Weather Studies

Question 1

What is the difference between weather and climate?

Answer 1

1.
Time:

Weather —> shorter duration e.g hours

Climate —> longer duration
Minimum:30 years
For e.g. Indic’s tropical monsoon climate

2.
Space:
Weather: applicable to smaller area (small island) micro climate—> has variation of temp in different parts

Climate:
Can apply to larger area and smaller area e.g. like between latitude 30 degrees north and altitude 30 degrees south has a certain climate e.g. regions continent

3.
Weather: weather conditions in the atmosphere
Climate: average weather conditions

To put it simply, climate is what you expect weather is what you get.

Question 2

What is atmosphere?

Answer 2

Atmosphere is the layer of gas around earth.
Consisting of gases, water vapour and dust particles.

5 layers (increasingly further from the earth’s surface)
- Troposphere (you only need to know this)
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere

Each layer has different characteristics, and is separated from each other by transition boundaries.

Question 3

What is the most important layer that you should know? Provide more details of what you know about troposphere.

Answer 3

Troposphere. (The lowest layer of Earth’s atmosphere)

Lowest layer — closest to earth surface
0 - 11km
Contains more than 50% of the earth’s atmosphere —> greatest concentration of gases, water vapour and dust particles
Conditions in troposphere result in changes in our weather

Question 4

What are the conditions of the atmosphere/ weather elements to study?

Answer 4

(Relative) Rainfall
Wind
(Relative) humidity
Temperature
(Air) pressure

Question 5

Why does air temp vary across Earth’s surface?

Answer 5

Air temp vary across Earth’s surface due to factors of latitude and altitude.

Question 6

What is the formula of mean annual temperature and annual temperature range?

Answer 6

Formula of mean annual temperature:
Sum (12 mean monthly temperatures of a year)/12

Formula of annual temperature range:
Highest monthly mean- lowest monthly mean (one number)
For e.g.
Working: 27-10 =17 17 degrees celcius (17 degrees celcius is the annual temperature range)

Question 7

What is the definition of mean annual temperature?

Answer 7

Average of mean monthly temperatures of the 12 months in a particular year.

Question 8

What is the definition of annual temperature range?

Answer 8

Difference between the mean monthly temperature of the warmest month and that of the coolest month in a particular year.

Question 9

How does latitude cause a variation of air temperatures across Earth’s surfaces?

Answer 9

The spherical shape of the Earth—> unequal distribution of solar energy over the Earth’s surface

The sun’s rays strike different parts of the Earth’s surface at different angles. The angle at which the sun’s rays strikes the Earth’s surface is called the angle of incidence.

For higher latitudes (smaller angle of incidence): (places further N/S of the equator)
Temperatures are lower at higher latitudes because the angle of incidence is smaller, which means that the sun’s rays strike at a slanted/smaller/oblique angle and the solar energy is spread out over a larger area, and hence heat is more dispersed/less concentrated.

The sun’s rays pass through a longer distance through the atmosphere, causing more solar energy to be lost by reflection, scattering and absorption by dust particles and water in the atmosphere and resulting in lower temperatures.

E.g. Vladivostok (Russia)

For lower latitudes: (larger angle of incidence (90 degrees) (places at/near the equator)
Temperatures are higher at lower latitudes because angle of incidence is large as they receive sun’s rays which are vertical, striking at a right angle. The solar energy is hence more concentrated over a smaller area.

The sun’s rays and solar radiation also pass through a shorter distance through the atmosphere, causing lesser solar energy to be lost by reflection, scattering and absorption by dust particles and water in the atmosphere and resulting in more heating over a smaller area.

With more intense heating over a smaller area, it results in higher temperature in general and higher solar energy absorbed by equator.

E.g. Singapore latitude (1.3 degrees N)

In Summary

higher latitudes —> smaller angle of incidence is—> lower concentration of solar energy —> hence, lower temperatures

Lower latitudes —> larger angle of incidence is—> higher concentration of solar energy —> higher temperatures,

Question 10

How does altitude cause a variation of air temperatures across Earth’s surfaces?

