Geography Form One Notes – Weather
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WEATHER
Concept of Weather
Meaning of Weather
Define weather
Weather is defined as conditions of the atmosphere which occur at a place at specific time
periods, that is, from hour to hour or day to day It changes ftom time to time and from place to
place. For example it may be raining inthe morning and sunny inthe afternoon
Weather may also be defined as the day-to-day state of the atmosphere, and its short-term
‘aration in minutes to several weeks
How do you feel when seated in a classroom on a cloudy day? You probably fel cold, Don’t
you? Now, suppose you move outside the classroom on a sunny day and stay there for several
minutes. Your body will obviously feel bot and may even start to sweat. What does this
experience ell you about the weather?
The weather is all around us, all the time, It isan important part of our lives and one that we
cannot control. Instead the weather often controls how and where we live, what we do, what we
wear and what we eat.
‘The scientific study of weather is called meteorology and a person who studies weather is called
meteorologist.
Importance of Weather
Describe the importance of weather
‘Weather isan important part ofthe natural environment. I directly or indirectly affects many of
cour activities. The following are some of the reasons why weather is important to mankind and
the surrounding environment:
1. Weather is one of the fundamental processes that shape the Earth. The process of
‘weathering breaks down the rocks and sols into smaller fragments and then into their constituent
substances. In this way, weather plays a major role in erosion of the surface sol, hence shaping
the earth
2. ‘The weather of any given region i important because it has a considerable impact on the
water, sunlight and temperature of an ecosystem, Variation in long-term weather patterns and
tendencies can result in certain regions getting more or less water or sunlight than other areas.
These factors play an important role by influencing the type of plants and animals that can
survive inthe area
3. Certain weather patterns can also cause dangerous storms and natural disasters. We tend
to be acutely aware of the weather when we are faced with exceptional or dangerous phenomena
that could endanger our property, safety or even lives. Such phenomena are, for example, strong
winds, hail, eavy rainfall, sleet, ie and frost.
4. Studying weather characteristics ofa given place over along period of time (usually 30 t0
40 years) enables the climatic conditions of that place to be established. Therefore, weather ean
be used as a basis for determining the climate ofa given place
5. The knowledge of weather (and hence climate) enables people to carry out their
economic activites depending on the weather and climatic conditions of their localities. For
example, people living in cold areas which receive high rainfall can engage in dary farming and
the growing crops suchas tea, coffee, banana, ee.
‘The Relationship between Weather and Human Occupations
‘Show the relationship between weather and humans occupations
‘There i a direct relationship between the weather condition and nature of human activity. Due to
the fact that deserts experience very hot weather, it will be surprising to see tea or banana tree
srowing there. This way we ean see a clear connection between the two. Eg, during rainfall
construction companies experience lows in business and meanwhile floods hinder transport on
Elements of Weather
Elements of Weather
Name lemens of weather
Weather elements refer toa combination of natural phenomena that make up th weather. There
are several elements that make the weather and climate ofa place. The weather elements are
temperature, pressure, precipitation, wind, humidity, clouds and sunshine
‘The study ofthese elements can provide the basis for forecasting weather and defining the
climate. Now, let us study cach element in more details
‘Temperature
‘The temperature is how hot or cold the atmosphere i, usually measured by a thermometer and
expressed in degrees on a Centigrade or Fahrenheit scale, There are several pes of
thermometers. The maximum thermometer shows the highest temperature reached during a given
period, for example a day; while the minimum thermometer shows the lowes tmpertire
recorded (the igure below shows maximum and minimum thermometer)
Maximum and minimum thermometers
‘The maximum thermometer is made of glass and contains mercry in the bub. Theminimum
thermometer is also made of glass but contains lcobol instead of mercury. The thermometer is
smarked in degrees of Centigrade or Fahrenheit. When the tmperature iss, the mercury expands
and extends along a glass tube. Changes in temperate are shown bythe length of mercury. For
example, if the lowest temperature reads 12S°C and the maximum temperature reads 24.0 °C,
then the changes in temperature i calculated as 240 ~128= 11.5°C.
‘The Six’s thermometer can also be used for measuring maximum and minimum temperature.
