weather and hydrology

8/18/2019 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.

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