1 c Wind

8/15/2019 1 c Wind

1/20

6/7/16 C M E T,

WIND

8/15/2019 1 c Wind

2/20

6/7/16 C M E T,

WINDBeaufort Scale of Wind Force

The Beaufort scale is an measure that

relates wind speed to observed conditions at seaor on land. Its full name is the Beaufort windforce scale. It is a measure of wind speed andnot of force in the scientic senses.

The scale was devised in 180 b! "rancis#eaufort$ an Irish %o!al &av! o'cer$ whileservin( in )*+ Woolwich.

The scale was made a standard for ship,s lo(entries on non-naval ships from the 180s. In116$ to accommodate the (rowth of steampower$ the descriptions were chan(ed to how

the sea behaved. Toda!$ man! countries have

8/15/2019 1 c Wind

3/20

6/7/16 C M E T,

WINDBeufort Scale of Wind Forcehe Beaufort scale is an measure that

relates wind speed to observed conditions at seaor on land. Its full name is the Beaufort windforce scale. It is a measure of wind speed andnot of force in the scientic senses.

The scale was devised in 180 b! "rancis#eaufort$ an Irish %o!al &av! o'cer$ whileservin( in )*+ Woolwich.

The scale was made a standard for ship,s lo(entries on non-naval ships from the 180s. In116$ to accommodate the (rowth of steampower$ the descriptions were chan(ed to how

the sea behaved. Toda!$ man! countries have

8/15/2019 1 c Wind

4/20

6/7/16 C M E T,

WINDressure !radient Force

The chan(e in pressure measured across a (iven

distance is called a pressure (radient.

The pressure (radient results in a net force that

is directed from hi(h to low pressure and thisforce is called the pressure (radient force. The pressure (radient force is responsible fortri((erin( the initial movement of air.

8/15/2019 1 c Wind

5/20

6/7/16 C M E T,

WINDCoriolis Force the Coriolis e"ect is the apparent deection of

movin( ob2ects when the motion is describedrelative to a rotatin( reference frame. In areference frame with clocwise rotation$ thedeection is to the left of the motion of the

ob2ect3 in one with counter-clocwise rotation$the deection is to the ri(ht. 4lthou(hreco(ni5ed previousl! b! others$ themathematical epression for the Coriolis

force appeared in an 18 paper b! "renchscientist aspard-ustave 9oriolis$ in connectionwith the theor! of water wheels. :arl! in the;0th centur!$ the term Coriolis force be(an to beused in connection with meteorolo(!.

8/15/2019 1 c Wind

6/20

6/7/16 C M E T,

WINDCoriolis Force The 9oriolis e

8/15/2019 1 c Wind

7/206/7/16 C M E T,

WINDCoriolis Force

%ather than owin( directl! from areas of hi(h

pressure to low pressure$ as the! would in a non-rotatin( s!stem$ winds and currents tend to owto the ri(ht of this direction north ofthe e=uator and to the left of this direction south

of it.

8/15/2019 1 c Wind

8/206/7/16 C M E T,

WINDBu#s $allot%s Law

Bu#s Ballot%s law, the relation of wind

direction with the hori5ontal pressure distributionnamed for the @utch meteorolo(ist 9.).@. #u!s#allot$ who rst stated it in 187. Therelationship states that in the &orthern

)emisphere a person who stands facin( awa!from the wind has hi(h pressure on the ri(ht andlow pressure on the left3 in the +outhern)emisphere$ the reverse would be true.

8/15/2019 1 c Wind

9/206/7/16 C M E T,


Theoreticall!$ the relationship states that the

an(le between the wind and the pressure(radient is a ri(ht an(le. This is almost eactl!true in the free atmosphere$ but not near thesurface. &ear the (round$ the an(le is usuall!

less than 0A because of friction between the airand the surface and the turnin( of the windtoward areas of lower atmospheric pressure atthe same altitude.

8/15/2019 1 c Wind

10/206/7/16 C M E T,


Caution w&en a''l#in( Bu#s Ballot)s Law

1. Near t&e e*uator+ #u!s #allot,s law shouldnot beapplied within a few de(rees of the e=uator. Thisis

because 9oriolis force is ne(li(ible at thee=uator andtherefore the winds blow directl! across theisobars

from )B to CB areas.;. In t&e icinit# of land+ The windeperienced ma!not be the free unobstructed wind. It ma! bewind

8/15/2019 1 c Wind

11/206/7/16 C M E T,

WINDT-UE .ND ..-ENT WIND

There are two inds of wind3 true and

apparent. De call the wind that blows across theland or water$ the true wind. This is the windtaled about in the weather forecast. It is thewind we feel when we are outside at rest and notmovin(.

The other ind of wind$apparent$ is the wind that is

(enerated b! our movement incombination with the true wind.

8/15/2019 1 c Wind

12/206/7/16 C M E T,


The onl! time there is no apparent wind is

when we are at rest and onl! feelin( the e

8/15/2019 1 c Wind

13/206/7/16 C M E T,


In this illustration we

have calm conditions so wemove ahead at notsproducin( an apparentwind of nots fromstrai(ht ahead.&o wind from our ship,sforward motion. The true

wind is 10 nots andthat,s what we feel onthe ship.

8/15/2019 1 c Wind

14/206/7/16 C M E T,


De see the

combined ethe

arrow is lon(er? and is comin( from further

8/15/2019 1 c Wind

15/206/7/16 C M E T,

WINDT-UE .ND ..-ENT WIND4pparent wind is the resultant

of true wind and ship,s reversedmovement >correct speed butopposite course?.

The solution of problems on trueand apparent wind involves theapplication of the trian(le of

forces.

WIND

8/15/2019 1 c Wind

16/206/7/16 C M E T,

WINDT-UE .ND ..-ENT WINDConsider a triangle OA T where,

4T is the course and speed of the vesselET is the direction and speed of true windE4 is the direction F speed of apparent wind.Gnowin( an! two ofthe above$ the thirdcan be found b!simple construction$

somewhat similar toradar plottin(

WIND

8/15/2019 1 c Wind

17/206/7/16 C M E T,

WINDT-UE .ND ..-ENT WINDWor/ed e0a1'le 2H

9ourse 0A speed1 nots.4pparent wind100A at ;0 nots."ind the directionand speed of truewind.

Note+ &orth-+outhlines are to bedrawn throu(h 4and T$ neer

throu(h E.

WIND

8/15/2019 1 c Wind

18/206/7/16 C M E T,

WINDT-UE .ND ..-ENT WINDWor/ed e0a1'le 3+

9ourse ;000 speed 1 nots. True wind 000 at18nots. "ind thedirection andspeed ofapparent wind.

WIND

8/15/2019 1 c Wind

19/206/7/16 C M E T,

WINDT-UE .ND ..-ENT WINDWor/ed e0a1'le 4+ 9ourse 160A speed 10

nots. @irection of wind >obtained b! observin(line of waves? was ;70A. Dind speed b!shipboard anemometer was 17 nots. Dhatdirection andforce of wind isto be enteredinto the ship,s

lo(booJ.

WIND

8/15/2019 1 c Wind

20/206/7/16 C M E T

WINDT-UE .ND ..-ENT WINDWor/ed e0a1'le 5+

9ourse ;0A speed 1; nots out inopen sea.Dind force >16 nots?$estimated b! appearance of thesea surface. +moe from thefunnel was observed to beblowin( to 00A. Dhat entr! is to

be made in the weather reportre(ardin( wind direction andspeedJ

1 c Wind

Documents

Transcript of 1 c Wind