UNIVERSITY OF BRISTOL
Summer 2015 Examination Period
School of Earth Sciences
Year 2 Examination
EXAM PAPER CODE EASC20027
ATMOSPHERIC PROCESSES
TIME ALLOWED:
2 HOURS
This exam contains 2 sections
Section A = Questions 1 – 9
Section B = 10-12
All students must answer all questions.
Section A is worth 25% of the total marks for the exam and contains
9 multiple choice questions. The mark for each question is given in the square
brackets. You should spend about 30 minutes on this section.
Section B is worth 75% of the total marks for the exam and contains 3 questions.
Each question in this section is worth 25% of the total marks available for the
exam. You should spend about 30 minutes on each question. Relevant physical
quantities are given at the bottom of each question.
OTHER INSTRUCTIONS
Answer both Section A and Section B in a single pink answer book.
Clearly indicate the question numbers and remember to put your
candidate number on the booklet.
ADDITIONAL INFORMATION
NON-PROGRAMMABLE AND NON-GRAPHIC CALCULATORS ARE PERMITTED
IN THIS EXAMINATION.
TURN OVER ONLY WHEN TOLD TO START WRITING
Answer both Section A and Section B in a single pink answer book.
A: MULTIPLE CHOICE (25% of total marks)
[marks for each question given in square brackets]
1: What are the THREE main constituents of dry air on Earth? [2]
(a) CO2
(b) Ar
(c) N2
(d) O2
(e) O3
2: Pluto has a surface gravity of 0.58 ms-2, a radius of 1200 km, and a
tenuous atmosphere with a surface pressure of 0.3 Pa. What is Pluto’s
total atmospheric mass? [3]
(a) 3.1x1012 kg
(b) 2.3x1012 kg
(c) 9.4x1012 kg
(d) 8.7x1012 kg
(e) 2.1x105 kg
3: What is the main reason why the observed tropospheric lapse rate is
less than the calculated dry adiabatic lapse rate? [2]
(a) Water vapour has a larger heat capacity than air
(b) Direct solar heating
(c) Convection
(d) Release of latent heat of condensation
(e) The presence of an ocean
4: The Earth’s ocean reduces the effects of human-induced climate
change by which TWO mechanisms [3]
(a) Acting as a heat sink
(b) Having a high Bond albedo
(c) Redistributing energy from the tropics to the poles
(d) Its ability to rapidly reverse the direction of the thermohaline
circulation
(e) Dissolving atmospheric CO2
5: The figure shows a potential temperature profile determined from
balloon measurements. Answer the following: [3]
(i)
Which letter indicates the most stable layer?
(ii) Which letter indicates the most unstable layer?
(iii) Which letter indicates a layer with neutral stability?
6: Which TWO factors cause equatorial trade winds to blow from East to
West? [3]
(a) Coriolis Force
(b) Pressure gradients
(c) Friction
(d) Centrifugal/Centripetal force
(e) Adiabatic heating
7: Which TWO factors work together to drive the present-day
thermohaline circulation? [3]
(a) Large-scale ocean gyres
(b) Equatorial evaporation
(c) Radiative cooling of polar seas
(d) High-latitude fresh water influx from precipitation
(e) Freezing of sea water at the poles
8: What are the correct units of the reaction constant k for the ozone
creation reaction: O + O2 + M  O3 + M ? [3]
(a) cm6 molecule-2 s-1
(b) cm3 molecule-1 s-1
(c) cm6 molecule3 s-1
(d) cm9 molecule-3 s-1
(e) cm3 molecule-2 s-1
9: Which TWO of these effects caused by increasing evaporation due to
rising global temperatures are positive climate feedbacks? [3]
(a) Increasing albedo due to clouds
(b) Increased salinity of equatorial seas
(c) Increased snow fall at high latitudes
(d) Increased atmospheric water vapour
(e) Increased nocturnal cloud cover
B: LONG QUESTIONS (75% of total marks, 25% for each question)
[Percentage mark for each part given in brackets]
10:
(i) Sketch the Earth’s temperature profile as a function of altitude from
the surface to the mesopause. Annotate your plot, including the names of
important atmospheric regions, and briefly explain the origin of
temperature gradients in the troposphere and stratosphere. [25]
(ii) The figure shows a satellite measurement of the Earth’s infrared
spectrum (solid line) overlain with reference blackbody curves for a
range of temperatures (dashed lines in units of K). What would be the
best wavelength to use for measuring the Earth’s surface temperature?
Justify your choice. [20]
(iii) Use the spectrum to estimate the surface temperature, stating any
assumptions. [15]
(iv) Use the spectrum to estimate the tropopause temperature, explaining
your reasoning. [15]
(v) Sketch two weighting functions: one for 14μm; and one for the
emission peak at 15μm. Explain why there is a difference in radiance and
the origin of the emission peak. [25]
11:
(i) Explain the physical mechanism that causes the Coriolis force. [10]
(ii) With the aid a sketch, show how the Coriolis force affects the
circulation of a northern hemisphere low-pressure system. [20]
(iii) For a Geostrophic flow, the Coriolis force is assumed to be balanced
by the pressure gradient force. Derive an expression for the pressure
gradient force acting on an air parcel and by assuming Geostrophic
balance show that the Geostrophic wind v is given by: [25]
where:



dp/dx
=
=
=
=
Rotation rate of the Earth (radians/s)
Density of air (kg/m3)
Latitude
Pressure gradient (Pa/m)
NB. The Coriolis force on mass m moving at velocity v is given by:
Fc = 2mv sin.
(iv) The figure shows a map of surface pressure for the UK on Friday 13th
February 2015 with a low-pressure system to the west. Use Geostrophic
balance to calculate an approximate surface wind velocity and direction
for Belfast. [25]
(v) How and why would the actual surface winds be different to your
prediction? [20]
[Useful quantity: Density of air 1.2kg/m3]
12:
(i) Use the Stefan-Boltzmann law to derive an expression for the solar
constant S of a planet distance R from the Sun in terms of R, the Sun’s
surface temperature Tsun, and the Sun’s radius rsun. Use your expression to
calculate S for Venus using the physical constants below. [20]
(ii) Venus has a thick atmosphere of almost pure carbon dioxide and
water vapour with a Bond albedo A=0.75. Derive an expression for the
radiative equilibrium temperature Teq of Venus in terms of A and S and
calculate its value. [20]
(iii) Consider a simple radiative balance model of Venus’ stratosphere,
where it is assumed that the stratosphere is transparent at visible
wavelengths and optically thin at infrared wavelengths. Sketch this
simple model, marking on the visible and infrared fluxes, and use it to
derive the stratospheric temperature. [30]
(iv) Observations at radio wavelengths (where the atmosphere is
transparent) show that Venus has a surface temperature of 750K. If the
lapse rate on Venus is 10.5 K/km, calculate the altitude of the tropopause.
[15]
(v) Briefly discuss the limitations of this simple radiative balance model
if it were applied to Earth’s stratosphere. [15]
[ Physical constants:
Stefan-Boltzmann constant,
Sun surface temperature,
Sun radius,
Venus-Sun distance
 = 5.67x10-8 Wm-2K-4,
Tsun = 5800 K,
rsun = 700 000 km,
R = 108 000 000 km
]