TY - JOUR
T1 - Sensitivity of spatial aerosol particle distributions to the boundary conditions in the PALM model system 6.0
AU - Kurppa, Mona
AU - Roldin, Pontus
AU - Strömberg, Jani
AU - Balling, Anna
AU - Karttunen, Sasu
AU - Kuuluvainen, Heino
AU - Niemi, Jarkko V.
AU - Pirjola, Liisa
AU - Rönkkö, Topi
AU - Timonen, Hilkka
AU - Hellsten, Antti
AU - Järvi, Leena
PY - 2020
Y1 - 2020
N2 - High-resolution modelling is needed to understand urban air quality and pollutant dispersion in detail. Recently, the PALM model system 6.0, which is based on large-eddy simulation (LES), was extended with the detailed Sectional Aerosol module for Large Scale Applications (SALSA) v2.0 to enable studying the complex interactions between the turbulent flow field and aerosol dynamic processes. This study represents an extensive evaluation of the modelling system against the horizontal and vertical distributions of aerosol particles measured using a mobile laboratory and a drone in an urban neighbourhood in Helsinki, Finland. Specific emphasis is on the model sensitivity of aerosol particle concentrations, size distributions and chemical compositions to boundary conditions of meteorological variables and aerosol background concentrations. The meteorological boundary conditions are taken from both a numerical weather prediction model and observations, which occasionally differ strongly. Yet, the model shows good agreement with measurements (fractional bias < 0.67, normalised mean squared error < 6, fraction of the data within a factor of 2 > 0.3, normalised mean bias factor < 0.25 and normalised mean absolute error factor < 0.35) with respect to both horizontal and vertical distribution of aerosol particles, their size distribution and chemical composition. The horizontal distribution is most sensitive to the wind speed and atmospheric stratification, and vertical distribution to the wind direction. The aerosol number size distribution is mainly governed by the flow field along the main street with high traffic rates and in its surroundings by the background concentrations. The results emphasise the importance of correct meteorological and aerosol background boundary conditions, in addition to accurate emission estimates and detailed model physics, in quantitative high-resolution air pollution modelling and future urban LES studies.
AB - High-resolution modelling is needed to understand urban air quality and pollutant dispersion in detail. Recently, the PALM model system 6.0, which is based on large-eddy simulation (LES), was extended with the detailed Sectional Aerosol module for Large Scale Applications (SALSA) v2.0 to enable studying the complex interactions between the turbulent flow field and aerosol dynamic processes. This study represents an extensive evaluation of the modelling system against the horizontal and vertical distributions of aerosol particles measured using a mobile laboratory and a drone in an urban neighbourhood in Helsinki, Finland. Specific emphasis is on the model sensitivity of aerosol particle concentrations, size distributions and chemical compositions to boundary conditions of meteorological variables and aerosol background concentrations. The meteorological boundary conditions are taken from both a numerical weather prediction model and observations, which occasionally differ strongly. Yet, the model shows good agreement with measurements (fractional bias < 0.67, normalised mean squared error < 6, fraction of the data within a factor of 2 > 0.3, normalised mean bias factor < 0.25 and normalised mean absolute error factor < 0.35) with respect to both horizontal and vertical distribution of aerosol particles, their size distribution and chemical composition. The horizontal distribution is most sensitive to the wind speed and atmospheric stratification, and vertical distribution to the wind direction. The aerosol number size distribution is mainly governed by the flow field along the main street with high traffic rates and in its surroundings by the background concentrations. The results emphasise the importance of correct meteorological and aerosol background boundary conditions, in addition to accurate emission estimates and detailed model physics, in quantitative high-resolution air pollution modelling and future urban LES studies.
U2 - 10.5194/gmd-13-5663-2020
DO - 10.5194/gmd-13-5663-2020
M3 - Article
AN - SCOPUS:85096475916
SN - 1991-959X
VL - 13
SP - 5663
EP - 5685
JO - Geoscientific Model Development
JF - Geoscientific Model Development
IS - 11
ER -
