SASS EGeog Weather & Climate Gateway 1

SASS Geography Notes Variable Weather and Changing Climate 1 Geography Variable Weather and Changing Climate Gateway 1: Why do different places experience different weather and climate? A. What is the difference between weather and climate? B. What are the elements of weather? C. What are the climatic types and where are they experienced? A. What is the difference between weather and climate? Weather is the condition of atmosphere at a particular place and particular time. Climate is the average condition of the atmosphere of a particular place over a long period of time, usually 30 years. B. What are the elements of weather? The elements are: 1. Temperature, 2. Relative humidity, 3. Clouds, 4. Rainfall, 5. Air pressure 6. Wind. 1. Temperature - The degree of hotness or coldness of a place in the atmosphere (temperature of the air) - Can be measured in oC (Celsius) or oF (Fahrenheit) - Air is warmed by means of radiation, conduction and convection

SASS Geography Notes Variable Weather and Changing Climate 2 Therefore, the nearer the Equator, the higher the temperatures. The further from the Equator, the lower the temperatures. The South Pole is completely shielded from the sun’s rays and experiences months of darkness without sunlight. As the solar angle is high at the area between the Tropic of Cancer and the Equator, heat from the sun is concentrated on a small area. Temperatures are higher at lower latitudes such as the tropics, which is located between 23.5°N and S of the Equator Temperatures are lower at higher latitudes because the solar angle is lower, which means that rays strike at a lower angle and the solar energy is spread out over a wider area. During summer in the northern hemisphere, the North Pole is completely exposed to the sun’s ray due to the tilt of the earth. This results in the North Pole experiencing months of sunlight. Factors influencing temperature at different locations are 1.1. Latitude – the most important factor affecting temperature 1.2. Altitude – affects temperature of highland 1.3. Distance from the sea – summer temp, winter temp. Overall annual temperature range 1.4. Cloud cover – diurnal temperature range • Latitiude: Distance of any point on the earth measured north or south from the Equator. • Imaginary horizontal lines east to west of Equator. • Equator is at a latitude of 0° ➢ North Pole is 90°N. ➢ South Pole is 90°S. • For example: ➢ Singapore at 1°N experiences summer whole year round with temperature between 23 to 34°C and a temperature range of 11 °C while North pole at 90°N experiences long and cold winters, short and cool summers with temperature between -40 to 10°C and a temperature range of 50 °C *Latitude is the most important factor affecting temperature!* • Altitude: the height of a place in relation to sea level. • There is a general decrease of 6.5°C for every 1,000 m increase in altitude. This is known as the normal lapse rate. • Distance From Surface To Earth: - Places at low altitude (near the sea level) are warmer because the Earth’s surface is heated by short wave radiation from the Sun directly. - Longwave radiation is heat emitted by the earth after absorbing shortwave radiation from the sun - Most heat absorbed by the earth at lower altitudes while at high altitudes there is less heat being absorbed resulting in lower temperature. • Density Of Air: - Air at high altitudes is thin and is unable to absorb heat as effectively as dense air because it has smaller concentration of gases to trap heat.

SASS Geography Notes Variable Weather and Changing Climate 3 • Distance From The Sea: • Sea heats up and loses heat more slowly than land thus it has a moderating influence on the temperatures of coastal areas. • Distance from sea affects the temperature for both coastal and inland areas: • Coastal areas in temperate areas (maritime climate) • Inland areas far away from the sea (continental climate) Maritime Effect Continental Effect Is the effect of large ocean bodies on climate of coastal areas. is the effect of huge land surfaces have on climate of inland areas. Areas near the coast experience cool summers and warm winters due to the moderating effect of the sea. Land heats up faster and loses heat faster, thus inland areas experience hot summers and cold winters Thus, coastal areas have a smaller annual temperature range. Thus, inland areas have a larger annual temperature range. LOCATION LATITUDE DISTANCE FROM SEA TEMPERATURE RANGE ANCHORAGE 61.2° N 1 KM 20°C FAIRBANKS 64.8° N 420KM 40°C

SASS Geography Notes Variable Weather and Changing Climate 4 • Cloud Cover: is the extent of sky covered by clouds • A thick cloud cover reflects some of the sun’s solar radiation in the day • At night, the clouds prevent much of the outgoing terrestrial radiation from escaping back to space • Equatorial areas with high temperature/rainfall and thick cloud cover have a small diurnal (daily) range of 100C of less In the day: Cooler • sun gives out shortwave radiation • clouds reflect most of sun’s shortwave radiation back to space. At night: Warmer • land give out longwave radiation • clouds prevent the longwave radiation from escaping into space. Thus, areas with cloud cover experience a smaller daily temperature as it has cooler days and warmer nights. In the day: Warmer • without the presence of clouds, large amount of sun’s shortwave radiation reaches earth’s surface At night: Cooler • the absence of clouds, allows more heat radiated from ground to escape into space. Thus, areas without cloud cover experience a larger daily temperature as it has warmer days and cooler nights. 2. Relative Humidity • Ratio (usually expressed in percentage) between the actual amount of water vapour present in a mass of air and the maximum amount of water vapour the air can hold at a given temperature • For example: o At 15°C, can contain a maximum of 10 g/m3 of water vapour. However, the amount of water vapour in the air is only 5 g/m3. This means that the relative humidity is at 50%. o If water vapour in the air holds increases to 6 g/m3, relative humidity will increase to 60 percent instead. • The effect of temperature on relative humidity o At higher temperatures, the air will be able to hold more water vapour. o As air molecules are more spread out, more water vapour can fill the spaces. o Therefore, assuming the actual water vapour in air is constant, relative humidity is lower at higher temperatures and higher at lower temperatures. o For example: • At 15°C, the amount of water vapour in the air is 5 g/m 3. This means that the relative humidity is at 50%. • If the temperature increases to 18°C, the capacity of water vapour it can hold will increase. Thus, the maximum increases to 15 g/m3 of water vapour. So, if water vapour in the air is still 5 g/m3, relative humidity will decrease to 33.3 percent instead.

SASS Geography Notes Variable Weather and Changing Climate 5 3. Clouds • Clouds are visible masses of water droplets or ice crystals that are suspended in the atmosphere from the condensation of water vapour, which may eventually grow large enough to fall to the earth’s surface as precipitation. • Evaporation is a process in which liquid water is converted to water vapour, whole condensation is process in which water vapour changes to a liquid form by cooling. • When relative humidity is at 100% (saturation) and more evaporation continues to takes place as a results, clouds will be formed when dew point temperature is reached. • This happens when condensation takes place if there are tiny particles (condensation nuclei), such as dust, for the water vapour to condense on. • The water droplets in the air will merge and become larger in a process called coalescence, forming clouds