Evaluation of MUSICA IASI tropospheric water vapour profiles using theoretical error assessments and comparisons to GRUAN Vaisala RS92 measurements
Evaluation of MUSICA IASI tropospheric water vapour profiles using theoretical error assessments and comparisons to GRUAN Vaisala RS92 measurements
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DOI：
10.5194/amt-11-4981-2018
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发表时间：
2017-10
影响因子：
3.8
通讯作者：
C. Borger;M. Schneider;B. Ertl;F. Hase;O. García;M. Sommer;M. Höpfner;S. Tjemkes;X. Calbet
中科院分区：
文献类型：
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作者：
C. Borger;M. Schneider;B. Ertl;F. Hase;O. García;M. Sommer;M. Höpfner;S. Tjemkes;X. Calbet
抽象的。利用MUSICA(研究大气水循环的多平台同位素遥感)处理器，从红外大气测深干涉仪(IASI)光谱中反演了体积混合比水汽廓线。对与在全球气候观测系统参考高空网络(GRUAN)框架下进行的Vaisala RS92无线电探空仪测量相一致的IASI观测进行的反演是在三个不同的气候带进行的：热带(马努斯岛，2°S)、中纬度(林登堡，52°N)和极地地区(Sodankylä，67°N)。对地面以上1公里处至对流层上层的垂直H2O分布显示出较好的敏感性。典型的DOFS(信号自由度)值热带地区约为5.6，夏季中纬度约为5.1，冬季中纬度约为3.8，夏季极地约为4.4。考虑许多不确定性源的影响，对Musica IASI水汽廓线的误差进行了理论估计。对于所有三个气候区域，未被识别的卷云和大气温度的不确定性已被确定为最重要的误差源，它们可以达到约25%。Musica IASI水汽剖面已与100个单独重合的Gruan水蒸气剖面进行了比较。数据之间的系统差异在12公里以下的11%以内；然而，在更高的海拔，Musica IASI数据相对于Gruan数据显示出高达21%的干偏差。近地表的散布最大(30%)，但在海拔1公里以上的散布不超过21%。对比研究表明，MUSICA IASI反演处理器提供的H2O剖面捕捉到了从离地面1公里到接近对流层顶的高度H2O体积混合比剖面的巨大变化。在5公里以上，Gruan数据的观测散布与Musica IASI和Gruan随机误差的组合是合理一致的。较低高度的散射增加可能是由于夏季大陆站点Lindenberg和Sodankylä的地表发射率不确定造成的，而对流层上层的干偏差可能表明在正确模拟水蒸气的谱线形状方面存在缺陷。
Abstract. Volume mixing ratio water vapour profiles have been retrieved from IASI (Infrared Atmospheric Sounding Interferometer) spectra using the MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) processor. The retrievals are done for IASI observations that coincide with Vaisala RS92 radiosonde measurements performed in the framework of the GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN) in three different climate zones: the tropics (Manus Island, 2° S), mid-latitudes (Lindenberg, 52° N), and polar regions (Sodankylä, 67° N). The retrievals show good sensitivity with respect to the vertical H2O distribution between 1 km above ground and the upper troposphere. Typical DOFS (degrees of freedom for signal) values are about 5.6 for the tropics, 5.1 for summertime mid-latitudes, 3.8 for wintertime mid-latitudes, and 4.4 for summertime polar regions. The errors of the MUSICA IASI water vapour profiles have been theoretically estimated considering the contribution of many different uncertainty sources. For all three climate regions, unrecognized cirrus clouds and uncertainties in atmospheric temperature have been identified as the most important error sources and they can reach about 25 %. The MUSICA IASI water vapour profiles have been compared to 100 individual coincident GRUAN water vapour profiles. The systematic difference between the data is within 11 % below 12 km altitude; however, at higher altitudes the MUSICA IASI data show a dry bias with respect to the GRUAN data of up to 21 %. The scatter is largest close to the surface (30 %), but never exceeds 21 % above 1 km altitude. The comparison study documents that the MUSICA IASI retrieval processor provides H2O profiles that capture the large variations in H2O volume mixing ratio profiles well from 1 km above ground up to altitudes close to the tropopause. Above 5 km the observed scatter with respect to GRUAN data is in reasonable agreement with the combined MUSICA IASI and GRUAN random errors. The increased scatter at lower altitudes might be explained by surface emissivity uncertainties at the summertime continental sites of Lindenberg and Sodankylä, and the upper tropospheric dry bias might suggest deficits in correctly modelling the spectroscopic line shapes of water vapour.