AOSC 200 Lesson 3

1
AOSC 200Lesson 3
2
Fig. 3-1, p. 54
3
Diurnal temperature cycle
Fig. 3-3, p. 56
4
Air temperature data

• Daily mean temperature is determined by two
  methods, (a) average of 24 hourly measurements
  (b) the average of the maximum and minimum
  temperatures for the day.
• Daily temperature range is the difference
  between the max and min temperatures.
• Monthly mean temperature is obtained from the
  average of the daily mean for the month
• Annual mean temperature is the average of the
  monthly means
• Annual temperature range is the difference
  between the coldest monthly mean and the warmest
  monthly mean

5
CONTROLS OF TEMPERATURE

• LATITUDE
• SURFACE TYPE
• ELEVATION AND ASPECT
• DIFFERENTIAL HEATING OF LAND AND WATER.
• OCEAN CURRENTS.
• CLOUD COVER AND ALBEDO

6
Fig. 3-4, p. 57
7
Fig. 3-5, p. 57
8
Fig. 3-6, p. 58
9
Fig. 3-7, p. 59
10
The effect of Aspect
Fig. 3.8
11
Fig. 3-9, p. 60
12
Differential Heating of Land and Water

• AS WATER IS HEATED CONVECTION DISTRIBUTES THE
  HEAT THROUGH A LARGE MASS.
• IN CONTRAST, HEAT DOES NOT PENETRATE DEEPLY INTO
  SOIL OR ROCK - HEAT CAN ONLY BE TRANSFERRED BY
  CONDUCTION.
• NET RESULT IS THAT A RELATIVELY THICK LAYER OF
  WATER IS HEATED TO MODERATE TEMPERATURES, WHILE
  ONLY A THIN LAYER OF LAND IS HEATED TO MUCH
  HIGHER TEMPERATURES.
• SPECIFIC HEAT (AMOUNT OF HEAT NEEDED TO RAISE THE
  TEMPERATURE OF ONE GRAM OF A SUBSTANCE 1 DEGREE
  CELSIUS) IS ALMOST THREE TIMES GREATER FOR WATER
  THAN FOR LAND

13
Fig. 3-10, p. 60
14
Fig. 3-11, p. 61
15
Effect of clouds on the daytime energy budget at
the surface
16
Fig. 3-13, p. 62
17
Fig. 3-16, p. 67
18
DAILY MARCH OF TEMPERATURE

• AT THE BEGINNING OF THE DAY, WITH NO SOLAR
  RADIATION, THE TEMPERATURE IS CONTROLLED BY NET
  THERMAL RADIATION LEAVING THE SURFACE ---- THE
  GROUND COOLS.
• AS SUN COMES UP , SOLAR RADIATION IS ABSORBED AND
  THE TEMPERATURE OF THE GROUND INCREASES -
  INCREASING THE NET THERMAL RADIATION LEAVING THE
  GROUND.
• HOWEVER, IN GENERAL THE INCOMING SOLAR ENERGY IS
  MORE THAN THE NET OUTGOING THERMAL ENERGY, SO THE
  GROUND HEATS UP.
• THE GROUND WILL CONTINUE TO HEAT UP UNTIL THE
  AMOUNT OF INCOMING SOLAR ENERGY EQUALS THE AMOUNT
  OF OUTGOING THERMAL ENERGY.
• THIS OCCURS TYPICALLY AT ABOUT THREE/FOUR IN THE
  AFTERNOON.
• SIMILAR ARGUMENTS EXPLAIN THE LAG SEEN IN THE
  WINTER AND SUMMER.

19
CONTROLS OF DIURNAL TEMPERATURE RANGE

• LATITUDE - DETERMINES THE INTENSITY OF THE SUN,
  AND THE LENGTH OF THE DAY
• SURFACE TYPE - LAND AND WATER CONTRAST, BARE SOIL
  VERSUS VEGETATION
• ELEVATION AND ASPECT
• RELATIONSHIP TO LARGE BODIES OF WATER - LARGE
  BODIES OF WATER ACT LIKE A THERMOSTAT -
  TEMPERATURE RANGE IS SMALLER
• OCEAN CURRENTS.
• CLOUD COVER - REDUCES THE DIURNAL TEMPERATURE
  RANGE.

20
Fig. 3-14, p. 63
21
Interannual Temperature Variations

• AVERAGE OR NORMAL TEMPERATURES
• ANOMALIES
• VOLCANOES
• EL NINO / LA NINA

22
Volcanoes
Fig. 3-15a, p. 66
23
Picture taken by astronauts on the Space Shuttle
3 weeks after the eruption of Mt. Pinatubo
Fig. 3.15b
24
Temperature in Spokane and Boise after the
eruption of Mount St. Helens
Box 3-1, p. 64
25
http//www.youtube.com/watch?vdQeCEqkE9eE http//
www.youtube.com/watch?vdQeCEqkE9eE
26
Fig. 3-17, p. 72
27
(No Transcript)
28
Fig. 2.7
29
Adiabatic Cooling and Warming

• A RISING PARCEL OF AIR ALWAYS EXPANDS
• AS THE PARCEL EXPANDS IT WILL COOL
• ADIABATIC PROCESS - NO HEAT EBERGY IS GAINED OR
  LOST BY THE PARCEL
• THE RATE OF COOLING WITH ALTITUDE DUE TO THIS
  PROCESS IS CALLED THE DRY ADIABATIC LAPSE RATE
• USUALLY THE AIR CONTAINS SOME WATER VAPOR
• AS THE PARCEL RISES AN ALTITUDE WILL BE REACHED
  WHEN THE WATER VAPOR CONDENSES
• BUT THIS RELEASES LATENT HEAT OF CONDENSATION TO
  THE AIR PARCEL
• THEREFORE THE TEMPERAURE OF THE PARCEL WILL NOT
  DROP OFF AS MUCH AS FOR A DRY PARCEL OF AIR
• WET ADIABATIC LAPSE RATE

30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
Fig. 3-18, p. 73
34
Lapse Rates and Stability

• Lapse rate is the rate at which the real
  atmosphere falls off with altitude the
  environmental lapse rate
• An average value is 6.5 ºC per kilometer
• This should be compared with the adiabatic lapse
  rate of 10 ºC.
• If the environmental lapse rate is less than 10
  ºC, then the atmosphere is absolutely stable
• If greater than 10 ºC, it is absolutely unstable

35
Fig. 3.12

• Lifecycle of a nocturnal (radiative) temperature
  inversion
• Mid-afternoon
• Evening
• Sunrise
• Mid-morning

Fig. 3-19, p. 75
36
Temperature Inversions

• When the temperature profile increases with
  altitude, this is known as a temperature
  inversion
• Two main types subsidence inversion and
  radiation inversion (nocturnal inversion)
• Very important during pollution events trap
  pollutants close to the surface.

37
Temperature Inversions
38
Effect of a temperature inversion
Fig. 3-20, p. 77
39
Wind Chill Factor

• The wind chill factor describes the increased
  loss of heat by the movement of air
• It cannot be measured, so it is calculated
• Wind chill equivalent temperature

40
Table 3-1, p. 78