Four-dimensional data assimilation in the monsoon region. Part II: role of temperature and moisture data

In addition to assessing the relative importance of update variables, the present study investigates the role of model physics in data assimilation. The assimilation-forecast system for all of the experiments comprises a 12h assimilation phase followed by a 24h forecast period. In all experiments, updating is done via the Newtonian nudging approach. It is found that the wind data were more valuable than the temperatures. Although temperature assimilation alone had some unexpected positive results, it did not offer appreciable improvement over wind-only assimilations when the two variables were inserted together. On the other hand, a combination of wind and moisture data produced the most positive results. Finally, it has been found that the incorporation of physical parameterizations during the assimilation period is important for a proper spinup of the model and its smooth transition into the forecast stage. -from Authors