Chapter 6 - Atmospheric Conditions Flashcards
What are high pressure systems called?
Anticyclones
Weather forecasts
Global patterns of weather
What are the three kinds of barometer?
Mercury
Aneroid
Barograph
How does a maximum thermometer work?
○Measures highest temperature for the day
○Contains mercury which rises up the tube as the temperature increases
○Pushes pin in tube upwards
○Pin stays at highest point reached that day
__% of solar radiation directly heats the earth
50% of solar radiation directly heats the earth
Isotherm
Line on a weather map joining places of equal temperature
How does a Campbell-Stokes sunshine recorder work?
►Glass sphere
►Focuses sun’s rays onto a sensitive strip of paper slotted into a semi-circular frame behind the ball
►Sun’s rays scorch the paper
►As the earth spins, the position of the sun changes -> burn mark moves along the paper
►Scorch indicates duration and times of sunshine for day
How does a thermometer work?
►Glass rod with thin tube
►Liquid supplied from bulb - mercury or alcohol
►Temperature of liquid in bulb increases and it expands
►Rises up tube
►Fall in temperature causes liquid to contract and fall
►Tube marked with a scale in ºC
How does a wind vane work?
►Horizontal arm at one end and a tail at the other -> tail larger than arrow
►Wind blows tail around and points arrow to the direction from which the wind id blowing
How is a warm front formed? What weather occurs because of it?
○When a warm air mass moves into a cold air mass
○Because the warm air is less dense,it slides up over the colder air
○First cumulus clouds may appear; characterised by several days of rain
○May be followed by stratus clouds and some precipitation
What are the weather characteristics?
Temperature Humidity Atmospheric pressure Precipitation Wind direction and speed Sunshine Cloud amounts
Weather
The day-to-day condition of the atmosphere
Describe the characteristics of tropical continental air masses
○From Sahara
○Bring dry, sunny weather
Describe winter in terms of its relation to the tilt of the earth’s axis
○Northern hemisphere tilts away
○Days are short and temperatures are low as it receives the less solar radiation
○Sun located over Tropic of Capricorn
Describe summer in terms of its relation to the tilt of the earth’s axis
○Northern hemisphere tilted towards the sun
○Long days, receive the most solar radiation
○Sun located over the Tropic of Cancer
Solar radiation is transmitted in…
…rays, waves or particles
What is the Beaufort scale?
○Measures wind force
○Shows force of wind and resulting damage caused
○Recorded on a scale of 0-12
Describe the characteristics of polar maritime air masses
○From northeast Atlantic
○Bring cold, wet air and showers
What weather is associated with anticyclones?
○Clear cloudless skies
○Calm
○Dry
○Summer: Good weather. Hot with lots of sunshine
○Winter: Days sunny nights very cold and frosty. Clear skies allow heat to escape at night
Stevenson Screen
Meteorological screen used to shield instruments from wind, precipitation and direct heat from the sun
What weather occurs after a warm front passes?
○Sky clears, air pressure rises
○Temperatures also increase as the warm air replaces to cold air
○Air becomes warmer and more humid
Weather maps/synoptic charts
Summarise weather over a wide area using lines and symbols
Saturated
When air has absorbed as much moisture as it can
Describe how occluded fronts form and what weather is associated with them
○When cold front catches up with a warm front○Warm air is completely lifted off the ground by cold air in front and behind
○Changeable weather
Thermometer
Instrument used to measure temperature
Mean monthly temperature
Add mean daily temperatures and divide by the number of days in a month
What is the unit of measurement for humidity?
%
Doldrums
○Area of calm weather
○Area near the equator where trade winds meet and die out
○No steady surface winds
How does high pressure occur?
When Cold, heavy air sinks
Describe cumulus clouds
○Cumulus means heap ○Look like puffs of cotton in the sky ○Mid altitude below 5,000m ○Flat on bottom, lumpy tops ○Weather conditions associated: can cause heavy showers in warm weather
Altostratus
Formless grey/bluish clouds. If they darken and blot out the sun/moon, precipitation will follow
What are the characteristics of an anticyclone?
►Winds blow in a clockwise direction ►Up to 1,000 km in diameter ►Made of a single air mass i.e. no fronts ►Air descends and warms ►Very slow moving ►Isobars well spaced - calm/light winds ►Forms over land
What unit is used to measure atmospheric pressure?
millibars or hector pascals
What is the unit of measurement for rainfall?
