Map assignment

LECTURE 5: OCEANALITY AND CONTINENTALITY

Oceanality and Continentality are referred to as differential heating. These are temperature

characteristics which we designate for regions near the ocean or large bodies of water (San

Francisco, Boston, Miami, Stockton....) or regions which are inland and affected by the temperature

characteristics of land (Greenbay, Modesto, Wichita...). These characteristics explain the annual

range of temperature we experience on earth, see Figure 4.31, Global Annual Temperature Range, p.

106, Christopherson or Normal Average Range of Temperature, p. 17, Goode’s World Atlas.

Oceanic or Marine climates exhibit a moderate range of temperatures on an annual and

diurnal basis.

Continental climates exhibit an extreme range of temperature on an annual and diurnal basis.

In order to clearly understand the concepts of oceanality and continentality, it is important to

examine the temperature characteristics of land and water. These characteristics can be used to

address any material, natural or man-made.

I try to break down the scientific terms to an understandable level to most non-science majors.

Three temperature characteristics can be used to explain these conditions.

1. SPECIFIC HEAT: defined as the energy (measured in calories) required to raise one gram of a

substance by one degree Celsius.

* land has a LOW specific heat- meaning that land heats rapidly

* water has a HIGH specific heat- water requires approximately six times the energy as land to raise

it's temperature by one degree Celsius.

This concept is important to maintaining the stability of earth's temperature. Luckily the earth is

composed mostly (71%) of water, which means that due to the high specific heat of water, our planet

takes a long time to heat. Changes to the atmosphere or the solar constant will not create an abrupt

change in our temperature.

2. HEAT CAPACITY: this can be defined as the ability of a substance to retain heat.

* land has a LOW heat capacity - land loses heat rapidly

* water has a HIGH heat capacity - water retains heat

Often this is discussed by scientists as one characteristic of specific heat. I like to separate it so that

we can see the benefits of water in moderating global temperatures and land releasing energy rapidly.

3. ALBEDO: defined as the percentage of solar radiation which a surface reflects

* land has a LOW albedo - it does not reflect much solar radiation, one reason that land heats rapidly.

* water has a HIGH albedo - it reflects (does NOT absorb) a large amount of solar radiation, one

reason for water taking a long time to heat.

Please see the graph on page 83 (Christopherson) to select specific percentages of albedo for land

and water surfaces. The corresponding global maps on pages 88-89 show even greater correlations

with insolation patterns.

In total, * land heats and cools rapidly, demonstrated by extreme range of temperature (annually and

diurnally) in continental regions.

* oceans heat and cool slowly, demonstrated by a moderate range of temperature (annually and

diurnally) in oceanic or marine regions.

Examples: Try to find examples from the text (chapter 4) which demonstrate oceanality and

continentality. Specifically, examine pages 98, 102, 103 and refer to this data in your essay to

validate your ideas. Be sure the comparison you make is examining locations at the same

latitude. These areas receive the same amount of solar radiation. Therefore, variations in

temperature demonstrate how the surface alters the absorption and retention of solar radiation. It is

inaccurate to compare range of temperature between the tropics and the poles to show differential

heating, this would only demonstrate the variation of SR receipt between these two regions.

Example of Oceanality: latitude? annual range of temperature? annual average temperature?

Example of Continentality: latitude? annual range of temperature? annual average temperature?

OCEAN CURRENTS: Due to the temperature characteristics of water, oceans are often considered the storehouses of global

energy. Luckily, water is also mobile. This allows the earth to maintain a global temperature

equilibrium. You will recall from lecture two, that the distribution of solar radiation (p. 81 text) is not

equally distributed across the earth's surface. Tropical regions receive an energy surplus and polar

regions receive an energy deficit. Ocean currents obtain their temperature based upon their area of

origin. For example, if you look on page 20-21 in the Goode's atlas, you will see that the Gulf Stream

originates in the Caribbean (tropics) and moves warm water from the tropics to the poles (see also,

page 100 text). As the Gulf Stream moves into higher latitudes it warms regions, providing such

areas with warmer temperatures and higher levels of humidity than characteristic of their latitude.

Similarly, the California current is a cold body of water

originating in the polar regions of the Pacific Ocean. This current moderates the temperature of

regions along the California coast by cooling us during the summer.

Ocean currents redistribute energy (surplus and deficit) on a global basis. This mobility, along with

the heat capacity and specific heat of water, allows the earth to reach an energy equilibrium.

CRITICAL THINKING: Consider how the temperature characteristics of land and water may affect our calculations of global

warming. Which substance would best be utilized to measure global warming? As you examine the

related websites in lecture 3, remember that NASA used air temperatures to assess the level of global

warming taking place, as compared to NOAA's examination of ocean temperatures. Which would be most

valuable to compare? Why?