Answer 10

Higher altitude
- lower air density (air becomes less dense due to weaker gravitational force)
- weaker gravitational force
- less air molecules
- lower ability to absorb and radiate heat
- Air also contains less dust and water vapour —> less heat is trapped
- heat from the earth’s surface at higher altitude escapes more rapidly because rarefied air contains little dust and water vapour
- lower temp at higher altitudes

Low pressure causes rarefied air

At lower altitudes:
- Air becomes more dense due to stronger gravitational force–> more air molecules–> higher ability to absorb & radiate heat
- air also contains more dust and water vapour–> more heat is trapped
- heat from the earth’s surface at lower altitude does not escape as easily (heat energy escapes more slowly because dense air contains more dust and water vapour)
Hence, higher temp at lower altitudes.

Don’t repeat the ans twice if it is a comparison question. just use comparative words e.g. “er” lower, higher.

Higher pressure causes dense air

Question 11

For every 1000m increase in height, there will be a _______.

Answer 11

For every 1000m increase in height, there will be a drop of 6.5 degrees celcius.

Question 12

What is the position of earth in relation to the sun, the solar radiation and the temperature during day time of the day?

Answer 12

Position of earth in relation to the sun
- earth is facing towards the sun.

During midday:
- The sun is directly above the earth’s surface.

before and after midday:
- the sun is not directly overhead

Solar radiation and
Due to earth’s spherical shape,

During midday:
Temperature is highest in the day because at lower latitudes, the earth receives sun’s rays which are vertical, strikes at a right angle, so the angle of incidence is at a right angle. The solar energy and radiation is hence concentrated over a smaller area. Solar radiation is spreads order a smaller area and hence is more concentrated.—> add in angle of incidence

Before and after midday:
Solar radiation is spreaded over a larger area and hence is less concentrated.

Temperature:
Midday:
Temperature is highest in the day.

Before and after midday:
The temperature is lower than midday.

Question 13

What is the position of earth in relation to the sun, the solar radiation and the temperature during night time of the day?

Answer 13

Position of earth in relation to the sun
- Earth is facing away from the sun.

Solar radiation
- It does not receive Solar radiation and loses heat in the form of long wave radiation.

temperature:
Hence it experiences lower temperature. The temperature is lowest just before sunrise as the place has lost heat for the longest period of time.

Question 14

What happens in the NH during the march Equinox (~21 March)?

Answer 14

Sun overhead: equator
Solar radiation: increasing in NH (moderate)
Season: Spring begins.
Day/night ~ 12 hours each
Temp trend: gradual warming

Question 14

What happens in the NH during the June Solstice (~21 June)?

Answer 14

Leans more towards the sun, hence will receive more direct solar radiation and will experience higher temperatures.

Sun overhead: Tropic of Cancer (23.5 degrees N).
Solar radiation: peak intensity in NH.
Season: summer begins
Day/night: longest day, shortest night.
Temperature trend: hottest in July (lag)

Question 15

What happens in the NH during the September Equinox (~23 Sept)?

Answer 15

Sun overhead: equator.
Solar radiation: decreasing in NH (moderate).
Season: Autumn begins.
Day/night: ~ 12 hours each (slightly longer night).
Temperature trend: Gradual cooling.

Question 16

What happens in the NH during the December solstice (~21 Dec)?

Answer 16

Leans away from the sun, hence will receive less direct solar radiation and will experience lower temperatures.

Sun overhead: Tropic of Capricorn (23.5 degrees S)
Solar radiation: Lowest intensity in NH.
Season: Winter begins.
Day/night: Shortest day, longest night.
Temperature trend: Coldest in January (lag)

Question 17

How does solar radiation differ between the March Equinox and June Solstice in the NH?

Answer 17

March Equinox: Moderate, increasing.
June Solstice: Peak intensity.
Reason: Sun moves from equator to Tropic of Cancer.

Question 18

Why does the SH experience winter during the NH’s June Solstice?

Answer 18

Solar radiation: SH receives least radiation (Sun overhead at Tropic of Cancer → NH).
Day length: Shortest days in SH.
Season: SH winter.

Question 19

Why is July hotter than June in the NH despite the June Solstice having peak sunlight?

Answer 19

Thermal inertia: Land/oceans take weeks to absorb heat.
Solar radiation accumulation: Continues warming after solstice.

