ABSTRACT:
In this paper, a description of the setup for a local assimilation system for a limited area model, ALADIN (Aire Limiteé Adaptation Dynamique dévelopement InterNational), is given with a comprehensive description of the assimilation techniques used. The assimilation system at DHMZ (Meteorological and Hydrological Service of Croatia) consisted of two parts: the surface assimilation, which was used to change the state of a model land surface variables, and the upper air assimilation, which changed the upper air model fields. The surface assimilation was performed by the optimal interpolation (OI) technique, while the upper air assimilation was conducted using the 3D variational technique (3DVAR). In a previous research study, surface assimilation and upper air assimilation were used independently and were determined to be beneficial to forecast quality. Currently, they can be combined to improve forecast quality for both the low-level and upper-level fields. A basic verification for a period of 10 months was performed for a forecast starting from the initial state given by the assimilation system and the operational forecast. The verification results showed a positive impact of assimilation on forecast for the upper airfields and for screen-level variables.
