Climate Notes Topic 1-3

🌡 Climate Topic 1.1 Weather and Climate Climate An average state of atmosphere at a place over a period of time 25 years] Tropical equatorial Between 10°N and 10°S of equator) Generally high temp 27°C Small annual temp range High annual evenly spread precipitation 2000mm E.g. Singapore Tropical monsoon climate Between 30°N and S of equator) Generally high temp 25°C Small annual temp range 34°C High annual precipitation 1500mm with distinct wet and dry seasons E.g. Kochi, India Cool temperate climate Between 45° and 60°, N and S of equator) Climate 1

4 distinct seasons (spring, summer, autumn, winter) Large annual temperature range 21°C Moderate evenly spread precipitation 300900mm) E.g. London, UK | Paris, France Climatic hazards Changes due to natural and human-induced causes Weather patterns become increasingly unpredictable Extreme weather events (heat waves, droughts, floods) Topic 1.2 Weather and Climate - Variations in Air Temperature Across the Earthʼs Surface Variations of air temperatures across time Air temp over time in a day (due to rotation of earthʼs own axis) Midday (Due to Earthʼs spherical shape) Sun is directly overhead, radiation spread over a smaller area and is more concentrated Temp is highest of the day Before and after midday (Due to Earthʼs spherical shape) Sun is not directly overhead, radiation spread over a larger area and is less concentrated Temp is lower than midday Before sunrise Night Climate 2

Does not receive solar radiation Loses heat in form of longwave radiation Temp lowest just before sunrise as place lost heat over longest time Air temperature variations over time in a year (due to Earthʼs revolution around sun at 23.5° tilt) June: Northern hemisphere leans towards sun > Receive more direct solar radiation > Higher temp Southern hemisphere leans away from sun > Receives less direct solar radiation > Lower temp December: Northern hemisphere leans away from sun > Receives less direct solar radiation > Lower temp Southern hemisphere leans towards sun > Receive more direct solar radiation > Higher temp March & September Neither hemisphere lean towards sun > Moderate temp Northern hemisphere > Spring March & Autumn Sep Southern hemisphere > Autumn March & Spring Sep Areas in topics (close to equator) receive direct solar radiation throughout year > Higher temp throughout Variations more significant in places outside of tropics Variation of air temperatures across places Latitude Due to Earthʼs spherical shape…) Temp are generally lower at at higher latitudes > Solar angles changes varies at different parts of Earth Climate 3

Higher altitude: Solar radiation less concentrated > Spread over a larger area > Lower temp Lower altitude: Solar radiation more concentrated > Spread over a smaller area > Higher temp E.g. Beijing 40°N) has temp averaging 12°C while in SG 1°N) has average temp of 29°C Altitude Higher altitude > Air less dense and air pressure is less (gravity pulls air molecules towards surface) Fewer molecules > Lower ability to absorb and radiate heat > Lower temp Every 1000m, temp changes by 6.5°C E.g. Genting Highlands 1700m has an average temp of 21°C while surrounding areas is about 32°C Factors affecting air temperature at specific places Type of surface Dark surface (soil) > Absorb more solar radiation & radiate more heat > Higher temp Light-coloured surface (cloud) > Reflect more solar radiation & radiate less heat > Lower temp Urban areas have higher temp Urban Heat Island Effect) Has large area with dark surfaces > Absorb more solar radiation & radiate more heat Has glass-covered skyscrapers that reflect sunlight to the ground > Increase solar radiation absorption E.g. Night time SG CBD generally 2°C warmer as compared to MacRitchie Reservoir Distance from sea Climate 4

Coastal areas Maritime effect > Cooler summers and warmer winters Annual temp range is lower Summer > Sea is cooler than land > Heat up slower than coast > Cools coast Winter > Sea is warmer than land > Cools down slower than coast > Warms coast Inland areas Continental effect > Warmer summers and cooler winters Annual temp range is higher Summer > Heats up quickly > Higher temp Winter > Cools down quickly > Lower temp E.g. Alaska, USA Anchorage (coastal) has a temp range of 23°C Fairbanks (inland) has a temp range of 40°C Topic 1.3 Weather and Climate - Variations in Precipitation Across Earthʼs Surface Water cycle Water vapour enter atmosphere thru evapotranspiration Heat from sun causes water bodies to evaporate > From WV Plants give out WV during transportation As WV rises > Cools & condense into tiny water droplets at dew pt temp > Form clouds Water droplets in cloud become big and heavy enough > Fall back to ground as precipitation Water on surface infiltrates subsurface soil & rock Water flows as surface runoff and enters a body of water Climate 5

Water moves horizontally above impermeable rock and moves at different rates due to… Type of soil Infiltrate faster in soil which has larger pores (sandy) than soil with smaller pores (clayey) Built up areas Infiltrate rates lower in build up areas > Covered in concrete Fewer obstructions > Speed of surface run off higher on smoother ground surface (roads) Presence of natural vegetation More vegetation > More roots to loosen soil > More open space > Infiltrate and groundwater flows faster Stems and roots of plants act as barriers > Increase surface roughness > Surface runoff slower on vegetated areas Affect of temperature on relative humidity on place at specific time Relative humidity is the ratio of amount of WV in air to the max amount of WV the air can hold at given temp Temp increase > Amount of WV air can hold increase > Humidity decrease Water molecules move faster and spread further apart > Max amt of WV that can hold increase When humidity is 100% air is now saturated and hits dew point temperature When 100% achieved condensation occurs when WV is added to the air via evaporation or temp drops Cloud formation Air rises up > Cools > Reduce amt of WV it can hold Amt of WV exceeds max amt air can hold at dew point temp > Air condense into water droplets on condensation nuclei Climate 6

Condensation nuclei provides surfaces where WV can change into water droplets or solid ice crystals and form clouds Rain formation Formation of conventional rain Daytime > Heat from sun warms surface > Air gains heat and rises Condenses at dew pt temp on condensation nuclei > Clouds formed Water droplets in the clouds collide and coalesce > Become heavier and bigger > Large enough > Fall back onto surface as rain Formation of relief rain Prevailing winds pick up moisture over sea > Push moist air up windward side of mountain Condenses at dew pt temp on condensation nuclei > Clouds formed Water droplets in the clouds collide and coalesce > Become heavier and bigger > Large enough > Fall back onto windward side as rain Most of the moisture fallen on windward side > Leeward side experiences dry descending air E.g. USA Sierra Nevada mountain ranges (windward) receive higher rainfall > Lush forests Leeward side hot and dry > Create Death Valley Desert Topic 1.4 Weather and Climate - Variations in Wind Direction and Wind Speed Across the Earthʼs Surface Wind formation Wind occurs due to unequal distribution of air temperature > Uneven distribution of pressure gradients Place with higher temp > Air gains heat and rise > Create area with low pressure Climate 7

Place with lower temp > Air lose heat and sink > Create area with high pressure Air moves from area of high to low pressure to fill void > Winds formed Speed of winds Strength of pressure gradient Smaller pressure gradient > Smaller difference in pressure > Slower wind speeds Larger pressure gradient > Larger difference in pressure > Faster wind speeds Friction Winds come in contact with variations of Earthʼs topography > Frictional drag formed > Reduce wind speeds Greatest when there is uneven relief