Generally, spatial and temporal fluctuations in concentrations of methane are poorly understood. For this reason, a project has been started with the title: "Sources, regional scaling and validation of CH4 and N2O emissions from the Netherlands and Northwest Europe. As part of this project we deal here with the detection of local emission sources from temporal concentration patterns in The Netherlands.

Longitudinal and lateral dispersion coefficients are computed for the Ems Estuary using a modified version of the tidal random walk model developed by Zimmerman. This model relates the mixing properties of the flow to the velocity and length scales of the tidal current and the residual eddies. It is found that values of the longitudinal dispersion coefficient are 200–1200m2s−1, depending on the position in the estuary, and lateral dispersion coefficients are a factor ofc. 50 smaller. These results are three to four times larger than earlier reported values, which were determined from field observations. This difference is attributed to the fact that in the tidal random walk model, the dependence of the dispersion mechanism on the detailed kinematics of the flow is neglected, since a statistical distribution of residual eddies is assumed. However, the model predicts the spatial distribution of the dispersion coefficients in the estuary quite well. Particular attention is paid to the presence of three peaks in the dependence of these coefficients on the distance to the river mouth. Using the concepts underlying the tidal random walk model, these peaks are related to the presence of tidally induced residual circulations around sand banks. It is also concluded that the effect of shear dispersion on the horizontal mixing processes in the Ems Estuary can be neglected.

The atmosphere is a very complex, open, dynamic and multi-causal relation system in which non-linear processes and feedback mechanisms play an important role. Research within this subtheme in NRP-1 focused on uncertainties in our understanding of three issues i.o. o − the role of clouds and aerosols on the radiation budget − the role of atmospheric ozone in global change and the effect of atmospheric change on UV-B climatology − trophospheric budgets of non CO2 greenhouse gases These issues are being dealt with in 12 projects. On average good progress has been made in many of the projects and through there are some weaknesses, the overall quality of science and technological developments is good and in some cases even excellent in comparison to international standards. Links with international programmes such as IGBP, CEC, EUREKA/EUROTRAC are well established.

Methane emissions from the oil and gas industry contribute significantly to the total methane emissions. For this reason, methane emissions from this sector are further quantified for The Netherlands. This quantification, based on both a detailed engineering study and on measurements, indicates dutch methane emissions to be about 30 to 50 ktonne higher than previously expected. The main reason for this difference is, that in this quantification emissions during exploitation and fugitive and incidental emissions are incorporated, whereas they have been neglected earlier.