AWH 5-11

Chapter 5, Heat and Temperature 5-11 Figure 5-7. Variation of Mean Daily Temperatures for San Francisco (Maritime) and St. Louis (Continental) 5.8 Temperature Variations with Altitude A lapse rate of temperature is defined as a decrease in temperature with height. In Figure 4-2, it was stated that the temperature decreases 6.5 °C/km (3.57 °F/1,000 ft) in the standard atmosphere. But since this is an average, the exact value seldom exists. In fact, temperature in the troposphere sometimes remains constant or even increases with height. Caution should be taken when using the standard lapse rate to estimate the freezing level. Quite often the boundary layer is dry adiabatic, and the estimate of freezing level could be in error. 5.8.1 Atmospheric Sounding An atmospheric sounding, or simply sounding, is a plot of the vertical profile of one or more atmospheric parameters, such as temperature, dewpoint, or wind above a fixed location. Soundings are used extensively by meteorologists to determine the state of the atmosphere. 5.8.2 Isothermal Layer An isothermal layer is a layer within the atmosphere where the temperature remains constant with height (see Figure 5-8).