‘The thermometer consists ofa U-shaped glass tbe. The metal index nearest tothe bul indicates
the minimum temperature andthe other metal index records the maximum temperature
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Sis’ Thermometer. Can you read the max temperature and min temperature?
‘Temperature isa very important factor in determining weather. It influences or contol other
clement of weather, such as precipitation, humidity, clouds and sunshine. The factors affecting
(cvodifying) temperature include latitude, altitude, distance tothe ocean andor sea, orientation of
‘mountain ranges toward prevailing winds (aspect) and ocean currents
Reading and recording temperature
‘The maximum and minimum temperatures which ae recorded for the day are used to calculate:
daly range of temperature, which is the difference between the maximum and minimum
temperatures; and
the daily mean, which isthe average of maximum and minimum temperatures
‘Maximum + Minimurm/2 = Daily mean
The monthly range of temperature is the difference between the highest daily mean temperature
and the lowest daily mean temperature, To get the lowest mean temperature for a particular
‘month, add up the mean daily temperatures and divide by the number of days in that month, For
example, the mean monthly temperature for January is given by
My +Mz-#My +… My/32 where My, Ms, Ms…..Myare the mean daily temperatures for days
1, 2, 3…m; and 31 is the number of days in January. The same formula ean be applied to
coblain the maximum daily mean temperature for a particular month
‘The annual range of temperature in a particular year is the difference between the highest mean
‘monthly temperature and the lowest mean monthly temperature
‘When reading and recording of data is done over a period of time, the obtained data can be
shown on maps. These maps are called temperature maps. When comparing the temperature in
different parts of the world, itis usual to make use of temperature maps. Different places with
the same temperature conditions can be joined on the map by lines called isotherms,
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Relationship between temperature and alitude
Temperature decreases atthe rte of 06°C for every 100 metres inrese in ate. Therefore,
temperatures in highland areas are lower than temperatures in lowlands.
‘Apart fen isoterss, another way of presenting the temperature data is using a graph, In this
case, emperatre figures ae plotted on the graph and pont are joined by a smoot ine
Average monthly temperature fr Staton X
Precipitation
This refers to the deposition of moisture on the canh’s surface fom the atmosphere, This
ostriches rain, snow, ie, hai, mist and slet
Demonstrating the formation of in
Boil some water in pot. Jus asthe water tarts boiling, old a container filled with cold water
cover the pot. As the stam comes in contact with the container, it condenses to form droplets
which wil then fal down. This explains how sin is formed.
‘The sun’s heat causes water to evaporate from the surfice ofthe osc, aks, rive other water
bois, and land. This vapour rises into the atmosphere where it condenses to form clouds
case the aris cole t higher altitude, the vapour is cooled to form small droplets tha join
together to form larger drops which are then to heavy to remain in thea, othe fll sin
‘The diagram below shows the water eye, also called the hydrologic eyele
H The Water Cycie ]
F (The Hydrologic Cycte) :
: > q
: —. j
{Condensation precipitation Condensation:
Mt t (Ciowds form
Hey Runoff :
H < Evaporation —
The hydrologic cycle
Types ofan
‘There are three types ofan as explained below
Convection rain
This is a rain formed through the rising of the moist air currents, which condenses at higher
altitudes to form clouds that result to rainall
Warm air rises, cools
and condenses,
forming clouds
Convection rain
Orographie rain or relief rain
‘Sometimes moist winds are forced by a high mountain to rise and the moisture in it condenses to
{oem rain. Rain formed in this way is called orographic rain. The side of the mountain facing
away from the direction of wind gets little or no rain, This phenomenon is called the rain shadow
cffect,
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‘An example of the rin shadow effect in Tanzania is found on the weser side of Mount
Kilimanjaro. Winds low fom the Indian Ocean in the east and are fe by this Convection
fain mountain ose up and drop moisture onthe eastern nd southwestern slopes. When hese
winds blow over to the westem side of the mountain, they are already relatively dry. As a result,
they being very litle rin the Masi steppe Other examples ar the Rocky Mounts which
affect the nearing winds from the Pacfie; andthe Andes in Chile which fet the ain
bearing winds fom th Pacific onthe Patagonia plea,
Cen a
Cyclone rin oecurs when large masses of ar wih diferent characteris of temperature and
rite mee. As the warmer and cit ai fered up ove the cole and dy ae, i expands,
cool and water vapour condense to for cloud and an
‘Condensation Condensation ocaur
forms 7 rapidly along front
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FRONT difference
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Gyelonic rain
(nthe other hand, tropical eyclones are formed over oceans in the topics between nitude 8°N
and 8°S, They usually bring very heavy rainfill and are associated with thunderstorms and very
fast moving winds which often cause destructions along coastal settlements In the Caribbean
and USA, tropical eyclones are called hurricanes. In Aftca they are known as cyclones, while in
CChina and Japan they are called typhoons but in North Australia they are known as Willy
Willies.
