1. Geography Weather And Climate
2. Physical Geography Weather And Climate
3. Unit 2.3: Weather And Climate Geography Climate

This article throws light upon the six factors that influencing temperature. The factors are: 1. Latitude 2. Altitude 3. Continentality 4. Ocean Currents and Winds 5. Slope, Shelter and Aspect 6. Natural Vegetation and Soil.

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Swenson's test!:d Taken October 14, 2011:/ Typical summer storms or showers in tropical and continental climates are a type of precipitation. Weather is the combination of sunlight, wind, precipitation (rain, sleet, snow, and hail), and temperature in a particular region at a particular time. Scientists measure and record these conditions to describe the weather and to identify patterns over time. Weather scientists (meteorologists) forecast severe weather. A synoptic weather chart is the name for a map or chart which shows more than one piece of weather data on it at the same time. It can include symbols, lines and numbers to help people interpret the weather in a particular location for a particular day or week. Lines on some synoptic weather chart. Symbols on some synoptic weather charts.

Factor # 1. Latitude:

Due to the earth’s inclination, the mid-day sun is almost over­head within the tropics but the sun’s rays reach the earth at an angle outside the tropics. Temperature thus diminishes from equatorial regions to the poles.

This is illustrated in Fig. 107. It shows two bands of rays coming from the sun to two different latitudes on the earth’s surface. Band RI falls vertically over the equatorial latitudes on surface E. Band R2 falls obliquely over the temperate latitudes on surface T. RI travels through a shorter distance and its concen­trated solar insolation heats up a smaller surface area; temperature is thus high.

On the other hand, R2 travels through a longer distance and much of its heat is absorbed by clouds, water vapour and dust particles. Its oblique ray has to heat up a large area; temperature is therefore low.

Factor # 2. Altitude:

Since the atmosphere is mainly heated by conduction from the earth, it can be expected that places nearer to the earth’s surface are warmer than those higher up. Thus temperature decreases with increasing height above sea level.

This rate of decrease with altitude (lapse rate) is never constant, varying from place to place and from season to season. But for all practical purposes, it may be reckoned that a fall of 1°F. occurs with an ascent of 300 feet or 0.6°C. per 100 meters. It is usually more in summer than in winter.

For example in temperate latitudes, in summer, an ascent of only 280 feet will cause the temperature to drop by 1°F., whereas in winter it requires 400 feet. Similarly, the lapse rate is greater by day than at night, greater on elevated highlands than on level plains.

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In tropical countries where the sea level temperature is 80°F., a town that is located at a height of 4,500 feet (shown as X in Fig. 108) will record a mean temperature of 65°F.

Factor # 3. Continentality:

Land surfaces are heated more quickly than water surfaces, because of the higher specific heat of water. In other words, it requires only one-third as much energy to raise the temperature of a given volume of land by 1°F. as it does for an equal volume of water. This accounts for the warmer summers, colder winters and greater range of tem­perature of continental interiors as compared with maritime districts.

Factor # 4. Ocean Currents and Winds:

Both ocean currents and winds affect temperature by transporting their heat or coldness into adjacent regions (Fig. 109). Ocean currents like the Gulf Stream or the North Atlantic Drift warm the coastal districts of Western Europe keeping their ports ice-free. Ports located in the same latitude but washed by cold currents, such as the cold Labrador Current off north-east Canada, are frozen for several months.

Cold currents also lower the summer temperature, particularly when they are carried landwards by on-shore winds. On the other hand on-shore Wester­lies, convey much tropical warm air to temperate coasts, especially in winter.

The Westerlies that come to Britain and Norway tend to be cool winds in summer and warm winds in winter and are most valuable in moderating the climate. Local winds, e.g. Fohn, Chinook, Sirocco, Mistral, also produce marked changes in temperature.

Factor # 5. Slope, Shelter and Aspect:

A steep slope ex­periences a more rapid change in temperature than a gentle one. Mountain ranges that have an east- west alignment like the Alps show a higher temper­ature on the south-facing ‘sunny slope’ than the north- facing ‘sheltered slope’.

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The greater insolation of the southern slope is better suited for vine cultivation and has a more flourishing vegetative cover. Conse­quently, there are more settlements and it is better utilised than the ‘shady slope’ (Fig. 110).

In hilly areas a hot day followed by a calm, cloudless night during which the air cools more rapidly over the higher ground may induce cold, heavy air to flow down the slope and accumulate at the valley bottom pushing the warmer air upwards.

The temperature may then be lower in the valley than higher up as the slopes as show in Fig. 111. A reversal of the lapse rate has taken place. This is called a temperature inversion.

Geography Weather And Climate

Factor # 6. Natural Vegetation and Soil:

There is a definite difference in temperature between forested regions and open ground. The thick foliage of the Amazon jungle cuts off much of the in-coming insolation and in many places sunlight never reaches the ground.

Physical Geography Weather And Climate

It is, in fact, cool in the jungle and its shade temper­ature is a few degrees lower than that of open spaces in corresponding latitudes. During the day trees lose water by evapotranspiration so that the air above is cooled. Relative humidity increases and mist and fog may form.

Light soils reflect more heat than darker soils which are better absorbers. Such soil differences may give rise to slight variations in the temperature of the region. As a whole, dry soils like sands are very sensitive to temperature changes, whereas wet soils, like clay, retain much moisture and warm up or cool down more slowly.

Unit 2.3: Weather And Climate Geography Climate