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Term Project Recommendations 1.Start project very soon. Preferably now. 2.Scientific exchange with other students is OK, but the paper that you submit must be your own and reflect your final thoughts. 3.Turnitin software will be used to identify possible cases of plagiarism.
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NATS 101
Lecture 6 TRTemperature Variations
Term Project
Term Project Description• One of Two Options
1. Scientific analysis of one of two films on climate change.2. Analysis of the daily afternoon weather for Tucson over a three-week period.
Term Project
• Recommendations1.Start project very soon. Preferably now.2.Scientific exchange with other students is OK,
but the paper that you submit must be your own and reflect your final thoughts.
3.Turnitin software will be used to identify possible cases of plagiarism.
Temperature Questions
• What causes diurnal temperature variations?
• What physical processes can influence daily temperature variations?
• Why is MAX temperature after solar noon?• Why is MIN temperature just after sunrise?• What is Wind Chill Factor? (if time allows)
MAX Temperature near Surface
2) Conduction2) Conduction
1) Solar SW1) Solar SW
Ahrens, Fig 3.1
3) Convection3) Convection
4) Air near ground is heated the most
MIN Temperature near SurfaceAhrens, Fig 3.31) Outgoing 1) Outgoing
InfraredInfrared
3) Absorbed 3) Absorbed & Re-emitted & Re-emitted
InfraredInfrared
2) Conduction2) Conduction
INVERSION – Temp increases w/height
4) Air near ground is cooled the most
Daily Range of TemperaturesAhrens, Fig 3.10
MAX-MIN difference decreases with height above ground
12 and 00 UTC TUS Sounding
MAX-MIN Range 0oC at 700 mb-2400 m
2oC at 850 mb-800 m
6oC at 910 mb-150 m
12oC at 925 mb-ground
Range decreases with height
isotherm
sisobars
Inversion-Warmer with Height
Rapid Cooling with Height
Diurnal Range
Growth and Decay of Inversion Evening Morning
Temperature
Hei
ght
t1
t2
t3
Temperature
Hei
ght
t2
t3
t1
t4t4
Cooled the most at the ground level Warmed the most at the ground level
What Affects Inversion Strength?
Cloud CoverClear skies-strong inversionCloudy skies-weak inversionLand CharacteristicsSnow cover-strong inversionBare ground-weaker inversionWind SpeedCalm winds-strong inversionStrong winds-weak inversion
Weak IR Strong IR
Absorption Re-Emission
Warm
Cold
Mixing with Fast Winds
When Does MAX-MIN Occur?
Ahrens, Fig 3.2
Ahrens, Figs. 3.8, 3.9Ahrens, Figs. 3.8, 3.9
100100ooFF 1010ooFF
DJFDJF
JJAJJA
Winter-Summer Temperature Variations at
Sea LevelContinents undergo
larger changes than oceans
High latitudes undergo larger changes than low latitudes
Controls of Temperature
• LatitudeAverage temperatures in middle latitudes change by 5-10oC every 10o latitude change
• ElevationLapse rate in troposphere is 6.5oC/kmTucson (2,500 ft) July Max - 100oFMt. Lemmon (8,500 ft) July Max - 76oF
Controls of Temperature
• Ocean Currents and Prevailing WindsWarm-Gulf StreamCold-California Current
• Land versus WaterHeat capacity of water is 5X that of landAbsorbed solar energy is distributed a greater depth in water than in land
Specific Heat CapacityHeat required to raise the temperature of
1 gm of mass 1oC.Water has higher heat capacity than rock.
Material Specific Heat Capacity (Cal gm-1 oC-1)
Still Water 1.00 Dry Air 0.24 Granite (Rock) 0.19
Still water warms or cools very slowly compared to air and land
Water-Soil Heating Depth
Deep Penetration
Shallow Penetration
Consider the Fate of Incoming Solar Radiation Penetrating Water vs. Soil
Convective Mixing
Small warming over great depth Large warming in shallow layer
Conduction No mixing
Large Heat Capacity Small Heat Capacity
Soil Temperature
Wallace and Hobbs
Wallace and Hobbs
Ocean Temperature
Wind Chill
Still air is poor conductor; lack of wind allows insulating layer of still air to form next to skin
Wind blows insulating layer of air from skin Forced convection or heat transport by advection
The main reason for seasons is?
1. Eccentricity of the earth’s orbit2. Tilt of the earth’s axis (obliquity of the
ecliptic)3. Precession of the equinox4. Millennium variations in earth-to-sun
distances at aphelion and perihelion
Which statement is not a reason that coastal sites experience less extreme
seasons than inland sites?1. Water has a higher heat capacity than soil2. Convective heat transfer is far more
efficient in water than soil3. Water has a higher thermal conductivity
than soil4. Sunlight penetrates deeper into water than
soil
Summary • Balance between incoming and outgoing energy
controls temperature rises and fallsMAX late afternoon, MIN just after sunrise
• Diurnal temp. changes are largest at groundAffected by wind, cloud cover, land type
• Winter-Summer differencesLargest over land, high latitudes
• Temperature controlsLatitude, Altitude, Land-Sea, Ocean Currents
Next Class AssignmentAtmospheric Moisture
• Reading - Ahrens3rd-Pg: 75-86, B: 426, D: 429-4324th-Pg: 77-89, B: 430, D: 433-4365th-Pg: 79-91, B: 440, D: 443-446
• Homework03 - D2L (Due Monday Feb 8th)3rd-Pg 106: 4.1, 4.2, 4.5, 4.6, 4.9, 4.104th-Pg 108: 4.1, 4.2, 4.5, 4.6, 4.9, 4.105th-Pg 108: 4.1, 4.2, 4.5, 4.6, 4.9, 4.10
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