Climatology Grade 11 PDF

CLIMATOLOGY  Temperature and Pressure LP HP High temperature Low temperature Rising air Sinking air Convergin...

CLIMATOLOGY  Temperature and Pressure LP HP High temperature Low temperature Rising air Sinking air Converging air Diverging air Clockwise Anti - Clockwise Cloud formation and Dry conditions wet conditions Unequal heating of the atmosphere Earth is heated by incoming solar radiation (insolation) Earth then transfers heat energy to the atmosphere Amount of heat energy in the atmosphere depends on the insolation Insolation depends on 2 FACTORS : 1. LATITUDE 2. SEASONS Global air circulation:https://youtu.be/7fd03fBRsuU Latitude ANGLE at which the sun's rays strike the surface of the earth. Surface area? DISTANCE from the sun to the earth – lost through reflection and scattering Unequal heating of the atmosphere Changes with seasons and with latitude in January southern hemisphere has summer and is hotter and northern hemisphere has winter and is colder (in July vice versa). Places near the equator (about 20 degrees) do not have marked differences in temperature. The position of the heat equator changes during the year. It is north of the equator in July and south of the equator in January. Some of the heat energy at low latitudes is transferred to higher latitudes. Heating imbalances due to latitudinal differences Mechanisms responsible for the poleward transfer of energy 1. Winds : warm moist air – pole ward from tropics 2. Ocean currents : currents ( moving streams of water in the oceans) move warm water to colder places and vice versa. Deep ocean currents : driven by differences in density of water. Colder, saltier water is more dense. Activity Construct a diagram showing 22 June and 22 December solstice positions in relation to the sun, as follows: Draw a line 13cm long At each end of the line draw a circle with a radius of 2.5cm Write SUN at the centre of the line Place the June solstice on the left side in relation to the sun 1. include the tilt 2. the important lines of latitude 3. use arrow heads to show the direct sun rays of the Sun Currents Surface currents move in circulation patterns called gyres clock wise in the northern hemisphere and anti clockwise in the southern hemisphere. The surface currents carry warm water pole ward and cold water equatorward. Energy transfer by wind Wind is air that moves horizontally across Earth. Some winds blow pole ward from the tropics carrying heat energy to higher latitudes. Other winds blow from polar regions moving cold air to lower latitudes. All these winds form part of the global circulation. Movement of heat in the winds – helps global energy balance. Unicellular model of global circulation  Important forces CORIOLIS FORCE ? FERREL'S LAW ? PRESSURE GRADIENT FORCE ? World Pressure Belts Pressure is arranged in belts of high pressure and low pressure than run from east to west across earth. The pattern is the same in each hemisphere The pressure belts are all associated with the latitudinal differences in temperature and with patterns of ascending and subsiding air. The three-cell circulation model associated with the following pressure belts: Equatorial low – A belt of low pressure associated with the rising air in the ITCZ. (The rising of warm air heated at the Equator causes an area of low pressure called Equatorial Low. As the air rises, creates clouds and precipitation.) Subtropical high – A belt of high pressure associated with the sinking air. (At the subtropics the air cools and descends creating areas of high pressure with clear skies and little precipitation, called the Subtropical High. The descending air is warm and dry, and produces deserts in these regions.) SPLP – A belt of low pressure associated with the polar front. Polar high – A high pressure associated with the cold, dense air of the polar regions  The three-cell circulation model associated with the following Surface winds pressure belts: Easterly Winds : Surface winds of the Hadley cell Easterly winds are drawn into teh equatorial low from the STHP Caled the tropical easterlies because of their location within the tropics NE in the NH and SE in the SH Westerly Winds Blow the STHP belts towards the SPLB Surface winds of the Ferrel Cell In the SH westerlies blow from he NW and in the NH westerlies blow from the SW Polar Easterlies : Surface winds of the polar cell SHIFTING OF THE ITCZ  WIND: moving air that blows from HP to LP GEOSTROPHIC WIND PRESSURE GRADIENT : amount of change to atmospheric pressure between High and Low pressure areas PRESSURE GRADIENT FORCE: causes air to move from a HP to a LP along the pressure gradient CORIOLIS FORCE : the force that deflects wind due to the earth’s rotation FERREL’S LAW: as a result of the Coriolis force the winds are deflected to the left in the SH and to the right in the NH  MONSOON WINDS (Seasonal change in the direction of the prevailing wind ) MONSOON SUMMER CONDITIONS air is warmer on land than over surrounding seas. warm air rises over land causing a LP Pressure is lower over land and higher over the ocean - so wind blows from sea to land bringing moist air (Indian ocean very warm – lots of evaporation) this moist air moves onto the land bringing heavy rains that last months MONSOON WINTER CONDITIONS air is cooler over mountains than over the surrounding seas the cold air sinks over the mountains creating a HP. the pressure is lower over the seas so wind blows from mountain to seas. dry, pleasant weather is experienced  FOHN WINDS warm, dry winds that descend on the leeward slopes of mountains moist air rises up windward slope: – air cools as it rises at dry adiabatic lapse rate until it reaches condensation level – then it cools at the wet adiabatic lapse rate – as it cools water vapour condenses to form clouds, rain and even snow. air descends on leeward slope – very little moisture left so air warms at the DALR – this is the Föhn wind results in much warmer temps and drier conditions on leeward side than windward side.  IMPACTS OF BERG WINDS Can encourage the spread of veld fires veld fires impact natural environment, animals and humans farmers may lose housing, equipment and livestock natural bush and grazing may be lost animal habitats may be destroyed Dry warm conditions can cause heat stroke and discomfort People and animals can suffer from dehydration