Geography

• Water Vapour is 0 - 4 % of the atmosphere.
• Moisture can be added to the atmosphere through evaporation or transpiration.
• The atmosphere undergoes a continuous exchange between evaporation, transpiration, condensation and precipitation.
• Absolute Humidity is the actual amount of the water vapour present in the atmosphere (𝑔𝑚𝑐𝑚3).
• The ability to hold water depends on temperature.
• Relative Humidity is the % moisture as compared to full capacity; greater over the oceans and least over the continents.
• Saturated Air is air containing moisture to its full capacity at a given temperature.
• Coastal areas receive more rain than inland areas.
• Rainfall decreases towards the poles.
• Rain is more likely to fall on the windward side than the leeward side.
• Cyclonic rainfall is due to cyclone formation.
• Between 35° and 40° N and S of the equator, rain is heavier on the eastern coasts and decreases towards the west.
• Between 45° and 65° N and S of the equator, rainfall is first received on the western margins of the continents and decreases towards the east due to westerlies.
• The capacity of soil to take in moisture increases as it dries out, resulting in a dry leeward side.
• Dew point is the temperature at which saturation occurs in the sample of air.
• Evaporation is the change from water from liquid to gas.
• Latent Heat of Vaporization is the temperature at which water starts evaporating.
• Condensation is the transformation of water vapor to water (by loss of heat).
• Condensation in free air occurs when the temperature of the air is reduced to dew point with its volume remaining constant.
• Condensation can occur when moisture is added to the air through evaporation.
• Increase in temperature increases water absorption and retention capacity of the given parcel of air.
• Condensation also occurs when both the volume and the temperature are reduced.
• Sublimation is the change from solid to gas.
• Forms of condensation can be classified based on temperature and location.
• Condensation takes place when the dew point is lower than or higher than the freezing point.
• Mists are frequent over mountains as the rising warm air up the slopes meets a cold surface.
• When resistance of the air fails to hold condensed particles against the force of gravity, they fall on to the earth’s surface and release moisture, resulting in rainfall.
• Clouds are formed by water droplets or ice crystals formed by condensation at free air at a reasonable height.
• Fogs are mini clouds in which condensation takes place around nuclei provided by the dust, smoke.
• Orographic (Relief) rainfall occurs when a saturated air mass comes across a mountain, it is forced to ascend and as it rises, it expands; the temperature falls, and the moisture is condensed, resulting in more rainfall on the windward side.
• Dew formation requires dew point to be above freezing point.
• Fog is prevalent where warm currents meet cold currents.
• Clouds are grouped under four types: Cirrus, Cumulus, Stratus, and Nimbus.
• Frost forms on cold surfaces when condensation takes place below freezing point, resulting in minute ice crystals and a clear sky, calm air, high relative humidity, and cold and long nights.
• Fog is a cloud with its base at or very near to the ground, where condensation takes place within itself on fine dust particles, forming a mist.
• Conventional rainfall is caused by the heating of air and rising air mass, typically seen in the summer and hot part of the day in equatorial regions and interior of continents.
• Smoke and fog together form smog.
• Snowfall occurs when temperature is less than 0 °C, resulting in hexagonal crystals.
• Sleet is a mixture of frozen raindrops and refrozen melted snow-water.
• Mist contains more moisture than the fog.