Satellite system for monitoring atmospheric characteristics is a major component of the global observing system. In the immediate future, the launch of the ENVISAT satellite with the SCIAMACHY device is planned. This device will measure the vertical column amount and profile of many trace gases by using measurements of sunlight transmitted, reflected, and scattered by the Earth's atmosphere or surface, in both nadir and limb viewing geometries. The SCIAMACHY mission aims to improve our knowledge of a variety of issues of importance for the chemistry and physics of the Earth's atmosphere.
Validation of satellite measurements by comparing with independent data is crucial for estimating and enhancing the real accuracy and hence the use of satellite data, as well as for correcting the interpretation methods.
The NIS countries have a rather extensive network of ground-based stations for measuring the total content, near-surface concentration and vertical profile of the ozone and other trace gases. They take also part to measurements of atmospheric trace gases between Moscow and Vladivostok from a specially equipped railroad truck. Up to now, these data have been little used for validation of satellite measurements. This Project will allow to remove this deficiency, to extend the geographical regions and measurement conditions of the comparisons, to carry out needed longitudinal investigations and, as a consequence, to enhance the quality of satellite data and their use in the investigation of recent environmental changes.
The primary goals of the project are:
1) To generate a consistent database of trace gases measurements from the NIS ground-based monitoring network;
2) To validate the SCIAMACHY satellite measurements of ozone and other trace gases on the basis of correlative observations from the NIS ground-based monitoring network;
3) To develop and improve retrieval algorithms for the interpretation of space-based radiance measurements by SCIAMACHY.
The following studies will be performed to meet the project objectives:
1. Mutual calibration of methods of measuring and interpreting the direct solar spectra in near-IR spectral range used by SPbSU, IAP and KSNU will be done;
2. Ground-based measurements of the spectra of direct and scattered solar radiation in UV, visible and near-IR spectral ranges will be carried out in various regions of the NIS;
3. Data on the CH4, CO, H2O, CO2, O3, N2O, NO2 total contents will be retrieved from the ground-based solar spectra measurements;
4. In situ measurements of the near-surface concentrations of various atmospheric gases will be performed in different regions of the NIS;
5. Ground-based (remote and in situ) measurements of the atmospheric trace gases between Moscow and Vladivostok will be carried out from the railroad truck specially equipped;
6. Comparison of the total contents of various trace gases retrieved from collocated (in space and time) ground-based and SCIAMACHY satellite measurements will be done to validate the satellite measurements;
7. Based on validation results, further investigation of the quality of SCIAMACHY retrieval algorithms and data products will be carried out;
8. New improved methods for retrieving some trace gases from the SCIAMACHY data will be developed on the basis of analysis of recent inverse algorithms and comparison of ground-based and satellite measurements.
The expected results are:
1. Estimation of the accuracy of the SCIAMACHY measurements of the CH4, CO, H2O, CO2, O3, N2O, NO2 total content by comparing with the ground-based network data;
2. New improved methods of interpreting the satellite outgoing radiation measurements (nadir measurement geometry) by the SCIAMACHY instrument.
