Factors affecting Temperature Unit 2.4 - Weather Factors affecting Temperature

Factors affecting Temperature Temperature varies across the world because of the variations in the following factors: Latitude Altitude Distance from the sea Cloud cover Winds and ocean currents

Latitude This refers to the angular distance of any point on the Earth’s surface measured north or south of the Equator.

Latitude Is temperature higher at higher latitudes or lower latitudes? Why? High Latitude North Pole 90ºN 66½ºN Middle Latitude 23½ºN Low Latitude 0º 23½ºS 66½ºS South Pole 90ºS

Latitude The amount of heat received by the Earth’s surface decreases as latitude increases. Areas with a tropical climate are called “Low latitudes” because they are nearer the equator. The average annual temperature is 26.5ºC. Areas with polar climate are called “high latitudes. Temperatures in these latitudes are never warm. The average temperature of the warmest month is <10ºC.

Latitude – Reasons for variance 1 Along the Equator, the Sun’s rays strike the Earth’s surface perpendicularly. This high angle of incidence causes the solar radiation to be concentrated over a smaller area, causing more intense heat hence the equatorial region experiences a higher temperature.

Latitude – Reasons for variance 1 At the higher latitudes, the Sun’s rays strike the Earth’s surface at smaller angles of incidence. This causes the solar radiation to be spread over a larger area, hence the higher latitudes experiences a lower temperature.

Latitude – Reasons for variance 2 About 50% of the solar energy that reaches the atmosphere's upper layers are absorbed by oxygen, ozone and other molecules before it reaches the surface. More solar energy would have been lost at the higher latitudes as the Sun’s rays need to travel over a greater distance through the atmosphere before reaching the Earth’s surface.

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Factors affecting Temperature Temperature varies across the world because of the variations in the following factors: Latitude Altitude Distance from the sea Cloud cover Winds and ocean currents

Altitude Altitude refers to the height of a point in relation to the sea level. Temperature are quite different at different altitudes. Temperature decreases as altitude increases. Temperatures generally decrease by 6.5°C with every 1000m increase in altitude. This decrease in temperature is called lapse rate.

Based on the location of Quito, Ecuador, what type of climate do you think it should have? What about Guayaquil, Ecuador?

Quito, Ecuador Guayaquil, Ecuador Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec 14 15 Guayaquil, Ecuador Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec 27 28 25.5 25 26

Altitude – Reasons for variance 1 About 45 % of the sun’s energy is directly absorbed by the Earth’s surface, which in turn radiates this back as heat. Temperature falls with altitude due to the increased distance from the earth’s surface – which is acting as a source of heat.

Altitude – Reasons for variance 2 The atmosphere consists of water vapour and other gases which absorb heat from the Sun. Due to the force of gravity, there is a higher concentration of atmospheric molecules at or near sea level hence most of the Sun’s heat is absorbed at that level. In addition, the same atmospheric molecules are warmed by heat radiated from the Earth’s surface hence temperature is higher at the lower altitudes.

Factors affecting Temperature Temperature varies across the world because of the variations in the following factors: Latitude Altitude Distance from the sea Cloud cover Winds and ocean currents

Distance from the sea This refers to how far away from a large body of water an area is located. Land and water react differently to solar heating which in turn exerts a strong influence on the atmosphere. Seas and oceans take a longer time to heat up, but once heated up will retain heat longer. Land, on the other hand, heats up very quickly and loses heat quickly.

Distance from the sea Interiors will be hotter in the summer and colder in winter than maritime regions at the same latitude. The ocean significantly moderates the temperatures of the coastal (maritime) regions of a continent. The ocean will have a cooling effect in summer and a warming effect in winter.  These areas tend to have smaller annual temperature ranges. Places inland are generally warmer in summer and cooler in winter. These areas tend to have larger annual temperature ranges.

