Weather and climate
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Weather and climate
weather
weather
Refers to the conditions of the atmosphere, temperature, pressure and humidity of a place for a short period of time.
generally refers to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods of time
e.g.Too rainfallWind direction and strengthCloud cover and;sunshine
climate
climate
Is the average state of the atmosphere over a long period of time.
the weather averaged over a long period.
The standard averaging period is 30 years.
season
season
A season is a subdivision of the year, marked by changes in weather, ecology, and hours of daylight. Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth’s axis relative to the plane of revolution.
"Climate is what you expect, weather is what you get."
The main elements of the atmosphere that determine weather and climate at a given place are:
TemperaturePrecipitation (including humidity and
clouds)Air pressureWinds storms and;visibility
Doppler radar - in Virac, Catanduanes. The equipment, developed by the Japan Radio Co. (JRC), is the first facility in the world to use the Solid-State Meteorological Radar System technology, which has 95 percent accuracy.
visibility
Factors interacting to cause weather are:
Heat energyAir pressureWinds and;Moisture
How are typhoons formed?
Typhoons start off as tropical thunderstorms. The strong winds pull in moisture from the oceans. The thunderstorms convert the moisture into heat. The heat causes more air to flow to the center of the storm which causes more evaporation. All the heat and air flow toward the eye creating the typhoon.
Difference between weather and climate
Weather differs from climate due to:
Latitude – determines the angle at which the sun’s rays strike the earth’s surface and their effectiveness;
Distribution of lands and water;Winds;Altitude;Mountain barriers;Big semi-permanent high and low
pressure centers; ocean currents; andDifferent kinds of storms.
Combinations of these factors in different intensities change
temperature that makes weather different from climate.
temperature
temperature
The degree of hotness and coldness of a substance.
ThermometerShows that the amount of
change is different for different materials.
Temperature is the most important element of weather because weather changes are brought about by the change in temperature of the different parts of the atmosphere.
Temperatures in the continental climates differ according to where air masses that blow come from.
Large & dry continents = desertsMountains = cooler climatesoClimates in the cities are warmer than
open countries.
Water vapor
Water vapor in the air is humidity.Comes from the evaporation of: Oceans; Rivers;
Lakes; Soil; Plants; and Animals.Warm air can hold more moisture than
an equal volume of cold air. Why?
Relative humidity
The amount of moisture in the air or the percentage of the moisture the air can holds a definite temperature
Relative humidity
The relative humidity of an air-water mixture is defined as the ratio of the partial pressure of water vapor (H2O) in the mixture to the saturated vapor pressure of water at a prescribed temperature.Relative humidity is normally expressed as a percentage and is calculated by using the following equation:
%100 w
w
e
e
Dry-bulb
a. 27°C
b. 20°C
c. 15°C
d. 17°C
e. 30°C
Relative Humidity
%
%
%
%
%
Wet-bulb
25°C
16°C
12°C
12°C
29°C
Based on the percentage relative humidity obtained tells when (a-b-c-d-e)1. It is driest2. It is warmest3. It is coldest4. Rain will soon fall
Air motion and Air pressure
Air moves either horizontally as wind or vertically as currents.
Winds and currents transfer heat from the equator to the poles.
Heat comes directly from the earth and indirectly from the sun.
Air has weight.
Cold Air1cm3 Warm air
1cm3
More molecules?
Denser?
Temperature and amount of water vapor determine the density of air. The weight of the air at any given place is Air Pressure.
It is measured by an instrument called barometer.
Mercurial barometer
The first mercurial barometer was made by Torricelli, a student of Galileo.
Aneroid barometer
If the pressure increases, the sides of the container bend inward. If air pressure decreases the sides bulge out again.
Can be used both for measuring air pressure and altitude above sea level. – Altimeter
The higher the altitude, the thinner the air, the lighter it becomes.
Which zone has the lowest and highest air pressure? Why?
Cool pole air flows toward the equator and forces warm air up in the upper atmosphere, warm
air flows toward the poles.
Air pressure is determined by:Altitude
- the higher you go, the lower the air pressure, as the amount of air molecules decreases.Temperature
- cold air has more air molecules than hot airWater vapor
Temperature and amount of water vapor determine the density of the air.
Local winds
Local winds
At daytime, air over land areas is warmer than air over bodies of water.
- Flow of air from the sea to land is called sea breeze
At night, land cools faster than water bodies. Sea air is warmer than land air. Sea air rises, land air takes its place. This is the Land Breeze.
The name of the wind tells where it originates.
Huge land and sea breezes are called monsoons. –seasonal winds.
Northeast monsoonOctober – FebruaryWinds blows from cooler continent to warmer
ocean.It comes from northern Asia and blows toward the
Pacific Ocean.Cold season – Philippines – cool, dry season to
the northern.Winter season – north temperate and polar areas.“Hanging Amihan”
Southwest monsoonWinds blows from cooler ocean to
warmer continent.It comes from the Pacific Ocean and
brings rainy and typhoon season to the Philippines.
Oceans winds bring in warm, moist air, therefore heavy rains and warm temperatures over the land
“Hanging Habagat”
Major wind systems of the
earth
Factors affecting the winds in the earth are:
The earth’s rotation, Pressure belts, Differences in topography and In the heating of air masses over land and water.
Ferrell's lawThe law that wind is deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.The force that deflects it is the Coriolis Force.
Wind system
DoldrumsTrade windsHorse latitudesPrevailing westerly winds and;
Polar winds
DoldrumsA region of hot air, low air pressure
and calm.Air currents move upward or
downward.
Trade windsSlanting windsBlow in form north and south toward
the doldrums
Horse latitudesA regions of high pressure between the
trade wind belts and westerlies.Air that rises in the doldrums sinks to the
earth.From the HPA of the horse latitudes, air
moves toward the equator and toward the poles.
If the equator has a LPA due to heat, the poles have high pressure areas due to their coldness. The cold polar winds move toward the sub-polar low pressure belts, turn to the east, according to ferrel’s law, and become the polar easterlies.
Prevailing westerliesMoves away from the horse latitudes
toward the sub-polar low belts, but they are turned to the east by the earth’s rotation. As they come from the west, they are called the westerlies