Title: Understanding Weather and Climate 4th Edition Edward Aguado and James E. Burt
1Understanding Weather and Climate4th
EditionEdward Aguado and James E. Burt
Take Roll!!!
Energy Balance and Temperature
Geosystems 6e An Introduction to Physical
Geography
Chapters 4 5
Chapter 4
Robert W. Christopherson Charles E. Thomsen
2Introduction
- Solar radiation is the atmospheres heat source
- Most gases are transparent to solar radiation
- They do absorb terrestrial radiation
- Gases also scatter energy
- The global energy budget
- A balance between incoming solar radiation and
outgoing terrestrial radiation
3Insolation at Earths Surface
Figure 4.2
4Atmospheric Influenceson Insolation
- Radiant energy is absorbed, reflected, or
transmitted when it enters the atmosphere - Transmission
- Includes scattering and refraction
- Energy transmitted through objects
- Varies diurnally from place to place
5Atmospheric Influences on Insolation
- Refraction
- Radiant energy (i.e., sunlight) travels through
the vacuum of space and enters the atmosphere,
i.e., a medium of different density - The radiant energy/incoming sunlight experiences
a change in speed and direction
6Refraction
- Refraction
- Change in Direction and Speed of Light
- Does not increase heat
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7Refraction
Figure 4.4
8Atmospheric Influences on Insolation
- Absorption
- Particular gases, liquids, and solids absorb
energy - Heat increases
- Gases are poor selective absorbers of energy
9- Reflection
- Redirection of energy
- Does not increase heat
- Albedo percentage of reflected energy
- Scattering
- Scattered energy diffuses radiation
- Changes direction but not wavelength
- Reduces intensity
- Type determined by size of scattering agents
10Albedo and Reflection
Figure 4.5
11July and January Albedos
Figure 4.6
12Clouds and Albedo
Figure 4.7
13Scattering
- Rayleigh Scattering
- Scattering agents are smaller than energy
wavelengths - Forward and backward scattering
- Partial to shorter wavelengths
- Causes blue sky
14Rayleigh Scattering
15- Mie Scattering
- Larger scattering agents (aerosols)
- Interacts with wavelengths across visible
spectrum - Hazy, grayish skies
- Sunrise/sunset color enhancement
16Longer radiation path lengths greater Mie
Scattering and reddish skies
17(No Transcript)
18- Nonselective Scattering
- Very large scattering agents (water)
- Scatter across the visible spectrum
- White or gray appearance
- No wavelength especially affected
- Transmission
- Energy transmitted through objects
- Varies diurnally from place to place
19Energy Pathways
Figure 4.1
20- The Fate of Solar Radiation
- A constant supply of radiation at top of the
atmosphere - Entering energy is transmitted, absorbed, or
scattered - A Global Energy Budget
- Assumes global annual insolation 100 units
- Atmosphere absorbs 25 units
- 7 units absorbed by stratospheric ozone
21- Atmospheric Reflection 25 units
- 19 reflected to space by clouds
- 6 units back-scattered to space
- Remaining 50 units are available for surface
absorption. Of the 50 Units of Energy to reach
the surface - 5 reflected back to space
- Remaining 45 absorbed at surface
- Heats surface and overlying air
22Incoming Radiation
23- Surface-Atmosphere Radiation Exchange
- Surface emission (terrestrial/longwave radiation)
- Much is absorbed by atmospheric gases
- H2O and CO2
- Increases air temperature
- Some energy is reabsorbed at the surface
- Additional surface heating
-
24- Greenhouse gases absorb terrestrial radiation
- The atmospheric window - non-absorption of
wavelengths between 8-15 µm
The atmospheric window
25The atmospheric window
26- Clouds absorb virtually all longwave radiation
- Results in warmer cloudy nights
27- Net radiation difference between absorbed and
emitted radiation - The atmosphere absorbs 25 units of solar
radiation but undergoes a net loss of 54 units - net deficit 29 units
- The surface absorbs 45 units of solar radiation
but has a longwave deficit of 16 - net surplus 29 units
- Net radiation deficit equals net surplus, i.e.,
the surplus and deficits offset
