Mixing layer height measurements determines influence of meteorology on air pollutant concentrations in urban area

The mixing layer height (MLH) is a crucial parameter in order to investigate the near surface concentrations of air pollutants. The MLH can be estimated by measurements of some atmospheric variables, by indirect estimates based on trace gases concentration or aerosol, or by numerical models. Here, a modelling approach is proposed. The developed modelling system is based on the models WRF-ARW and CALMET. This system is applied on Firenze-Prato-Pistoia area (Central Italy), during 2010, and it is compared with in situ measurements. The aim of this work is to evaluate the use of MLH model estimates to characterize the critical episodes for PM10 in a limited area. In order to find out the meteorological conditions predisposing accumulation of PM10 in the atmosphere’s lower level, some indicators are used: daily mean wind speed, cumulated rainfall, and mean MLH estimates from CALMET model. This indicator is linked to orography, which has important consequences on local weather dynamics. However, during critical events the local emission sources are crucial to the determination of threshold exceeding of PM10. Results show that the modelled MLH, together with cumulative rainfall and wind speed, can identify the meteorological conditions predisposing accumulation of air pollutant at ground level.

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Effects of Meteorological Parameters on Gaseous Air Pollutant Concentrations in Urban Area of Gwalior City, India

Environmental Claims Journal ◽

10.1080/10406026.2018.1507508 ◽

2018 ◽

Vol 31 (1) ◽

pp. 32-43 ◽

Cited By ~ 1

Author(s):

Banwari Dandotiya ◽

Nimisha Jadon ◽

Harendra K. Sharma

Keyword(s):

Urban Area ◽

Meteorological Parameters ◽

Air Pollutant ◽

Pollutant Concentrations ◽

Air Pollutant Concentrations

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Mixing layer height as an indicator for urban air quality?

10.5194/amt-2017-53 ◽

2017 ◽

Author(s):

Alexander Geiß ◽

Matthias Wiegner ◽

Boris Bonn ◽

Klaus Schäfer ◽

Renate Forkel ◽

...

Keyword(s):

Air Quality ◽

Mixing Layer ◽

Clear Correlation ◽

Emission Sources ◽

Near Surface ◽

Layer Height ◽

Diurnal Cycles ◽

Pollutant Concentrations ◽

Novel Approach ◽

Mixing Layer Height

Abstract. The mixing layer height (MLH) is a measure for the vertical turbulent exchange within the boundary layer, which is one of the controlling factors for the dilution of pollutants emitted near the ground. Based on continuous MLH measurements with a Vaisala CL51 ceilometer and measurements from an air quality network, the relationship between MLH and near surface pollutant concentrations have been investigated. In this context the uncertainty of the MLH retrievals and the representativeness of ground-based in-situ measurements are crucial. We have investigated this topic by using data from the BAERLIN2014 campaign in Berlin, Germany, conducted during June and August 2014. To derive the MLH three versions of the proprietary software BL-VIEW and a novel approach COBOLT were compared. It was found that the overall agreement is reasonable if mean diurnal cycles are considered. The main advantage of COBOLT is the continuous detection of the MLH with a temporal resolution of 10 minutes and a lower number of cases when the residual layer is misinterpreted as mixing layer. We have calculated correlations between MLH as derived from the different retrievals and concentrations of pollutants (PM10, O3 and NOx) for different locations in the metropolitan area of Berlin. It was found that the correlations with PM10 are quite different for different sites without showing a clear pattern, whereas the correlation with NOx seems to depend on the vicinity of emission sources in main roads. In case of ozone as a secondary pollutant a clear correlation was found. We conclude that the effects of the heterogeneity of the emission sources, chemical processing and mixing during transport exceed the differences due to different MLH retrievals. Moreover, it seems to be unrealistic to find correlations between MLH and near surface pollutant concentrations representative for a city like Berlin, in particular when traffic emissions are dominant. Nevertheless it is worthwhile to use advanced MLH retrievals for ceilometer data, e.g. for the validation of chemical transport models.

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Mixing layer height as an indicator for urban air quality?

Atmospheric Measurement Techniques ◽

10.5194/amt-10-2969-2017 ◽

2017 ◽

Vol 10 (8) ◽

pp. 2969-2988 ◽

Cited By ~ 40

Author(s):

Alexander Geiß ◽

Matthias Wiegner ◽

Boris Bonn ◽

Klaus Schäfer ◽

Renate Forkel ◽

...

Keyword(s):

Air Quality ◽

Mixing Layer ◽

Clear Correlation ◽

Emission Sources ◽

Near Surface ◽

Layer Height ◽

Diurnal Cycles ◽

Pollutant Concentrations ◽

Novel Approach ◽

Mixing Layer Height

Abstract. The mixing layer height (MLH) is a measure for the vertical turbulent exchange within the boundary layer, which is one of the controlling factors for the dilution of pollutants emitted near the ground. Based on continuous MLH measurements with a Vaisala CL51 ceilometer and measurements from an air quality network, the relationship between MLH and near-surface pollutant concentrations has been investigated. In this context the uncertainty of the MLH retrievals and the representativeness of ground-based in situ measurements are crucial. We have investigated this topic by using data from the BAERLIN2014 campaign in Berlin, Germany, conducted from June to August 2014. To derive the MLH, three versions of the proprietary software BL-VIEW and a novel approach COBOLT were compared. It was found that the overall agreement is reasonable if mean diurnal cycles are considered. The main advantage of COBOLT is the continuous detection of the MLH with a temporal resolution of 10 min and a lower number of cases when the residual layer is misinterpreted as mixing layer. We have calculated correlations between MLH as derived from the different retrievals and concentrations of pollutants (PM10, O3 and NOx) for different locations in the metropolitan area of Berlin. It was found that the correlations with PM10 are quite different for different sites without showing a clear pattern, whereas the correlation with NOx seems to depend on the vicinity of emission sources in main roads. In the case of ozone as a secondary pollutant, a clear correlation was found. We conclude that the effects of the heterogeneity of the emission sources, chemical processing and mixing during transport exceed the differences due to different MLH retrievals. Moreover, it seems to be unrealistic to find correlations between MLH and near-surface pollutant concentrations representative for a city like Berlin (flat terrain), in particular when traffic emissions are dominant. Nevertheless it is worthwhile to use advanced MLH retrievals for ceilometer data, for example as input to dispersion models and for the validation of chemical transport models.

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