Tephi and Stability

7/26/2019 Tephi and Stability

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ATSC 3032Tephigrams, and static stability

sources:

-handout text

-online module called Se! T mastery"
http://www.meted.ucar.edu/mesoprim/skewt/http://www.meted.ucar.edu/mesoprim/skewt/


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#$ Aerological diagrams

% &adiosonde 'or ra!insonde( data

) *aps) +ertical proiles

Instrument contains:

Hygristor, thermistor, aneroid barometer, and

radio transmittor

At the ground, a highly directional radio

direction finding antenna is used to obtain the

wind speed and direction at various levels in the

atmosphere by tracking the radiosonde and

determining the azimuth and elevation angles.


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Aerological diagrams

% ydrostatic balance

% .deal gas la!

% ypsometric e/uation


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Aerologicaldiagrams: dierent

types

emagram


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Stue

temperature

p

d

c

R

p

p

ressure


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Stue


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Skew T log p


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Fig 1d. Elements of a tephigram. irst, the ! lines are shownseparately, and then they are combined in the lower"right image.


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2$ using a tephigram


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tephi


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#$# %lifting condensation level&

Applications

'. (etermine the height of the base of cumulus clouds, given surface

observations of ) and )d :

*. (etermine the cloud base temperature:

ground

+

d

Tdd

d

LCL

TTTTH

=

=

#$#

LCLsurfacecloudbase HTT ',=


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potential

temperature

wet"bulb

potential

temperature


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e-uivalent

potential

temperature

saturated

e-uivalent

potential

temperature


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!et bulb temperature:energy balance on the damp soc:1 1 4 u 5esat'T!(-e6 7 u 5T-T!6'&egnault balance(


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A li i


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'. #ayer thickness %between poand p&

z ' )

z

Applications


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*. /recipitable water


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3$ Chinoo '89hn( eect


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west eastCascade Mountains


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7$ subsidence


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$ Turbulent mixing, mixed layer 'stratus(, *C1


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0akland


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Consered or not consered;&adiational T aporationotential instability

/otential instability: dz

d e

dz

d wor


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#ifting a potentially

unstable layer

# i bili


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#atent instability

3#4: wet"bulb lapse rate

deep conectionsource layer


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Stability indices


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Signiicant leel indices

% ?@0: ?et bulb ero, T! 0BC ideally -D,000t *S1, yet !ell belo! the 81

% >?AT: >recipitable !ater 'mm( the higher the better

% 1C1: 1iting condensation leel 'mb, rom surace data( the lo!er the better

% TET1: Total totals index T F0GTd F0- 2T 00'BC( the higher the better,thunderstorms probable !hen TET1H:0

% I.JK: I index T F0G Td F0-T 00-'T-Td(00'BC( the higher the better

% S?T: S!eat index or seere !eather threat - the higher the better, or seerestorms, S?H300 S?T #2=TdF0 G20='TET1-7D( G 2=LF0 GL00 G#2='0$2Gsin( !here 5!ind direction 00 - !ind direction F0 6

L is expressed in ts and TET1-7D is set to 0 i TET1M7D% *1T and *1*&: mean mixed layer 'lo!est 00 m( potential temp and mixing ratio

e$g$ L? sounding site


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Lifted indexuses:

Actual sc temporstimated max sc tempor*ean mixed-layer temp

'note: al!ays use irtualtempN(

>A&C1 indices
http://weather.uwyo.edu/upperair/sounding.htmlhttp://weather.uwyo.edu/upperair/sounding.html


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5howalter inde6

5I)!")p,+!

>A&C1 i di


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>A&C1 indices

% 1.8T: 1ited index 'BC( must be negatie1. T:00) T parcel,near-sc5a 0 mb deep mixed layer is oten used6

% 18T+: lited index, but Tis used$% SE?: Sho!alter index 'BC, as 1. but starts rom F0mb( must be negatie

SE? T:00) T parcel,F:0% CA>: Conectie aailable potential energy - should be oer :00O+: CA> using T

% C.JS: Conectie inhibition 'external energy( - ideally #00-300 O: Cap strength 'C( Ten)TparcelP1C1 - should be M:BC

% 18C: 1eel ree conection '18CT and 18CT( 'mb( - should be close to the 1C1% Q1: /uilibrium leel or leel o neutral buoyancy 'Q1T and Q1+('mb( - should be high% *>1: *aximum parcel buoyancy leel 'mb( - leel !here buoyancy 'Tp-Ten( is maximum


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?ind parameters

% ST*: stimated storm motion 'nts( rom 0-20,000t AR1 layer, spd o mean, dir 30 deg eer 'to the right( rom mean !ind$

% 1: Storm relatie helicity 0-#0,000t AR 'total alue(

% S&G: >ositie shear magnitude 0-3000m AR 'sum o eering shear alues(

% S&S: Storm relatie directional shear 0-3000m AR 'directional dierenceo storm relatie !inds(

% .: nergy helicity index 'prop to positie helicity = CA>(% @&J: @ul &ichardson number 00-4000m AR '@&J CA>


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example mid-term /uestions


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example mid-term /uestions

% As a rule o thumb, thunderstorms are possible !hen 1.M0, and seere thunderstormsare liely i 1.M-F$ Assuming surace alues T32BC, Td22BC, T:00-BC, calculate Tatthe surace, and the lited index 1. based on both T and T$

) Jote that traditionally 1. !as calculated based on T, but the more correct procedure usesT$ The dierence is small but not negligibleN

% Lsing a gien sounding on a tephigram, graphically determine, or an air parcel at F0mb, the ollo!ing: 1C1, T! , r, rs, e, es, &, , !, e=, e,

% Lsing a gien sounding on a tephigram, graphically determine layers o:) absolute instability) conditional instability) potential instability) dra! a parcel ascent path and shade the areas o

% positie energy 'CA>(% negatie energy 'C.J(


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#I)"7 8

$A/E'97 ;


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Tephi and Stability