Homework # 5 Solutions
1. (Yes or No) Are isolines and isopleths the
same thing?
Yes. Isopleth is just a fancy way to say isoline.
2. Does the following
station plot give you the dewpoint or the dewpoint depression?
The temperature for this upper-level plot is 46 degrees Celsius. Where the dewpoint would normally be in a surface plot, there is a 12. We know that the dewpoint temperature can never be greater than the actual temperature. Therefore we know that this plot is showing us the dew point depression.
3. What is this
station's dewpoint?
Now that we know we have the dewpoint depression, the dewpoint can be calculated as follows.
Dewpoint = Temperature Dewpoint Depression = - 46 12 = - 58 degrees Celsius.
4. If this station
plot is taken from a 250 mb chart, what is the geopotential height at that level (in meters)?
If this were taken from a 250 mb chart, we would have to take the height given (069) and decode it by multiplying the value by ten and then adding 10,000. This would give the geopotential height in meters.
Height (m) = 069 *10 = 690 + 10,000 = 10,690 m
Part 2--Use the 500mb
map provided to answer the following:
Omaha, Nebraska (OAX)
Temperature:
This is in the upper left part of the plot. 17 degrees Celsius
Dewpoint Depression:
This is the lower left part of the plot and is 21. (This is not the dewpoint!)
Dewpoint:
This is calculated by subtracting the Dewpoint Depression from the Temperature
- 17 21 = - 38 degrees Celsius
Wind Speed:
There is one triangle flag (50 knts), and 3 long flags (3*10 knts = 30 knts). Therefore, the total wind speed is found by adding.
50knts + 3 * (10knts) = 80 knots
Wind Speed (in miles per hour): (Remember that 1.15 mph = 1 knt)
80knts * 1.15 (mph/knt) = 92 miles per hour
Wind Direction in
Degrees:
Apparently, I was in an evil mood the day I made this. It is very difficult to judge degrees from a station plot. As long as you said something close to 270 degrees, I gave you credit.
Wind Direction
(Cardinal N,S,E,W):
This is far simpler. The wind is almost due West (W). However, I did accept a little variability with this as well.
Geopotential Height:
This is given by the 563 in the upper right part of the plot. This needs to be decoded though. 563 is not the correct answer. The map I gave you was at 500mb. Therefore, to decode the height, you must multiply what is given at the station by 10. Therefore:
563 * 10 = 5630 m
Geopotential Height (in feet): (There are 3.28 feet in
one meter)
This is just a straightforward plug-and-chug conversion using the answer you found above.
(5630 m) * (3.28 ft/m) = 18,466 feet
Pressure:
This question takes a moment of
thought. You were told that you were
given a map on a constant 500 millibar pressure
surface. Therefore, no matter where you
go on the map, you will be at 500 millibars. That is why the geopotential
height is given. It tells you how high
the 500 millibar pressure surface is at any given
station. Therefore, the pressure at
Temperature:
This is given in the upper left part of the station plot and is 7 degrees Celsius.
Dewpoint:
The value given in the lower left is not the dewpoint. It is the dewpoint depression because it is warmer than the actual temperature. Therefore, the dewpoint must be calculated.
- 7 2 = - 9 degrees Celsius
Geopotential Height:
This is given by the value to the upper right and must be decoded at 500 mb.
591 * 10 = 5910 meters
Geopotential Height (in kilometers): (1 km = 1000 m)
The conversion is to just divide the value we found above by 1000.
(5910 m) * ( km / 1000 m) = 5.91 kilometers
5. If we accept that
this is a typical 500mb map, what generally happens to temperatures as you move
poleward at 500mb?
Lets look at a few temperatures starting in the south and going north.
DRT (
AMA (
DDC (
LBF (
BIS (
This pattern shows that the temperature at 500 millibars decreases as you move north.
6. What happens to geopotential heights as you move poleward?
I will do the same comparison.
DRT = 5860 meters
AMA = 5810 meters
DDC = 5760 meters
LBF = 5650 meters
BIS = 5470 meters
Again, this pattern shows that the geopotential heights at 500 millibars decrease as you move poleward.