Browsing by Author "Podstawczyńska, A"

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    Characterising diurnal & synoptic timescale changes in urban air quality using Radon-222
    (Europenan Geosciences Union, 2020-05-01) Chambers, SD; Kikaj, D; Podstawczyńska, A; Williams, AG; Crawford, J; Griffiths, AD
    Urban air quality is strongly influenced by the atmosphere’s ability to disperse primary emissions and opportunities for secondary pollution formation. In mid- to high-latitude regions that experience enduring winter snow cover or soil freezing, regional subsidence and stagnation associated with persistent anti-cyclonic conditions such as the “Siberian High” can lead to “cold pool” or “persistent inversion” events. These events can result in life-threatening pollution episodes that last for weeks. While often associated with complex topography [1,2], persistent inversion events can also influence the air quality of urban centres in flat, inland regions [3]. This presentation will describe a recently-developed radon-based technique for identifying and characterising synoptic-timescale persistent inversion events, which is proving to be a simple and economical alternative to contemporary meteorological approaches that require regular sonde profiles [1]. Furthermore, key assumptions of the radon-based technique to characterise diurnaltimescale changes in the atmospheric mixing state described by Chambers et al. [4] are violated during persistent inversion conditions. Here we demonstrate how atmospheric class-typing, through successive application of radon-based techniques for identifying synoptic- and diurnaltimescale changes in the atmospheric mixing state, improves understanding of atmospheric controls on urban air quality in non-summer months across the full diurnal cycle. This knowledge translates directly to statistically-robust techniques for assessing public exposure to pollution, and for evaluating the efficacy of pollution mitigation measures. Lastly, we show how atmospheric class-typing can be used to enhance the evaluation of chemical transport models. © Author(s) 2020
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    Characterizing the State of the Urban Surface Layer Using Radon‐222
    (American Geophysical Union (AGU), 2019-01-27) Chambers, SD; Podstawczyńska, A; Pawlak, W; Fortuniak, K; Williams, AG; Griffiths, AD
    Four years of summertime paired urban‐rural meteorological and radon observations in central Poland are used to assess the relationship between atmospheric stability and urban‐induced changes to the radiation balance and surface energy budget. An existing radon‐based technique for nocturnal stability classification is improved and extended to also infer daytime mixing conditions. The radon‐based scheme is shown to provide a simple, effective, objective means of investigating urban energy budget closure over a range of meteorological conditions, which promises to improve estimates of energy storage and loss terms associated with urban canopies. Special attention is paid to quantifying atmospheric characteristics associated with the arbitrarily assigned radon‐derived stability categories in terms of the more conventional measures: bulk Richardson number and the Monin‐Obukhov stability parameter (z/L). The bulk Richardson number approach is demonstrated to be less effective at grouping periods of similar mean stability, and less selective of extremely stable conditions, than the radon‐based technique. A simple box model is used in conjunction with radon observations and an assumed source function of 15 mBq·m−2·s−1, to show that nocturnal effective mixing heights were deeper and less variable over the urban region. On stable nights hourly median effective mixing heights were 15–20 m over the rural region compared to 40–45 m over the urban region. ©2018. American Geophysical Union. All Rights Reserved.