geography wa2

• Evaporation


  The process of water changing from liquid to gaseous state
• Transpiration


  The process by which water is lost through the surface of a plant
• Condensation


  The process of changing from a gaseous state to liquid state
• Precipitation


  Water that falls from clouds towards the ground
• Infiltration


  The process by which water enters the ground or soil
• Percolation


  Downward flow of water through soil into the groundwater due to gravity
• Surface runoff


  Water that travels over the surface of the ground to reach streams and rivers
• Groundwater flow


  Very slow movement of water below Earth's surface
• Relative Humidity


  A measure of the actual amount of water vapour in the air compared to the total amount of water vapour that the air can hold at its current temperature.
• Absolute Humidity


  The actual amount of water vapour that the air can hold at a given temperature.
• How is Temperature and Relative Humidity related?

  They are inversely (negatively related). When temperature increases, relative humidity decreases. When temperature increases, air expands and its ability to hold water also increases. With the same amount of moisture in the air that exists in this air that has now expanded, relative humidity has decreased because it is now less humid (i.e. same number of water droplets in a bigger space)
• Saturation


  Saturation occurs when relative humidity is at 100%. (When air hold the maximum amount of air it can hold, the air is saturated)
• Dew Point Temperature


  The temperature at which Saturation occurs
• What are Clouds?


  A visible mass of water droplets or ice crystals that are suspended in the atmosphere
• Convectional Rain


  Surface of the earth is heated intensely which warms the air near the surface

  The air expands and rises as it is heated, its capacity to hold water vapour also increases

  As warm air rises, it cools gradually and can no longer hold as much water vapour, relative humidity of the parcel of air increases

  At a certain altitude, the relative humidity of the air reaches 100%. Condensation occurs and tiny droplets of water condenses around the dust particles in the air

  Tiny water droplets merge (coalescence) to form clouds. High evaporation and rapid condensation result in cumulonimbus clouds to form, leading to convectional rain

  Convectional rain (thunderstorms) usually associated with lighting and thunder

  Convectional rainfall is intense - large amount of water fall as rain over a short period of time

  (image: clouds is cumulo-nimbus clouds and there should be a line under the clouds showing the height)
• Relief Rain


  A parcel of air blows across a water body and picks up moisture

  As this parcel of air approaches a mountain, the moist air is forced to rise up the slope

  As warm air rises, it cools gradually and can no longer hold as much waster vapour, relative humidity of the parcel of air increases

  At a certain altitude, the relative humidity of the air reaches 100%. Condensation occurs and tiny droplets of water condenses around the dust particles in the air

  Tiny water droplets merge (coalescence) to form clouds.

  When the water droplets are heavy enough, they fall as rain on the side of the mountain where it was forced to rise (windward side)

  The other side of the mountain is usually dry (leeward side/ rain shadow area) because as the parcel of air decreases in altitude, it warms up and can hold more water vapour (relative humidity decreases)

  (image is questionable)
• What instrument is used to measure relative humidity?

  Sling Psychrometer
• How does the Sling Psychrometer work?

  Dry bulb: measures atmosphere temperature

  Wet bulb: as the water evaporates, the bulb cools, producing a temperature difference between the two thermometers. The amount of evaporation, and hence cooling of the wet bulb, depends on the relative humidity of the air.

  Wet bulb depression: the difference between the dry bulb temperature and wet bulb temperature.

  Relative humidity: compare readings against calculation table
• What is the procedure of using the Sling Psychrometer?


  Ensure that there is water in the enclosure and close the cap (For the wet bulb thermometer to function)

  Hold the Sling psychrometer at one arm's length (Avoid picking up body heat that affects reading; safety reasons of not hitting yourself)

  Swing it 360 degrees for 1 minute (Maximize exposure to the surrounding unsaturated air and allow for the water to evaporate)

  Read and record the temperature on the two thermometers (wet and dry), repeat steps 1 to 4 at least two times (More readings to average out inconsistencies, discrepancies. Ensures accuracy)

  Calculate the wet bulb depression, compare against table
• How do we measure rainfall?

  Rain gauge
• Where do we place a rain gauge?

  On short grass in an open area (Prevent water collected on leaves of trees from dripping in)

  Far away from buildings and other obstructions. (Prevent water collected on roofs of buildings from dripping in)

  Sunk into the ground with the rim 30 cm above ground (Prevent toppling over by human or other living things)

  Avoid hard ground surfaces such as concrete (Prevent rainwater from splashing into it from the hard surface.)
• What do flat lines represent?

  Location: close to the equator

  Temperature: has even temperatures all year
• What to look out for Precipitation

  High low or moderate? (by calculating total rainfall)

  Distinct wet or dry seasons?
• What is considered High and low temperature

  under 10C = low

  over 15C = high
• How is climate and natural vegetation related?

  Climate is directly related to plant growth because the main determinants of climate are temperature and the amount of rainfall an area receives.

  Thus, regions in the tropics are often abundant in trees and forests
• Distribution of tropical rainforests

  Mostly found between 0- 23.5 North and South, mostly near the Equator.

  Can be found in Central & South America, West & Central Africa, South & Southeast Asia (Amazon Rainforest, Congo Rainforest, Forests of SEA)

  Found at tropical climate with high rainfall of more than 1500mm and temperature of more than 20°C
• General characteristics of tropical rainforests

  Thick (Dense- spaced very closely together)

  Luxuriant (Abundance → a lot of growth of plants)

  Evergreen trees → they do not shed all their leaves at the same time.

  Rich biodiversity (Large range of plant & animals species found in an area)
• Characteristics of the Emergent layer


  (above 30m)

  Uppermost layer where some trees rise and tower above other trees

  Can grow up to 50m - 80m

  The emergent layer is formed by the crowns of these trees.

  Trees in this layer usually have tall, straight and smooth trunks with few branches

  E.g. Tualang tree, Kapok tree
• Characteristics of the Canopy layer

  (20-30m)

  The trees grow to heights of 20 - 30m to reach for sunlight.

  Trees grow close together (dense)

  Crowns interlock to form an almost continuous cover

  This blocks up to 97 to 98% of the sun's rays from reaching the forests floor
• Undergrowth layer


  (below 20m)

  Dark because sun's rays blocked by the canopy.

  Vegetation is mostly sparse

  Not many plants can grow except smaller ones that are able to grow in the shade and the seedlings of taller trees.

  Consists of plants such as moss, ferns, some lianas and epiphytes.

  Thin layer of leaf litter due to rapid decomposition caused by hot and wet environment.
• saturation=100% relative humidity
• less than 250mm -very dry

  500mm -dry

  1000mm -wet

  more than 1500mm -very wet
• Mean Annual Temperature:

  High- more than 20 C

  Low- less than 10 C

  Annual Range of Temperature:

  High- more than 15 C

  Low- less than 10 C

  Bump- summer

  Dip- winter