A fast method for ammonia emission reduction scenario studies: Combining EMEP4NL with the SHERPA tool

Abstract

We present a fast method for calculating the effects of ammonia emission reduction scenarios on reduced nitrogen components over the Netherlands. The method combines the EMEP4NL model, which is a full atmospheric chemical transport model (ACTM), with the SHERPA tool, which is an approximate representation of a full ACTM. The SHERPA tool uses a geographically weighted regression method to derive source-receptor relations, based on a limited number of “training” runs of the ACTM (here, EMEP4NL). The training runs consist of a base run of the year of interest plus uniform emission reduction runs for the primary pollutants of interest. Once the source-receptor relations are derived, scenario studies can be performed at a much lower computational cost with SHERPA (i.e. order 104–105 more efficient) as compared to a full run with the EMEP4NL model. Here, we study five specific ammonia emission reduction scenarios, in which a 30% emission reduction is enforced for specific regions in The Netherlands, Germany and Belgium. Our analysis shows that the EMEP4NL model and the SHERPA tool yield similar results in terms of the reduction of the yearly average concentration and deposition of reduced nitrogen components. Because of its computational efficiency and ability to adequately reproduce the results of the EMEP4NL model, the SHERPA tool is relevant for policy making. It can provide predictions of the effects of many different local emission reduction measures in a computationally efficient manner.