Aircraft millimeter-wave passive sensing of cloud liquid water and water vapor during VOCALS-REx
Aircraft millimeter-wave passive sensing of cloud liquid water and water vapor during VOCALS-REx
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DOI：
10.5194/acp-12-355-2012
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发表时间：
2012-01
影响因子：
6.3
通讯作者：
P. Zuidema;D. Leon;A. Pazmany;M. Cadeddu
中科院分区：
文献类型：
--
作者：
P. Zuidema;D. Leon;A. Pazmany;M. Cadeddu
抽象的。常规液态水路径测量和水蒸气路径对于多云海洋边界层的过程研究和大型模型的评估很有价值。 VOCALS 区域实验尊重这一目标，在 NCAR C-130 飞机的 14 次研究飞行中安装了一个小型、廉价、向上的毫米波无源辐射计，即 G 波段 (183 GHz) 蒸气辐射计 (GVR)。辐射计允许在云上检索自由对流层水蒸气路径（WVP）。检索到的自由对流层（云上）水汽路径具有很强的纵向梯度，离岸值为一到两毫米，近海岸值达到十毫米。 VOCALS-REx 自由对流层比往年干燥。通过结合 GVR、遥感云边界信息和现场热力学数据，从子云和云基飞机腿中检索云液态水路径 (LWP)。对于混合良好的条件，1 Hz（~100 m）分辨率下 LWP 检索的绝对（腿间）和相对（腿内）精度分别估计为 20 g m−2 和 3 g m−2 ，对于输入 WVP 规范更加不确定的解耦条件，估计绝对不确定度为 25 g m−2 。检索到的液态水路径与从同时云厚度测量得出的绝热值非常匹配。 GVR 数据集的一个重要贡献是薄云的扩展信息，检索到的 LWP 占 62% (28%)
Abstract. Routine liquid water path measurements and water vapor path are valuable for process studies of the cloudy marine boundary layer and for the assessment of large-scale models. The VOCALS Regional Experiment respected this goal by including a small, inexpensive, upward-pointing millimeter-wavelength passive radiometer on the fourteen research flights of the NCAR C-130 plane, the G-band (183 GHz) Vapor Radiometer (GVR). The radiometer permitted above-cloud retrievals of the free-tropospheric water vapor path (WVP). Retrieved free-tropospheric (above-cloud) water vapor paths possessed a strong longitudinal gradient, with off-shore values of one to two mm and near-coastal values reaching ten mm. The VOCALS-REx free troposphere was drier than that of previous years. Cloud liquid water paths (LWPs) were retrieved from the sub-cloud and cloudbase aircraft legs through a combination of the GVR, remotely-sensed cloud boundary information, and in-situ thermodynamic data. The absolute (between-leg) and relative (within-leg) accuracy of the LWP retrievals at 1 Hz (~100 m) resolution was estimated at 20 g m−2 and 3 g m−2 respectively for well-mixed conditions, and 25 g m−2 absolute uncertainty for decoupled conditions where the input WVP specification was more uncertain. Retrieved liquid water paths matched adiabatic values derived from coincident cloud thickness measurements exceedingly well. A significant contribution of the GVR dataset was the extended information on the thin clouds, with 62 % (28 %) of the retrieved LWPs