Intercomparison of midlatitude tropospheric and lower-stratospheric water vapor measurements and comparison to ECMWF humidity data
Intercomparison of midlatitude tropospheric and lower-stratospheric water vapor measurements and comparison to ECMWF humidity data
复制标题
DOI：
10.5194/acp-18-16729-2018
复制
发表时间：
2018-11
影响因子：
6.3
通讯作者：
中科院分区：
文献类型：
--
作者：
抽象。对流层顶附近气候敏感区水汽的精确测量是非常具有挑战性的。由于机载平台上不同仪器在低水汽混合比下的测量结果之间存在无法解释的系统差异，因此限制了我们充分解决该地区湿度分布、云形成和气候影响等一些相关科学问题的能力。因此，在过去的十年中，科学界做出了巨大的努力来理解这些差异，并提高水蒸气测量的质量。本研究对2014年在中欧上空进行的中纬度CIRRUS（ML-CIRRUS）活动期间DLR（德国航空航天中心）研究飞机HALO（高空和远程研究飞机）上部署的机载最先进原位湿度计进行了全面的相互比较。仪器比对表明，湿度计测量值在其组合精度范围内（± 10%至15%，取决于湿度状况）;总平均值在2.5%范围内。然而，当混合比低于百万分之十（ppm）H2O时，发现系统差异约为10%，最大可达15%。卷云内相对湿度的比较并不表明对流层上部水汽或温度测量中存在系统性仪器偏差。此外，在现场测量进行比较，从欧洲中期天气预报中心（ECMWF）的模型数据，内插沿着ML-CIRRUS飞行轨迹。我们发现，在整个对流层中，平均一致率在± 10%以内，在对流层顶附近的平流层中，模型中的湿偏差约为100%至150%。与以往的研究结果一致，分析表明，对流层顶的湿度梯度太弱是造成模式亏损的主要原因。
Abstract. Accurate measurement of water vapor in the climate-sensitive region near the tropopause is very challenging. Unexplained systematic discrepancies between measurements at low water vapor mixing ratios made by different instruments on airborne platforms have limited our ability to adequately address a number of relevant scientific questions on the humidity distribution, cloud formation and climate impact in that region. Therefore, during the past decade, the scientific community has undertaken substantial efforts to understand these discrepancies and improve the quality of water vapor measurements. This study presents a comprehensive intercomparison of airborne state-of-the-art in situ hygrometers deployed on board the DLR (German Aerospace Center) research aircraft HALO (High Altitude and LOng Range Research Aircraft) during the Midlatitude CIRRUS (ML-CIRRUS) campaign conducted in 2014 over central Europe. The instrument intercomparison shows that the hygrometer measurements agree within their combined accuracy (±10 % to 15 %, depending on the humidity regime); total mean values agree within 2.5 %. However, systematic differences on the order of 10 % and up to a maximum of 15 % are found for mixing ratios below 10 parts per million (ppm) H2O. A comparison of relative humidity within cirrus clouds does not indicate a systematic instrument bias in either water vapor or temperature measurements in the upper troposphere. Furthermore, in situ measurements are compared to model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) which are interpolated along the ML-CIRRUS flight tracks. We find a mean agreement within ±10 % throughout the troposphere and a significant wet bias in the model on the order of 100 % to 150 % in the stratosphere close to the tropopause. Consistent with previous studies, this analysis indicates that the model deficit is mainly caused by too weak of a humidity gradient at the tropopause.