Das Projekt "GOME Assimilated and Validated Ozone and NO2 Fields for Scientific Users and for Model Validation GOA" wird vom Umweltbundesamt gefördert und von Universität Heidelberg, Institut für Umweltphysik durchgeführt. GOA is a short, two year project with a limited budget and a clear aim: Extend and improve the O3 and NO2 data products of GOME. Generate and distribute a five year data set of assimilated fields of ozone and NO2 based on GOME observations. This data set will be validated with other observations obtained during measurement campaigns and from monitoring networks. Confront this data set of two key chemicals of the atmosphere with output from global chemistry-transport models (CTM's) to improve their modeling capability of current and future changes of tropospheric and stratospheric ozone and chemically active greenhouse gases. The GOA objectives are: -To generate a 5-year data set of ozone fields (level-4 products) based on the measurements (available level-2 data) of the GOME spectrometer on board of the ESA ERS-2 satellite. -To validate these ozone fields with an extensive set of independent ground based and satellite observations. Improve and monitor the quality of the ground based observations. -To provide these fields to the scientific community by means of a web site and CDroms. -To estimate the tropospheric ozone content by using total column ozone data and ozone profile retrievals for GOME in a single assimilation. -To improve the GOME NO2 product by using position and time dependent model-predicted profiles of NO2 for the determination of the air-mass factor in the DOAS retrieval of NO2. -To validate this set of NO2 fields with independent ground based and satellite observations. -To provide assimilated NO2 (NOx) fields (target year 1997) to the scientific community. -To estimate the tropospheric NO2 column based on the assimilation and by exploiting the differences in spatial distribution of stratospheric and tropospheric NOx. Comparison with model results. -To identify NOx emission source strengths, by performing model studies and compare with the GOME NO2 observations. -To use this extensive combined data set of ozone and NO2 to validate the performance of chemistry-transport models concerning the modeling of the oxidation capacity, affecting chemically-active greenhouse gases, and the modeling of the seasonal and year to year variation in stratospheric ozone.