LEO: Combination of a Plume and Grid Model in the Netherlands

Abstract

We present the chemistry transport model LEO: a hybrid model, which combines the Eulerian grid model LOTOS-EUROS with the Gaussian plume model OPS. LEO is a new model under development in the Netherlands, which combines high resolution plume calculations around sources with large-scale transport and chemistry from a Eulerian grid model. In this way, we combine the best of both worlds into a new state-of-the-art model. The aim of LEO is to have a new calculation tool available in the Netherlands at a high resolution (typically 1 × 1 km²), which can (among others) deliver data input for the yearly produced maps of concentrations and deposition over the Netherlands. In the presentation a brief overview of the LEO model is given, and results of calculations are presented for calculating annual averaged concentrations of pollutants and deposition of acidifying and eutrophying components over the Netherlands. Furthermore, preliminary results are shown for LEO in its Plume-in-Grid (PinG) configuration, i.e., the transport of the mass released from a number of point sources is initially calculated with a plume description, after which the mass of the plumes is dumped into the grid. We will illustrate the performance of LEO by analysing existing multi source situations for ammonia with high time resolution measurements of ammonia.

Questions and Answers

Questioner: T. Dore

Question: The use of ‘colors’ in LOTOS-EUROS suggests that source attribution can be calculated in a single model run. How flexible is the model assignment of colors regarding contributions from different numbers of country or sector emissions?

Answer: Indeed, the LOTOS-EUROS model can calculate a different numbers of country or sector emissions in a single model run. The number of ‘colors’ which can be used in a single model run is not limited by the source apportionment module itself: obviously computation time increases as one increases the number of ‘colors’.

Questioner: B. Carissino

Question: You mention that the plume chemistry is linear, presumably mixing with the background. How does that impact the results and is it possible to improve it by adding first order non-linear effects such as HDMR?

Answer: Large-scale chemistry in the OPS model is parameterized. The LEO model improves this by combining the LOTOS-EUROS model with the OPS model, such that one yields a good performance of large-scale chemistry (LOTOS-EUROS), without losing the high resolution near the areas with sources (OPS). Nevertheless we indeed will look in a later stage into the possibility of adding simple first-order reaction schemes.

Questioner: S. Hanna

Question: You mentioned that a Gaussian plume model is used in the near field. Is it a straight-line model or does it bend or curve its trajectory?

Answer: The OPS model is a Gaussian plume model approach for local applications with a Lagrangian trajectory model for long range transport. This means that for example a change in wind direction over time is taken into account by the OPS model, such that one obtains curved trajectories. The OPS model used in the LEO model can hence be considered as a segmented plume model, and not as a straight-line model.