Millimeters
When millibars are close together it indicates…
High winds
How does a barograph work?
►Instrument which connects a barometer to an inked pen resting on a chart placed on a drum which rotates
What is the importance of weather in everyday life to aviation?
Icy conditions in the atmosphere or on the ground might affect flights
What is a depression?
Area of low pressure that develops when a warm front meets a faster cold front
What is atmospheric pressure measured by?
Barometer
Describe the characteristics of Arctic air masses
○From north pole
○Bring cold weather
What is the importance of weather in everyday life to farmers?
Dry conditions are needed to harvest crops
Describe autumn in terms of its relation to the tilt of the earth’s axis
○Northern hemisphere begins to tilt away
○Days get shorter, temperatures drop
Cyclonic/frontal rainfall
○Occurs when two air masses meet, forming a front
○Occurs when lighter warm air is forced to rise over the heavier cold air
○Moisture in the warm air condenses and causes clouds and rain
○Precipitation falls over a wide area
○Fronts occur over the North Atlantic and are a reason for the changeable Irish weather
○Most common rainfall in Ireland
Isobars
Lines on a weather map showing areas of equal atmospheric pressure
What weather is associated with low pressure systems?
○Cloudy skies ○Windy conditions ○Wet weather ○Unpredictable ○Changeable
Convectional rainfall
○Caused by sun heating earth’s surface
○Warm air rises, cools and condenses to form clouds
○Found all year found in regions close to the equator (i.e the Tropics) as it is hot
○May occur in Ireland during the summer
○If the air is hot enough, it rises very quickly and thunderstorms occur
What is the unit of measurement for wind speed?
knots or km/p/h
Atmosphere
Thin layer of gases surrounding the earth
Condensation
Occurs when water vapour in the air gets cooled and condenses changing back into water droplets which then form clouds
If air masses form over arctic regions they are defined as…
arctic (A)
Meteorologist
Person who studies and predicts weather
Horse latitudes
○Areas of still, dry weather found at 30° north and south of the equator
○Tends to be weak winds○Ships tried to avoid this zone
If air masses form over polar regions they are defined as…
polar (P)
Clouds
Collection of tiny water droplets and/or ice crystals held in the atmosphere
Describe the characteristics of polar continental air masses
○From northeast Europe
○Bring dry, cold,frosty nights and snow
When millibars are further apart it indicates…
Low winds
How is a cold front formed? What weather occurs as a result of it?
○Forms where cold air mass moves into a warm air mass
○Cold air is heavier than the warm air, so cold air pushes underneath the warm air
○This forces the warm air mass upwards where it cools and condensation takes place
○Cumulus clouds develop and brief, heavy showers/thunderstorms may be found
What are cold currents?
○Flow from areas of high latitude to low latitude
○○e.g. Labrador Current
○This travels southwards along the north east coast of North America past the coasts of Greenland and Canada
○It freezes water, reduces ocean temperature and ice-bergs may be found along its route
List the different gases in the atmosphere and their percentages
78% nitrogen
21% oxygen
1% trace gases (argon, carbon dioxide, and others)
How are winds named?
Winds are named according to the direction from which they blow
What is the importance of weather in everyday life to sports?
Horse racing can be cancelled due to the ground being soaked. Outdoor sport evets are affected by weather
Temperature range
Difference between highest and lowest temperature
Dines tube
Measures direction and strength of wind
How does low pressure occur?
When warm, light air rises
Pressure
Force of air on the earth’s surface
Prevailing westerlies
○a.k.a Westerlies ○30°-60° ○Winds moving towards poles ○Curve east ○Responsible for weather movements across Europe
Briefly describe the Coriolis effect
○Global winds are deflected when the earth rotates
○The earth rotates on its axis from west to east
○Result-> winds are deflected:
-To the right of its direction of motion in the northern hemisphere
-To the left of its direction of motion in the southern hemisphere
What are the 3 zones separating the three major wind belts?
Doldrums
Horse latitudes
Polar fronts
What weather occurs after a cold front passes?
○Wind changes direction, sky clears and temperature drops
○When cold front passes through; temps can drop more than 15°C in the first hour
What is the role of clouds?
Provide precipitation
Provide shade from the sun
Keep heat in the atmosphere
How are low pressure systems represented on a weather map?
