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A Study of the Chemical Composition of the Atmosphere using Assimilation of Satellite Measurements
Mr. Seppo Hassinen(1), Dr. Erkki Kyrölä(1)
, and Dr. Johanna Tamminen(1)
(1)
Finnish Meteorological Institute,
P.O.BOX 503,
00101 Helsinki,
Finland
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symposium presentation
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Abstract
In this study we will produce 4D atmospheric data set using the chemical data assimilation. The novel feature we are introducing is that we are assimilating profiling instruments: GOMOS onboard Envisat satellite and OSIRIS onboard Odin satellite. GOMOS (Global Monitoring of Ozone by Occultation of Stars) is an stellar occultation instrument. With it we can get good profiles from the night time conditions of the atmosphere which has not been possible before. With the OSIRIS, which measures scattered Sun light, we can cover day time conditions. Both of these instruments are measuring in limb geometry, so the vertical sampling resolution is very good and this is great advantage in chemical data assimilation – we are able to get true profiles and therefore able to study the dynamics and chemistry of the atmosphere more carefully. Using these two instruments together, we are able to cover the atmosphere both in day and night conditions. Furthermore, including more traditional total ozone measurements from OMI instrument onboard Aura satellite we are able to fullfill the possible caps in spatial coverage of the profiling instruments.
The assimilation system FASP (FinRose Assimilation System for Profiles) is based on assimilation code and the atmospheric model. The assimilation code is provided NCAR (Khattatov et all) and the approach is sequential assimilation and it provides also estimates of the analysis errors. The assimilation sheme is one variant of suboptimal Kalman filter.The atmospheric model is FinRose-CTM which is based on the famous ROSE model. Together, the assimilation code, FinRose-CTM, interfaces to ECMWF meteorological data and to satellite data make up FASP.
The main ojectives of this study are to prepare FASP for all of these instruments and validate the system. Furthermore, the aim is to peform stydies of chemistry and dynamics of the atmosphere and to provide 4D data sets of ozone for other studies.
In presentation, I will introduce the assimilation system FASP, the satellite data sources and give examples and preliminary results. Special focus is in the ozone conditions over China.
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