Reason for variance Maritime effect: the effect that oceans have on the climate of coastal areas. During summer, the air over the sea is cooler than the air over the land as land heats up quickly while the sea heats up slowly. The cooler air over the sea helps lower the temperature of coastal areas, leading to cool summers. During winter, the air over the sea remains warmer than the air over the land as the sea cools more slowly than the land, leading to warmer winters.

Reason for variance Continental effect: the effect that continental areas have on the climate of inland areas far away from the sea. During summer, the air over the land heats up quickly leading to warmer summers. During winter the air over the land loses heat quickly leading to colder winters..

Factors affecting Temperature Temperature varies across the world because of the variations in the following factors: Latitude Altitude Distance from the sea Cloud cover Winds and ocean currents

Cloud Cover – the effect This refers to the amount of clouds over an area. Clouds influence the amount of solar radiation entering / leaving an area. The presence or absence of cloud cover affects how high temperatures may reach during the day and night. In this way it will also affect diurnal temperature range.

Cloud Cover – the effect 1 Temperatures are higher on days where clouds are absent. The absence of clouds allows large amounts of the sun’s energy to reach the Earth. This heats up the Earth’s surface which in turn heats the air near the Earth’s surface. Temperatures are lower on nights where clouds are absent. The absence of clouds allows more of the heat radiated from the earth’s surface to escape into space. This causes temperatures to fall at night.

Cloud Cover – the effect 2 Temperatures are lower on cloudy days. Clouds reflect a large portion of the sun’s energy (solar radiation) back to space. Temperatures are higher on cloudy nights. Clouds absorb more of the heat that is radiated from the Earth’s surface and prevent it from escaping into space. This allows nighttime temperatures to remain high.

Cloud Cover – the effect 3 Places with no cloud cover Places with dense cloud cover Desert areas have little to no cloud cover, due to low humidity in the air. The land gets very hot during the day and very cool at night. Such areas experience a larger difference between daytime and nighttime temperatures. Tropical areas have dense cloud cover, due to high humidity. Clouds absorb heat radiated from the Earth’s surface during the day and night. They will experience a smaller difference between daytime and nighttime temperatures. Cloud Cover – the effect 3

Factors affecting Temperature Temperature varies across the world because of the variations in the following factors: Latitude Altitude Distance from the sea Cloud cover Winds and ocean currents

Winds and ocean currents The general circulation of the ocean is a significant mechanism of global heat transfer. Ocean currents are able to transfer heat from warm (low) latitudes to cooler (higher) ones. Winds blowing over these currents in turn transfer the heat (or cold) to the adjacent coastal regions. Major surface ocean currents move warm water from the equatorial regions toward the poles, and bring cool water from the poles back toward the equator. In each of the main ocean basins, warm water is moving toward the poles off the east coasts of continents (making adjacent land warmer) while cool water is moving toward the equator off the west coasts of continents (making adjacent land cooler).

Winds and ocean currents The west coast of Britain is kept warmer in winter than other places in similar latitudes by one such current of warm water, the North Atlantic Drift (also known as the Gulf Stream).  Durban and Port Nolloth are both found at 30°S and at sea level, but have very different climates. Durban’s temperatures are consistently warmer than Port Noloth’s. This is due to the warm Mozambique current flowing South past Durban and the cool Benguela current flowing north past Port Nolloth. These currents act to regulate the temperatures of the places found near them.   Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr Durban (°C) 24.3 24.5 23.7 21.9 19.5 17.5 17.2 18.2 19.4 20.5 23.3 21.0 Port Nolloth(°C) 16.3 16.5 16.0 15.2 14.5 14.2 13.1 12.9 13.3 14.1 16.1 14.8

Hopedale, Newfoundland and Labrador The Gulf Stream Hopedale, Newfoundland and Labrador Latitude = 55.45o N Avg. Temp. = -2.0o C Stornoway, Scotland Latitude = 58.22o N Avg. Temp. = 9.4o C