Validation of the MetOp-A total ozone data from GOME-2 and IASI using reference ground-based measurements at the Iberian Peninsula

One of the most important atmospheric composition products derived from the first EUMETSAT Meteorological Operational satellite (MetOp-A) is the total ozone column (TOC). For this purpose, MetOp-A has two instruments on board: the Global Ozone Monitoring Experiment 2 (GOME-2) that retrieves the TOC data from the backscattered solar ultraviolet-visible (UV-Vis) radiance, and the Infrared Atmospheric Sounding Interferometer (IASI) that uses the thermal infrared radiance to derive TOC data. This paper focuses on the simultaneous validation of the TOC data provided by these two MetOp-A instruments using the measurements recorded by five well-calibrated Brewer UV spectrophotometers located at the Iberian Peninsula during the complete 2009. The results show an excellent correlation between the ground-based data and the GOME-2 and IASI satellite observations (R² higher than 0.91). Differences between the ground-based and satellite TOC data show that the IASI instrument significantly overestimates the Brewer measurements (about 4.4% when all five ground-based stations are jointly used). In contrast, the GOME-2 instrument shows a slight underestimation (~ 1.6%). In addition, the absolute relative differences between the Brewer and GOME-2 data are quite smaller (about a factor higher than 2) than the Brewer-IASI absolute differences. The satellite viewing geometry (solar zenith angle and the view zenith angle) has no significant influence on the Brewer-satellite relative differences. Moreover, the analysis of these relative differences with respect to the ground-based TOC data indicates that GOME-2 instrument presents a slight underestimation for high TOC values. Finally, the IASI-GOME-2 correlation is high (R² ~ 0.92), but with a mean relative difference of about ± 6% which could be associated with the bias between UV-Vis and infrared spectroscopy used in the retrieval processes.     

利用 IASI资料反演平流层大气温度

红外大气探测干涉分光仪(Infrared Atmospheric Sounding Interferometer, IASI)能够获取平流层的大气温度廓线,而且由其 提取的大气温度扰动信息可用于平流层的重力波特征分析。基于神经网络方法,利用典型 大气廓线库和大气辐射传输模式建立了由IASI反演25～60 km高度范围内的平流层大气温度廓 线的算式,并结合再分析资料对反演结果进行了检验。模拟试验结果表明,平流层大气 温度反演的偏差主要在0 K附近且不超过1 K,均方根误差处在2～6 K之间,且50～5 hPa之间的均方 根误差在3 K以内。对比验证结果表明,本文的平流层大气温度反演与欧洲中期天气预报中心(European Centre for Medium-range Weather Forecasts, ECMWF)的再分析资料在总体上具有可比性,而且反演速度更快,覆盖的区域更完整。