|
Geography
304 - Observations in Meteorology
Surface Weather
Maps
Homework 1
Due Monday, September 25, 2006
Educational
Outcomes:
Weather is the state of the atmosphere
at a particular time and place, mainly with respect to its impact upon life
and human activity. It is defined by the various weather elements
including air temperature, humidity, cloudiness, precipitation, visibility,
air pressure, and wind speed and direction. The surface weather
map is a useful tool for depicting weather conditions over broad areas.
After completing this activity, you
should be able to:
- Decode
the symbols appearing on a surface
weather map and describe weather conditions at various
locations on the map.
- Identify
fronts appearing on the map, the weather
likely to be occurring on either side of a front, and the motions of
fronts.
- Describe
general relationships between wind patterns and centers of high and
low air pressure shown on weather
maps.
- Hypothesize
what weather conditions may be
like in the next day or two at specific locations.
Background Information
You will need the following images which
may be downloaded and printed.
The following links will be helpful in answering the questions in
this
assignment.
Z-Time
on Weather Maps, and Reading
the Surface Station
Model
Investigations:
Before you begin this section, download
and print the answer sheet. Unless told otherwise, put all your
answers on this answer sheet.
1) Examine the surface
weather map presented in Image
1. The weather symbols
shown are those commonly seen on television and in newspapers. The
H's and L's identify centers of relatively high and low air pressure
compared to their surroundings. These pressure systems are commonly
500-1000 miles across. The "H" positioned in Texas locates
the center of a high pressure system; atmospheric pressure increases
horizontally inward toward this "H" and decreases horizontally
outward away from the "H". Moving outward horizontally from
the "L" located in lower Michigan, air pressure
[ A) increases B)
decreases ].
2) The thick curved lines on the map are air mass
boundaries. In the atmosphere, broad expanses of air with generally
uniform temperature, humidity, and density come in contact with other
masses of air having different temperature, humidity, and density.
Because air masses of different densities do not readily mix, the boundaries
separating air masses tend to remain distinct. These boundaries,
which are actually narrow zones of transition, called fronts,
typically separate warm and cold air. The leading edge of advancing
cold air is a cold front and, as shown in the lower part of Image 1,
is signified by triangle symbols which are pointing in the direction toward
which the cold front is moving. The leading edge of advancing warm
air as it moves into a region of relatively cooler/colder air, is a warm
front and is signified by semi-circles on the side of the front's
forward movement. (a) The front in the Southeastern U.S. is
a [ A) cold front B) warm
front ]. (b) According to the map,
persons living in South Carolina can expect [
A) colder B) warmer ] weather after the front passes.
3) Precipitation is depicted on weather maps
by a variety of symbols including dots or periods for rain, horizontal
lines for fog, and stars or asterisks for __________________ .
4) Refer to the model legend in Image
2 to interpret this plotted data.
a) Temperature:__________
F.
b)
Wind direction is shown by the
"arrow" shaft drawn into the circle representing the
station. Unless otherwise noted, north is to the top on the page
(map) and east is to the right. Wind is always named for the
direction from which it blows. In the above depiction, the
wind direction is from the _________________________.
c)
Wind speed is rounded off to the
nearest 5 knots and is symbolized by "feathers" drawn on the
clockwise side of the wind-direction shaft. A full feather represents
10 knots (11.5 mph) and half feathers indicate 5 knots. A pennant
indicates 50 knots and a circle drawn around the station circle signifies
calm conditions. In this case, the reported wind speed is
____________ knots.
d)
Air pressure (adjusted to
sea-level) is reported as a coded number to the nearest tenth of a millibar
(mb). To decipher the plotted pressure value, first place a decimal
point between the second and third number from the left. Then add a
"9" or "10" to the left so that the resulting number
falls within the range of air pressures that commonly occur at sea level
(usually between 960 mb and 1050 mb). For example, a plotted value of
126 represents 1012.6 mb and 863 denotes 986.3 mb. The air pressure
reported above is ______________mb.
e)
Sky coverage (total amount of
cloud cover) is reported inside the station circle. An empty circle
indicates no cloud, a half-shaded circle means four-eights of the sky is
cloud-covered, and fully shaded circle stands for a completely overcast
sky. The reported cloud cover is _________________ .
f)
Current weather is plotted at the "9 o'clock" position on
the station model (to the left of the station circle) using a variety of
symbols representing the particular weather
conditions. The reported current weather
is ____________________ .
