60 years of UK visibility measurements: impact of meteorology and atmospheric pollutants on visibility

Abstract

<p><strong>Abstract.</strong> Reduced visibility is an indicator of poor air quality. Moreover, degradation in visibility can be hazardous to human safety; for example, low visibility can lead to road, rail, sea and air accidents. In this paper, we explore the combined influence of atmospheric aerosol particle and gas characteristics, and meteorology, on long-term visibility. We use visibility data from eight meteorological stations, situated in the UK, which have been running since the 1950s. The site locations include urban, rural and marine environments. <br><br> Most stations show a long term trend of increasing visibility which is indicative of reductions in air pollution, especially in urban areas. Additionally, the visibility at all sites show a very clear dependence on relative humidity indicating the importance of aerosol hygroscopicity on the ability of aerosol particles to scatter radiation. The dependence of visibility on other meteorological parameters, such as wind speed and wind direction is also investigated. Most stations show long term increases in temperature which can be ascribed to either climate change, land-use changes (e.g. urban heat island effects) or a combination of both; the observed effect is greatest in urban areas. The impact of this temperature change upon local relative humidity is discussed. <br><br> To explain the long term visibility trends and their dependence on meteorological conditions, the measured data were fitted to a newly developed light extinction model to generate predictions of historic aerosol and gas scattering and absorbing properties. In general, an excellent fit was achieved between measured and modelled visibility for all 8 sites. The model incorporates parameterizations of aerosol hygroscopicity, particle concentration, particle scattering, and particle and gas absorption. This new model should be applicable and is easily transferrable to other data sets worldwide. Hence, historical visibility data can be used to assess trends in aerosol particle properties. This approach may help constrain global model simulations which attempt to generate aerosol fields for time periods when observational data are scarce or non-existent. Both the measured visibility and the modelled aerosol properties reported in this paper highlight the success of the UK’s Clean Air Act, which was passed in 1956, in cleaning the atmosphere of visibility reducing pollutants.</p>

Kinetics, mechanisms and ionic liquids in the uptake of n-butylamine onto low molecular weight dicarboxylic acids

“…[8][9][10] At and above B100 nm, particles scatter light efficiently, reducing visibility, 11,12 and they can also act as cloud condensation nuclei, [13][14][15][16] affecting climate and air quality. [17][18][19][20][21] Inhalation and deposition of particles into the human respiratory system [22][23][24][25][26] can cause deleterious health effects 17,[25][26][27][28][29][30][31][32][33][34] including increased mortality.…”

The Effects of PM2.5 Concentrations and Relative Humidity on Atmospheric Visibility in Beijing

“…The atmospheric total optical extinction coefficient is defined as the sum of the extinction due to the gas phase and the particle phase (Cheng, Zhang, et al, ; Malm, ; Singh et al, ). The impacts of gas‐phase molecules on visibility include Rayleigh scattering of air molecules and the absorption of solar radiation by NO 2 (X. Deng et al, ; Pitchford et al, ; Pui et al, ; Sati & Mohan, ).…”

“…Visibility is the maximum distance at which an observer can discern the outline of an object against the horizon sky (Singh et al, ; K. Wang et al, ). Historically, routine meteorological measurements of visibility were observed manually four times per day.…”

“…Considerable attention has been paid to these particles, given their negative effects on human health, society, and public welfare (Han & Tong, ; Inoue & Takano, ; Kan et al, ; Silva et al, ); moreover, these particles play a critical role in driving climate change because they scatter and absorb solar radiation (Ding et al, ; C. Fu et al, ; Jacobson, ; L. Lin et al, ; J. Li et al, ; Xia, ). Aerosol particles are efficient in absorbing and scattering solar radiation, and changing the intensity and direction of sunlight and resulting in a reduction in the atmospheric horizontal visibility (Barber, ; Husar & Jd, ; Pan et al, ; Singh et al, ). Therefore, atmospheric visibility provides the public with an intuitive grasp of air quality (Jacob, ).…”

Patterns, pace, and processes of water‐quality variability in a long‐studied estuary

“…Changes detected in long-term observations have motivated many other kinds of policies and documented some impressive successes, such as reduced atmospheric nitrogen deposition in estuarine watersheds (Eshleman and Sabo 2016); recovery of fish and whale populations decimated by fishing (Richards and Rago 1999;Lyons 2016), brown pelicans extirpated by pesticides (Holm et al 2003), and forest ecosystems damaged by acid precipitation (Likens et al 1996); improved air quality in the UK after passage of its 1956 Clean Air Act (Singh et al 2017); and returns of oxygen and fish communities to rivers after upgrading sewage treatment processes (Andrews and Rickard 1980). Every multidecadal observational record is valuable because of its rich information content.…”