At the very bottom of the 5 A.M. sounding (below 850 mb) the temperature actually increases with altitude.  This is NOT the stratosphere.  We must go through the troposphere before we get to the stratosphere.  This often referred to as the boundary layer.  Here the temperature is most influenced by the transfer of heat via conduction and convection of energy from the surface.  Above this region (about 850 mb), the transfer of heat is influenced more by IR radiation from both the surface and the atmosphere itself.  So, even though the temperature actually increases with altitude right next to the surface, this is still in the troposphere.

• Rule of thumb for change with altitude is 10 mb per 100 meters.
• More accurate rule of thumb would be Pressure = 1013mb x exp(-Altitude/8.5), where Altitude is the altitude above sea level

• Units are lbs/square in., inches of mercury or millibars (We'll use millibars = mb)
• station pressure - Actual measured pressure.
• sea level pressure - The atmospheric pressure at mean sea level, either directly measured or most commonly mathematically converted from the measured station pressure.  This allows one to compare pressures at different locations even though they are at different elevations.
• altimeter pressure - The value of atmospheric pressure to which the scale of a pressure altimeter is set.  In the U.S. the setting represents the pressure required to make the altimeter indicate the elevation of the airfield.

•  http://www.usatoday.com/weather/wbarocx.htm
•  Pressure calculator to convert between station pressure, sea level pressure and altimeter pressure
•  Pressure graph for Tucson
•  Current sea level pressure map with isobars (lines of equal pressure) and the IR satellite image.