Weather elements (3) Air Pressure and Winds

Question 1

Define air pressure

Answer 1

• downward force exerted on a unit of area of earth surface by weight of a column of air above
• lower altitude, air denser, more compressed, higher air pressure
• measure in millibars (mb)
• pressure lines: isobars

Question 2

Air direction

Answer 2

• N. Hemisphere: anti-clockwise
• S. Hemisphere: clockwise
• from high to low pressure

Question 3

Barometer

Answer 3

• measures air pressure
• 2 needles: measuring hand (measure air pressure), other needle (reference)
• check how much measuring hand has moved (pressure fall if hand moves to left vice versa)

Question 4

Relationship between air pressure and temp

Answer 4

• high temp, molecules move away frm each other, lighter, rises, create area of low pressure
• low temp, molecules move closer tgt, heavier, sinks, create area of high pressure

Question 5

Relationship between temp and altitude (anomaly)

Answer 5

• low alt, air denser (gravity), higher pressure
• high alt, air thin, lesser air particles, low pressure
• (usually temp increase as altitude increase, but in this case temp increase when alt increase)

Question 6

Define wind

Answer 6

• movement of air
• occurs when there is diff in air pressure between 2 areas
• wind always blow frm area of high pressure to low pressure
• larger air pressure diff, stronger wind
• described in speed, frequency, wind direction

Question 7

Wind speed

Answer 7

• rate at which air moves
• km/h
• anemometer/Beaufort scale

Question 8

Wind direction

Answer 8

• direction of where wind blows

- wind vane (pts at direction of wind)

Question 9

Wind Frequency

Answer 9

• percentage of time wind blows from particular direction
• direction where wind blows most frequently: prevailing winds
• use Wind Rose

Question 10

Small-scale winds

Answer 10

• land and sea breeze
• experienced at coastal areas
• winds resulted from diff in rate of heating up and cooling down of sea and land

Question 11

Sea breeze

Answer 11

• during day
• land heats up more quickly than sea, air over coastal land heats up, expands, rise, form area of low pressure
• sea heats up slower, air over sea cooler, area of high pressure formed
• sea breeze blows from high to low pressure (sea to land)
• cooling effect on coastal areas
• draw annotated diagram

Question 12

Land breeze

Answer 12

• during night
• coastal land cools down faster, cooler air over land sinks, area of high pressure formed
• sea cools down slower, warmer air over it rises and expands, area of low pressure
• land breeze blows from high to low pressure (land to sea)

Question 13

Define monsoon winds

Answer 13

• regional wind patterns
• reverse direction seasonally
• caused by extreme heating and cooling of huge land masses in relation to sea
• large diff in air pressure between land masses and seas
• result in movement of large-scale winds from high to low pressure areas
• lvl of rainfall increase/decrease with occurrence of monsoons, lead to either dry or wet seasons

Question 14

Monsoon examples

Answer 14

• major Monsoons affect Asia and Australia
• Northeast monsoon (SG get lots of rain from oct-feb)
• Southwest Monsoon (huge impact on food production/security for India, June to Sept,80% India’s rainfall)

Question 15

Coriolis effect

Answer 15

• affects Monsoon winds
• a force produced by earth’s rotation
• changes course of moving objects, cause wind to bend
• strongest near poles, weak in tropics, not felt at equator
• N. Hemisphere: C. effect cause winds to deflect to their right
• S. Hemisphere:cause winds to deflect to their left

Question 16

Northeast Monsoon

Answer 16

• Oct-Feb
• summer in S. hemisphere (low pressure(why?), Australia)
• winter in N. Hemisphere (high pressure(why?) , Indian sub-continent, Central Asia)
• air moves from area of high air pressure to area of low air pressure (general direction: South)
• coriolis effect cause winds to be deflected to right at N. Hemisphere, aka Northeast Monsoon
• Northeast Monsoon winds cold, dry, bring little rain to India and Bangladesh (cold, dry weather)
• as wind cross equator, Coriolis effect deflect winds to ITS left, become Northwest monsoon , warm up when heading towards Australia, bringing rainfall along

Question 17

Southwest monsoon

Answer 17

• June - Sept
• summer in N. Hemisphere (low pressure (why?), India, Central Asia)
• winter in S. hemisphere (high pressure(why?), Australia)
• air move from high to low pressure (Australia to India, Central Asia) (general direction: North)
• Coriolis effect cause winds to be deflected to ITS left in S. hemisphere (Southeast monsoon)
• as winds cross equator, C. effect cause winds to deflect to its right, become known as Southwest monsoon
• SW monsoon blows over Indian Ocean, picks up moisture, bring heavy rain to SW India and Bangladesh (hot and wet weather)