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Air Pollution Meteorology and Air Pollutant Concentration Models
Published in Jeff Kuo, Air Pollution Control Engineering for Environmental Engineers, 2018
Keeping other variables constant, the temperature of air decreases as atmospheric pressure decreases. Lapse rate is the rate of change in temperature with altitude. Under adiabatic conditions (i.e., no heat exchange with the surrounding air), a rising warm air parcel would behave like a rising balloon [Note: an air parcel is a body of air, having a constant number of molecules, and it acts as a whole]. Due to the lower ambient pressure, the air within the parcel will expand until its own density is equal to the density of the surrounding air. The rate of adiabatic cooling of this air parcel, due to its expansion, is 10 °C/km (9.81 °C/km to be exact). In this context, the air is considered dry, as long as water in the air parcel remains in a gaseous state. It is a fixed rate, independent of ambient air temperature and the starting position of the air parcel rising or descending. The dry adiabatic lapse rate is central to the definition of atmospheric stability.
Applications of Chemical Kinetics in Environmental Systems
Published in Kalliat T. Valsaraj, Elizabeth M. Melvin, Principles of Environmental Thermodynamics and Kinetics, 2018
Kalliat T. Valsaraj, Elizabeth M. Melvin
We saw in Chapter 2 that temperature gradient in the atmosphere determines whether the atmosphere is stable or unstable. The variation in temperature with height determines the extent of buoyancy-driven mixing within the atmosphere. To do so, we consider the ideal case where a parcel of dry air is allowed to rise adiabatically through the atmosphere. The air parcel experiences a decrease in temperature as it expands in response to decreasing temperature with increasing elevation. This is called the “adiabatic lapse rate,” Γadia (= dT/dz), and is a standard value of 1°C/100 m for dry air, as we saw in Chapter 2. For a saturated air, this value is slightly smaller (0.6°C/100 m). If the prevailing atmosphere has an “environmental lapse rate,” Γenv > Γadia, the atmosphere is considered unstable and rapid mixing occurs thereby diluting the air pollutant. If Γenv < Γadia, the atmosphere is stable and little or no mixing occurs.
Air Pollution and Its Control
Published in Danny D. Reible, Fundamentals of Environmental Engineering, 2017
We now see that in the atmosphere, the temperature changes associated with a rising air parcel mean that the neutrally stable atmospheric condition in which turbulence is neither enhanced nor damped is one in which the background temperature gradient decreases at the same rate as air rising from the surface, that is 9.8°C/km. When the background temperature decreases more slowly or even increases with height the atmosphere is stable since the rising air parcel would cool more rapidly and then become more dense than its surroundings as it rises. Air in which the background temperature decreases more rapidly with height is unstable since the rising air parcel would cool less rapidly than the surroundings and be less dense than its surroundings as it rises.
Vertical handover in heterogeneous networks using WDWWO algorithm with NN
Published in International Journal of Electronics, 2021
M Naresh, D Venkat Reddy, K Ramalinga Reddy
The metaheuristic algorithm optimises the deep residual network weight value to achieve better handover decision in heterogeneous networks. This optimisation technique reduces the training error of the neural network. The Wind Driven Optimisation (WDO) algorithm easily falls into the local best value but accuracy is less. So the Water Wave Optimisation (WWO) propagation is added to the velocity of WDO to enhance the overall performance and accuracy (Zhang et al., 2019). The WDO consider some parameters based on Newton’s law such as trajectory of air parcel, air parcel pressure, and including forces as gravitational, pressure gradient, coriolis, and friction force. The applied force direction is same as the direction of air parcel as given in equation (16),