Energy, water and carbon exchange in a boreal forest landscape - NOPEX experiences

The role of the land surface in controlling climate is still underestimated and access to information from the boreal-forest zone is instrumental to i mprove this situation. This motivated the organisation of NOPEX (Northern h emisphere climate-Processes land-surface Experiment) in the southern part o f the European boreal zone. This paper summarises results from NOPEX in its first phase, dealing with spring- and summertime conditions. Two concentra ted field efforts (CFE1 on 27 May-23 June 1994, CFE2 on 18 April-14 July 19 95) were carried out with coordinated measurements of energy, water, and CO 2 budgets at 13 ground-based sites and at various airborne platforms. Flux aggregation was a central issue in the heterogeneous, patchy NOPEX landscap e. It is shown that simple land-use-weighted averaging of fluxes from field s/forests/lakes agree well with regional fluxes. Momentum fluxes can be par ameterised over the whole area with a roughness length of approximately 1.5 m, whereas fluxes of sensible heat and other scalars depend on the averagi ng scale, Local measurements of soil moisture can be classified and meaning ful averages can be deduced with a 1 km resolution. Lakes play an important role and differs in both diurnal and annual cycles compared to the forests and fields. Multiannual data from an agricultural and a forest site has al lowed quantification and modelling of seldom occuring phenomena. One unexpe cted result was that the Norunda Common forest acted as a source and not a sink of CO2. The successful completion of CFE1-2 and a pilot winter campaig n (CFE3) will lead NOPEX into its final phase, devoted to wintertime proces ses. Measurements and model results reside in SINOP. the System for Informa tion in NOPEX, open for NOPEX participants. Data from CFE1 and CFE2 are rel eased on CD as an integrated part of this Special Issue. (C) 1999 Elsevier Science B.V. All rights reserved.