Ladislaus Chang a Institute of Resource Assessment Tanzania Meteorological Agency

Transcription

1 Factors controlling climate Ladislaus Chang a Institute of Resource Assessment Tanzania Meteorological Agency Education Program on Climate Change and Biodiversity Conservation, Institute of Resource Assessment, University of Dar es Salaam, 19 July, rd September 2010

2 Controls of Climate n Latitude n Land and Water n Ocean Currents n Prevailing winds and mountain ranges n Local winds n Elevation n Cloud Cover

3 Latitude n Latitude is the measure of the distance north and south of the equator. Latitude is measured in degrees. Areas close to the equator, or 0 degrees latitude, receive the direct rays of the sun. These direct rays provide the most radiant energy. Areas near the equator have a warm climate. Polar regions have a cold climate.

4 Elevation n Elevation, or altitude, is the distance above sea level. As elevation increases, the air becomes less dense. This means there are fewer gas molecules in the air and they are spread far apart. Less- dense air cannot hold as much heat as denser air. So as elevation increases, temperature decreases.

5 Location n The surface temperature of water affects the temperature of the water above it. Warm water warms the air and cold water tends to cool it. Land areas near warm water currents have warm temperatures. The Gulf Stream is an ocean current that carries warm water along the eastern coast of the United States. The California Current travels toward the equator carrying cold water along the west coast of the United States.

6 The effects of prevailing wind and mountain ranges on climate n The two factors that affect the amount of precipitation at a particular location are prevailing winds and mountain ranges.

7 Prevailing Winds n A wind that blows more often from one direction than from any other direction is called a prevailing wind. Prevailing winds have a great influence on the climate of regions in their path. Different prevailing winds carry different amounts of moisture. The amount of moisture carried by a prevailing wind affects the amount of precipitation a region receives. Winds formed by rising warm air tend to bring precipitation.

8 Direction of Prevailing Winds n The direction from which a prevailing wind blows also affects the amount of moisture it carries. Some prevailing winds blow from the water to the land (sea breeze).

9 Mountain Ranges n The amount of precipitation at a particular location is also affected by mountain ranges. A mountain range acts as a barrier to prevailing winds. The windward side of a mountain has a wet climate. On the leeward side, relatively dry air moves down the side of the mountain and results in very little precipitation.

10 Effects of mountains

11 Local Winds n Generally move short distances and can blow in any direction n Caused by geographic features that produce temperature differences

12 Sea Breezes n High pressure is created over the ocean during the day and low pressure over land due to uneven heating n Air moves from the ocean to the land creating a sea breeze

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14 Land Breezes n Low pressure occurs over the ocean during the night and high pressure over land due to the uneven heating of earth n This causes wind to move from the land to the ocean creating a land breeze

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16 n Ocean currents are organized movements of ocean water created by persistent wind patterns. Ocean Currents

17 Fig. 7.29

18 Effect of Clouds (Day) First, assume no clouds present Lots of sunlight reaches surface

19 Lots of sunlight is reflected back into space Send in the clouds! Less sunlight reaches the surface Result: cooler temperatures

20 Effect of Clouds: Night n n Clouds reduce flow of infrared radiation to space Result: Warmer temperatures

21 Diurnal Temperature Range (DTR) n DTR = Daily Maximum Temperature minus Daily Minimum Temperature n Clouds reduce DTR