Optional Assignment #1 Answers


If you doubled N and T, P would increase by a factor of 4.  But then when you double V, the pressure is divided in half.  So the net result of doubling N, T, and V is to increase the pressure by a factor of 2.

The important thing to remember is that a mercury barometer is a balance.  The balance part of the barometer is colored red above.  On the left a tall column of air (light brown) is balanced by a much shorter column of mercury (green).  No air is able to get into the top of the right tube of the barometer.  So there is not any pressure pushing on the top of the mercury column.

It is not necessary, but if you were to decode all of the plotted pressure data you would see that the pressure values get  smaller as you move into the center of the pattern.  This is a center of low pressure.  Surface winds spin counterclockwise and spiral inward into centers of low pressure in the northern hemisphere.


Cold fronts are normally drawn blue, warm fronts are red.  An occluded front is usually colored purple.  A stationary front has alternating blue and red segments and the triangles and half circles point in opposite directions.

Pressure changes at a rate of 1 mb per 10 meters of altitude change.

In A:  Multiply 500 m by the 1 mb/10 m rate of change.  You get a total change of 50 mb.  Thus the station pressure is 1003.7 mb - 50 mb = 953.7 mb.  You must subtract the correction because pressure decreases with increasing altitude.

In B: Multiply 750 m by 1 mb/10 m and you get 75 mb.  You must add this correction to the measured station pressure.  935.1 mb + 75 mb = 1010.1 mb.

In C: First subtract 915.9 mb from 1005.9 mb. You get a total change of 90 mb.  Next you diivide this by the 1 mb/10 m rate of change of pressure.  You get 900 meters.


The altitude and the relative humidity are not given.  If the dew point and the air temperature were the same you could say the relative humidity was 100%.

The effects of upper level and surface divergence and convergence are shown below



Convergence (either at the surface or aloft) will add air to the cylinder.  The cylinder will weigh more and since sea level pressure is determined by the weight of the air overhead, the surface pressure will increase.
Surface or upper level divergence will cause the surface pressure to decrease.