Methods Fuzzy- Logic enables the modeling of rule based knowledge by the use of fuzzy criteria instead of exact measurement values or threshold values. The Method contains three steps: fuzzification, Implementation and application of a set of rules and defuzzification of the results. 1. Fuzzification is the relation of filter parameters to defined criteria which each form an own fuzzy set. By the means of statistical methods a value for the degree of membership is determined for each measurement value and trajectory dataset 2. The criteria and processes of the project are organized as a set of rules. 3. The link of the fuzzy input with the set of rules happens in the defuzzification. This creates a continuous value for the possible influence of ground based air masses in the measured time series. Abb. Sceme for fuzzification of a measured time series with the example of carbon dioxide. Background Im Rahmen des Global Atmosphere Watch (GAW) - Projektes wird am Standort Zugspitze/ Schneefernerhaus eine Global- station zur Messung von klimawirksamen und reaktiven atmosphärischen Spurengasen vom Umweltbundesamt aufgebaut. Dazu werden vom Deutschen Wetterdienst die GAW- Komponentenklassen meteorologische Parameter, atmosphärische Radioaktivität und Aerosole gemessen. Die kontinuierliche Erfassung des luftchemischen Hintergrunds mit dem Ziel der Früherkennung atmosphärischer und klimatischer Veränderung ist eine Kernaufgabe des GAW- Programms. Um dieser Aufgabe zu entsprechen, ist die Kenntnis der Raumzeitlichen Repräsentanz des Standortes Zugspitze/ Schneefernerhaus von Bedeutung. Project The determination of the time space representativity at the measurement site requires the identification of locally influenced air masses. This results in development and application of filtering functions. The development of filter functions using fuzzy logic is a central topic of this project. The principal idea is based on a direct pattern recognition of a local influence from the measured air chemistry time series and the underlying meteorological influence. Information about trajectory data, criteria for atmospheric stability, tracer substances and typical patterns of ground related trace substances is used for filtering criteria. Also in order to resolve the problematics ot threshold criteria the continuous change of processes is modelled in an appropriate manner with the fuzzy logic method in the filtering methods. The project is targeting at the development of filtering functions for the identification of air masses influenced from ground layer processes. The results are integrated in an database oriented applicaiton. Investigation of Time Space Representativity of GAW- Measuring Site Zugspitze/ Schneefernerhaus - Introduction of the project - Ruhr-Universität Bochum, Geogr. Institut, AG Klimaforschung LeitungProf. Dr. H. Fleer BearbeitungI. Kürbis, Dipl.-Geogr. Laufzeit Förderung Fraunhofer Gesellschaft, aus Mitteln des Bundesministeriums für Bildung und Forschung