New version page

UNC-Chapel Hill GEOG 111 - Air Pressure

Documents in this Course
Load more

This preview shows page 1 out of 2 pages.

View Full Document
View Full Document

End of preview. Want to read all 2 pages?

Upload your study docs or become a GradeBuddy member to access this document.

View Full Document
Unformatted text preview:

GEOG 111 1st Edition Lecture 15 Outline of Last Lecture I. Temperature (cont’d)a. Apparent temperatureb. Vertical temperature patternsc. Horizontal temperature patternsOutline of Current Lecture I. Air PressureII. Winda. Wind systemsCurrent LectureI. Air Pressure- the pressure exerted by winda. P=FORCE/AREAb. Gases moving about randomly create collisions when they run into a surface. The collective force of all of those collisions is the air’s force or atmospheric pressurec. By adding more air to a concealed room, the collisions and the pressure increasesd. Basically air pressure is proportional to density of the aire. Barometer- instrument used to measure air pressurei. Ex. Hurricanes are low pressure systems so as it comes closer there is less air and the mercury in a barometer goes downii. A bar (b) is a unit of pressuref. Pressure changes with altitudei. Decreases most rapid at low elevations and gradually tapers off (to 0 bar) a greater altitudesg. Air pressure is identified on a map by plotting isobarsi. Isobar- a line connecting points with equal atmospheric pressure at a given timeii. Pressures are standardized to sea level1. Therefore, they can see real patterns and identify where weather systems are locatediii. Moving perpendicular with isobars indicates changing pressureiv. Winds blow parallel to isobar lines1. Pressure determines winds which determine weatherh. Vertical air pressure patternsi. Distribution of air molecules in the atmospheric columnii. Atmosphere is extremely compressible and expandable1. Warming causes the column to expanda. Molecules on the bottom of the column that are heated will convect upward to a higher placeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Pressure drops at the bottom of the column and pressure increases at the top2. Conversely, cooling causes the column to compress3. Halfway up is the 500 mb levela. A warm column will have a higher 500 mb level while a cool column will have a lower 500 mb levelb. Isobars tell how high you have to go upc. Trough in the Eastern U.S. is coolest because the 500 mb levels are lower than the ridges in the Western U.S.d. Trough- elongated region of relatively low atmospheric pressuree. Ridge- elongated region of relatively high atmospheric pressure (the opposite of a trough)iii. Examples of the negative relationship between surface temperature and pressure1. Thermal low- atmospheric pressure is lowest because temperature is highesta. Why is it so hot in the southwestern U.S.? Absence of clouds andvegetation in the desert; incoming shortwave radiation is extremely high; virtually no evapotranspiration so all radiation goes into the sensible heat flux.2. Arctic high- cold area of high pressure3. Temperature isn’t the only factor of pressurea. The Bermuda High- area of high pressure in a warm oceanII. Wind- generated by pressure differencesa. Common wind systemsi. Monsoon (in India)- seasonal reversal of winds1. Winds blow in opposite direction at the changing of the seasons2. Land warms much quicker than water so we have higher pressures over water and lower pressure over land in the summera. Air wants to move from higher to lower pressure3. Summer: hot land  low pressure  onshore flow of air starting at the end of May moisture/lift/raina. Warmest month is May because a lot of energy is going into the sensible heat flux; very dry4. Winter: cooler land  higher pressure  offshore flow of air  dry air from inland


View Full Document
Loading Unlocking...
Login

Join to view Air Pressure and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Air Pressure and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?