1. Heat, heat transport and weather
EOS 365
Lecture 4
Spring 2013
Heat, heat transport and weather

2. = no motion of molecules
Temperature and Heat
Kinetic energy = 1/2 mv2
Heat: The total kinetic energy of the atoms/molecules making up some substance
Temperature: A measure of the average kinetic energy of the individual atoms/molecules making up the same substance
Temperature Units
Celsius (oC), Fahrenheit (oF) or Kelvin (K):
K = °C
°C = K –
°C = 5/9 × (°F – 32°)
°F = (9/5 × °C) + 32°
0 K = –273.2 °C = –459.7 °F
= no motion of molecules

3. Heat Units Transport of Heat
Calorie: Amount of heat required to raise the temperature of 1
gram of water from 14.5 °C to 15.5°C (not used much now)
Joule: 1 Joule = (kg m2)/s2 = Force {kg m/s2} × Distance {m}
1 Joule = calories
1 calorie = Joules
Transport of Heat
Temperature Gradient: A change in temperature with distance
e.g. Equator (warm) to Pole (cold)
e.g. Earth's surface (warm) to Tropopause (cold)
Heat always flows from hot to cold e.g. via:
Conduction
Convection
Advection
Radiation

4. Conduction
Conduction occurs within a substance or between substances that are in direct physical contact
Kinetic energy of atoms/molecules (heat) is transferred by collisions between neighbouring atoms or molecules
Different substances conduct heat differently (i.e., more or less readily)
e.g. styrofoam cup, metal spoon + hot coffee
e.g. new, thick snow, vs. old, packed snow.
Heat is conducted from warm Earth's surface to the overlying air.
Air is not a very good conductor
Conduction is only significant in a very thin layer of air in immediate contact with the Earth's surface

5. Convection Conduction + Convection = Sensible Heating
Much more important and effective than conduction in transporting heat vertically in the the troposphere.
Convection is the transport of heat within a fluid via motion of the fluid itself. In Meteorology and Oceanography, the term is usually applied to the vertical transfer of heat.
Convection in the atmosphere:
Conduction from the ground to the overlying air:
 Warms overlying air Warmed air rises, colder air sinks
process repeats
Conduction + Convection = Sensible Heating
sensible since heating can be felt or sensed as temperature changes directly

6. Advection: The horizontal transport of heat by the winds
Radiation: Already discussed

7.  water said to possess:
Specific Heat
Specific Heat: The amount of heat required to change the
temperature of 1 gram of a substance by 1°C.
Substance
Specific Heat
Water
1.000
Ice at 0°C
0.478
Wood
0.420
Aluminum
0.214
Sand
0.188
Dry Air
0.171
Copper
0.093
Silver
0.056
Gold
0.031
Note: Five times more heat required to raise water by 1°C than sand by 1°C.
High specific heat of water:
 surface temperature of land is more variable with time than that of a body of water
 water said to possess:
Thermal Stability
Check out

8. Implications for climate
Air temperatures are regulated by the temperature of the surface over which the air resides.
Maritime and Ultramaritime localities exhibit smaller seasonal variations than do subcontinental and continental localities.
Index of Continentality
At our latitudes: Winds tend to blow from west to east, so Maritime and
Ultramaritime regions are generally in the west.

9. Climate is what you expect and
Heat imbalances and weather
Weather: The state of the atmosphere at some place and time described in terms of such variables as temperature, cloudiness, precipitation, and wind.
Climate: Weather conditions at some locality averaged over a period of time.
Climate = The statistics of weather
Climate is what you expect and
weather is what you get

10. Heat imbalances and weather
Imbalances in rates of heating and cooling from one place to another within the atmosphere produce temperature gradients
The atmosphere and ocean circulate and redistribute heat
The Earth’s energy balance

11. The Earth’s energy balance
Sensible Heating
Latent Heating

12. Sensible and latent heating
Sensible Heating: Sensible heating = conduction + convection
Latent Heating: Latent heating is the movement or transfer of heat
as a consequence of changes in the phase of water
e.g. liquid  gas, gas  liquid, liquid  solid, solid  liquid,
gas  solid, solid  gas
Phase change of water from liquid to vapour can occur at any temperature

13. Latent heat loss from the Ocean

14. Heat Transport
At high latitudes, the rate of infrared cooling exceeds the rate of solar radiational warming (averaged over the whole year)
The opposite occurs at low latitudes.
Q: Why don't the tropics continually warm and the midlatitude/polar regions continually cool?
A: Poleward transport of heat by the atmospheric and oceanic circulation (including latent heat transport)

15. Temperature Gradients
Weather Response to Heat Imbalances
Solar radiation drives the entire air-sea-ice system
In the atmosphere:
 Imbalances in rates of radiational heating and cooling set up
Temperature Gradients
 Atmosphere responds to redistribute the heat, causing
Weather
Seasonality:
 The need for heat redistribution varies with season
 Atmospheric response and hence weather vary
throughout the year
e.g. Winter in North America:
very strong temperature gradients from, say, the
southern U.S. to northern Canada
 Often get stronger storms, winds than in the summer.

16. The Controls of Temperature
Radiational controls:
Conditions that influence local radiation balance and hence local air temperature:
1. Time of day and year (solar altitude)
Temperature as a function of month, Clevelandia, Amazon Basin, 4°N, 52°W
Very little seasonal variation.
Night/day variation larger than seasonal variation.

17. The Controls of Temperature
Radiational controls:
Conditions that influence local radiation balance and hence local air temperature:
2. Cloud cover

18. The Controls of Temperature
Radiational controls:
Conditions that influence local radiation balance and hence local air temperature:
3. Surface cover (albedo) or (specific heat)
Astronaut photo of an area
in eastern Bolivia

19. South Cascade Glacier, Washington
1928
2000

20. The Controls of Temperature
Air mass controls:

21. Global Distribution of Temperature
Temperature decreases poleward from the tropics

22. January global mean sea-level temperatures
Isotherm – a line connecting places of equal temperature
January
Temperatures are adjusted to sea level

23. Global Distribution of Temperature
Temperature decreases poleward from the tropics
Isotherms exhibit a latitudinal shift with the seasons

24. January
July

25. Global Distribution of Temperature
Temperature decreases poleward from the tropics
Isotherms exhibit a latitudinal shift with the seasons
Warmest and coldest temperatures occur over land

26. January
July

27. Global Distribution of Temperature
Temperature decreases poleward from the tropics
Isotherms exhibit a latitudinal shift with the seasons
Warmest and coldest temperatures occur over land
Southern hemisphere isotherms are straighter

28. July global mean sea-level temperatures
Isotherm – a line connecting places of equal temperature
July
Temperatures are adjusted to sea level

29. Global Distribution of Temperature
Temperature decreases poleward from the tropics
Isotherms exhibit a latitudinal shift with the seasons
Warmest and coldest temperatures occur over land
Southern hemisphere isotherms are straighter
Annual temperature range:
Small near the equator
Increases with latitude
Greatest over the continents

30. Small changes over ocean Large changes over land
January-July surface air temperature difference
Small changes over ocean
Large changes over land

31. The End