LES study of the spatial representativeness and imbalances of scalar fluxes determined by the temporal EC method
Responsible: Gerald Steinfeld
Project type: Research project (funded by ​DAAD)
Duration: 01/05/2004 - 30/09/2005

Several of the former projects of the PALM group have dealt with the so-called energy imbalance problem so far. However, during the last years, several papers, dealing with the analysis of field experiments, have reported on the fact that not only an imbalance of energy fluxes could be observed, but that a similar rate of underestimation of carbon dioxide fluxes could also be stated. A detailed understanding of how mass is partitioned at the earth's surface is of particular importance for the derivation of appropriate parameterisation schemes in global climate models. Global climate models will even gain in importance in the context of the monitoring of the agreements on carbon dioxide emission, that are defined in the Kyoto protocol, as they offer the only possibility to get area-wide data on carbon-dioxide fluxes.

In this study, which is a joint project together with Atsushi Inagaki from the working group of Manabu Kanda, ​Department of International Development Engineering, Tokyo Institute of Technology, Japan, a systematic investigation of the question, whether the phenomenon of an underestimation of the true representative fluxes in connection with the application of the temporal EC method is restricted to temperature fluxes or whether it has also to be stated for fluxes of a passive scalar, such as carbon dioxide. The simulation of EC measurements of scalar fluxes will be carried out for homogeneously as well as heterogeneously heated/cooled boundary layers and under a variation of the magnitude and direction of the geostrophic wind, of the thermal stratification and of the parameters describing the near-surface heat flux inhomogeneity. Moreover, the impact of an inhomogeneous near-surface scalar flux on a potential underestimation of the representative flux will be examined in detail.