NAME: ________________________________________________ QUIZ SECTION: ________
ATMS 101 Autumn 2008
Homework #3: 20 points (Due Wednesday, October 22)
Please show all work and write neatly in the space provided.
Be concise.
point values are shown (in parentheses)
1.(2) Explain how a 500 mb shortwave and longwave interact (or “line up”) to create a region
favorable for storm development.
Both shortwaves and longwaves have a region where we’d expect enhanced clouds/precip. The region is
between the upstream trough and the downstream ridge. When this region of a shortwave lines up with
this region of a longwave, we create a region that is particularly
favorable for storm development.
2. (2) The image at right depicts 500 mb heights over the
north Pacific, with lower heights generally to the north.
First, draw lines to identify two shortwave trough axes.
Second, use a pencil to shade one region we can expect
cloud cover. Third, circle one region we can expect clear
skies.
3. (2) During cold nights in Western Washington, there can be
a line of clouds over the center of Puget Sound while the
sky is clear over the land on both sides. Explain. Hint:
Puget Sound and the land areas are NOT similar in temperature.
This is a land-breeze set-up. On cold nights, water is warmer than land. The warmer water and colder
land cause a circulation to develop in which warmer air above the water rises and condenses, forming
clouds. See the textbook for a good description of land- and sea-breezes.
4. (2) Fifty million years ago, Earth was warmer and the difference in temperature between
the poles and equator was much less than today. How did the strength of the jet stream in
that period compare to the jet stream of today? Explain.
We’ve learned that one of the reasons for westerly winds (and the jet stream) is the difference in
temperature between the equator and the pole. Greater temperature differences lead to a stronger jet
stream and – to answer this question – a weaker difference results in a WEAKER jet stream. More
explanation: This temperature difference leads to pressure differences at upper levels, causing the winds
to blow; since the resulting PGF aims north, the resulting wind is West. A stronger temperature
difference (like in our winter versus summer) leads to a stronger jet.
5. (2) a. Is solar radiation affected by clouds? If so, how?
Yes: clouds reflect solar radiation.
(2) b. Is infrared radiation affected by clouds? If so, how?
Yes: clouds absord infrared radiation (and emit it).
(2) c. How do your answers to 5a and 5b explain the effect of cloudiness on minimum
and maximum daily temperatures? What affect does cloudiness have on the difference
between daytime and nighttime temperatures?
Because clouds reflect solar radiation (which only occurs during the day), less solar radiation reaches the
earth on cloudy days, leading to cooler temperatures. Because clouds absorb and re-emit radiation that
is emitted from Earth, less radiative cooling takes place on a cloudy night, leading to warmer nights.
Cloudiness decreases the difference between daytime and nighttime temperatures.
6. (2) The National Weather Service issues a forecast that includes fog for tomorrow
morning’s commute. When you’re going to bed at midnight you see the moon so you know
it’s not foggy. You check your home weather station and note a dewpoint depression of 3
degrees C.
Are your observations consistent with the forecast? Explain.
Yes. A dewpoint depression of 3 degrees C means the temperature only has to drop by three degrees C
for the air to be saturated and form fog. Early morning is the coldest time period, so there are hours of
potential cooling ahead, and a 3 degree cooling is very reasonable. Additionally, we know that there are
no clouds to keep the nighttime temperature warm, so it will likely cool off considerably.
7. Refer to the image from the Camano Island radar on the Quiz Section website:
www.atmos.washington.edu/~w/101 The radar is located in section B3. To make the
geography more clear, a map without plotted precipitation is also available. You may want
to refer to a map of western Washington State (widely available on the internet) if you aren’t
familiar with local geography.
(1) a. Why does the radar indicate no precipitation in portions of grid boxes B3 and C3?
Because there is no precipitation falling. It is common for this area to be dry when other areas are
experiencing precipitation because of the rain shadow effect of the Olympic Mountains.
(1) b. Why does the radar indicate no precipitation in portions of grid boxes C2 and D2?
The radar is blocked by the Olympic Mountains, so it cannot tell whether or not precipitation is present.
(1) c. Which grid box has the heaviest precipitation rate? Choose only one.
D3
(1) d. Can we tell whether there is precipitation where the letters (A, B, C, D) are
written to the right of the red grid lines? How can we tell or why can’t we tell?
Accepted answers: 1) No, we can’t tell because the Cascade Mountains are blocking; 2) No, we can’t tell
because it is too far from the radar. Answer (1) is more correct.