Weather and Hydrology
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Transcript of Weather and Hydrology
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WEATHER AND HYDROLOGY
Weather the state of the atmosphere, to the degree that it
is hot or cold, wet or dry, calm or stormy, clear or
cloudy. Most weather phenomena occur in the
troposphere, just below the stratosphere.
refers, generally, to day-to-day temperature and
precipitation activity.
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Climate the term for the average atmospheric conditions
over longer periods of time.
Hydrology
is the study of the movement, distribution, andquality of water on Earth and other planets,
including the hydrologic cycle, water resources
and environmental watershed sustainability.
A practitioner of hydrology is a hydrologist,working within the fields of earth or
environmental science, physical geography,
geology or civil and environmental engineering.
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Water Cycle
also known as the hydrologic cycle or H2O cycle
describes the continuous movement of water on,
above and below the surface of the Earth.
Water can change states among liquid, vapor, and
solid at various places in the water cycle.
Although the balance of water on Earth remains
fairly constant over time, individual water
molecules can come and go, in and out of the
atmosphere.
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The water moves from one reservoir toanother, such as from river to ocean, or from
the ocean to the atmosphere, ! the ph!sica"processes of evaporation, con#ensation,precipitation, in$"tration, runo%, an#susurface &ow.
invo"ves the e'chan(e of heat ener(!, which"ea#s to temperature chan(es. )s"i#e *+
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in the process of evaporation, water taes up ener(!from the surroun#in(s an# coo"s the environment
-onverse"!, in the process of con#ensation, water
re"eases ener(! to its surroun#in(s, warmin( theenvironment.
The water c!c"e $(ures si(ni$cant"! in themaintenance of "ife an# ecos!stems on Earth.
! transferrin( water from one reservoir to another,the water c!c"e puri$es water, rep"enishes the "an#with freshwater, an# transports minera"s to #i%erentparts of the ("oe.
/t is a"so invo"ve# in reshapin( the (eo"o(ica"
features of the Earth, throu(h such processes aserosion an# se#imentation.
/n a##ition, as the water c!c"e a"so invo"ves heate'chan(e, it e'erts an in&uence on c"imate as we"".
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0OLAR AND EARTH RAD/AT/ON
0o"ar Ra#iation
the earth1s chief source of ener(! #etermines weather an# c"imate
0un an# earth ra#iate essentia""! as "aco#ies
Ra#iation wave"en(ths are (iven in micrometers )2m, 34*+
0o"ar -onstant
the tota" ra#iation ener(! receive# from the 0un perunit of time per unit of area on a theoretica" surfaceperpen#icu"ar to the 0un5s ra!s an# at Earth5s mean #istance
from the 0un. /t is most accurate"! measure# from sate""ites where
atmospheric e%ects are asent.
The va"ue of the constant is appro'imate"! 3.6 i"owatts pers7uare meter.
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Solar Radiation at Earths Surface
Insolation
incident solar radiation
Albedo
or reflection coefficient, is the diffuse reflectivity or
reflecting power of a surface.
It is defined as the ratio of reflected radiation from thesurface to incident radiation upon it.
The term is derived from Latin albedo "whiteness”
Being a dimensionless fraction, it may also be expressed as
a percentage, and is measured on a scale from zero for no
reflecting power of a perfectly black surface, to 1 for perfectreflection of a white surface.
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Heat a"ance of Earth1s 0urface an#
Atmosphere
- The Earth1s surface ra#iates at a meantemperature of aout 384-. This emissionhas een estimate# to e aout 9 : times
the so"ar ra#iation asore#.- Net "oss of heat is prevente# an# a heat
a"ance maintaine# ecause the atmospherere&ects ac to the surface aout ;8< of the
emitte# ra#iation. Were it not for thisgreenhouse e%ect, the mean temperature ofthe earth wou"# e aout =644-.
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Ra#iometer
• A ra#iometer is a #evice for measurin( the ra#iant &u'
)power+ of e"ectroma(netic ra#iation. Genera""!, the termra#iometer #enotes an infrare# ra#iation #etector, !et ita"so inc"u#es #etectors operatin( on an! e"ectroma(neticwave"en(th.
• -rooes Ra#iometer
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There are five types:
1.pyrheliometer
.
is an instrument for direct measurement of solar irradiance.
Sunlight
enters the instrument through a
window and is directed onto a
thermopile which converts heat toan electrical signal that can be
recorded. The signal voltage is
converted via a formula to
measure watts per square metre.
It is used with a solar tracking
system to keep the instrument
aimed at the sun
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A research (ra#e p!rhe"iometer
)3+ protection cap, )9+ win#ow with heater,
)>+ si(ht,
)8+ sensor,
)?+ humi#it! in#icator,
)34+ ca"e for heater
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@!ranometer
is a t!pe of actinometer use# to measure roa#an# so"ar
irra#iance on a p"anar surface an# is a sensor that is #esi(ne#
to measure the so"ar ra#iation &u' #ensit! )in watts per metres7uare+ from a $e"# of view of 3;4 #e(rees.
The name p!ranometer stems from Gree, p!r meanin( $re
an# ano meanin( aove, s!.
@!ranometer
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@!r(eometer
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Pyrradiometer
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Net @!rra#iometer
measures the net tota" ra#iation &u' )so"ar, terrestria", an#
atmospheric+ #ownwar# an# upwar# throu(h a horiBonta" surface./t is suita"e for so"ar ener(! stu#ies in a(ricu"ture an#meteoro"o(!.
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Genera" -ircu"ation
0ome /mportant TermsC
ean Dai"! Temperature
- /s the avera(e of the #ai"! ma'imum an# minimumtemperature.
- -an e otaine# ! avera(in( >=or=*=hour oservation.
Norma" Dai"! Temperature
- the avera(e #ai"! mean temperature for a (iven #ate
compute# for a speci$c >4=!ear perio#.
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Dai"! Ran(e in temperature
= The #i%erence etween the hi(hest an# "owesttemperatures recor#e# in a particu"ar #a!.
ean onth"! Temperature
= The avera(e of the mean month"! ma'imum an#minimum temperature.