METR 104 Background for Lab #7. Remember isotherms (contours of temperature)? They are lines on a temperature map that connect places with the same temperature. In Lab #6, if your contour analysis was correct, you could have colored in areas between contours in your map.
Pressure is the collective force exerted by a parcel's molecules in random motion, colliding with the parcel's surroundings (or vice-versa)
• Inches of mercury (“in Hg”) (U.S. only)
• What is the global, long-term average pressure at sea level?
1013.25 mb(29.92 in Hg)
• How much does pressure change over distance?
Vertical pressure gradient: Very large!
= (1020 mb – 200 mb)/11 km
=74 mb per km vertically
Horizontal pressure gradient: Much smaller!
(1030 mb – 990 mb)/1000 km = 40 mb/1000 km
= 0.04 mb/km