Question 20

Why doesn’t Singapore experience four seasons?

Answer 20

• Singapore is located within the tropics (Equatorial zone)
• Very close to equator
• Receives direct sunlight/ solar radiation throughout the year
• Hence, experience high temperatures throughout the year
• resulting in small temp variations

Question 21

What other factors can cause temperature variations in a day? Hint: Singapore vs Sahara Desert

Answer 21

Cloud cover

Question 21

What is the definition of cloud cover?

Answer 21

Cloud cover is the extent of the sky that is covered by clouds.

Question 22

Explain the purpose of clouds.

Answer 22

Clouds
- act as a “blanket”
- reduce amount of solar radiation that reaches the earth’s surface (incoming) &
- reduce re-radiation that leaves the earth’s surface (outgoing)
- result —> small diurnal range of temperature

Question 23

Explain the effects of clouds cover in tropical/equatorial areas

Answer 23

Day —> dense cloud cover—> reflects a large amount of sun’s energy back to space —-> less short wave radiation —> earth’s surface kept cooler —> lower day temperatures Night —> thick clouds prevent rapid loss of heat from the earth’s surface —> therefore, night temperatures do not fall too much On top of that, high humidity also helps trap heat—water vapour is a greenhouse gas, meaning it absorbs and re-radiates heat back to Earth. So, both clouds and humidity work together to keep nighttime temperatures from falling too much. Result —> Diurnal temperature range for tropical equatorial regions, such as Singapore is small. other than that in tropical/equatorial areas, there is also high humidity, it means there’s lots of moisture in the air. Moist air heats up more slowly than dry air, because energy is used to evaporate water (latent heat). So, high humidity + cloud cover = reduced heating during the day. Therefore Water vapour (from high humidity) also acts as a greenhouse gas, slowing both daytime heating and nighttime cooling. As a result, the diurnal temperature range remains small. At the same time, high humidity

Question 24

Explain the effects of cloud cover in desert areas.

Answer 24

Day —> little or no cloud cover due to relative absence of water —> sun’s energy reaches earth’s surface easily —> hence, there is maximum solar heating of the earth’s surface in the day—> high day temperatures (more than 40 degrees celcius) ➡️ Low humidity makes it worse: Deserts have very little water vapour in the air. Since water vapour helps absorb and hold heat, its absence means more heat goes directly to the surface, not the air. This causes the ground to heat up quickly, but the air remains relatively dry and thin. Night—> the little/no cloud cover allows rapid loss of heat from the earth’s surface by radiation from the heated land surface —> night temperatures can fall to 21 degrees celcius or below There's nothing in the sky to trap this outgoing heat, so temperatures drop quickly. Because deserts also have very low humidity, there’s almost no water vapour to help trap and re-radiate heat back to the surface. Result —> diurnal temperature range for desert regions, such as Sahara Desert is larger.

Question 25

What is the definition of relative humidity?

Answer 25

Ratio of the actual amount of water in the air compared to the maximum amount of water vapour that a volume of air can hold at a given temperature. - expressed in %

Question 26

What is the formula of relative humidity?

Answer 26

Calculating relative humidity = (Actual amount of water vapour in the air (g/m to the power of 3)/ max amount that the air can hold (g/m to the power of 3) x 100%

Question 27

What is the definition of absolute humidity?

Answer 27

- how many grams of water vapour in the air —> current water vapour - amount of water vapour present in a given volume of air at a certain temperature - expressed in g/m to the power of 3

Question 28

Air at room temperature can contain _________ as much water at 0 degrees.

Answer 28

3 times

Question 29

What is the definition of humidity?

Answer 29

- Amount of water vapour present in a particular parcel/volume of air - From evaporation and transpiration - Amount of water vapour in the air varies over space and time

Question 30

What are the two types of humidity?

Answer 30

- Absolute humidity - Relative humidity

Question 31

At higher temperatures, what happens to the warm parcel of air?

Answer 31

Expansion of warm air: - reduced density (packing of molecules) Able to hold greater amount of water vapour I.e. capacity is higher Rate of evaporation increases: greater amount of water vapour in the air Amount of water vapour may remain unchanged Thus, R.H. Is lower

Question 32

At lower temperatures, what happens to the colder parcel of air?

