Pressure, altitude variation

FIGURE 2 Seasonal variations of ozone as function of pressure (altitude) for 170°W, in volume mixing ratio (ppb). Contours are given every 10 to 150 ppb, and every 25 to 500 ppb. This climatology is mainly based on ozone sonde measurements of the years 1980 to 1993. (From Logan, J. A. (1999). J. Geophys. Res. 104,16, 115-149.)... 

Answer by author The system maintains constant operating pressure over the range of altitude variation. An absolute pressure regulator to perform this specific function is included as an integral component of the system. 

According to Henry s law, gases become more soluble as pressure increases. This solubility property has minimum effects on everyday life, because changes in altitude or weather cause only modest variations in atmospheric pressure. Scuba divers, however, must pay careful attention to the solubility equilibria of gases. 

It may not be well known that the weather bureau reports of barometric pressure are corrected to sea level even though describing conditions in the mountains, etc. Table IV gives the barometric pressure at various altitudes these should be used when applicable in equations 5 and 6. Representative cities and the variations in their respective altitudes are given in Table V. 

The variation of atmospheric pressure with altitude, z, above the surface can be estimated by calculating the weight of a column of air of density, p, given by ... 

Variations of temperature and pressure with altitude and the consequences for chemistry... 

At sea level, Pj is approximately 1 atm, but exhibits some temporal and spatial variability. For example, the annual mean pressure in the northern hemisphere is 0.969 atm and in the southern hemisphere is 0.974 atm, with monthly averages varying by as much as 0.0001 atm, i.e., about 1 mbar (1 atm = 1013.25 mbar). These fluctuations are caused by spatial and temporal variations in atmospheric temperature and water vapor content associated with weather, and seasonal and longer-term climate shifts. Pj is also affected by diurnal atmospheric tides, and it decreases with increasing altitude above sea level. Some gases, such CO2 and O2, exhibit seasonal variability that is caused in part by seasonal variability in plant and animal activity (see Figures 25.4 and 6.7). 

FIGURE 1.1 Typical variation of temperature with altitude at mid-latitudes as a basis for the divisions of the atmosphere into various regions. Also shown is the variation of total pressure (in Torr) with altitude (top scale, base 10 logarithms) where 1 standard atmosphere = 760 Torr. 

This relationship for the variation of pressure with altitude can be converted into that between temperature and altitude as shown in Eq. (N) below for a parcel of dry air that rises without heat exchange occurring between it and the surrounding air this is known as an adiabatic process. 

Concentrations of contaminants in the atmosphere may vary significantly from time to time due to seasonal climatic variation, atmospheric turbulence, and velocity and direction of wind. The most important meteorological factors are (1) wind conditions and the gustiness of wind, (2) the humidity and precipitation, (3) the temperature, which varies with latitude and altitude, (4) barometric pressure (varying with the height above the ground), and (5) solar radiation and the hours of sunshine, which vary with the season. 

At an altitude of 30,000 m the atmospheric pressure is approximately 1200 Pa and the temperature is approximately -4S°C. Assuming a turbulent boundary layer flow over an adiabatic flat plate, plot the variation of the adiabatic wall temperature with Mach number for Mach numbers between 0 and 5. 

Formula (4.1) is often called the barometer formula, since it gives the variation of barometric pressure with altitude. It indicates a gradual decrease of pressure with altitude, going exponentially to zero at infinite height. 

Fig. 13.2 Atmospheric pressure variations as a function of altitude. (From the U.S. Standard Atmosphere, 1962.) Correction factors on the right axis serve to convert values at sea level (Fig. 13.1) to solubility values at desired altitude (dividing by the factor) or to normalize data at a given altitude to the corresponding value at 0 masl (multiplying by the factor). The last conversion is needed to read intake (recharge) temperatures from Fig. 13.1, which is for sea level (i.e., 760mmHg) (Mazor, 1975).

The pressure of the air, as already mentioned, varies with altitude indeed, at one and the same place it does not remain constant in consequence of variation m composition, the influence of wind, etc. A standard pressure, known as an atmosphere, has been chosen. The British unit is a column of mercury 29-905 inches in height, measured at 82° F. m London, and is equivalent to a pressure of 14-78 lb. per square inch. 

Recent measurements of the melt-water from high-altitude snow in Greenland and the Himalayas have given pH values of 5.15 instead of the expected value. Some of this difference can be explained by the variation of the equilibrium constants as a function of temperature, (a) Please calculate the pH of water at 0°C in equilibrium with C02 at its current partial pressure, (b) What would the partial pressure (in ppm) of C02 have to be in order to get precipitation of pH = 5.15 at this temperature (c) What do you conclude Note that at 0°C p/s(H = l.ll, pKai = 6.57, and pK = 10.62. 

The variation of temperature and pressure with altitude. Note that the pressure steadily decreases with increasing altitude but that the temperature does not change monotonically. 

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