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Rate Processes
Published in Danny D. Reible, Fundamentals of Environmental Engineering, 2017
Often neutral, stable, or unstable stratification does not apply to a body of water or to the atmosphere but only to a small region within the fluid. In the atmosphere, the near surface layer of the atmosphere is often unstable and relatively well mixed while above 1 to 2000 m, the atmosphere might exhibit a temperature that increases (density decreases) with height. This layer is stably stratified and very poorly mixed. Temperature normally decreases with height in the atmosphere, and an increase with height is termed a temperature inversion. In a lake, the near-surface environment might be relatively well mixed due to friction at the air-water interface and the resulting wind-driven currents. Because the surface tends to be warmer than the deeper waters below, there is often a poorly mixed region that represents the transition from the warmer water above to the cooler water below. This is termed a thermocline and like a temperature inversion in the atmosphere, it is a layer that is stable and significantly limits vertical transport of heat, mass, or momentum.
Environmental exposure
Published in Frank Collins, Frédéric Blin, Ageing of Infrastructure, 2018
Background levels of acidic gases (CO2, SO2 and NO2) in the air become more concentrated within industrial and city/urban locations due to higher amounts of emissions arising from burning of fossil fuels. At particular locations, the cooler air pollutants become trapped at ground level by an overlying layer of warm air, commonly termed a ‘winter temperature inversion’. The effects of the inversion are made worse where the terrain and urban topography restricts the dispersion of the gases by prevailing winds.
Temperature inversions in China derived from sounding data from 1976 to 2015
Published in Tellus B: Chemical and Physical Meteorology, 2021
Tingting Xu, Bing Liu, Minsi Zhang, Yu Song, Ling Kang, Tiantian Wang, Mingxu Liu, Xuhui Cai, Hongsheng Zhang, Tong Zhu
Temperature inversion, which is defined meteorologically as a layer of air where the temperature increases with altitude (Bilello, 1968), plays an essential role in determining atmospheric stability and has a considerable influence on meteorological and environmental issues (Anfossi et al., 1976). The temperature inversion layer generally acts as a ‘lid’ that constrains vertical airflow through the layer (Hudson and Brandt, 2005; Gramsch et al., 2014) and strongly depresses the transfer of momentum, heat, and moisture in the air (Serreze et al., 1992; Kahl et al., 1996), resulting in high humidity and weak winds. The presence of temperature inversions is not favourable for the development of deep local circulations, because the vertical extension of local circulations is hindered by strong stratification (Ganbat and Baik, 2016). Pollutants that are emitted into an inversion layer are difficult to dilute by vertical mixing (Abdul-Wahab, 2003; Abdul-Wahab et al., 2004). The stagnant conditions resulting from temperature inversion also favour chemical reactions in liquid and heterogeneous phases that benefit the formation of new secondary aerosols (Silva et al., 2007). Serious atmospheric pollution events have been attributed to continuous long-lived temperature inversion layers (Gao et al., 2015, 2016; Yang et al., 2015; Zhang et al., 2015; Zhong et al., 2018).
Cable Surface for the Reduction of Risk Associated with Bridge Cable Ice Accretions
Published in Structural Engineering International, 2019
Lubomir Matejicka, Christos Thomas Georgakis, Andreas Schwarz, Philipp Egger
Based on the collected data and photographic evidence of various icing events on bridges, the prevailing source of ice accretion on bridge cables is precipitation icing.3 Precipitation icing forms either from supercooled water droplets as freezing rain or from snow and sleet accumulating as wet snow. This type of accretion is characterised by “wet” growth and results in the formation of glaze ice, characteristic for its high density, transparent appearance and strong adhesion. This phenomenon occurs in specific meteorological conditions when a warm front colliding with cold air below 0°C is pushed over the cold-air layer (temperature inversion).4 Falling snow crystals from higher altitudes are then melted into raindrops at the warm upper inversion layer. Next, they fall into the freezing layer near the ground, where they become supercooled and subsequently freeze after hitting an object or the ground. Another type of precipitation icing leading to bridge closures is dry and wet snow accretion caused by adhesion of snowflakes to the cables.