FLOOD10041

• County: Boulder
• Basin: South Platte
• Title: Twentieth-Century Change in the Climate Record for the Front Range
• Date: 1/1/2000
• Prepared For: Boulder County
• Floodplain - Doc Type: Educational/Technical/Reference Information

j::::LII !::::l~,~...
I . . ...... ......."'c"c..c'"e'."
."' ..... "" 952~J997) 8-?O mb
..... .M.. <S. CS. <N" "" osphenc l~vel5 (J
. . .~. .. 'S .. C < I=su al differ",g Olm
Ire umcy of SH'apllC C
FIGURE 6 Dafi"Y 195t/997 orrlv
juque"c'tsau or

Sea-le...el

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~ '00.

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750 mb

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Positive vonicilY;5 associated
rous Z meaSUreS VOM!Clly thanucyclones 1lIeob-
vIga d ll~gauvc vortICIty WI (Z F. and
WIth cyclones an <kcldcdllu-oughcompansono.
ct:uvecJasslticauon IS and W)
~ow direcllon (obta.med from~ foc dIfferent synoptiC catcga-
Examples of pressure <; ~e synopuc classlticallon can
ncs are shown 10 FIgure 1~mb pressure pallem tends ItO ~
change wlthbe'ghl a$ the lome syslcms are well deveope
I lIlan al sea level eye he Front RilIlg:c where-
sImp cor wnll ......^ucnt upslope lIow m 1 s mmC! cspc"lally
UI spnng..."", ore COnullOll In U .
as anucycloruc c1llS5es arem f largeupperlevelndgeleadmg
11700 mb A Soocl e>;amPI:a~O: IS shown for 16 June 1988
to an anlleycloruc classd'i tupperlevelSlsrcpreKntedby
whereas a good cycloruc storm: anero IS a strong zooal tlow
o A 11995 Another commo Pless commott. such as the
I Mpn 1984) Some strual10ns are 2 M h 1994. of wblch
(24 ay 00 b bownfor I an; ff
AEclasSllicauonal7 m s In this case. despue the cut-o
there were only three eJUlmPleS,on flow over Colorado IS IIth-
the Four Comers rcg .
10;1:~~ due to the ndge over wyo'":l:i classes a.l dlffereOl al
cy FreQUencYbUilOgramsofSY;:::'atb,gberleVelstheC,fCU
mosphenc levels (F,g 6) show tn a Illpld Increase In the class
mes less variable. Wit amJ a decrease In
~;:::;e::,:: of weslerly dommated ~~~:at::~':es (1952-1997) al
frequencies of easterly Slluallons

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TABLE 5
. W F. and Z. Va/IOn for
Mean ""/..es of cjrc..IQI;;~:-1~c;;, ;;'/y (as opposed /0 195Z-
850 mb arc basfld 1;~7 for all a/her le~els)
,

1..cvel
Sea le..,I/lD13mbJ
~,~
700mb
500mb

w

-0.7
-2t'-2
-20.~
-20,6

->0
28,7
67,)
121.6

.,
M,'
89.)
1546

-2.5
-IB,O
-25.9
-30.1

'"

"0

'"

Ai..PtNE REsEARCH
140 I ARCTIC, ANTARcnC, AND

850 mb

"

500 mo

,
,

show slIonger zonal flow
th four aunosphenc levels {Tab~e ~ There IS relal1vely Imle
atehiih levels (mcreased wanOnd1ll0nSaremoreanllCYclOO,C
emSw,thhe,ght Meanc dical1ve ofa mean upper
c~a;~ z.) In the high atmospher:~:a110nISanabSlIaC110n .he
( 11lesea-levelsynophcclas, I I but was retameddue
:~~~ region bemg well above se: ~:e uenc,es Sea level clas
to the equ,table dlslIlbullon of ~~seful;n other studies of wes'l
slficalloru;havCbeCn!ihOWn~O 1981) espeCially SlOce !iea-leve
em U S clima(C ~~::b~ fo; long Ittne penods
pressure datil arc

/(esulu om:lated wilh the four indices of
Firsl.lapse tales wcrc cd second. mean lapse rail'S were
cin:ulalion on a dally basiS. an S i;orrelationsbetweenoveraJl
calculated ror each SYllOP~cl;l:d' indices shaw diffe~ences be.
a se Illte (Longmont vs com:lation wuh Z IS POSlllve
l~en day and nigtu (Table 6). ~:loniC condiuons (posHlve Z)
'ng steeper lapse rates for Y ight. Rdauon!ihips be.
~:;elaliOnSItiPisespedallystrongatn "

TABU 6 d
ra/e (u.."llmo'" vs.DII""
Correlalionl between over:III;~~~ 700 mb: (al d<.l.vWlle '''P~;
cm;ulo/i~ll india:,u': l/::;:r:/aru). (bl 1llghwme lapu r<.l
rale ("ally max'(daily ,"",imam tempera/aiel)
W

,

(olDoyupoeRale
S"a'e_'
700mb
1I.) Nilh't..;opo.c R"'e
Sealevel
700mb

021N'
0.47'"

-0.38)6'
0,0..\35'

-0,0109
0,0472'

-U.(76)'
o.uun

o 28SU'
0.21IU'

-U2111'
0.05)2'

-()nw"
-olms'

Oll4l~'
-00423'

..= ,ilnilk'I>I"'O,I~

N. PEPIN I 141