Rainfall is measured by an instrument called rain gauge. Normally, the reading is done once
every 24 hours. If need be, comments on the nature, time and duration of rainfall should be
auded to the record
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THE RAIN GAUGE
Rain il girs catered in the record bok forthe mocth or seve month cn be epesnted in
the form of graphs known as histograms (se the histogram below). Mean monthly rainfall
records are unaly cbsined by adding wp rainfall of « particular mouth (uy Jamory) for a
umber of yrs ny 30 year) and dividing this by the sme number of years
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Total annual rainfall recorded t Weather Station X
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Rain is an important component ofthe water cycle and is responsible for depositing most of the
fresh water on the earth. It provides suitable conditions for many types of ecosystems, as well as,
water for hydropower plants
Humidity
Humidity is the state ofthe atmosphere in relation to the amount of water vapour it contains.
Humidity indicates the degree of dampness of the air, and is one of the main influences on
weather. It is expressed in ether absolute or relative terms. Absolute humidity is the actual
amount of water vapour present in a certain volume of air ata given temperature, expressed in
‘grams per cubic metre. Relative humidity is the amount of water vapour present in a mass of sir,
expressed as a percentage of the total amount of water vapour that would be present when that
air is saturated at that temperature. Airis saturated when the atmosphere cannot hold any more
‘water vapour. This condition depends onthe temperature and pressure of the ait
‘Humidity is measured by an instrument called hygrometer, which consists of wet and dry bulb
thermometers. The wet bulb thermometer is kept moist (wet) by wrapping it in a muslin bag
Which is dipped in a container of distilled water. When the air is not saturated, water evaporates
from the muslin and this cools the wet bulb causing mercury to contract. The dry bulb is not
affected in the same way. So the two thermometers show different readings. But when the air is
saturated the two thermometers show the same readings. Therefore, when there is a big
difference in readings between the two thermometers, humidity is low and when there isa small
difference, humidity is high
Alygrometer
‘The hygrometer consists of dry (let) and wet (right) bulb thermometers. Can you notice a muslin
bag dipped ina container of water?
Absolute humidity is calculated after finding the dew point. Dew point i the critical temperature
at which air becomes saturated with water vapour. Further condensation causes the formation of
tiny drops of water called dew.
Atmosphere pressure
‘The air around us has weight. Atmospheric pressure (or air pressure) is the weight of the air
resting on the earth’s surface. It isthe weight exerted by air on the earth’ surface
‘The force with which air presses down on a unit area is called atmospheric pressure. But this
pressure is exerted equally in all directions. Atmospheric pressure can be demonstrated by the
following experiment:
‘Take a glas full of water, cover the top of the glass witha piece of thin paper, and then hold the
lass upside down. The water in te glass will not spill out because pressure of the aris pressing
the paper so that it does not fll out.
Atmospheric pressure is measured by an instrument called a barometer. There are two types of
barometers, mercury barometer, and aneroid barometer. Mercury barometer measures pressure in
millimetres, usually expressed symbolically as mmllg, read as millimetres of mercury. The
pressure at sea level is 7 mmHg. This i called standard pressure.
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joining places with the same pressure are called isobars.
