Interruptions in the Normal Westerly Flow of the General Circulation of the Atmosphere Citation Smith, Theodore Beaton (1949) Interruptions in the Normal Westerly Flow of the General Circulation of the Atmosphere. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/s796-wx62. https://resolver.caltech.edu/CaltechTHESIS:07312025-211042466 Abstract Certain effects associated with the intrusion of stable, persistent high pressure cells into the normal westerly flow of the general circulation of the atmosphere are investigated. These intrusions are termed Blocking Action processes. By means of empirical and semi-statistical procedures these processes are found to cause the development of long stable wave patterns in the atmosphere downstream from the point of inception. These wave patterns may exist for periods of a month or more. The wave length of these stationary long waves is found to be longer than that determined by other investigators. This is explained on the basis of the larger amplitude of the long waves associated with the Blocking Action process. A theory of the formation of these blocking high cells is suggested based on the accumulation of heat in low latitudes and the necessity for the readjustment of the general circulation to redistribute this heat. One means of dissipation of the blocking cells is shown to be the formation of a wave pattern in the atmosphere which is out of phase with the stable wave pattern formed by the blocking High. The optimum mean pressure chart is discussed in terms of the long period Blocking Action processes. The optimum length chart is found to cover a three day period or a period of greater than twenty days depending on the use to be made of the chart. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: (Meteorology and Aeronautics) Degree Grantor: California Institute of Technology Division: Geological and Planetary Sciences Major Option: Meteorology Minor Option: Aeronautics Thesis Availability: Public (worldwide access) Research Advisor(s): Elliott, Robert Dunshee Thesis Committee: Unknown, Unknown Defense Date: 1948 Record Number: CaltechTHESIS:07312025-211042466 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:07312025-211042466 DOI: 10.7907/s796-wx62 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 17580 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 01 Aug 2025 16:59 Last Modified: 01 Aug 2025 17:03 Thesis Files PDF - Final Version See Usage Policy. 55MB Repository Staff Only: item control page

~ om m 'IDE MOBMAL Vi!!SmRLY ll'IJj'{f OF 'lliE Oli1'IBRAL CIROU!.JI..TIOU OF THE A'l!,,100?.JFlRB 'lhesis by '!heodore Dea.ton 3!l11th In Partial Fulfillment of the Require..'ilents t~ tr.s De~e ot Doctor (1f PhilO&0phy California Inatit"Ute of 'l'$ehnoloe:, B:lsadena; Cali:rorn'-8 1940 ACT.flfOWLEOOMElJ:~ 'Iba autho:r wishes to e~preas his apl.)reeiation to the Ott1oe of lla'lml R8S$;l,Nh without Whose support this investigation could not ha.VO been carried. out. Re is e.lso indebted to Protesaor Robert D. Elliott 'tor his original detinition ot the problem end to Dr. Irving l'.->. F'rt4k and Pro.tessor Elliott tor tliair inte:rest and helpf'Ul SU{Y.,gestious throughout the ttork. UUtlh ~redit is due to Mesda!\Ws Gere.nd, DillQ!l, Robert;s• Gottlieb end m.ss Kine 'tor pertol"ming mny ot the tedious calculations neceesar-1 1.n this r.ttu<ly. Certain etreats asaoeia.ted with the intrusio..11. of sta.ble 1 :peraistent h15h pressure eells in-to the no:rma.1 westerly flaw . (]£ the gene:ral. oi.roulation of the atmosphere are inveisti~ted. These intrusio.na at"e temed mocking Action proees~s. By r'l8an8 ot empirical a.."l.d $8m!-stat1Gt1oe.l :proceduree these proa.ssee are :t'ou.nd to cause the deve~t ot long stable wave ,P9.tte,r ns in the a.tmosphei-e downstream tran the point of inception. These. we.v. patterns my enst tor periods or a month or more. The •ve 1~"1ih ot these ete.tiOlllU'Y long waves is found to bf longer than that dete~ by other investiga.tors. This is explained on the bas.ts ot the ~ r amplitude of the 1011€ wavee aaaoeiated with ti. BJ.ookine Aotion ~ss. A theory of the tormaticn of then bloeldng high oelll ia sugge$ted baeed on the aeoumulation ot heat in lav latitudes and the necesaity for the readjustment ot the general e1NUlat1on to "Matrl bute this beat. One means ot dissipa:t1on or the bl..oold.ng oells is: shown to bt the :rorrntion of ~ wave i;atwm. in the atmosphere which is out of phase w1 th the stable wra'Vf) p:;i.ttern formed by the bl.ooldng !!1,gh. '1M optimum. mean pressure ellSl't is d:1aeUS$&d in tmns of the lcm,g pe:,ied Bl.ocldng Aet1on processes. 