Global Ozone Monitoring Experiment ozone profile characterization using interpretation tools and lidar measurements for intercomparison

Abstract

Global ozone profiles are derived from the ultraviolet and visible part of the spectra of the nadir‐viewing Global Ozone Monitoring Experiment (GOME), which is mounted on the polar orbiting second Earth Remote Sensing satellite (ERS‐2). These profiles need to be characterized, especially since the product includes a priori knowledge and so‐called averaging kernels. This additional information needs to be taken into account when comparing the profiles to correlative measurements. We perform an intercomparison between the ground‐based stratospheric lidar system in Lauder, New Zealand, and collocated GOME data. Here, the satellite profiles are retrieved with the algorithm of the Royal Netherlands Meteorological Institute (KNMI), which uses the optimal estimation method. In the comparison study significant differences are revealed which vary with season and altitude, indicating errors in the retrieval system. However, any quality assessment will just be one part of characterizing an ozone profile product that includes averaging kernels and a priori information. Data users need to be aware of the inherently complicated nature of such products that can only be fully understood when taking into account this additional information. In the second part of the study, the complex relation between the retrieved and the true profile is clarified using several interpretation tools. Applying these tools, we conclude that below 17‐km altitude the GOME profiles can only be used with appropriate use of averaging kernels (e.g., in data assimilation). Above 17 km up to 50 km the GOME spectra contain useful profile information, but the retrieved profiles have a moderate vertical resolution of about 11 km and contain a substantial fraction of a priori information of about 50%.

Review of ozone and temperature lidar validations performed within the framework of the Network for the Detection of Stratospheric Change

“…Mean differences were within ¡10% from 10 to 45 km as reported by Meijer et al 50 Such experiments can be used for long-term comparisons because instruments, using a very similar method, are expected to be launched successively in the future. However, the satellite product includes a priori information, and spectral calibration can introduce significant bias.…”

Comparison and validation studies related to ground-based microwave observations of ozone in the stratosphere and mesosphere

“…Previous comparison studies demonstrated that both observations should have a horizontal distance of less than 800 km and a time separation of less then 20 h (Meijer et al, 2003;Veiga et al, 1995). In the mesosphere (beyond 50 km altitude), the diurnal variation of ozone requires a stricter time criterion.…”

GOMOS ozone profile validation using ground-based and balloon sonde measurements

“…Differences in vertical resolution are not taken into account for the lidar data, because the effect is considered relatively small given the similar resolution of GOMOS. If we are to apply the averaging kernels and consider the a-priori information from the microwave radiometer data, the GOMOS data will be degraded and no longer independent from the microwave radiometer data (Meijer et al, 2003). The effect of not taking this resolution difference into account should lead to an increased standard deviation of the differences between GOMOS and the microwave retrievals.…”