L
Air mass
A large body of air that has similar temperature, pressure and moisture levels throughout
Describe the characteristics of tropical maritime air masses
○From southwest
○Thunderstorms in summer and heavy rainfall in winter
Tropical Easterlies
○a.k.a Trade winds
○0°-30°
○Air movements towards the equator
○Curve west
What are the negative effects of ocean currents?
- Ice-bergs
- Colder winds
- Difficult sailing conditions
How is rain formed?
○Occurs when air is forced to rise ○Air cools and loses its ability to hold moisture ○Becomes 100% saturated ○Condensation occurs ○Water vapour turns back into droplets ○Fall as rain
Climate
The average weather conditions of an area, recorded over a long period of time
How does a minimum thermometer work?
○Measures lowest temperature for the day
○Contains alcohol
○As temperature drops, the pin falls
○Pin stays at the lowest point reached that day
What is the unit of measurement for temperature?
ºC
Isohels
Lines on a weather map showing equal sunshine
Hygrometer
Measures relative humidity
Altocumulus
Larger than cirrocumulus and are considered fair weather clouds, often following a storm
Wind blows from areas of _____ ________ to ____ _____
Wind blows from areas of high pressure to low pressure
Latitude
Angular distance north and south of the equator
Mean annual temperatures
Add mean monthly temperatures and divide by 12
Precipitation
Any form of moisture from the atmosphere, e.g. rain or snow
What is the unit of measurement for atmospheric pressure?
Millibars or hector pascals
What are warm currents? Give an example
○Flow from areas of low latitude to high latitude
○○e.g. Gulf Stream originates in Gulf of Mexico
○Veers northeastwards into the Atlantic
○Splits to form:-warm North Atlantic Drift-cold Canary Current
○NAD flows past the west coasts of Ireland and Scandinavia and keeps the prots ice-free
What is the importance of weather in everyday life to tourists?
Checking forecast for the destination will allow suitable clothing to be packed for the visit
If air masses form over oceans they are defined as…
maritime (m)
How does an anemometer work?
►Three cups which pivot and pivot according to the force of the wind acting upon them
►Each rotation makes an electrical contact and the number of turns is recorded
How is an anticyclone represented on a weather map?
H
Anemometer
Measures wind speed
What is the unit of measurement for sunshine?
Hours per day
Isohyets
Lines on a weather map joining places of equal rainfall
Describe cirrus clouds
○Cirrus means curl
○Wispy, high up in the sky
○Above 8,000m
○Weather conditions associated: fair weather when scattered in clear sky
Meteorology
Study of weather. Focuses on weather processes and forecasting
Cloud names with the prefix ‘-cirr’ are found at what altitudes?
Located at high altitudes from above 6,000 m
__% of salor radiation is absorbed by the atmosphere and clouds
20% of salor radiation is absorbed by the atmosphere and clouds
What is the most common type of precipitation in Ireland
Rain
How are clouds formed?
When water vapour condenses and turns back into liquid, creating water droplets
Relief rainfall
○a.k.a Orthographic rainfall
○Affected by mountains
○Occurs when warm, water bearing air is forced to rise when it reaches a mountain range
○Air is forced up over an area of high land and it cools and condenses forming clouds and rainfall
○Rain falls on the windward side of the mountain
○Air descends on the leeward slope and this region is called the rain shadow
○Experienced in the west of Ireland
Polar fronts
○Lie about 60° north and south of the equator due to tilt of the earth and angle of the sun’s rays
○Location varies with seasons-> moves south in winter and north in summer
How does a hygrometer work?
►Combination of wet and dry bulb thermometers
►Wet bulb is surrounded by piece of muslin which hangs into a container of water which keeps the thermometer moist
►When air passes over the muslin, it takes up some of the moisture. This depends on the air temperature
►If the air is not saturated, evaporation takes place. The bulb cools and the temperature drops
►The dry bulb is an ordinary thermometer measuring air temperature
►Difference in temperature between the two thermometers is used to find the relative humidity
If air masses form over tropical regions they are defined as…
tropical (T)
Temperature
Measures how hot or cold air is
What are the two main factors that affect the amount of insolation actually absorbed by the earth’s surface?
Angle of the sun’s raysContent of the atmosphere
Isobars
Lines on a weather map joining places of the same atmospheric pressure
Front
Boundary between two air masses
What is the unit of measurement for wind direction?
NSEW
What are the three wind belts?
