A two-channel, tunable diode laser-based hygrometer for measurement of water vapor and cirrus cloud ice water content in the upper troposphere and lower stratosphere
A two-channel, tunable diode laser-based hygrometer for measurement of water vapor and cirrus cloud ice water content in the upper troposphere and lower stratosphere
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DOI：
10.5194/amt-8-211-2015
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发表时间：
2015-01-01
影响因子：
3.8
通讯作者：
Fahey, D. W.
中科院分区：
文献类型：
--
作者：
Thornberry, T. D.;Rollins, A. W.;Fahey, D. W.
最近开发的诺阿水仪器是一个双通道、闭路、可调谐二极管激光吸收光谱仪，设计用于测量美国航天局全球鹰无人驾驶飞机系统或其他高空研究飞机上的对流层/平流层下层水蒸气和增强的总水（蒸气+惯性增强的凝聚相）。该仪器采用波长调制光谱技术，在2694 nm附近进行二次谐波检测，通过79 cm的双通光路实现高精度。检测池在恒定的温度、压力和流量条件下运行，以保持对H2O的恒定灵敏度，与周围采样环境无关。机载校准系统用于执行定期的现场校准，以验证飞行期间仪器灵敏度的稳定性。对于水蒸气通道，环境空气垂直于经过飞机的气流进行采样，以排除云颗粒，而总水通道使用加热的前向入口对水蒸气和云颗粒进行采样。总水入口次等速地操作，从而惯性地增强样品流中的云颗粒数，并提供增加的云含水量灵敏度。2013年2月至3月，在NASA全球鹰无人机系统上进行的第二次空中热带对流层顶实验（ATTREX）期间，NOAA水仪器首次飞行。该仪器的典型飞行精度（1 s，1 sigma）优于百万分之0.17（ppm，10（-6）mol mol（-1）），总体H2O蒸汽测量不确定度为5% +/- 0.23 ppm。ATTREX飞行条件下卷云粒子采样的惯性增强范围从33到48的直径大于8 μ m的冰粒，主要取决于飞机的高度。所得冰水含量检测限（2 σ）为0.023-0.013 ppm，相当于约2 μ g m（-3），估计总体不确定度为20%。
The recently developed NOAA Water instrument is a two-channel, closed-path, tunable diode laser absorption spectrometer designed for the measurement of upper troposphere/lower stratosphere water vapor and enhanced total water (vapor + inertially enhanced condensed phase) from the NASA Global Hawk unmanned aircraft system (UAS) or other high-altitude research aircraft. The instrument utilizes wavelength-modulated spectroscopy with second harmonic detection near 2694 nm to achieve high precision with a 79 cm double-pass optical path. The detection cells are operated under constant temperature, pressure, and flow conditions to maintain a constant sensitivity to H2O independent of the ambient sampling environment. An onboard calibration system is used to perform periodic in situ calibrations to verify the stability of the instrument sensitivity during flight. For the water vapor channel, ambient air is sampled perpendicular to the flow past the aircraft in order to reject cloud particles, while the total water channel uses a heated, forward-facing inlet to sample both water vapor and cloud particles. The total water inlet operates subisokinetically, thereby inertially enhancing cloud particle number in the sample flow and affording increased cloud water content sensitivity. The NOAA Water instrument was flown for the first time during the second deployment of the Airborne Tropical TRopopause EXperiment (ATTREX) in February-March 2013 on the NASA Global Hawk UAS. The instrument demonstrated a typical in-flight precision (1 s, 1 sigma) of better than 0.17 parts per million (ppm, 10(-6) mol mol(-1)), with an overall H2O vapor measurement uncertainty of 5% +/- 0.23 ppm. The inertial enhancement for cirrus cloud particle sampling under ATTREX flight conditions ranged from 33 to 48 for ice particles larger than 8 mu m in diameter, depending primarily on aircraft altitude. The resulting ice water content detection limit (2 sigma) was 0.023-0.013 ppm, corresponding to approximately 2 mu g m(-3), with an estimated overall uncertainty of 20 %.