FACTORS INFLUENCING WEATHER AND CLIMATE

Factors influencing weather and climate

Usually, the elements of weather (which make up climate) vary from place to place. In the lesson on weather we learned about the elements of weather. Because climate is influenced by weather, the elements of weather are the same as the elements of climate. Therefore, the factors that cause variation in weather elements will likewise influence the climate. The factors influencing climate and weather are discussed below:

1. Latitude:This factor influences temperature and rainfall. Areas around and close to the equator experience higher temperature and receive higher rainfall than those farther away. So the rainfall and temperature decreases as one moves away from the equator.The amount of heat received at any place on the earth’s surface depends on the angle at which the sun’s rays strike the surface of the earth and the duration of the sunshine. At the equator, the sun’s rays fall on the Earth’s surface at almost right angles throughout the year, but the angle at which the sun’s rays strike the Earth’s surface decreases as one moves towards the poles.Therefore, temperatures decrease with increase in latitude because the equator receives vertical rays of sunlight while the north and the south poles receive slanting rays. Because of this fact, the equator and places near the equator are hotter while places in or near the south and north poles are colder.

2. Altitude:This influences temperature and atmospheric pressure of an area. Temperature decreases with increasing altitude at the rate of 0.6°C for every 10 metres rise in altitude. Therefore, low-altitude areas are warmer than high altitude areas. Atmospheric pressure decreases with increasing altitude. Pressure at sea level is higher than pressure at the summit of a high mountain.

3. Ocean currents:The nature of the ocean current influences the temperature of the wind blowing over it and transfers this influence to the land adjacent to the ocean. This will either lead to reduction or increase in the temperature of the land depending on the type of the ocean current. The wind blowing over warm ocean currents will pick moisture from the ocean and often causes heavy rainfall over the land while the wind blowing over the cold ocean current brings little or no rainfall to the land.

4. Distance from the sea:This influences temperature and rainfall. Places located near the sea experience high temperature and receive high rainfall than those located farther away. This is because of high rates of evaporation from the water surface, which eventually causes heavy rainfall along the coastal areas. For this reason, coastal regions often experience higher temperatures and rainfall than inland areas.

5. Aspect:This term refers to the direction in which a slope faces. It influences temperature and rainfall. For example, the south facing slopes in the northern hemisphere are always warmer than the north-facing slopes. Also the windward side of the mountain receives heavier rainfall than the leeward side.

6. Wind and air masses:Wind carries moisture with it as it flows. Warm wind blowing over a cold region warms the cold region over which it flows. However, if the wind is cold, it cools the region.Warm, moist wind blowing towards a cold, dry region may lead to formation of rainfall in the destination region. Cold, dry wing blowing over a dry region brings no rainfall and if the blowing is repeated over several years, it may cause aridity in that region.

7. Alignment of the coastline:This refers to the arrangement of the region’s coastline in relation to the direction of the wind. If the winds blow across the coastline they cause rainfall. If they blow in parallel to the coastline, they cause drought.

8. Intertropical Convergence Zone (ITCZ):This is a low-pressure area around the equator. The moist winds meet within this region. Places farther away from this zone experience only one rainy season while places close to the zone experience two seasons of heavy rainfall. This is because the winds converge around this region twice a year.

9. Forests:Areas covered with forests normally receive high rainfall as compared to those with little or no vegetation. This is because of high rates of evaporation and transpiration, leading to high humidity. Therefore, these areas often, receive high amounts of rainfall and have a modified climate.

10. Human activities:A range of human activities such as agriculture, mining, transportation, construction, etc affects the climate. For instance, clearing of the forests to get land for agriculture and settlement leads to the loss of biodiversity, making the land arid and unproductive.