HR: 08:45h
AN: A51B-04    [PDF]
TI: Emission Verification of Greenhouse Gases on the Sub-continental Scale Using Tall Tower Observations and Inverse Trajectory Modeling
AU: * Vermeulen, A T
EM: a.vermeulen@ecn.nl
AF: ECN, Westerduinweg 3, Petten, 1755 LE Netherlands
AU: Hensen, A
EM: hensen@ecn.nl
AF: ECN, Westerduinweg 3, Petten, 1755 LE Netherlands
AU: Bulk, P v
EM: vandenbulk@ecn.nl
AF: ECN, Westerduinweg 3, Petten, 1755 LE Netherlands
AU: Erisman, J
EM: erisman@ecn.nl
AF: ECN, Westerduinweg 3, Petten, 1755 LE Netherlands
AB: Inert (on the time scale of several days) greenhouse gases like CH$_{4}$, N$_{2}O$ and SF$_{6}$ are almost ideal gases to model in trajectory models, as (photo)chemistry and uptake processes can be neglected. The forward and backward (inverse) calculations of atmospheric transport presented here have been performed by using a simple trajectory model, utilizing 3D 96 hour backward trajectory data based on ECMWF analysed windfields. The trajectories were calculated using the FLEXTRA model v3.3 ({\it Stohl et al., 1999}). The most important factor determining the atmospheric concentrations besides the greenhouse gas emission strengths obviously is the atmospheric mixing layer height. This mixing height is determined in the model by following a critical Richardson number scheme. We used a long time series of 3 years of continuous high precision vertical concentration gradient measurements of CH$_{4}$ and N$_{2}O$ at the tall tower of Cabauw in the center of the Netherlands to derive estimates of the West European spatial distribution of emissions of these gases and the corresponding trends. The forward and inverse calculations and the high resolution vertical concentration gradient data provide maps of both the local and more remote distribution of the sources. The inverse calculation uses the SVD matrix inversion technique to determine the best fitting solution to the overdetermined system that follows from the combination of the source receptor matrix derived from the trajectory model and the observed concentration data. The resulting best estimate for the emissions of CH$_{4}$ are for most parts of Western Europe in agreement with the current inventory data. The inherent uncertainty of the transport model and measurements and how these uncertainties translate into the uncertainty of the inverse calculated emissions is estimated by using a Monte Carlo error analysis technique. Other error estimations are determined from using ensemble trajectories with horizontal and vertical deviations. Several problems related to solving overdetermined problems still remain and options to overcome these will be discussed. {\bf References} Stohl, A., L. Haimberger, M.P. Scheele, and H. Wernli (1999): An intercomparison of results from three trajectory models. Meteorol. Applications 8, 127-135.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting