lenges are described in Ganguly and Steinhaeuser (2009) together with a case studyon heat wave data.Understandability Many tools have been developed that display the data in differentviews and allow for interactive analysis (cf. the above listed sites of organizationsin earth science). Mapping found patterns on Google maps, for instance, helps tounderstand the data. Since the complexity of several data generating principles oftenexceeds human capabilities of understanding, decomposing the data or factorizationhelps to single out aspects. Understandability is stressed by Schwabacher et al.(2007).