Abstract
A Zeppelin airship was used as a platform for in-situ measurements of greenhouse gases and short-lived air pollutants within the planetary boundary layer in Germany. A novel quantum cascade laser-based multi-compound gas analyzer (MIRO Analytical AG) was deployed to simultaneously measure in-situ concentrations of greenhouse gases (CO2, N2O, H2O, and CH4) and air pollutants (CO, NO, NO2, O3, SO2, and NH3) with high precision at a measurement rate of 1 Hz. These measurements were complemented by electrochemical sensors for NO, NO2, Ox (NO2+O3), and CO, an optical particle counter, temperature, humidity, altitude, and position monitoring. Instruments were operated remotely without the need for on-site interactions. Three two-week campaigns were conducted in 2020 comprising commercial passenger as well as targeted flights over multiple German cities including Cologne, Mönchengladbach, Düsseldorf, Aachen, Frankfurt, but also over industrial areas and highways. Vertical profiles of trace gases were obtained during the airship landing and take-off. Diurnal variability of the Zeppelin vertical profiles was compared to measurements from ground-based monitoring stations with a focus on nitrogen oxides and ozone. We find that their variability can be explained by the increasing nocturnal boundary layer height from early morning towards midday, an increase in emissions during rush hour traffic, and the rapid photochemical activity midday. Higher altitude (250–450 m) NOX to CO ratios are further compared to the 2015 EDGAR emission inventory to find that pollutant concentrations are influenced by transportation and residential emissions as well as manufacturing industries and construction activity. Finally, we report NOx and CO concentrations from one plume transect originating from a coal power plant and compare it to the EURAD-IM model to find agreement within 15 %. However, due to the increased contribution of solar and wind energy and/or the impact of lockdown measures the power plant was operated at max. 50 % capacity; therefore, possible overestimation of emissions by the model cannot be excluded.
Highlights
Favorable meteorological conditions can trigger severe pollution episodes in which anthropogenic emissions of pollutant concentrations accumulate and drastically exceed the world health organization (WHO) guideline values
During the period from 08:00 to 10:00 UTC, an increase of NOX at all heights compared to 06:00 UTC was evident in Frankfurt, whereas in Bonn, NOX was similar to earlier hours with a slight increase of ground-level NOX to 9.2 (3.1–14.5) ppbv
From 10:00 to 190 18:00 UTC, the lower planetary boundary layer (PBL) was well mixed with NOX and O3 concentrations agreeing within their variability at all heights from 25 m up to 375 m
Summary
Favorable meteorological conditions can trigger severe pollution episodes in which anthropogenic emissions of pollutant concentrations accumulate and drastically exceed the world health organization (WHO) guideline values. Induced air pollution is consistently observed globally in Asia (He et al, 2017; Li et al, 2019; Cai et al, 2017; Zhao et al, 2019), America (Jury, 2020; Zhao et al, 2011; Lin and McElroy, 2010), and Europe (Dupont et al, 2016; Pernigotti et al, 2012) even during periods when certain anthropogenic emission sectors are diminished (Gkatzelis et al, 2021a). An essential first step towards this goal is to accurately determine the effect of local meteorological parameters such as surface relative humidity, wind speed, turbulence, and planetary boundary layer (PBL) depth development on pollutant concentrations. Various studies highlight the need for accurate PBL depth data as they pose the most uncertain parameter for efficient air quality forecasts (e.g. Dupont et al, 2016; Lin and McElroy, 2010; Silcox et al, 2012; Horel et al, 2016). Vertical mixing of air tracers within the PBL can influence their tropospheric distributions with a turbulent mixed layer leading to a more uniform vertical distribution and a stable boundary layer resulting in greater vertical gradients
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