Answer 32

Contraction of colder air: - increased air density Reduced capacity for water vapour Rate of evaporation decreases: lesser amount of water vapour in the air

Question 33

What is the definition of saturation point?

Answer 33

Saturation point: amount of water vapour present in a parcel of air is equal to the maximum amount of water vapour that the air can hold

Question 34

What is the definition of dew point temperature?

Answer 34

Temperature at which the saturation point is reached.

Question 35

What happens if saturated air continues to be cooled?

Answer 35

When RH = 100% —> air can no longer hold any more water vapour, as it is saturated Hence, condensation takes place to remove the excess water vapour At this temperature (dew point temperature), air condenses into water droplets on condensation nuclei, forming precipitation - Condensation nuclei (e.g. dust and ash particles from volcanoes) provide surfaces where water vapour can change into water droplets or solid ice crystals and form clouds.

Question 36

What is the definition of condensation nuclei?

Answer 36

- Condensation nuclei (e.g. dust and ash particles from volcanoes) provide surfaces where water vapour can change into water droplets or solid ice crystals and form clouds.

Question 37

Describe the formation of precipitation.

Answer 37

Essentially: upward movement of air, resulting in condensation of water vapour Moist air rises —> however, air cools as it rises —> hence, amount of moisture the air can hold decreases - Leads to condensation of water droplets - Water droplets are kept aloft by updrafts of wind, and continue to rise and collide with other water droplets, forming larger droplets - Eventually fall as precipitation, when the gravitational force on the large droplets exceeds the strength of the updraft

Question 38

What is precipitation?

Answer 38

Solid or liquid water that falls from clouds to reach the Earth’s land or sea surface.

Question 39

What are the two main ways/types of precipitation?

Answer 39

- Convectional - Relief/ orographic

Question 40

How is convectional rain formed?

Answer 40

Moist air is heated up —> results in lower density —> ultimately, moist warm air rises, however, air cools as it rises, hence amount of moisture air can hold decreases —> leads to condensation of water droplets are kept—> continues to rise and collides with larger droplets —> therefore forms larger droplets —> eventually falls as precipitation

Question 41

Describe the characteristics of convectional rain.

Answer 41

- Can take the form of light drizzles/showers, or thunderstorms Duration: - short - usually an hour or less - usually in the later afternoons Location: - localised, covering a few km square - tropical areas

Question 42

Describe the characteristics of orographic rain.

Answer 42

Common in areas with mountain ranges - not intense all the time - longer - not only in the late afternoon

Question 43

How is relief rainfall formed?

Answer 43

Moisture laden air (near-saturated warm maritime air) blows across/off the sea with the prevailing wind * Air is forced to rise rapidly where confronted by a coastal mountain barrier * Air cools at higher altitudes → relative humidity increases → reduces water holding capacity * Dew point temperature (saturation point) reached → water vapour condenses to form water droplets (clouds) Moist rain falls on the windward side of the mountain when water droplets get heavy Leeward side —> dry air descends and becomes compressed and warmed —> relative humidity decreases —> able to hold more moisture/water —> condensation ceases X Creates a rain-shadow effect where little rain falls Moist air is lifted up due to mountainous barrier —> results in lower air temperatures however amount of moisture air can hold decreases leads to condensation of water droplets —> therefore, falls as precipitation on the windward side of the relief but leeward side often in a dry rain shadow.

Question 44

With reference to Figure 1, Mount K is located near the coast. At the base of the mountain (sea level), the temperature is 30 degrees celcius and the relative humidity is 70 degrees celcius. As moist air from the sea is forced up the mountain slope, it cools. Explain how the relative humidity of the air changes as it rises up the mountain.

Answer 44

As the air rises up the mountain slope, it cools because the temperature drops with altitude. Cooler air cannot hold as much water vapour so the relative humidity increases. If cooling continues, the air eventually becomes saturated (relative humidity reaches 100%)

Question 45

With reference to Figure 1, Mount K is located near the coast. At the base of the mountain (sea level), the temperature is 30 degrees celcius and the relative humidity is 70 degrees celcius. As moist air from the sea is forced up the mountain slope, it cools. (Bi) At a certain height, clouds start to form. Using your knowledge of temperature and relative humidity, explain why cloud formation begins at this point. B(ii) Describe how this process contributes to rainfall on the windward side of the mountain. B (iii) What do you think will happen on the leeward side of the mountain? Why?