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Winds
Wind is the movement f air masses especially on the earth’s surfuce. Heated air expands,
bbecomes less dense and rises up. Cooled air contracts, becomes denser and sinks down. When ait
sinks, its pressure increases because it is compressed, but when air rises, its pressure decreases
because its molecules are spread over a large area. Areas from where heated air is rising are
called areas of low pressure, while areas in which cool air is sinking are called areas of high
pressure
Usually, there is a movement of air from high pressure to low pressure areas, which is caused by
Aifferences in heating of air over different pars ofthe earth’s surface. The air that moves from a
region of high pressure to that of low pressure is called wind, Wind is air in motion, from high
pressure areas to low pressure areas.
During the day the land is usually warmer than the sea, and the air pressure on the land is lower
than that over the sea. Therefore, air blows from sea to land. This kind of air movement (wind) is
known as sea breeze, But during the night the land is cooler than the sea and there is low
pressure on the sea. Therefore, winds blow from the land to the sea, This air movement is
called land breeze.
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‘Seabreeze day) and land rece night)
(nthe Eanh’s surface, the regions ofthe north and south poles are very cold and have high
[retsure while the bel along the equnor is very hot and has lw presue. This makes at move
from the poles towards the equator. In the equatorial belt, rising air is replaced by air moving in
fiom the north and south ofthe equator. We shuld then expect two belts of wind blowing
towards the equator. Bu this is not exactly so because the ath rotates fom west to eas, and
according to Feral’ lw sro water moving fely in any direton ove the Farth’s src is
tured (deflected) to the right ofits course in the norterm hemisphere and to the let in the
southern hemisphere. Therefore, ny winds blowing ftom the noth towards the emai the
nortern hemisphere wil Bow fom the north east and not fom the moth, and any winds
blowing from the south towards the equator in the souther hemisphere will blow fom the south
east and not from due south
a en
—_»
ers
Winds blowing from NE and SE
In the equatorial belt of low pressure, between S°N and S°S latitudes, intense solar heating
causes the most aro rise in great convection columns. This belts called the doldrums or low
pressure belt. The rising air spreads out and moves towards the poles. In 0 doing, it cols and
thus contracts, and develops high pressure. This occurs around 30°N and 30S. Thus, the air
sinks and builds up high pressure at these latitudes. These latitudes are called hore latitudes or
subtropical high pressure ells
In latitudes 30°N and 30°S some of the high pressure air moves over the surface towards the
csuator as the north east and south east trade winds, Some moves over the surface towards the
poles as westeties
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Wind belts ofthe world
In each hemisphere, there are three wind systems which operate between the indicated latitudes:
+The Polar wind system (between the North Pole and 60°N; and between the South Pole
and 60°S),
+ The tropical wind system (between 30°N and 60°N; and 30°S and 60°S)
+The equatorial wind system (between 30°N and 30°S),
(Occasionally inthe westerly wind system, depressions and anticyclones develop. A depression is
an area of low pressure in which winds blow inwards in a circular motion. This motion is anti-
clockwise in the northem hemisphere and clockwise inthe southern hemisphere. A depression
evelops when cold heavy air comes in contact with warm most air. Depressions are usually
associated with cyclonic rains. Anti-cyelones are areas of high pressure in which winds blow in a
clockwise, circular motion in the northern hemisphere. They are associated with cool fine
‘weather with no rain and they normally follow a depression,
Wid direction is measured by a wind vane or wind sock
The wind vane consists ofa freely rotating arm, fitted over a central rod. The arrow ofthe wind
‘vane always points inthe direction from which the wind blows, and the wind is named after this
direction, Four arms marking the direction of the cardinal points are fixed to the stationary
central rod
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Cloud cover
by using eyes. There is no special instrument for recording the cloudiness. Okta is the usual unit
of measurement ofthe cloud cover. One okta represents approximately 1/8 of the sky with loud
cover If approximately 3 segments out of 8 are covered in clouds, then the cloud covers writen
2848 cloud cover. These ae 3 oktas. 8° means the cloud is completely covered by clouds. The
figures below represents the symbols used to represent cloud cover in oktas
©) Clear sky
iS) One-eighth cover
oO Two-eighths cover
ie) Three-eighths cover
@ Half of the sky covered
ge Five-eighths cover
@ ‘Three quarters cover
fia Seven-eighths cover
@ ‘Complete cloud cover
@ Sky obscured, e.g. by fog
Symbols used 1 show cloud cover
Simple observation can be made suc as:
+ Clear=no cloud cover
+ Parly cloudy es than half loud cover
+ Mainly cloudy – more than halfcloud cover but with some breaks in the cloud
Sunshine
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Inponance of sunshine
The energy from he sun canbe tapped, harnessed and pu ino various uses including cooking
cating lighting and operating machines I also affects the amount of eat reesved on he ca
When the sun shies for many hous, the temperature of he earth rises and when there is 0
sunshine the temperature drops down,
The sun’s energy is used by geen plants to make their own food though the process of
photosynthesis. Solar energy is also used to dry crops, clothes, etc. Our skins are also capable of
converting he solar energy it vitamin D.
