Notes for Meteorology 356

September 15, 2004

Frank Sanchez

Hilary Price

Assignments:

reading: Williams through ch. 5, reader: 117-8, 257,261-2,,268, 273, 268,292,316, 335-47,518-529

Housekeeping:

Nothing new

Homework:

Homework 1 due; Friday 24 September o4

Reviewed

Atmosphere pressure, breakdown of comparison:

If 10 bricks were stacked creating 1000 lbs of pressure at the bottom of the bricks (sfc), because bricks don't compress then at 5 brick up (midpoint) the pressure would be 500 lbs.

Pressure:

Logic says that if you have (4 mi.) 600 km (the extent of the Earths atmosphere) and the surface is equal to 1000 millibars then 500 mb. would be at 300 km (half the distance from the surface of the Earth to the end of the atmosphere). HOWEVER, this is NOT the case because atmospheric pressure compresses air molecules in each "brick" of atmosphere. This causes the "bricks" at sea level (sfc) to be smaller than the "bricks" at the top of the atmosphere. Thus, the 500 mb (midpoint) is not at 300 km. rather it is at a mere 6 km. (18,000 ft.)

Sea level atmospheric pressure is roughly 1000 mb. (millibars) or 14 lbs/sq.in. This is very high pressure. The variation of atmospheric pressure at sea level is very small, roughly 960-1050 mb's

Coding of pressure symbols on a weather map is a 3 digit number. For example, 084 would be written as 1008.4 mb. First you take the 3 digit number and add the unit. 084mb. Second, you add a decimal point at the ten thousandths mark, 08.4mb. Third, you add a 10 or a 9 at the beginning of the 3 digits. This will depend on the understanding of the variation of sea level pressure between 960-1050 mb. So 08.4 mb would be witten finally as 1008.4 mb. because 908.4 would be to low. (960.0mb)

We Then looked at satellite images and our hand out to reinforce this concept of atmospheric pressure.

An Isobar is a line of equal pressure. Iso bar= equal pressure.

We then looked a images of Hurricane Ivan.

We talked about the Rings in the projected forecast of the movement of "Ivan"

Outer ring= wind speeds over ocean w in. over 20 kts.

Second outer ring= wind speeds over ocean w in. over 50 kts.

Inner ring= wind speeds w in. 75 kts.