Nowadays, we can use several meteorological databases through the Internet. They are, however, heterogeneous in access methods, data formats, available items etc., so that clients applications are generally tightly linked to particular databases. This causes inefficiency in developing client applications [1]. To solve this issue, we developed a data broker named MetBroker ([2] ((Laurenson, http://www.agmodel.net/) that provides client applications consistent accesses to such heterogeneous databases, hiding the heterogeneity and virtually integrating distributed databases. The basic idea was to provide a remote wrapper application to each database that translates the heterogeneity to a standardized format (Figure 1). At the end of May 2006, it covers more than 22,000 weather stations from 25 weather databases of the world.