From   Charles’  law   we   learned   that   when   the temperature  increases,  the  volume  increases  and  the density decreases. Therefore, the thickness of a layer of air is greater when the temperature increases. To find the height of a pressure surface in the atmosphere (such as in working up an adiabatic chart), these two variables (temperature    and    density)    must    be    taken    into consideration.    By    working    upward    through    the atmosphere, the height of that pressure surface can be computed by adding thicknesses together. A good tool for  determining  height  and  thickness  of  layers  is  the Skew-T Log P diagram, located in AWS/TR-79/006. Since  there  are  occasions  when  Skew-Ts  are  not available,   a   simplified   version   of   the   hypsometric formula is presented here. This formula for computing the  thickness  of  a  layer  is  accurate  within  2  percent; therefore,  it  is  suitable  for  all  calculations  that  the Aerographer’s Mate would make on a daily basis. The thickness of a layer can be determined by the following formula: Z = (49,080 + 107t) ·^Po P Po P - + Z = altitude difference in feet (unknown thickness of layer) 49,080 = A constant (representing gravitation and height of the D-mb level above the surface) 107 = A constant (representing density and mean virtual temperature) t = mean temperature in degrees Fahrenheit Po = pressure at the bottom point of the layer P = pressure at the top point of the layer For  example,  let  us  assume  that  a  layer  of  air between 800 and 700 millibars has a mean temperature of 30°F. Applying the formula, we have Z = (49,080 + 107 × 30) ·⁸⁰⁰ 700 800 700 - + Z = (49,080 + 3,210) ·¹⁰⁰ 1 500 , Z = (52,290) ·¹ 15 Z = 3,486 feet (1,063 meters) (1 meter = 3.28 feet) REVIEW QUESTIONS Q2-7.    What three things does the behavior of gases depend on? Q2-8. According to Boyle's Law, how is volume and pressure related? Q2-9. According to Charles' Law, how is temperature and pressure related? Q2-10. What  is  the  formula  for  the  Universal  Gas Law? ATMOSPHERIC ENERGY LEARNING   OBJECTIVE:    Describe    the adiabatic  process  and  determine  how  stability and instability affect the atmosphere. There  are  two  basic  kinds  of  atmospheric  energy important   to   AGs—kinetic   and   potential.   Kinetic energy  is  energy  that  performs  work  due  to  present motion  while  potential  energy  is  energy  that  is  stored for  later  action.  Kinetic  energy  is  discussed  first  in relation to its effect on the behavior of gases. According   to   the   kinetic   theory   of   gases,   the temperature of a gas is dependent upon the rate at which the molecules are moving about and is proportional to the kinetic energy of the moving molecules. The kinetic energy of the moving molecules of a gas is the internal energy   of   the   gas;   it   follows   that   an   increase   in temperature   is   accompanied   by   an   increase   in   the internal energy of the gas. Likewise, an increase in the internal energy results in an increase in the temperature of the gas. This relationship, between heat and energy, is called thermodynamics. An  increase  in  the  temperature  of  a  gas  or  in  its internal energy can be produced by the addition of heat or  by  performing  work  on  the  gas.  A  combination  of these  can  also  produce  an  increase  in  temperature  or internal energy. This is in accordance with the first law of thermodynamics. FIRST LAW OF THERMODYNAMICS This law states that the quantity of energy supplied to any system in the form of heat is equal to work done by the system plus the change in internal energy of the system.    In    the    application    of    the    first    law    of thermodynamics  to  a  gas,  it  may  be  said  that  the  two main  forms  of  energy  are  internal  energy  and  work energy. Internal energy is manifested as sensible heat or simply   temperature.   Work   energy   is   manifested   as pressure  changes  in  the  gas.  In  other  words,  work  is 2-11