Answer 45

(Bi) Cloud formation begins when the rising s air cools to its dew point temperature, and the relative humidity reaches 100%. At this point, the air becomes saturated, and excess water vapour condenses into tiny water droplets, forming clouds. This usually happens at higher altitudes on the windward side of the mountain. (Bii) As condensation continues in the saturated air, water droplets grow and combine, eventually becoming heavy enough to fall as rain. This rainfall mainly occurs on the windward side. B (iii) After it rained, the moisture is “gone” —> air will still be present and go to the dry leeward slope —> the cold dry air will contract and since it is denser, it will start to sink. Nothing pushes the parcel of cold air up and it gets heated up by the ground, therefore becoming warm.

Question 46

On a typical afternoon in City J, which is located near the equator, the ground heats up quickly under the intense sun. the temperature rises form 26 degrees celcius in the morning to 34 degrees celcius by midday. Throughout the morning, moisture evaporates from nearby vegetation and water bodies. (A) Explain how the rising temperature affects the relative humidity of the air during the morning.

Answer 46

As the temperature increases from 26 degrees celcius to 34 degrees celcius, the air’s capacity to hold water vapour also increases. If the actual amount of water vapour stays the same, the relative humidity decreases. However, with high rates of evaporation from vegetation and water bodies, the air may still reach saturation by midday (12 noon). This prepares the conditions for condensation and cloud formation in the afternoon.

Question 47

On a typical afternoon in City J, which is located near the equator, the ground heats up quickly under the intense sun. the temperature rises form 26 degrees celcius in the morning to 34 degrees celcius by midday. Throughout the morning, moisture evaporates from nearby vegetation and water bodies. (b) By early afternoon, large cumulus clouds begin to form. Using your understanding of temperature and relative humidity, explains why this happens.

Answer 47

In the afternoon, the air near the surface becomes very warm. This warm, moist air becomes less dense and rises quickly through convection. As it rises, the air expands rises and cools. Once it cools to its dew point, the water vapour condenses to form cumulus clouds. The continued upward movement of air and condensation results in tall clouds and eventually leads to rainfall.

Question 48

On a typical afternoon in City J, which is located near the equator, the ground heats up quickly under the intense sun. the temperature rises form 26 degrees celcius in the morning to 34 degrees celcius by midday. Throughout the morning, moisture evaporates from nearby vegetation and water bodies. (c) Why is convectional rainfall common in equatorial regions like City J?

Answer 48

This type of rainfall is called convectional rain because it is caused by the upward movement of warm, moist air due to surface heating.

Question 49

What are the two characteristics of convectional rain?

Answer 49

1. It usually occurs in the late afternoon when surface temperatures are highest. 2. The rainfall is intense and short-lived, often accompanied by thunder and lightning.

Question 50

What are the characteristics of relief rain?

Answer 50

- not intense all the time - longer - not only in the late afternoon

Question 51

What conditions must be present for rain to form?

Answer 51

A. Air must be cooled to dew point temperature. R.H (relative humidity) reaches saturation point (100%) so that on further cooling, condensation may occur B. Presence of water vapour in the air/ sufficient moisture C. Presence of condensation nuclei —>for water vapour to condense on D. Air must be warm enough to rise Remember cold air sinks, hot air rises

Question 52

What are the similarities of the 2 types of precipitation?

Answer 52

Similarities - process of cloud formation - rising of parcel of air Similar in formation - both result in rainfall: Both processes lead to the formation of clouds and subsequent precipitation in the form of rain, sometimes heavy. —> reach saturation point , RH —> 100%. + condensation nuclei —> condensation Rising of parcel of air and condensation - both involve lifting of air: Both relief and convectional rainfall require air to rise to a sufficient altitude for cooling and condensation to occur.

Question 53

What are the differences between the two types of precipitation?

