Department of Earth & Climate Sciences
San Francisco State University
Name____________________
February 23, 2015
Metr 201 Quiz #2
100 pts.
A. Short Answer and Definitions. (4 points each for a total of 28 points in this section).
(a) The 500 mb level is found typically at what height (either in decameters or feet) 18000
ft or 600 dm or 6000 m
(b) The 700 mb level is found typically at what height (either in decameters or feet) _10000
ft or 330 dm or 3300 m
(c) The bottommost layer of the atmosphere characterized by a standard lapse rate of about
3.0F/1000 feet is known as the __troposphere
(d) environmental lapse rate --The environmental lapse rate is the rate at which temperature changes in the vertical
in the troposphere as observed by a radiosonde..
(e) A long arrow drawn tangent to the instantaneous wind vectors plotted next to the wind
observations on a weather map is known as a _streamline
(f) wave cyclone ---a low pressure area, on a weather map noted by at least one isobar
encircling a region of locally low values, in which fronts are found in a wave-like
configuration.
(g) inversion --- a structure that appears on soundings in which the usual temperature
decrease with height observed in the tropospheric environmental lapse rate is
reversed, with temperature increasing with height, usually in small layers, and
often based at the ground.
1
B.
Ideal Gas Law. (42 pts)
The Ideal Gas Law is
p = r RT
Your task here is to use the gas law to explain why along an isobar colder air
is denser than warmer air.
(a) Given the constraints of the problem, what is constant in the above
equation (give me the symbols and a short one sentence explanation); (6
pts)
The gas constant, R, by definition is constant, and by the additional
constraint that one is to consider the density of air along an isobar,
pressure is contant. Thus, p and R are constant.
(b) Solve the expression for density. (16 pts)
p = r RT
(1)
p
r=
(2)
RT
and along an isobar
1
r=k
T
(3)
2
(c) Now say why colder air is more dense, given the constraints of the
problem, using the equation you rewrote in (b) as an explanation. (20 pts)
According to equation (2) and (3) above, if pressure is constant, as it is
along an isobar, then temperature and density are inversely related.
Hence, the warmer the air along the isobar, the less dense it is and vice
versa.
C. Weather Chart Imagery
Questions are below. Answer in complete sentences. (30 points)
Figure 1. GOES-E Visible Satellite Image,1632 UTC 12 April 201
3
Figure 2. GOES-E Infrared Satellite Image,1632 UTC 12 April 2011
4
Figure 3. Surface weather map, 12 UTC 12 April 2011
5
1. Examine Figs. 1 and 2, the visible and infrared satellite images for 1632 UTC 12 April
2011. Note the locations A, B, and C annotated on both.
Of those three locations, which is likely to have cumulonimbus clouds. Explain why. (15
points)
The three locations, A, B, and C are in the midst of what appears to be dense cloud cover
on the visible image, Figure 1. However, the infrared satellite image indicates that only
Location C is in a region of very cold cloud tops. In particular, the colors at Location C
suggest that the cloud top temperatures are consistent with those associated with a cloud
form that towers through much of the tropopause, namely, cumulonimbus.
2. Examine Fig. 3, the surface weather map for 12 UTC 12 April 2011. You can consider the
time of this chart to be the same as that of the two satellite images.
An examination of Fig. 3 suggests that the cloudiness evident in Figs. 1 and 2 is associated
with a wave cyclone, both the cyclone itself and the fronts associated with it. How does the
surface chart suggest that this is so (in other words, describe what you see on the surface chart
that meets the definition of a wave cyclone)? (15 points)
The low pressure area on Figure 3 is located, basically, in the midst of the cloudiness
evident on Figs. 1 and 2, with the narrower cloud band that extends southward coincident
with the cold front drawn on Figure 3. The area of lower pressure on the surface map
was encircled by at least one isobar, and the analysis on Fig. 3 shows a frontal system in
that low, draped in a wave-like configuration. Thus, the pressure system on Fig. 3 is a
special form of a cyclone, called a wave cyclone, and that this wave cyclone was associated
with the cloudiness evident in Figs. 1 and 2.
6