Exam 1

Question 1

Distinguish between weather and climate; understand definition of climate change; distinguish between global climate change and global warming

Answer 1

Weather: condition of atmosphere at any particular time and place. Includes pressure, temperature, humidity, visibility, cloud type and amount, type and amount of precipitation, and wind’s speed and direction
Climate: area’s average weather conditions over thirty years or more. Includes extreme weather patterns and variations
Climate change: a statistically signification variation in either mean state of climate or its variability, persisting for at least 30 years
Difference: global warming refers to increasing global average temperatures over the last 100 years, but climate change also incorporates precipitation change and other atmospheric changes

Question 2

Two most abundant gases in atmosphere

Answer 2

Nitrogen at 78% of the atmosphere
Oxygen at 21% of the atmosphere
Argon at 0.93% of the atmosphere

Question 3

Distinguish between important GHGs

Answer 3

Water vapor: most abundant GHG and contributes to 90% of natural greenhouse effect, but not to CC because it is too short-lived to have long-term effect.
Carbon dioxide: 2nd most abundant GHG and most responsible for human-caused CC because of its abundance and long residence time in atmosphere.
Methane: 3rd most abundant GHG and 20 times more effective than CO2 in contributing to GHE and has residence time of 10-20 years

Question 4

Importance of ozone

Answer 4

~30 km in atmosphere. Protects biosphere by absorbing harmful UV radiation. Good ozone in the stratosphere and bad ozone is in the troposphere, where it’s an air pollutant. Good layer has been thinned by ozone-depleting compounds, CFCs

Question 5

Importance of aerosols

Answer 5

Non-gaseous components of atmosphere. Air pollutants. Can serve as cloud condensation nuclei, without which no clouds can form. Have a net cooling effect on climate by scattering sunlight and reducing amount of solar energy reaching Earth’s surface, making photosynthesis harder and creating a net surplus of energy on Earth

Question 6

Air pressure: definition, how pressure changes with altitude and why

Answer 6

Definition: pressure exerted by the weight of the column of the air above an area. Formula is P = P0 * (-z/18400), where P0 is pressure at sea level and z is altitude in meters
Pressure decreases exponentially with increasing altitude because mass of air column above rapidly decreases due to decrease of air density and decrease in the height of the column above

Question 7

Vertical structure of the atmosphere and major characteristics of troposphere and stratosphere

Answer 7

Vertical structure: troposphere, stratosphere, mesosphere, and thermosphere.
Troposphere: 0-10km. Air temperature decreases with increasing altitude because gases in the troposphere are poor absorbers of sunlight and efficient absorbers of Earth’s radiation. Where weather occurs, because water vapor is almost entirely found in this layer.
Stratosphere: 10-50 km. Good ozone layer. Air temperature increases with increasing altitude because this layer is heated by the ozone layer absorbing radiation.

Question 8

Evaporation and condensation

Answer 8

Evaporation: change from a liquid to a gas. Heat absorbed by water molecules, making it a cooling process to the atmosphere.
Condensation: change from gas to a liquid. Heat released by water molecules, making it a warming process to the atmosphere

Question 9

Saturation vapor content

Answer 9

Maximum amount of water vapor that one kilogram of dry air can hold before condensation can occur. Air can reach saturation when temperature drops or when moisture is added. Because climate change has led to an average increase in global temperatures, air can hold more water vapor, making precipitation less likely

Question 10

Relative humidity

Answer 10

How close the air is to saturation. Formula is actual water vapor content divided by the saturation water vapor content. Measured in g/kg. Increasing temperatures can hold exponentially increasing amounts of water. RH higher in the morning, then lower during the day, and then higher again in the evening

Question 11

P/PET ratio and the effect of global warming on P/PET

Answer 11

Percentage of precipitation over potential evapotranspiration. Because temperatures over land have increased faster than ocean temperatures, P/PET ratio over land has dropped, leading to drier conditions

Question 12

Mechanisms of energy transfer

Answer 12

Conduction: heat transferred by particles colliding into each other. Requires direct contact. Least important mechanism for the atmosphere
Convection: heat transferred through mass movement or circulation of a fluid or gas. Medium is needed
Radiation: heat transferred by flow of electromagnetic radiation. How energy from sun reaches the earth

Question 13

Laws that govern radiation

Answer 13

Planck’s law: all objects emit radiant energy at all times
Stefan-Boltzmann’s law: intensity of object’s radiation is directly proportional to the 4th power of its absolute temperature. E = σ*T^4
Wien’s displacement law: wavelength of peak radiation is inversely proportional to absolute temperature of emitting object. Λmax = 2898 micrometers * K / temperature in Kelvins

Question 14

Distinguish between solar radiation and Earth’s radiation

Answer 14

Solar radiation has a peak wavelength in visible light. Earth’s radiation has a peak wavelength in infrared light

Question 15

Greenhouse effect and how it works. The enhanced GHE

Answer 15

GHE: Certain gases absorb most of Earth’s outgoing radiation, which heats the lower atmosphere. Most of it is re-emitted back to Earth is IR radiation.
Most abundant GHGs are water vapor and CO2, then CH4, and N2O
Enhanced GHG comes from burning fossil fuels and deforestation. Too many GHGs makes Earth’s surface temperature increase because more IR heat is re-emitted back to Earth and less escapes to space

Question 16

Radiative forcing

Answer 16

RF describes net energy in Watts per square meter made available to Earth associated with the increase in the concentration of each GHG since 1750. RFE measures net energy increase associated with a 1 ppb concentration increase. RF = RFE * increase in concentration of a GHG. GHG’s contribution to global warming determined by its abundance in the atmosphere, its residence time there, and its instantaneous RF

Question 17

Albedo

Answer 17

The reflectivity of a substance, usually expressed as the percentage of incoming radiation reflected by a surface. High-albedo surfaces include snow, thick clouds, and light roofs. Low-albedo surfaces include grass, forests, and asphalts. Fewer high-albedo surfaces means that less heat is reflected to space, leaving more heat on Earth

Question 18

Forces that control wind

Answer 18

Pressure gradient force: generates wind. Associated with differences in pressure, with wind directed from high to low pressure areas. Stronger PGF is a faster wind.
Coriolis force: affects wind direction. Arises because Earth rotates. In northern hemisphere, deflects an object to the right-hand side of its motion. Magnitude determined by latitude and wind speed, with the force becoming stronger as either increases
Friction: slows down windspeed. Only significant near Earth’s surface. Direction is opposite to that of the wind

Question 19

Cyclones and anticyclons

Answer 19

Anticyclones: high-pressure systems. Winds blow clockwise and out from the center, with the air sinking. Associated with good weather and decreased relative humidity
Cyclones: low-pressure systems. Winds blow counterclockwise in to the center, with the air rising. Associated with bad weather and increased relative humidity.