Robert W. ChristophersonCharlie Thomsen

Chapter 5 Global

Temperatures

Frozen tundra, very sensitive to global temperature change. Temperature increase in the polar region is more than double the rate of the rest of the globe.

The Sad Face of Melting

Picture taken by Michael Nolan, a oceanic photographer, on July 16, 2009 in Norway

Temperature Concepts and Measurement  

Principal Temperature Controls  

Earth’s Temperature Patterns 

Air Temperature and the Human Body 

Global Temperatures

Temperature is a measure of average kinetic energy (motion) of individual molecules in matter.

Heat always transfer in the direction from higher temperature to lower temperature.

High temperature does not necessarily mean more heat.

Temperature

Temperature Scales Fahrenheit

Celsius

Kelvin 

Measuring TemperatureMechanical (shrink/expansion)

Electric  

Temperature Concepts and Measurement  

Temperature Scales

Figure 5.1

Thermometer and Instrument Shelter

Figure 5.2 Figure 5.3

Min-max thermometer

Electric Device: Thermal Couple and Thermistor

Thermistor: is a type of resistor whose resistance varies with temperature. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting over current protectors, and self-regulating heating elements.

Thermal Couple: In 1822, an Estonian physician named Thomas Seebeck discovered (accidentally) that the junction between two metals generates a voltage which is a function of temperature.

Unlike a thermometer, the electrical signals from a thermal couple or thermistor can be logged automatically with much higher accuracy.

What do we Care About Temperature

1. It is one of the most important weather and climate factors2. All living species, plants, animals or microbes, have a suitable

temperature range to live.3. All biological and many physical processes are influenced by temperature

i) Plant growthii) Decomposition of plant residualsiii) Melting of ice and snowiv) Evaporation of water

4. Commonly used temperaturei) Effective temperature: usually refers the temperature above the minimum required for a particular plant to be active (e.g. corn or peas ). For most plant, it is 5oC.ii) Growing Degree Days: sum of mean daily temperature above the effective temperature. A very good predictor for phenology, e.g. time to flowering, time to harvest etc.

iii) Extreme low/high temperature: can be a determinant factor limiting certain species spatial distribution.

Mean Temperatures

1. During the old days when there is no automatic data logging, staff at meteorological stations took a reading on their instrument four times a day: 02:00, 08:00, 14:00, and 20:00. The mean daily temperature is the mean of the four measurements.

2. Average of daily maximum and minimum temperature.

3. Modern automatic technology can set the instrument to measure the temperature every second and provide us with a mean at any time interval we want

4. Monthly Mean Temperature: adding daily mean temp and then divide the sum by the number of days in a month.

5. Annual Mean Temperature: adding the monthly mean temperature, and divide the sum by 12.

Latitude  Affects insolation, which is the primary factor causing the spatial variation of temperature on Earth surface.

Altitude  High altitude has greater daily rangeHigh altitude has lower annual average

Cloud Cover: Globally, 50% at any time.  High albedoModerate temperatures – cooler days, warmer nights

Sun Declination angle (Season)Land and Water  

Principal Temperature Controls  

Latitude and Temperature

Figure 5.4

Altitude

Figure 5.5

Evaporation

Transparency

Specific heat

Movement

Ocean currents and sea-surface temperatures

Marine vs. continental effects

Land–Water Heating Differences 

Land–Water Heating Differences  

Figure 5.7

Land Is Opaque

Figure 5.8

The Gulf Stream

Figure 5.10

Red/orange: 25-29oCYellow/green: 17-24oCBlues: 10-16oCPurple: 1-9oC

Marine and Continental Climates:Vancouvervs.Winnipeg

Figure 5.12

Figure 5.13

Marine and Continental Climates:San Franciscovs.Wichita, KS

Marine and Continental Climates:Trondheimvs.Verkhoyansk

Figure 5.16

January Temperature Map  Thermal equator movement southward

More pronounced over large continents

July Temperature Map  Thermal equator movement northward

More pronounced over large continents

Annual Temperature Range Map Continentality

Earth’s Temperature Patterns

(b)

(c)

(a)

January Temperatures

Figure 5.14

Isotherm (iso=equal, therm=temperature: a line collects the points on the map that have the same temperature.

The closer the line is, the greater the temperature gradient, i.e. the faster the temperature changes in space.

January Temperatures

Figure 5.14Note the coldest and hottest areas are both on land.

(c)

(b)

(a)

July Temperatures

Figure 5.17

Thermal equator migrated north.

July Temperatures

Figure 5.17

There is a greater seasonal N-S shift for the thermal equator on land than in oceans! Why?

Global Temperature Ranges

Figure 5.19

Wind chillCorrelates cold and wind speed

Heat indexCorrelates heat and humidity

Air Temperature and the Human Body

Wind Chill Table

Figure FS 5.1.1

Heat Index Table

Figure FS 5.1.2