Evaporimeter
‘An evapoimeter ian isrument used o measure the speed and amount of evaporation of water
from the surfice ofthe earth. There are two types of evaporimetes
Tank evaporimeter—measures evaporation fiom an open and fee water sufice. The an is
fled with water to a known level and then exposed in an open area which i fee from
ebstruction where water lef to evaporate, The water level is measured using a micrometer
screw gauge. Any reduction inthe level of waters because of evaporation
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Tank evaporimeter
Piche evaporimeter—measures evaporation fom a continuously wet and porous surface.
Importance of Elements of Weather
Explain the importance ofeach element
Importance of temperature
+ Temperatures an important fctorin rain formation, Temperature causes the evaporation
of water vapour from water bodies, land and plants. The resulting water vapour then condenses
to make clouds that form rain
+ Temperature isthe main factor inthe creation of wind. When the sun heats the eah’s
surface unevenly, the resulting changes in temperature create changes in pressure and density
‘The utimate result ofthese changes isthe movement ofr fom a region of high pressure (cold
area) tan area of low pressure (heated area). This movement of ais called wind
+ Plant growth and development is also highly influenced by temperature. It affects
transpiration, seed germination and the rate of photosynthesis indifferent ways
+ Temperature controls planting dates and the growth of plans as well a insect pests and
crop diseases. As an integral part of weather, temperature also determines the type of
precipitation that might occur if you are in a location that is experiencing near freezing
‘Weather Station
Meaning of Weather Station
Define weather station
‘A weather station is a facility, either on land or sea, with instruments and equipment for
‘measuring atmospheric conditions to provide information for weather forecasts and to study the
‘weather and climate. The measurements taken include temperature, barometric pressure,
humidity, wind speed, wind direction, and precipitation amounts,
Wind measurements are taken with as few as other obstructions as possible, while temperature
and humidity measurements are kept free from direct solar radiation, or insolation, Manual
observations are taken at least once daily, while automated measurements are taken at least once
an hour. Weather conditions out at sea are taken by ships and buoys, which measure slightly
different meteorological quantities such as sea surface temperature, wave height, and wave
period
‘Weather station data can be used to gauge current weather conditions and to predict the future
‘weather forecast, like temperature high/lows, cloud cover and probability of precipitation
Weather stations are used by meteorologists, weather buffs, gardeners, farmers, outdoor
enthusiasts, students pilots and anyone who enjoys weather data or relies on the weather to make
decisions.
How to Establish Elements of Weather
Explain how 1o establish elements of weather
Selecting an appropriate site for the weather station is critical for obtaining accurate
‘meteorological data. Typically, the site should represent the general area of interest, and be away
‘rom obstructions such as buildings and tees
‘When establishing a weather station the following guidelines must be considered:
1, ‘The station should be located on an open space with fee circulation of ar.
2. There should be a wide view of the surrounding landscape andthe sky.
3. The site should be five from obstructions by trees, buildings, mountains, ete. The station
should not be under the shadows of objects. The open areas should be covered by short grass, or
where grass does not grow, the natural earth. Avoid large industrial heat sources, rooftops, steep
slopes, sheltered hollows, high vegetation, shaded areas, swamps, areas where snow drifts occur
oF low places holding stagnant water after rains
4, The ground should be plain or gently sloping at gradient not more than S*
5. The station should be fenced to keep off intruders, trespassers and passers-by and should
always be locked. Only authorized people should have access into the station.