Tropical Easterlies
Prevailing Westerlies
Polar Easterlies
Campbell-Stokes sunshine recorder
Measures sunshine
Describe stratus clouds
○Stratus means layer
○Like a blanket they stretch out across the sky and block out sun
○Low altitudes below 2,000m
○Grey layer over sky
○Weather conditions associated: overcast, steady rain
What is the importance of weather in everyday life to fishermen?
If conditions at sea are stormy, vessels might have to stay in the harbour
Equator
An imaginary line dividing the two hemispheres at 0°
How does a mercury barometer work?
►Glass tube containing mercury
►Marked in millibars
►Mercury level rises as pressure on mercury rises
How does a rain gauge work?
○When 1mm has fallen it means if none of the water had run away, soaked into the ground or evaporated, it would cover the ground to a depth of 1mm
What are ocean currents?
○’Rivers’ of water which flow through the oceans
○Due to differences in temperature, the rotation of the earth and wind
○Can be warm or cold
○Cold currents bring cold temperatures
○Warm currents bring warm temps
What are the characteristics of a low pressure system?
►Winds blow in an anti-clockwise direction
►Air rises and temperatures fall
►Cold air forces warm air to rise
►Isobars close together - strong winds
►Rising air condenses forming clouds
►Cyclonic rainfall
►Warm tropical air meets cold polar air over Atlantic
Describe a Stevenson Screen
►Made from louvred (slanted) panels and is white to reflect sunlight
►Keeps and direct rays of the sun and rain but allows air to circulate into the box
►Raised on stilts 1.4m of the ground so there’s no effect from ground temperature
What are the positive effects of ocean currents?
- Ice-free coasts
- Warmer winds
- Good fishing grounds
How does an aneroid barometer work?
►Metal box with partial vacuum
►Air pressure rises -> box contracts
►Air pressure falls -> box expands
►As the sides of the box move in and out, a needle/pointer moves on a dial marked in millibars
Weather station
(a.k.a meteorological station) is a place with land based instruments and equipment where different aspects of weather are monitored and measured
Cloud names with the prefix ‘-alto’ are found at what altitudes?
Mid altitudes between 2,000m and 6,000 m
Why are areas closer to the poles warmer than the poles?
○Sun’s rays have a shorter distance to travel so they’re more intense
○Sun’s rays shine directly so concentrate on a small area
Cumulonimbus
Occur when air rises quickly and thunderstorms may form
Average/mean daily temperature
Add lowest and highest temperature for the day and divide by two
Wind
Movement of air caused by differences in temperature and pressure
Humidity
Amount of water vapour or moisture in the air
If a cloud name has ‘nimbus’ in it, what does it mean?
Precipitation is falling from the cloud
What is the purpose of the atmosphere?
It insulates the earth from extreme temperatures, it keeps heat in and protects the earth from the sun’s ultraviolet radiation
If air masses form over land they are defined as…
continental (c)
__% of solar radiation is reflected back through the atmosphere
30% of solar radiation is reflected back through the atmosphere
Wind vane
Measures wind direction
What is the troposphere?
○The lowest region in the earth’s atmosphere, reaches up to 17km above earth
○Weather and clouds occur here
○Heated by convection and radiation
Relative humidity
Amount of water vapour in the air compared to amount it would contain if saturated
How thick is the atmosphere?
480km
Atmospheric pressure
The weight of the atmosphere pressing down on the earth
How are depressions formed?
○The warm air mass and the cold air mass don’t mix easily and push against each other
○Warm air makes a dent in the cold air
○Warm air rises creating an area of low pressure
○Since air moves from areas of high pressure to low pressure, cold air swirls in an anticlockwise direction (NH) wrapping itself around the back of the incoming warm air
○So a large wave of warm air becomes surrounded by cold air
○The top wave is an area of low pressure
Rain gauge
Used to measure the amount of rainfall
The intensity of the sun’s rays reaching the earth depends on…
The tilt of the earthLines of latitude
Describe spring in terms of its relation to the tilt of the earth’s axis
○Northern hemisphere begins to tilt towards the sun
○Temperatures increase
Water/hydrological cycle
The continuous movement of water around the earths oceans, land and atmosphere
Hydrosphere
Collective mass of water found on, under and over the surface of the Earth
What are the four stages of the water cycle?
- Evaporation
- to.condensation
- Precipitation
- Run off