Questions 5-10 refer to the 00Z 08 FEB 2000 weather map (Image
3).
5) Click onto Image
3 which is the 00Z 08 FEB 2000 surface
weather map. It depicted weather conditions across the country as
a cooler continental polar air mass moved into central and eastern
U.S. Ohio is in the eastern time zone of the U.S. and is five
time zones west of the Prime Meridian. Weather
observations for the entire map were taken at what local time and day
(date) in Youngstown?
____________________________________________________________________________
6) The wind directions at stations in the central
U.S. and Canada region around the high pressure center centered
in Iowa generally showed the (a) [ A)
clockwise B) counterclockwise ]
and (b) [ A)
inward B) outward ] circulation
pattern typical of Northern Hemisphere high pressure systems.
7) At map time, St. Louis, on the eastern border of
Missouri along the Mississippi River, had winds from the (a) ______________
at about 5 knots and the air pressure corrected to sea level was (b) __________________
mb.
8) At North Platte, in central Nebraska, the
air pressure corrected to sea level was 1030.3 mb and at San Antonio, in
south-central Texas, it was 1024.2 mb. (a) Which
city, [ A) North Platte B) San
Antonio ], was cooler? The dewpoint
is the temperature to which air must be cooled (at constant pressure) to
achieve saturation (100% relative humidity). The higher the dewpoint,
the greater the concentration of water vapor in the air. (b)
From the reported dewpoints, the air in [
A) North Platte B) San Antonio ]
contained less water vapor. This is consistent with the Canadian
air mass that is affecting the north-central and north-eastern United
States.
9) The boundary of continental polar air
moving out of Canada is shown by a heavy line (blue if in color) with
triangles stretching from northeastern U.S. to northern Oklahoma.
This line locates the position of a cold front. Greensboro in
north-central North Carolina could expect [
A) cooler B) warmer ]
temperatures in the next day or so.
10) Locate the "H" over Iowa. Moving
outward horizontally for several hundreds of miles from the "H",
air pressure [ A) increases B)
decreases ]. Hint: examine the pressure values
displayed on the station models located progressively outward from the
"H."
Questions 11-13 refer to the 20Z 27
OCT 1999 surface weather map (Image
4).
11) Centered over the Dakotas is a low pressure center on
the 20Z 27 OCT 1999 surface weather map (Image
4). (a) Winds around this low pressure center are blowing
in a [ A) clockwise B)
counterclockwise ] manner. (b)
These winds are blowing [ A) inward
toward B) outward from ] the
center of the low pressure system.
12) Extending toward the southeast from the "L"
marking the center of the low pressure system over the Dakotas is a warm
front. This front is indicated by a line (red if in color) with
semi-circles pointing in the direction of the relatively warmer air as it
moves into a region of relatively cooler air. This front is moving
toward the [ A) north-northeast B)
south-southwest ].
13) Warm air can "hold" more water vapor than
cold air. The relative humidity is a ratio that compares the water
vapor content of the air with the air's water vapor capacity and is given
as a percentage. A parcel of air with a relative humidity of 60%
means that the parcel is "holding" 60% of the water vapor it
could hold at that given temperature. If the temperature and dew
point are close together, the relative humidity is high. If the
temperature and dew point are far apart, the relative humidity is low; that
is because the temperature of the air parcel must be cooled quite a
bit because it reach saturation (100% relative humidity). (a)
Which location, Nagagami, north-northeast of Lake Superior or Key
West at the southwest tip of Florida, experienced the higher relative
humidity [ A) Nagagami B) Key
West ] ? (b) Which location is actually
"holding the greater quantity of water vapor within the air [ A)
Nagagami B) Key West ]?
After
downloading and printing, please put your answers on the answer sheet and
only turn this sheet in on the due date.
|
