A temperature inversion-induced air pollution process as analyzed from Mie LiDAR data

Die Feinstaubbelastung Radfahrender im innerstädtischen Straßenverkehr

Fahrradfahren als Form der aktiven Fortbewegung bietet viele gesundheitliche Vorteile durch eine gesteigerte körperliche Aktivität. In städtischer Umgebung können diese Vorteile aufgrund der intensivierten Respiration beim Radfahren und der Nähe zum Fahrzeugverkehr mit einer assoziierten Exposition von verkehrsbedingter partikulärer Luftverschmutzung durch Feinstaub beeinträchtigt werden. Das Ziel dieser Übersichtsarbeit ist, eine Darstellung der aktuellen Literatur mit mobil erhobenen Daten zur Feinstaubbelastung Radfahrender im urbanen Raum zu geben sowie die darin beschriebenen Einflussfaktoren der Feinstaubkonzentrationen aus Meteorologie, Verkehr, Architektur und zeitlichen Bedingungen zu beschreiben. Fahrradfahren repräsentiert diesbezüglich eine effiziente Vorgehensweise zur Charakterisierung individueller Feinstaubbelastungen mit der Möglichkeit einer hohen räumlich-zeitlichen Auflösung. Unter Beachtung der Hintergrundkonzentration können Aussagen zur relativen Schadstoffexposition und des einhergehenden Gesundheitsrisikos mit Erkenntnissen zugunsten einer umweltverträglichen innerstädtischen Verkehrsplanung getroffen werden.

Spatio-temporally differentiated impacts of temperature inversion on surface PM2.5 in eastern China

Temperature inversion (TI) is one of the meteorological conditions that significantly affect regional air quality. Knowledge gap regarding the impacts of TI on surface PM_2.5 in different topographies still existed. In the present study, the occurrence frequency, temperature lapse rate (TLR), depth, and the diurnal variations of TI, surface-based TI (SBTI), elevated TI (ElTI), and multiple layers of TIs (MultiTI) and their impacts on near-surface PM_2.5 concentrations over eastern China that covers a range of topographies and climates, are systematically investigated based on global reanalysis ERA5 and the nationwide monitoring PM_2.5 dataset from 2014 to 2020. TIs occurred mostly in the early morning. Different types of TIs present distinctive seasonal and spatial patterns. The majority of SBTIs and ElTIs occurred during nighttime in northern China and daytime in southern China, respectively, as the result of their formation mechanisms. SBTIs usually had larger TLR while ElTIs had deeper depth. SBTIs showed strong enhancement effects on PM_2.5 concentration over the study domain while ElTIs showed more obvious impacts on northern nocturnal PM_2.5. The peak time of PM_2.5 was found around 18:00-22:00 LST, and TLR and depth of TIs are thought to be more relevant to PM_2.5 peak concentration due to their coincident peak times. The strength of TIs is therefore more crucial in regulating PM_2.5 than its occurrence frequency. Based on statistical analysis, our study provided a large picture of the generic spatiotemporal patterns of TIs and illustrated the impacts of different TIs on surface PM_2.5 pollution on a diurnal basis. For a deeper understanding of the formation of PM_2.5 pollution, more attention needs to be paid to the nocturnal PM_2.5 not only at surface level but also at higher levels in the presence of TIs.

Temperature inversions in the atmospheric boundary layer and lower troposphere over the Sichuan Basin, China: Climatology and impacts on air pollution

The Sichuan Basin (SB) is one of the four most severely polluted regions in China in terms of air quality, and the frequent generation of temperature inversions is a key factor. The deep mountain-basin topography and the geographical location adjacent to the Tibetan Plateau combine to make the inversion characteristics of this region unique. Knowledge regarding these characteristics remains limited, however. In this study, the radiosonde data at standard pressure levels and significant levels from all SB operational radiosonde stations over 2015-2018 were used to document the climatological features of the inversions from the surface to a height of 5500 m and to evaluate the impact on local air pollutant concentrations. Results revealed that the temperature inversion in the SB is a common and year-round phenomenon. The annual inversion frequency, depth, and strength values are 74.4%, 252.2 m, and 1.3 °C/100 m, respectively. The inversions are most frequent (95.4%), deepest (289.4 m), and strongest (1.6 °C/100 m) in winter. They tend to occur at one of two heights, either below 600 m or between 2200 and 3500 m. Based on their bottom heights, the inversions were divided into three groups: surface-based inversions (SIs), elevated inversions (EIs), and lower-troposphere inversions (LTIs). Annual LTI is most frequent (63.0%) and deepest (264.7 m), while annual SI is strongest (1.8 °C/100 m). Extreme contrasts exist in the seasonal properties of different inversion types. All types of inversions play a considerable role in air pollution, resulting in a high probability of severe and very serious pollution in winter. SI has a greater impact on pollutant concentrations than EI and LTI. The frequent generation of LTIs is a unique feature of the deep SB. LITs exert a significant impact on the formation of local heavy air pollution, but have not been given sufficient attention.