In search of the ‘typical’ year of forest-atmosphere exchange

Is there ever a year where forest-atmosphere exchange characteristics can be said to be just normal or typical? We analysed a total of eleven years of energy, water, and carbon fluxes from two sites in Indiana (Morgan-Monroe State Forest, MMSF) and Michigan (University of Michigan Biological Station, UMBS) to evaluate the forest-atmosphere exchange climatology. From these data we determine average annual fingerprints of fluxes, water-use efficiency, energy partitioning, canopy conductance and other indexes of ecosystem functioning. The anomaly fingerprints for fluxes and ecosystem indexes are interpreted in terms of site and location characteristics, bio-physical forcing variables and their anomalies, and set in context to large-scale climatic indicators such as drought index, and ENSO/NAO index. The question at the outset is based on the notion that a true ‘typical’ year or season does not exist if every year or season is dominated by anomalies. In that case, the ‘average’ year does not reflect realistic events in any given year, and this in turn has ramifications for the validity of models with long time steps.