Answer 53

1. Cause of air lifting Relief rain: - relief rain is caused by air being forced to rise over mountains Convectional rain: Convectional rain i caused by heating of the surface and rising of warm air 2. Spatial distribution/location Relief rain - relief rain is localised and associated with mountainous areas Convectional rain - convectional rain can occur more widely, especially in tropical regions and during the summer months in temperate regions (summer) 3. Duration and intensity Relief rain - relief rain may be more sustained and less intense ( generally) —> it may be more intense for certain areas. Since this is more localised, it can vary from places to places. Convectional rain: - tends to be short-lived and intense.

Question 54

What is the earth’s energy budget?

Answer 54

*****Slide for factors affecting temperature - Latitude, Altitude Refers to the balance between the radiant energy that reaches Earth from the sun and the energy that flows from Earth back out to space Vital in establishing the Earth’s climate When the energy budget balances, Earth’s temperature stays relatively constant, with no overall increase or decrease in average temperature.

Question 55

Describe and explain the heat balance of earth.

Answer 55

- The sun is the prime source of energy to all living systems on the earth. - Received in the form of shortwave radiation (insolation) - 55% reflected and scattered back to space (clouds, air molecules, gases, water vapour, dust particles) - 45% absorbed by ground —> warm ground radiates energy back to space in the form of long-wave terrestrial radiation —> absorbed by water vapour, CO2 as it goes through atmosphere - incoming solar radiation and outgoing terrestrial radiation —> determines the amount of energy (solar insolation)

Question 56

What are the six types of formula that is used to measure temperature?

Answer 56

Mean annual temperature Annual temperature range Mean monthly temperature Mean daily temperature Mean daily temperature (I don’t know why it is the same, need to ask Mrs Chee) Diurnal temperature range

Question 57

What is mean monthly temperature and what is the formula of it?

Answer 57

Average of the average daily temperature of the days of a particular month in a year = sum (average daily temperatures for the month)/ number of days in the month

Question 58

What is the meaning of diurnal temperature range and what is the formula?

Answer 58

Difference between the max and min temperature for any given day Max daily temp - min daily temp

Question 59

What is the meaning of altitude?

Answer 59

Altitude: the height of a place in relation to sea level (0m)

Question 60

How does air temperature vary within a day?

Answer 60

Due to Earth’s rotation on its own axis One complete rotation around the axis - 24h As earth rotates, the side facing the sun receiving solar radiation, experiences higher temps - DAY The side facing away from sun, does not receive solar radiation, experiences lower temps - NIGHT

Question 61

How does air temperature vary within a year?

Answer 61

Due to Earth’s revolution around the sun Earth’s axis tilted at 23.5 degrees As Earth revolves around the sun, the 2 hemispheres will experience different amounts of solar radiation at different times of the year

Question 62

What happens in the SH during the June Solstice (~21 June)?

Answer 62

Leans away from the sun, hence will receive less direct solar radiation and will experience lower temperatures.

Question 63

What happens in the SH during the December solstice (~21 Dec)?

Answer 63

leans more towards the sun, hence will receive more direct solar radiation and will experience higher temperatures.

Question 64

What happens in March and September?

Answer 64

Neither hemisphere leans towards the sun As a result, both experience moderate temperatures Northern hemisphere - spring in March and autumn in September South hemisphere - autumn in March and spring in September

Question 65

What is air pressure?

Answer 65

The weight of the air exerting a pressure on all objects on Earth at about 1.03 kg per cm square.

Question 66

What is the units of air pressure?

Answer 66

Measured in millibars (mb)

Question 67

What is the sea level pressure?

Answer 67

1013 mb

Question 68

Write a statement and an explanation to reflect the relationship between air pressure and altitude.

Answer 68

Statement: Air pressure generally decreases as altitude increases. Explanation: - there is less air above you (air becomes less dense) at higher altitude —> more space apart—> less dense - resulting in less weight pressing down and less pressure

Question 69

Write a statement and an explanation to reflect the relationship between air pressure and temperature.

Answer 69

1. Statement: Air pressure decreases as temperature increases (determining factor) Explanation: - Air warms and expands - Air molecules move further apart - Less air molecules in the same amount of space - Less weight exerted - Lower air pressure Statement: 2. Air pressure increases as temperature decreases (determining factor) Explanation: - Air cools and contracts - air molecules move closer together - more air molecules packed in the same amount of space - more weight exerted - higher air pressure