NATS 101 Lecture 6 TR Temperature 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 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.

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) Conduction 1) Solar SW Ahrens, Fig 3.1 3) Convection 4) Air near ground is heated the most

MIN Temperature near Surface Ahrens, Fig 3.3 1) Outgoing Infrared 3) Absorbed & Re-emitted Infrared 2) Conduction INVERSION – Temp increases w/height 4) Air near ground is cooled the most

Daily Range of Temperatures Ahrens, Fig 3.10 MAX-MIN difference decreases with height above ground

12 and 00 UTC TUS Sounding MAX-MIN Range 0 o C at 700 mb-2400 m 2 o C at 850 mb-800 m 6 o C at 910 mb-150 m 12 o C at 925 mb- ground Range decreases with height isotherms isobars Inversion-Warmer with Height Rapid Cooling with Height Diurnal Range

Growth and Decay of Inversion Evening Morning Temperature Height t1t1 t2t2 t3t3 Temperature Height t2t2 t3t3 t1t1 t4t4 t4t4 Cooled the most at the ground levelWarmed the most at the ground level

What Affects Inversion Strength? Cloud Cover Clear skies-strong inversion Cloudy skies-weak inversion Land Characteristics Snow cover-strong inversion Bare ground-weaker inversion Wind Speed Calm winds-strong inversion Strong winds-weak inversion Weak IRStrong IR Absorption Re-Emission Warm Cold Mixing with Fast Winds

When Does MAX-MIN Occur? Ahrens, Fig 3.2

Ahrens, Figs. 3.8, o F 10 o F DJF JJA Winter-Summer Temperature Variations at Sea Level Continents undergo larger changes than oceans High latitudes undergo larger changes than low latitudes

Controls of Temperature Latitude Average temperatures in middle latitudes change by 5-10 o C every 10 o latitude change Elevation Lapse rate in troposphere is 6.5 o C/km Tucson (2,500 ft)July Max o F Mt. Lemmon (8,500 ft) July Max - 76 o F

Controls of Temperature Ocean Currents and Prevailing Winds Warm-Gulf Stream Cold-California Current Land versus Water Heat capacity of water is 5X that of land Absorbed solar energy is distributed a greater depth in water than in land

Specific Heat Capacity Heat required to raise the temperature of 1 gm of mass 1 o C. Water has higher heat capacity than rock. 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 depthLarge warming in shallow layer Conduction No mixing Large Heat Capacity Small Heat Capacity

Soil Temperature Wallace and Hobbs

Ocean Temperature

Wallace and Hobbs, p348 Ice Formation

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 orbit 2.Tilt of the earth’s axis (obliquity of the ecliptic) 3.Precession of the equinox 4.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 soil 2.Convective heat transfer is far more efficient in water than soil 3.Water has a higher thermal conductivity than soil 4.Sunlight penetrates deeper into water than soil

Summary Balance between incoming and outgoing energy controls temperature rises and falls MAX late afternoon, MIN just after sunrise Diurnal temp. changes are largest at ground Affected by wind, cloud cover, land type Winter-Summer differences Largest over land, high latitudes Temperature controls Latitude, Altitude, Land-Sea, Ocean Currents

Next Class Assignment Atmospheric Moisture Reading - Ahrens 3 rd -Pg: 75-86, B: 426, D: th -Pg: 77-89, B: 430, D: th -Pg: 79-91, B: 440, D: Homework03 - D2L (Due Monday Feb 8 th ) 3 rd -Pg 106: 4.1, 4.2, 4.5, 4.6, 4.9, th -Pg 108: 4.1, 4.2, 4.5, 4.6, 4.9, th -Pg 108: 4.1, 4.2, 4.5, 4.6, 4.9, 4.10