Abstract Three years of measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on Aqua satellite has been used to develop a new approach to quantify the well-known, yet unresolved zonal bias in MODIS LWP of marine clouds. This new method utilizes two parameters: the solar zenith angle and cloud heterogeneity index, both of which are available for each MODIS pixel. Comparisons with collocated satellite and ground-based microwave measurements in carefully screened clouds shows that this new approach can effectively remove this large first order MODIS LWP bias. Applying this new approach to MODIS pixel level data collocated along the CloudSat footprint suggests annually averaged MODIS LWP overestimation gradually increases at higher latitudes and can reach over 50 g/m2 at latitudes greater than around 500. This overestimation can exceed 100 g/m2 for seasonal or monthly averages. MODIS LWP measurements were also reprocessed over land and snow/ice regions by eliminating data points with optical depth of 150, which indicates significant 3D bias. This reduces the average LWP by over 100 g/m2 in polar regions. The new and improved MODIS LWP dataset can be used to study related cloud processes and to constrain model simulations, especially in polar regions where observational dataset is limited and contain large uncertainties.

中文翻译：

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利用 MODIS 改进中高纬度云液态水路径测量

摘要 Aqua 卫星上的中分辨率成像光谱仪 (MODIS) 仪器进行了三年的测量，已被用于开发一种新方法来量化海洋云 MODIS LWP 中众所周知但尚未解决的纬向偏差。这种新方法使用两个参数：太阳天顶角和云非均质性指数，这两个参数均可用于每个 MODIS 像素。与仔细筛选的云中并置的卫星和地面微波测量结果的比较表明，这种新方法可以有效地消除这种大的一阶 MODIS LWP 偏差。将这种新方法应用于沿 CloudSat 足迹并置的 MODIS 像素级数据表明，每年平均 MODIS LWP 高估在高纬度地区逐渐增加，并且在纬度大于 500 的纬度可达到 50 g/m2 以上。对于季节性或每月平均值，这种高估可能会超过 100 g/m2。MODIS LWP 测量值还通过消除光学深度为 150 的数据点在陆地和雪/冰区域重新处理，这表明存在显着的 3D 偏差。这使极地地区的平均 LWP 减少​​了 100 多克/平方米。新的和改进的 MODIS LWP 数据集可用于研究相关的云过程和约束模型模拟，特别是在观测数据集有限且包含较大不确定性的极地地区。