Monthly isotopic signal of the precipitated water in the province of Trento: Lagrangian analysis and discussion of measurements

The present work has been performed in the framework of the research project AQUAPAST. The main focus of AQUAPAST is the reconstruction of past climate changes in the atmospheric circulation and in particular in the water vapour transport mechanism over the Mediterranean area starting from the analysis of the isotopic content of cave speleothemes in the Trentino Province (North-East of Italy). A Lagrangian methodology for the reconstruction and the analysis of the airstreams which govern the transport of water vapour has been applied to recent events. The average monthly isotopic signal of the precipitation water sampled in stations located in key geographic settings in the Province of Trento is used as tracer to infer the origin of the precipitating water and to validate the Lagrangian analysis. A comparison between the isotopic signal of November 2002 and November 2003 is here presented, as most of the yearly precipitation falls in November over the Eastern Alps. Hypotheses are proposed about the meteorological factors (e.g. monthly averaged sea surface temperature, atmospheric circulation, etc.) determining different isotopic signals in the two years.