Scale aggregation - comparison of flux estimates from NOPEX

The NOPEX two concentrated field efforts (CFEs) (June 1994 and April-July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of fluxes of latent and sensible heat, but these flux estimates are not directly comparable due to differences in temporal and spatial scales. The challenge here has been to overcome these difficulties so that the different estimates can be critically compared and evaluated in a systematical way. Five different approaches for the estimation of the regional flux of sensible and/or latent heat over the NOPEX area have been evaluated: (I) Direct aggregation - mixed layer evolution method, (2) Weighted averages of (a) aircraft measurements in the boundary layer and of (b) mast measurements, (3) Numerical models (a) ECOMAG - a distributed hydrological model and (b) MIUU - a mesoscale meteorological model.

In general, good agreement was found between the regional estimates of the sensible heat Bur, based on the mixed layer evolution method and land use weighted mast measurements. The aircraft measurements were found to be systematically smaller than the land use weighted mast estimates. For the latent heat flux good agreement was found between the regional latent heat Bur derived from airplane measurements, land use weighted mast estimates, and the two mesoscale numerical models. (C) 1999 Elsevier Science B.V. All rights reserved.