Quiz 5 Solutions

1.) What is the dew point temperature at Detroit?

The dew point temperature is given by the number in the lower left of the station plot, which is 48 degrees F.

2.) What is the temperature?

The temperature is located to the upper left part of the station plot and is 55 degrees F.

3.) This is a surface station plot. Is the temperature in degrees Celsius or Fahrenheit?

Since we are dealing with a surface plot, the temperatures are given in degrees Fahrenheit.

4.) What is the wind direction (N, S, E, W)?

The wind barb indicates from where the wind is blowing from. Therefore, in this station plot at Detroit, the wind is blowing from the West (W).

5.) What is the wind speed?

The wind barb has two long flags on it. Each long flag is worth 10 knots. Therefore, with two flags, the wind speed at Detroit is 20 knots. (Note: It will not have two short flags of 5 knots each since that can be written with a single 10 knot flag.)

6.) What type of cloud cover is Detroit experiencing?

Since there is no markings within the station plot circle, Detroit will have clear skies.

7.) What is the sea level pressure at the station?

This is a little trickier. The sea level pressure is plotted on the upper right side of the station plot. The sea level pressure is given as 115. This has to be decoded. Therefore, for a surface plot, you need to add a 9 or 10 in front of this, and add a decimal point between the 1 and the 5. If I add the 9 in front, the sea level pressure is 911.5 mb. This does not fall within the typical range of 970-1030 millibars, so I know I need to use the 10. Therefore, the sea level pressure at Detroit is:

1011.5 mb

8.) What significant weather (if any) is occurring?

Significant weather symbols would be placed between the temperature and dew point. As there are none plotted, Detroit has no significant weather occurring.

9.) From the reading, briefly define what is meant by lapse rate.

The definition I was looking for was: The change in temperature with height. There are several different values for lapse rate, depending on if the air is saturated or not, but as long as you made mention of temperature changing with height, you received credit.

10.) From the reading, is warm air atop cold air a stable or unstable situation?

The easiest way to think of stability is to remember that if an air parcel is warmer than its environment, it will rise. If it rises, the atmosphere is said to be unstable. For this question, our parcel starts near the surface and is considered to be cold air. If we lift this cold air, it moves into a region of warm air above it. Since the air parcel is colder than its surrounding air, it will sink back down to where it came from. Therefore, warm air atop cold air is a stable situation.