Dry Biases of Humidity Measurements from the Vaisala RS80-A and Meisei RS2-91 Radiosondes and from Ground-Based GPS
Dry Biases of Humidity Measurements from the Vaisala RS80-A and Meisei RS2-91 Radiosondes and from Ground-Based GPS
复制标题
维萨拉 RS80-A 和 Meisei RS2-91 无线电探空仪以及地面 GPS 湿度测量的干偏差
DOI：
10.2151/jmsj.2004.277
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发表时间：
2004
影响因子：
3.1
通讯作者：
A. Observatory
中科院分区：
文献类型：
--
作者：
Hajime Nakamura;H. Seko;Y. Shoji;A. Observatory
在2000年秋季的筑波GPS密集网观测中，我们使用两种类型的无线电探空仪进行了3小时的高空探测。一个是Meisei RS 2 -91，由Meisei Electric Co. Ltd.制造的日本气象厅（JMA）的业务探空仪，带有独立的薄膜电容传感器，另一个是Vaisala RS 80 - 15 G，带有A型Humicap湿度传感器（以下简称RS 80-A）。结果表明，Vaisala RS 80-A测得的大气可吸入水汽（PWV）比JMA RS 2 -91测得的和GPS观测分析的结果明显偏小（干偏差）3-4 mm（约4-6%）。维萨拉RS 80-A的干偏差误差也得到了装备维萨拉RS 80-A和JMA RS 2 -91仪器的双探空气球飞行以及两种类型的无线电探空仪几乎同时飞行的证实。结果表明，采用新的湿度传感器保护帽后，干偏误差有所减小，但干偏误差仍较大。我们进一步比较了湿度测量的两个无线电探空仪的冷镜露点湿度计使用双压力型湿度校准室。实验在室温条件下进行。结果表明，维萨拉RS 80- A测量的相对湿度比露点湿度计小约5 - 15%。在高湿度条件下，偏差较大。虽然在其他几项研究中已经指出了维萨拉RS 80-A无线电探空仪的干偏差，但本研究中揭示的干偏差比以前报告的要大得多，表明在日本等潮湿空气条件下进行的RS 80-A湿度测量仍然存在问题。相对于露点湿度计，RS 2 -91仅显示出较小的干偏差（小于4%）。然而，日本气象厅高空气象观测站报告说，他们自1999年以来改进了RS 2 -91湿度传感器（Shibue等人，2000年）。1999年之前和1999年制造的RS 2 -91探空仪具有与维萨拉RS 80-A相同数量级的干偏置。已经有几个报告（例如，Ohtani等人，2000年）认为，由GEONET（日本全国GPS阵列）和其他活动GPS观测得出的PWV与JMA或Vaisala无线电探空仪得出的PWV吻合得很好。无线电探空仪的干偏差误差对以前GPS研究的影响是，日本过去的GPS分析产生了比实际情况更干燥的大气。建议使用最先进的全球定位系统分析方法重新分析过去的全球定位系统数据，包括地球静止轨道网数据。
During the Tsukuba GPS (Global Positioning System) Dense Network Campaign Observations in the autumn of 2000, we performed 3 hourly upper air soundings using two types of radiosondes. One was the Meisei RS2-91, operational sonde of the Japan Meteorological Agency (JMA) made by Meisei Electric Co. Ltd. with an independent thin-film capacitive sensor, and the other was Vaisala RS80-15G with A-type Humicap humidity sensor (RS80-A hereafter). It was found that the Precipitable Water Vapor (PWV) measured by Vaisala RS80-A were clearly smaller (dry bias) by 3-4 mm (about 4-6%) than those by JMA RS2-91 and those analyzed from GPS observations. The dry bias error of Vaisala RS80-A was also confirmed with dual sonde balloon flights equipped with both Vaisala RS80-A and JMA RS2-91 instruments, and near simultaneous flights of two types of radiosondes. It was found that the dry bias error was reduced by the new tight protective cap for the humidity sensor, but substantial amount of dry bias error still remained. We further compared humidity measurements by the two radiosondes to a chilled-mirror dew-point hygrometer using a two-pressure type humidity calibration chamber. The experiment was conducted under room temperature conditions. It showed that relative humidity as measured by the Vaisala RS80- A was about 5 to 15% smaller than that of the dew-point hygrometer. The bias was larger in high humidity conditions. Although the dry bias of Vaisala RS80-A radiosondes has been pointed out in several other studies, the dry bias revealed in this study is much larger than previously reported, indicating that a problem still exists in RS80-A humidity measurements taken in moist air conditions such as Japan. The RS2-91 showed only small dry bias relative to the dew-point hygrometer (less than 4%). However, the Aerological Observatory of the JMA reported that they improved the RS2-91 humidity sensor since 1999 (Shibue et al. 2000). RS2-91 sondes manufactured before and in 1999 had a dry bias with the same order of magnitude as the Vaisala RS80-A. There have been several reports (e.g., Ohtani et al. 2000) that the PWV derived by GEONET (Japanese nationwide GPS array) and other campaign GPS observations agreed well with those by JMA or Vaisala radiosondes. The implication of the dry bias errors of the radiosonde to the previous GPS studies is that the past GPS analysis in Japan produced a drier atmosphere than actual conditions. It is recommended that the past GPS data, including the GEONET data, be reanalyzed using the most advanced GPS analysis methods.