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Precipitation
Published in Amithirigala Widhanelage Jayawardena, Fluid Mechanics, Hydraulics, Hydrology and Water Resources for Civil Engineers, 2021
Amithirigala Widhanelage Jayawardena
When unsaturated air is carried to higher altitudes, expansion will occur due to the reduction of pressure. This expansion is adiabatic except near the earth’s surface, i.e., no heat is added or taken away from the air from outside sources. However, its temperature is lowered because of the heat energy that is transformed into work in the process of expansion. The rate at which the temperature decreases with altitude is called the lapse rate. There are three lapse rates in meteorology.
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.
Air pollution modelling
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
As the saturated vapour pressure of water depends on both the temperature and pressure, the SALR is also variable (Table 8.1). The minimum values are found for surface pressures and the warmest temperatures. As the air also has to be saturated, this is more likely to be in the tropics than above the Sahara. Maximum values are found where the air is very cold, because then the water vapour content is low. The average lapse rate over the Earth is about 6.5°C km−1.
Degree-day building energy reference map for South Africa
Published in Building Research & Information, 2018
Dirk Conradie, Tobias van Reenen, Sheldon Bole
In order to prevent the melding of climatic zones, the 0.5-degree data received from the NRE were resampled by the authors to a 0.05 horizontal-degree grid through a lapse-rate adjustment. Lapse rate is defined as the rate at which atmospheric temperature decreases with an increase in altitude. The terminology arises from the word ‘lapse’ in the sense of a decrease or decline. Figure 4 illustrates the lapse-rate adjustment process.