-200 km) resolutions, respectively, the average noise errors in each profile are of the order of 10% for both methods. Depending on the climatology, the vertical range of IASI measurements is always several kilometers lower than that of DIAL. The performance of IASI degrades in dry atmospheres whereas the DIAL performance remains nearly independent of the climatology chosen. Bias errors show a similar behavior. Neglecting bias errors in the spectral measurements, from mid-latitudes to the tropics, IASI biases are < 2% in the vertical range where the noise errors remain < 20%. In the sub-arctic winter atmosphere, the bias increases to about -4% close to the ground. Space home DIAL bias profiles range between -2-1% under all conditions plus an additional height independent bias of about +/- 2 due to remaining uncertainties in absorption line spectroscopy.Operation in the region of clouds are not a focus of this publication but it is worth to mention that the results demonstrate that space home DIAL can perform measurements down to cloud tops and often through optically thin clouds. Particularly powerful is the synergistic combinations of both sensors in the future. Iteration between IASI temperature and DIAL water vapor retrievals will increase both accuracies. (c) 2005 Elsevier Inc. All rights reserved.
机译：比较了两种被认为是在太空中运行的遥感系统，即红外大气探测干涉仪（IASI）和太空水蒸气激光雷达实验（WALES）的测量方法和性能。重点是水蒸气的取回，这在IASI情况下由辐射传递方程的反演确定，在WALES情况下则由微分吸收激光雷达（DIAL）技术确定。已经认识到，存在用于错误规范的不同技术和定义，这在遥感界引起混乱。在澄清了这个问题之后，使用全球数值天气预报（NWP）模型提供的相同水蒸气气候和相同二维水蒸气场对IASI和WALES水蒸气取回进行了比较。在没有云的地区比较每种仪器的。据我们所知，这两种仪器都采用了端到端的模拟，系统误差可以进行长达16 km的比较。发现IASI取回对各种大气参数的依赖性会导致补偿作用。由于采用了多波长检索，因此可以部分抵消水蒸气光谱中的误差。通过根据几个大气变量对辐射传递方程进行反演来量化残余误差。相反，水蒸气DIAL的误差对激光光谱特性以及水蒸气光谱学的准确性非常敏感，因为单个水蒸气吸收线用于检索的每个垂直段。由于具有出色光谱规格的激光发射器是可行的，因此在所有大气条件下仍会导致非常低的系统误差，使用分析模型确定噪声误差，并在长达16 km的位置进行比较。分别在相同的垂直（1-2 km）和水平（100-200 km）分辨率下，两种方法在每个剖面中的平均噪声误差均为10％左右。取决于气候，IASI测量的垂直范围始终比DIAL的垂直范围低几公里。在干燥的大气中，IASI的性能会下降，而DIAL的性能几乎不受所选气候的影响。偏差误差显示出类似的行为。在从中纬度到热带的频谱测量中，忽略了误差，IASI误差在垂直范围内小于2％，而噪声误差仍然小于20％。在亚北极冬季大气中，靠近地面的偏差增加到约-4％。由于在吸收谱线中仍存在不确定性，在所有条件下，太空主场DIAL偏置曲线的范围在-2-1％之间，加上大约+/- 2的附加的高度无关偏置。在云区域中的操作不是本出版物的重点，值得一提的是，这些结果表明，太空之家DIAL可以进行到云顶的测量，并且通常可以通过光学上薄的云进行测量。未来两种传感器的协同组合将特别强大。 IASI温度和DIAL水蒸气取回之间的迭代将增加两个精度。 （c）2005 Elsevier Inc.保留所有权利。

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