Weather & climate 1 Flashcards
What is weather?
- —> condition of the atmosphere
- —> at a particular place and particular time
- —> shorter period of time
What is climate?
- —> climate is the average condition of the atmosphere
- —> over a long period of time, usually over 30 years
Elements of weather
Temp Relative humidity Clouds Rainfall Air pressure Wind
what is temp?
- —> degree of hotness/coldness of a place
- —> units: °C
- —> measured using digital thermometer and analogue
- —> high temp: >20°C
- —> low temp: <10°C
mean daily temp
the sum of hourly temp divided by 24h
Diurnal (daily) temp range
Diff btw max & min temp recorded in a day
Mean (average) monthly temp
Average of daily temp recorded in a month
annual (yearly) temp range
diff btw max & min mean monthly temp recorded in a year
What is relative humidity
Ratio btw the actual amount of water vapour present in a mass of air and the max amount of water vapour the air could hold at a given temp
what is relative humidity measure with
sling psychrometer
relative humidity’s relationship with temperature
As temperature increases, relative humidity decreases
- —> Warm air can hold more water vapour than cool air
- —> When temp increases, the amount of water vapour in the air stays the same
- —> But the rise in temp makes the air more able to hold water vapour
Saturation & condensation
Saturation
- —> relative humidity is 100%
- —> occurs at dew point temp
- —> condensation occurs at dew point temp
Condensation
—-> water vapour changes to liquid form by cooling
How are clouds formed?
- —> earth is heated up
- —> Evaporation occurs (water to water vapour)
- —> At dew point temp, condensation occurs if there are tiny particles for the water vapour to condense on
- —> Condensation nuclei: tiny particles like dust
- —> water droplets in the air will bump into each other
- —> become larger in a process called coalescence
What are clouds
- —> visible mass of water droplets/ice crystals suspended in the atmosphere
- —> water droplets eventually grow large enough to fall to the earth’s surface as precipitation
what is rainfall
- —> water in any form that falls from the atmosphere to the surface of the earth
- —> precipitation includes: hail, snow, sleet (rain & snow) and rain
- —> high rainfall: >1500mm
- —> low rainfall: <250mm
- —> measured using rain gauge
why does rain occur
- —> air instability
- —> tendency of parcel of air to rise rather than remain in its original position
process of convectional rain
- —> earth’s surface heated intensely
- —> warm surface heats the air around it
- —> air becomes unstable
- —> air expands & rises
- —> as the air rises, the temp drops
- —> air cools to dew point temp
- —> condensation
- —> clouds form
- —> water droplets heavy & large enough
- —> fall to the ground as rain
process of relief rain
- —> moist air passes over the sea
- —> arrives at the coast
- —> air is forced to rise up windward side of mountain
- —> air is forced to cool
- —> air reaches dew point temp
- —> condensation
- —> clouds form
- —> water droplets heavy and large enough
- —> fall as rain on the windward side
- —> leeward side: usually dry as most rain has fallen on the windward side
what is land breeze
----> blows from land to sea At night: ----> land loses heat faster than water bodies ----> sea has a higher temp ----> sea has lower air pressure ----> air moves from area of high pressure to low pressure ----> moves from sea to land ----> forms land breeze
what is sea breeze?
----> blows from sea to land Day: ----> land heats up faster than water bodies ----> land has a higher temp ----> land has higher pressure ----> air moves from area of high pressure to low pressure ----> air moves from land to sea ----> sea breeze
What are monsoon winds
- —> regional wind patterns that reverse direction seasonally
- —> brings seasonal changes in precipitation
- —> affected by the Coriolis effect
southwest monsoon
Takes place btw June and Sept
Northern hemisphere:
- —> summer
- —> air over central Asia heats up
- —> air expands and rises
- —> low pressure
Southern hemisphere:
- —> winter
- —> air becomes cold and dense
- —> high pressure
- —> Diff in pressure btw Central Asia & Australia
- —> Air moves from Australia to Indian sub-continent and Central Asia
- —> Southeast monsoon winds
- —> wind crosses the equator
- —> Coriolis effect deflects the wind to the right
- —> winds become southwest monsoon winds
- —> wind warm up
- —> picks up moisture in Indian ocean
- —> brings heavy rain to Indian-subcontinent
Northeast monsoon
takes place btw Oct & Feb
Northern hemisphere
- —> winter
- —> air becomes cold & dense
- —> high pressure
Southern hemisphere
- —> summer
- —> air heats up
- —> low pressure
- —> air moves from area of higher pressure to lower pressure
- —> air moves from central Asia to Australia
- —> northeast monsoon winds
- —> winds cross the equator
- —> Coriolis effect deflects them to the left
- —> northwest monsoon winds
- —> warm up
- —> warm air picks up moisture
- —> brings heavy rain to Australia
