Data assimilation

Assimilation At the end of each month phytoplankton concentrations in the surface level were adjusted according to the MERIS satellite chlorophyll-a concentrations of the corresponding month. The data assimilation is only done for shallow waters, with a water depth lower than 250 m (see Figure 2.1). 

Table 2.3 Parameters used for the discription of dissolution and remineralisation in HAMOCC5 in the aggregation experiment (AGG) and the satellite data assimilation experiment (SAT).

Fig. 2.1 a) Ocean waters with water depth lower than 250 m b) Total number of month per year in which MERIS data assimilation takes place. 

Acknowledgements. The presented study was funded by Deutscher Akademischer Austauschdienst (DAAD). It is pleasure to thank FJBaier, Prof. A.Ebel from University of Cologne and Dr. A.Krivolutsky from Central Aerological Observatory of Moscow, for their comments and useful advises. Thanks are also due to Dr.I.Stajner of NASA s Data Assimilation Office for supplying of the GEOS ozone data. 

Riishojgaard L.P., l.Stajner, G.-P.Lou (in press) The GEOS ozone data assimilation system Adv.Space Res., at present this paper is available at http //dao.gsfc.nasa.gov/DAO people/ivanka... 

How can weather forecast duration and reliability be improved by new space-based observations, data assimilation, and modeling ... 

Widmann M. Jones J.M. and von Storch H. (2004). Reconstruction of large-scale atmospheric circulation and data assimilation in paleoclimatology. PAGES News, 12(2), 12-13. 

Bioinformatics will play a vital role in overcoming this data integration and modeling challenge, because databases, visualization software, and analysis software must be built to enable data assimilation and to make the results accessible and useful for answering biological questions (p. 254). 

Fukumori I (2001) Data assimilation by models. In Satellite Altimetry and Earth Sciences. Academic Press, San Diego, p 237... 

Atmospheric Modelling and Data Assimilation Laboratory, Centre for Research in Earth and Space Science, York LFniversity, Toronto, Canada e-mail jwk wxprime.com... 

The current version of Enviro-HIRLAM has not previously been evaluated against ETEX-1 measurements. The ETX domain (Eig. 5.1) was used with at time-step fixed at 10 min, and initial and boundary conditions were post-processed from the European Centre for Medium-Range Weather Eorecasts operational model, IFS (Integrated Forecast System). No surface or upper air data assimilation was employed and the model was integrated 80 h into the future. The start time was on 23 October 1994 at 12 00 UTC, 4 h before the start of the release. Output was interpolated to measurement stations in order to compare to the observations and produce statistical measures. 

Coupling Global Atmospheric Chemistry Transport Models to ECMWF Integrated Forecasts System for Forecast and Data Assimilation Within GEMS... 

The main motivation for the development of the GRG coupled system was the need to account for sink and source processes, namely chemical conversion, in the assimilation of satellite observation of chemical tracers within the 4D-VAR data assimilation of the IFS. Since it appeared too costly to be costly to integrate complex chemical mechanisms in the IFS, tendencies describing sink and source processes should be provided by well established CTMs, being coupled to... 

In IFS tracer data assimilation mode, the IFS tracer forecast mode is applied in the outer loops of ECMWF data assimilation system, i.e. the calculation of the trajectories runs of the complete model of the 4D VAR (Mahfouf and Rabier 2000) The iimer loops used in the minimisation step with the tangent linear and adjoint model are currently run uncoupled, i.e. without the application of the source and sink tendencies from the CTM. 

The coupled long-term simulation and data assimilation runs are structured as a sequence of coupled runs (6 h in data assimilation, 24 h in forecast mode) because the IFS needs a re-start from a meteorological analysis as often as possible. The CTM provides the tracer initial conditions of the IFS for the first forecasts. There are three modes of how the initial conditions for the GRG-tracers are obtained in the subsequent forecasts (see Fig. 10.2). 

In the second mode, a consistent treatment of the emission injection and vertical transport would be achieved. In particular, the adjoint formulation of diffusion and convection in data assimilation would be consistent with the forward model. However, dislocation of the chemistry tendencies is more likely than in case 1 because the IPS concentration fields tend to differ more from the CTM fields. 

Since the satellite observations to be assimilated are NO2 data, a diagnostic NOx to NO2 inter-conversion operator// was developed. For the application in 4D VAR data assimilation it s tangent linear H and adjoint had to be coded. 

The inter-conversion operator links the NO2 to the O3 concentration in data assimilation. It is the first step towards the consideration of more chemical relationships within the GRG data assimilation system. 

Importance of Data Assimilation and Problems with Data Assimilation for Chemistry... 

Data assimilation (DA) is important for daily chemistry forecasts, but it also is a challenge. At the moment there are much fewer stations with chemistry observations than meteorological observations, and the observations from these stations may not always be available in real time. Also, the gradients in chemical species often are very sharp, which the current observation network and data assimilation schemes are not capable of representing. And last but not least, it is difficult to determine the assimilation increments with so many possible species and so few detailed observations. This is why ECMWF has limited the chemistry in their model and data assimilation to five species (in addition to the cost in computer power). 

---