6. The geographical location of the station should be established by placing a compass in
the station This will help in determining the direction of wind shown by a wind sock /vane put
inthe station
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Characteristics of a Stevenson Screen
Describe characteristics of «Stevenson screen
{A Stevenson sreen or instrument shelter is an enclosure intended to shield meteorological
insrumens agaist precipitation and direct heat ration from ouside sources, while sill
lowing arto ctcultefely around them. I forms part ofa tandard weather station.
or
Exterior ofa Stevenson screen
Characteristics and Functions of Instruments Used to Measure the Elements
of Weather
Describe the characteristics and functions of instruments used to measure the elements of
weather
The Stevenson screen holds instruments that may include thermometers (ordinary,
‘maximum/minimurm), a hygrometer a psychrometer, a dew cell, a barometer and a thermograph.
Its purpose is to provide a standardized environment in which to measure temperature, humidity,
dew point and atmospheric pressure
‘The traditional Stevenson Screen is a box shape, constructed of wood, in a doublelouvered
design. However, it is possible to construct a screen using other materials and shapes, such as a
pyramid. The World Meteorological Organization (WMO) agreed standard for the height of the
Stevenson Screen is between 1.25 m and 2 mabove the ground.
Interior ofa Stevenson screen
‘The sting of the sreen is very important to avoid data degradation by the effects of ground
cover, buildings and tees, It is recommended that the screen be placed atleast twice the distance
ofthe height ofthe object, eg, 20’m from any tre that is 10m high. In the northem hemisphere,
the door of the screen should always face north so as to prevent direct sunlight on the
thermometers. In polar regions with twenty-four hour sunlight, the observer must take care to
shield the thermometers from the sun and atthe same time avoiding a rise in temperature being
caused by the observer’ body heat.
The general purposes ofthe Stevenson Screen ae
+ twensure the safety ofthe delicate instruments kept init which could easly be damaged
kept inthe open sir
+ twensur accurate measurements ofthe meteorological data; and
+ to protect instruments against precipitation and direct sunlight and heat, while still
allowing air to circulate freely around them
Measuring Elements of Weather
Measure and record element of weather
De
Measure and record elements of weather
The Meaning of Weather Forecasting and How it is Done
Describe the meoning of weather forecasting and how itis done
Weather forecasting is the application of science and technology to predict the state of the
atmosphere for a given locaton
Weather forecasting methods
The nature of modem weather forecasting is not only highly complex but also highly
quantitative. There are several diferent methods that can be used to create a forecast. The
method a forecaster chooses depends upon the experience of the forecaster, the amount of
information available to the forecaster, andthe level of difficulty that the forecast situation
resents, The various methods used in forecasting the weather at as follows
Numerical method
More recently it has been realized that other methods can more accurately predict the faure
‘weather than was possible inthe past. The numerical method involves alot of mathematic. This
method is based on the fact that gases ofthe atmosphere follow a numberof physical principles.
Ifthe current conditions of the atmosphere are known, these physical laws may be used to
forecast the future weather.
