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Effects of point source emission heights in WRF–STILT: a step towards exploiting nocturnal observations in models

Maier, Fabian and Gerbig, Christoph and Levin, Ingeborg and Super, Ingrid and Marshall, Julia and Hammer, Samuel (2022) Effects of point source emission heights in WRF–STILT: a step towards exploiting nocturnal observations in models. Geoscientific Model Development, 15 (13), pp. 5391-5406. Copernicus Publications. doi: 10.5194/gmd-15-5391-2022. ISSN 1991-959X.

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Official URL: https://doi.org/10.5194/gmd-15-5391-2022

Abstract

An appropriate representation of point source emissions in atmospheric transport models is very challenging. In the Stochastic Time-Inverted Lagrangian Transport model (STILT), all point source emissions are typically released from the surface, meaning that the actual emission stack height plus subsequent plume rise is not considered. This can lead to erroneous predictions of trace gas concentrations, especially during nighttime when vertical atmospheric mixing is minimal. In this study we use two Weather Research and Forecasting (WRF)–STILT model approaches to simulate fossil fuel CO2 (ffCO2) concentrations: (1) the standard “surface source influence (SSI)” approach and (2) an alternative “volume source influence (VSI)” approach where nearby point sources release CO2 according to their effective emission height profiles. The comparison with 14C-based measured ffCO2 data from 2-week integrated afternoon and nighttime samples collected at Heidelberg, 30 m above ground level shows that the root-mean-square deviation (RMSD) between modelled and measured ffCO2 is indeed almost twice as high during the night (RMSD =6.3 ppm) compared to the afternoon (RMSD =3.7 ppm) when using the standard SSI approach. In contrast, the VSI approach leads to a much better performance at nighttime (RMSD =3.4 ppm), which is similar to its performance during afternoon (RMSD =3.7 ppm). Representing nearby point source emissions with the VSI approach could thus be a first step towards exploiting nocturnal observations in STILT. The ability to use nighttime observations in atmospheric inversions would dramatically increase the observational data and allow for the investigation of different source mixtures or diurnal cycles. To further investigate the differences between these two approaches, we conducted a model experiment in which we simulated the ffCO2 contributions from 12 artificial power plants with typical annual emissions of 1 million tonnes of CO2 and with distances between 5 and 200 km from the Heidelberg observation site. We find that such a power plant must be more than 50 km away from the observation site in order for the mean modelled ffCO2 concentration difference between the SSI and VSI approach to fall below 0.1 ppm during situations with low mixing heights smaller than 500 m.

Item URL in elib:https://elib.dlr.de/187470/
Document Type:Article
Title:Effects of point source emission heights in WRF–STILT: a step towards exploiting nocturnal observations in models
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Maier, FabianHeidelberg University, GermanyUNSPECIFIEDUNSPECIFIED
Gerbig, ChristophMax Planck Institute for Biogeochemistry, Jena, GermanyUNSPECIFIEDUNSPECIFIED
Levin, IngeborgHeidelberg University, GermanyUNSPECIFIEDUNSPECIFIED
Super, IngridDepartment of Climate, Air and Sustainability, TNO, Utrecht, NLUNSPECIFIEDUNSPECIFIED
Marshall, JuliaDLR, IPAhttps://orcid.org/0000-0003-2648-128XUNSPECIFIED
Hammer, SamuelHeidelberg University, GermanyUNSPECIFIEDUNSPECIFIED
Date:14 July 2022
Journal or Publication Title:Geoscientific Model Development
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:15
DOI:10.5194/gmd-15-5391-2022
Page Range:pp. 5391-5406
Publisher:Copernicus Publications
ISSN:1991-959X
Status:Published
Keywords:radiocarbon, Lagrangian transport modelling, nocturnal boundary layer, fossil fuel emissions
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:other
DLR - Research area:Raumfahrt
DLR - Program:R - no assignment
DLR - Research theme (Project):R - no assignment
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Trace Species
Deposited By: Marshall, Julia
Deposited On:15 Jul 2022 09:50
Last Modified:15 Jul 2022 09:50

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