Copyright © 2013 Pearson Education, Inc. The Atmosphere: An Introduction to Meteorology, 12 th By: Lutgens and Tarbuck Lectures by: Heather Gallacher, Cleveland State University Chapter 3: Temperature Copyright © 2013 Pearson Education, Inc.
For the Record: Air-Temperature Data Basic calculations: Daily mean Average of 24 hourly readings Daily temperature range Difference of daily high and low Monthly mean Average of daily means Annual mean Average of monthly means Annual temperature range Difference of highest and lowest monthly mean
Copyright © 2013 Pearson Education, Inc. For the Record: Air-Temperature Data Isotherms: Line connecting equal temperature
Copyright © 2013 Pearson Education, Inc. Why Temperatures Vary: The Controls of Temperature Controls of temperature: Differential heating of land and water Ocean currents Altitude Geographic positioning Cloud cover and albedo
Copyright © 2013 Pearson Education, Inc. Land and Water Water is mobile. Temperatures rise and fall slower on water than on land. Land is opaque. Heat is absorbed only on the surface. Specific heat is three times greater for water than land. Evaporation is greater over water.
Copyright © 2013 Pearson Education, Inc. Ocean Currents
Copyright © 2013 Pearson Education, Inc. Altitude Temperatures decrease with altitude. The atmosphere is thinner at higher altitudes. Higher altitudes produce a greater daily temperature range.
Copyright © 2013 Pearson Education, Inc. Geographic Position
Copyright © 2013 Pearson Education, Inc. Cloud Cover and Albedo More clouds cause lower surface temperatures during the day, but warmer temperatures at night. A high albedo reduces surface temperature.
Copyright © 2013 Pearson Education, Inc. World Distribution of Temperature
Copyright © 2013 Pearson Education, Inc. World Distribution of Temperature There is a smaller temperature range at the equator. There is a larger temperature range at higher latitudes. Interiors of continents have a higher temperature range. Coastal regions have a smaller temperature range.
Copyright © 2013 Pearson Education, Inc. Cycles of Air Temperatures Daily temperature variations: Vary by seasons. Vary with cloud cover.
Copyright © 2013 Pearson Education, Inc. Cycles of Air Temperatures Magnitude of daily temperature change: At mid and low latitudes, a high sun angle results in a large variation throughout the day. At higher latitudes, a low sun angle results in lower temperature variations. Windward coasts have small variations. Inland areas have larger variations. Temperature change depends on the amount of cloud cover and water vapor.
Copyright © 2013 Pearson Education, Inc. Cycles of Air Temperatures Annual temperature variations: Highest and lowest mean temperatures do not coincide with maximum or minimum incoming solar radiation. In the northern hemisphere, August has the highest mean temperature, while June has the highest incoming solar radiation.
Copyright © 2013 Pearson Education, Inc. Temperature Measurement Mechanical thermometers: Liquid in glass Maximum thermometer—mercury Minimum thermometer—alcohol Thermograph—bimetal strip Electrical thermometers: Thermistor—electrically resistant at different temperatures Very fast
Copyright © 2013 Pearson Education, Inc. Temperature Measurement Instrument shelters: White box Louvered sides Over grass 1.5 m above ground
Copyright © 2013 Pearson Education, Inc. Temperature Scales Fixed points: Ice point Ice melts 32° F, 0° C, 273 K Steam point Water boils 212° F, 100° C, 373 K
Copyright © 2013 Pearson Education, Inc. Temperature Scales Fahrenheit 1715 Celsius 1742 Kelvin Absolute, no negatives
Copyright © 2013 Pearson Education, Inc. Temperature Scales
Copyright © 2013 Pearson Education, Inc. Heat Stress and Wind Chill: Indices of Human Discomfort Apparent temperature is the temperature a person perceives. Heat stress is caused by high temperature and high humidity. Sweat does not evaporate from body. Feels hotter Heat stress index
Copyright © 2013 Pearson Education, Inc. Heat Stress and Wind Chill: Indices of Human Discomfort
Copyright © 2013 Pearson Education, Inc. Heat Stress and Wind Chill: Indices of Human Discomfort Wind chill is the cooling power of moving air. Evaporates moisture Cools body Feels colder Wind chill chart
Copyright © 2013 Pearson Education, Inc. Heat Stress and Wind Chill: Indices of Human Discomfort
Copyright © 2013 Pearson Education, Inc. End Chapter 3