[Numerical weather forecasting is made possible by making observations ofthe atmosphere by
means of radiosonde stations all over the world, A radiosonde isa small weather station coupled
with a radio transmiter. The radiosonde is attached to a helium or bydrogen-filled ballon,
encrally called a weather balloon, and the balloon lifts the radiosonde to altitudes exceeding 30
km, Dutng the radiosonde’s ascent, it transits data on temperature, pressure, and humidity to a
sea, air, of land-based receiving station. ORen, the position ofthe radiosonde is racked through
GPS, radar, o other means o provide data on the strength and direction of winds aloft. Thus the
radiosonde flight produces a vertical profile of weather parameters inthe area above which i
was launched
At precisely the same time each day (0000 and 2400 UTC), weather personnel across the planet
release radiosondes tothe sky. The data obtained are processed, corelated with data from other
radiosondes, and used to create an instantaneous picture of weather conditions throughout the
world. The data are used not only to understand current weather pattems but also as inputs for
Jonger-range computer-based forecasting models,
A radiosonde
Satellites
Radiosonde data are supplemented by means of radiometric observations from satellites which
also provide data on humidity and cloud cover. For viewing large weather systems on a
worldwide scale, weather satellites are invaluable. Satellites show cloud formations, large
weather vets ch as canes, and ther global water yates, With slits, freien
can sce wether scros th whole globe: the ora, coninent, nd poe, Recent slits dati
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Persistence method
This is the simplest way of producing a forecast. This method assumes that the conditions at the
time of the reas wil ot chang. For example, ie snny and 30°C today, the essence
tnt predicts wil be suny and 30°C tomorow. ten millimetres of ain fly, the
persistence meted would predict en mimes of fo tomorow
Trends method
This meted involves determining the ped and diction of mover for fos high nd low
prenre cente dae of loud nd precipi. Using his infomation, the rca can
predict where or he expects those features ob at some fur time. For example, isto
system is 10 kilometres west of your lation and moving to he esa 20 klomtes per dy,
sing te tends tod yon wold peti anv i your wen in S dey
Climatology mein
The Climatology Method is another simple way of producing a forecast. This method involves
verging wether sists scumulated over many year io make the forecast. or example i
you wer esing the climatology method oped the weather fr Dar Salaam on July th, you
would go though all the weather data that has been recorded for every July 4th and take an
average. Ifyou were making a forecast for temperature and precipitation, then you would use
this recorded weather data to compe the averages for temperature and precipitation.
It these averages were 33°C with 0.18 inches of an then the weather forecast for Dares Salam
on July Ath, using the climatology method, would call fora hightemperature of 33°C with 0.18
inches of rain. The climatology method only works well when the weather patter is similar
that expected forthe chosen time of year. I the pattem is quite unusual for the given time of
year the climatology method will fen fi
Importance of weather forecasting
Weather forecasters alr farmers of the prospects of and amount of rainfall hati expected in a
particular area Tis enables them to decide what kindof crops to grow. I the forecast indicates
lite rain then the farmers ae advised to grow crops that resist drought o thos that take
short time to mature. It, therefore, enables farmers to plan their farming activities well nd in
advance
‘Weather forecast nd warnings ae the most nmportan services provided by the meteorological
profesion. Weather wamings ae also important because they ate used to save lives and protect
property. The forecast saves lives and prevents the destruction of properties. For example,
forecasters often wam people about the coming of exteme weather events such as tsunamis,
carthquakes, foods, huicanes or strong winds so that they can vacate their residence to save
lives and property. This also enables people to get prepared to fae the aftermath of these
extreme weather event, In severe weather situations, short-term forecasts and warnings can help
save lives and protect prope.
Natural disasters such as buricanes and tomadoes result from cern weather pattern
combinations and can injure or kill thousands of people depending on their scope. These
disasters offen do lasting damage to cite and ecosystems as wel. Because ofthis, being able to
predict and understand weather patterns is very wefil skill when preparing fr disaster.
Forecast based on temperature and precipitation is very important to agriculture and therefore to
traders pochesing, ranspoting end seling agscuhral produce
Sailing and air travel are also highly controlled by the weather. We often hear of cancellation of|
air and sea travels due to harsh weather conditions. Accurate weather forecast therefore enables
the marine and air transport personnel to schedule thei travels in advance
(On everyday basis, people use weather forecast to determine what clothing to wear on a given
day. Since outdoor activities are severely curtailed by heavy rain, snow and wind, forecast can be
used to plan activities around these events and prepare to survive them.
Weather forecasting in Tanzania
In Tanzania, weather forecast is conducted by Tanzania Meteorological Agency (TMA). This is
4 government body responsible for weather forecasting and dissemination of forecasting
information to the general public. The agency forecasts weather on daily basis and alerts the
public about the prospects, intensity and the expected consequences likely to be caused by
‘weather phenomena such as rainfall, storm, sea waves, atmospheric pressure. Information about
the forecast is used by the government to protect life and property. It is also used by individuals
to plan a wide deal of their daily activities