28- Conduction
- Energy is transferred from the surface to the
atmosphere - Energy transferred to the laminar boundary layer
29Net radiation
30Energy surplus/deficit offsets between air and
surface
31- Convection
- When the surface temperature exceeds the air
temperature - Normal during the day
- Convection from
- Free convection
- Warmer, less dense fluids rise
- Forced convection
- Initiated by eddies and disruptions to uniform
airflow
32Free Convection
Forced Convection
33- Sensible Heat
- Readily detected heat energy
- Related to objects specific heat and mass
- 8 units transferred to the atmosphere as sensible
heat - Latent Heat
- Energy which induces a change of state (usually
in water) - Redirects some energy which would be used for
sensible heat
34- Latent heat of evaporation is stored in water
vapor - Released during condensation
- Globally, 21 units of energy are transferred to
the atmosphere as latent heat
35Heat content of substances
36- Net Radiation and Temperature
- Incoming radiation balances with outgoing
- If parameters are changed, a new equilibrium
occurs - Balances
- Global
- Diurnal
- Local
37- Latitudinal Variations
- Between 38oN and S net energy surpluses
- Poleward of 38o net energy deficits
- Winter hemispheres
- Net energy deficits poleward of 15o
- Mass advection neutralizes energy imbalances
38Annual average net radiation
39Ocean circulation
40- The Greenhouse Effect
- Gases trapping terrestrial radiation
- H2O, CO2, and CH4
- Without the greenhouse effect
- average Earth temperature -18oC (0oF)
- Human activities play a role
41A true greenhouse stems convection
42Insolation Receipt and Global Temperature
Distribution
- Temperatures decrease with latitude
- Strong thermal contrasts occur in winter
- Isotherms shift seasonally
- Greater over continents
- More pronounced in the northern hemisphere
43Shifting of Isotherms with Seasonal Variation in
Insolation Receipt
44Shifting of Isotherms with Seasonal Variation in
Insolation Receipt
45Shifting of Isotherms with Seasonal Variation in
Insolation Receipt
46Influences on Temperature
- Latitude
- Due to axial tilt
- Solar angles, daylengths, beam depletion, beam
spreading - Altitude
- Temperatures decline with altitude
- High altitudes have fairly constant temperatures
- More rapid diurnal fluxes
47Energy Budget by Latitude
Figure 4.13
48Temperature Variation with Altitude
49- Atmospheric Circulation
- Latitudinal temperature and pressure differences
cause large-scale advection - Contrasts between Land and Water
- Continentality versus maritime effects
50- Warm and Cold Ocean Currents
- Western ocean basins are warm
- Eastern ocean basins are cold
- Local Conditions
- Small spatial scale features impact temperatures
51Ocean circulation
52South-facing slopes have more vegetation
53The role of vegetation in a local energy balance
54- Daily and Annual Temperature Patterns
- Diurnal temperatures lag energy receipt
- Surface cooling rate is lower than the warming
rate - Due to stored surface energy
- Winds moderate temperature ranges
- Transfer energy through large mass of air
55Clear Skies
Diurnal energy
Overcast
56The Greenhouse Effect and Atmospheric Warming
- Atmosphere absorbs heat energy
- A real greenhouse traps heat inside
- Atmosphere delays transfer of heat from Earth
into space
57Clouds and Forcing
Figure 4.11
58Shortwave and Longwave Energy
Figure 4.11
59EarthAtmosphere Radiation Balance
Figure 4.12
60Energy Balance at Earths Surface
- Daily Radiation Patterns
- Simplified Surface Energy Balance
- The Urban Environment
61Daily Radiation Patterns
Figure 4.14
62Surface Energy Budget
Figure 4.15
63Simplified Surface Energy Balance
- NET R
- SW (insolation)
- SW (reflection)
- LW (infrared)
- LW (infrared)
Figure 4.16
64Global NET R
Figure 4.17
65Global Latent Heat
Figure 4.18
66Global Sensible Heat
Figure 4.29
67Solar Cooking Solution
Figure FS 4.1.1
68Solar Energy
Figure FS 4.1.2
69Radiation Budgets
El Mirage, CA
Pitt Meadows, BC
Figure 4.20
70The Urban Environment
Figure 4.21
71Urban Heat Island
Figure 4.22
72Urban Heat IslandPilotProject
Figure 4.23