Author(s)

H. J. Eskes & H. M. Kelder

Abstract

NO2 and ozone observations from space and the prospect for chemical forecasting H.J. Eskes & H.M. Kelder Royal Netherlands Meteorological Institute, POBox 201, 3 730 AE De Bilt, The Netherlands. Abstract A tropospheric chemical forecast system should consist of a reliable description of the dynamical state of the atmosphere, measurements of the global distribution of key chemicals, and realistic emission scenario’s. New satellite missions such as Envisat will provide unique information on the columns of several key tropospheric species, e.g. ozone, NO2, HCHO, CO, CH4. In this paper we will discuss difficulties in the retrieval of quantitative tropospheric columns of trace gases such as NO2 from GOME and SCIAMACHY satellite observations. A new integrated retrieval/modelling approach for tropospheric NO2 is discussed. Secondly, an operational ozone forecast scheme is presented. This system provides meaningful ozone and clear-sky UV distributions for a forecast period of about six days, and can be viewed as a first step towards a chemical forecast system. 1 Introduction For a successful chemical forecast several requirements have to be fulfilled. First, a state-of-the-art forecast model is needed. This model should be initialised by assimilating satellite and in-situ measurements of the dynamical state of the atmosphere, i.e. it should consist of chemical modules coupled (directly or off-line) to a numerical weather prediction model. As a second requirement, a realistic global (or regional) analysis of the chemical state of the atmosphere has to be constructed. This analysis should be based on as many high-quality chemical observations as possible. Since ground based observations are limited in number (they typically consist of ground stations in developed countries measuring surface concentrations), observations from satellites with a global coverage are to be preferred. Unfortunately, not many reliable quantitative measurements of tropospheric trace

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