An update on the uncertainties of water vapor measurements using cryogenicfrost point hygrometers
An update on the uncertainties of water vapor measurements using cryogenicfrost point hygrometers
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DOI：
10.5194/amt-9-3755-2016
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发表时间：
2016-08
影响因子：
3.8
通讯作者：
H. Vömel;T. Naebert;R. Dirksen;M. Sommer
中科院分区：
文献类型：
--
作者：
H. Vömel;T. Naebert;R. Dirksen;M. Sommer
抽象的。对流层和平流层基本气候变量的长期观测序列常常受到仪器不一致和数据解释不明确的影响。为了减少长期数据系列的这些问题，所有测量都应包括对其不确定性的估计和对其来源的说明。在这里，我们提出了一个更新的对流层和平流层水汽观测使用低温霜点湿度计（CFH）的不确定性。测量不确定性的最大来源是控制器的稳定性，这是在这里详细讨论。我们描述了一种方法来量化这种不确定性的基础上的测量每个配置文件。我们还显示了一个独立的地面检查，这是一个必不可少的工具，不断监测仪器变异性引入的不确定性的重要性。一个小的偏差，这是以前在较低的对流层测量表明，在这里详细描述，并已被纠正。在良好的条件下，使用CFH测量霜点或露点的所有来源的不确定度的总和可以优于0.2 K。对长期气候序列影响最大的系统误差小于0.1K。对于适当处理的无线电探空仪，无线电探空仪压力不确定性对混合比的影响被认为很小。混合比不确定性可以低至2%至3%。环境温度不确定性对相对湿度的影响一般大于霜点不确定性。相对湿度的不确定度在对流层低层可低至2%，在热带对流层顶区可低至5%。
Abstract. Long time series of observations of essential climate variables in the troposphere and stratosphere are often impacted by inconsistencies in instrumentation and ambiguities in the interpretation of the data. To reduce these problems of long-term data series, all measurements should include an estimate of their uncertainty and a description of their sources. Here we present an update of the uncertainties for tropospheric and stratospheric water vapor observations using the cryogenic frost point hygrometer (CFH). The largest source of measurement uncertainty is the controller stability, which is discussed here in detail. We describe a method to quantify this uncertainty for each profile based on the measurements. We also show the importance of a manufacturer-independent ground check, which is an essential tool to continuously monitor the uncertainty introduced by instrument variability. A small bias, which has previously been indicated in lower tropospheric measurements, is described here in detail and has been rectified. Under good conditions, the total from all sources of uncertainty of frost point or dew point measurements using the CFH can be better than 0.2 K. Systematic errors, which are most likely to impact long-term climate series, are verified to be less than 0.1 K. The impact of the radiosonde pressure uncertainty on the mixing ratio for properly processed radiosondes is considered small. The mixing ratio uncertainty may be as low as 2 to 3 %. The impact of the ambient temperature uncertainty on relative humidity (RH) is generally larger than that of the frost point uncertainty. The relative RH uncertainty may be as low as 2 % in the lower troposphere and 5 % in the tropical tropopause region.