'Ihe optir.m.m. length e.hart 1$ found te t .o ver a ~ aay period or a p&:riOd ot greater than tm.,nt:, days de-pending on the US$ to be mad♦ ot ths o.be.rt. TAJ:1£..B OF CC!1TElnB TITLE Introduction nart l :Fart II PAGE 1 The 1"tfecta of the Establiehnent of the nlockinc EiSh 5 The :rornation of the Blocking Ilgtion 51 I'.ddy I ~III The D1ssire.tion ot the Bloold.nt; 68 Action l:ddy ntrt IV cone1us1on The Opti.mum Use of 1 ~ Pr•aourie Cbarts 85 Un.RODUCTI<E 'lhe t'ol.lawine study is a pQJ:'tlon ot the research report su~ttecl to the Ott1ce of t-re:n.l Reaearoh ~der Contract No. NG om.--24-4. 'lld.s woz9.t llQS been carried on tor the Ill&t year by the ~ o g y Departl!!ent of the California Institute ot Teohnolesy under t.he superne1on of Protessor Robert n. ro.liott under the title of "Bloold:ng Acttcm.." For the p..u:oposes ot thi• investi©ltion the term ln.oakine Action baa been used to characterize the disturbed state ot the genenl o'ucu1ation ot the atmoaphere during periods or strong, pora1stent, muid1onal. type flow. On the &iily weather •P this d1sttll'b9d state le discernible as 1nt2'usiona of 1ta.ticmary or -very slowly MOVing htsh pteaSUH eel.la into the middlo latitudN nor.m.ll.y oceufd,ed by a general weste:rly' tlcw and n01'11Bll.y chnneterized by alternate ~sse.cos of m1e;ratory 010l.ones and ant1o,olonea. Stnoe the bl.ookil'l8 oell may ii. in existenoe for perloc1s ot a month o:r .more this IlJlBt constitute a ,raJor interruption in the norml ~ Pl'Ol:'!;reBS ot the m1e,.,atory oyol<meo and antio;yolones, .at lee.at in the area dominated by the blocld DB I:U.gh. In another phase oZ the project Proteseor Elliott (l) has tn,ated the seasonal variations in Hlooldne Action, lateral ml.Xing and meridional heat transport b1 uso ot the 'broe.dseale lateral turbulenoe prinoipl.os introduced by Dei"ant and tetto.u ( 2), ( 3). IJe has indicated that seascms ,rl.th excessive mockine Action are chf.utacterl.zed by excessive mixing and laree values for the meridional heat tranel)Ol't. The phase of the study which will 'be treated here is the fluctuations durinc periods ot twenty to thirty days ot the general o1rculation precoding o.nd following the inception or mocking Action. The problen £'BY be stated non: e:xpl.1eitly as the study ot: 1) Cha.ngeo in the ge-nernl eireul.e.tian ~ttern antecedent to the f'orration or -the blocking Hir)l, D) Cha."l.GGa 1n the cenerel. cirt:uletion -pattern otteotcd by the establishment of the blocking I:r1gh• 3) Chan.:_,"'8:S in the general emulation i:nttern a o ~ the dissi:pation ot the blocking Iligb.. From a consideration of the data available, two gen$ral .methods ot attack are possible in an investi~t1on of the dlJtails ot these ohei.nge.s in the g&neft1 cireul.e.tion. '1be :first involves a oaretul three dimens1oml.anal:,s1s of a tew examples or nl.oCJking Action. 'l1le aeoond t,molves the analysis or o. relatively largo nw:iber of cases uaine only auch date as oan be obtained troti surface weather c.harts. Tho s ~ ot the data tor the first method is somo six m.onths of r.:iorhll.ern I!a.11!1s];lhere daily surface maps and 500 m.b. mape, three to tour years ot oanpl.ete surf'aoe end upt>er level r.aps end ae;ro... loSioal soo.ndinee ror the North Amari can cont1n-ent only. Since th& aspect of greatest 1ntereot ie the ehnnse in ei.reUlation pattern e.t pcinta considerably removed f'ron1 the im:Jedie.to area or the blocldDG litgh, tho source ot three dimansional. data is ~atricted to auoh ~ Qxt,ent th.at the tirat method bas been conoidereci unQatistaotcry for the purposes ot: this imreatieation. The so~ ot ~ tla:ta tor tho aeoond method 1a the forty ~r series ot &dly m.stor1oal. ~ r n <'71 J Hemiepllere aee. level charts trom lfhich sea level pressures and to a limited extent surface ten.peretill'G data can be obtained. 'file bae1o date. t-aken from these charts have been sea level pressu:ree et the interaectiOP..s of ea.oh ten deereea of longitude and five degrees of' Jatittlde in the a:ree. bounded by longitudes 14.0° E and 400 E ( t.b»ough looO) arid by lati tudea soO !if and 00° !!• This ~ comprises the largest area on the forty year i1orthern I!ernisph&re fllP series for whi.o,h the analz,Boa oan be oonaidered as reliable. Extensions of the area ~ s1 beria. a.."ld north ot G<:P U would be hi@lly desirable but a.re not practicable fron this series o.f rnps. The pressuro drrta 'ba.14'..en fra..1 tho above intersectione have been used to oor.ipute dailr aeJ;X,.rturoo f:ron the nonnal pressure at each ct thoa$ 111terseot1ons tor the t'o:-t:, January...i?ebruary "s8a$0W!1" ineluded in the Northern Y~.rnis)?hbre r:ep SOl'iea. The data ho.ve boen divided• in f':8!1m"8.l, into the eire11 yeara as o. dwelop!:X)nt sample a..~ the odd yoars as a chock sample. 'i!1ese :prtlSsure departures have formed the basis tor nost of the work undertaken in this inveati©,;1tion. T.b.c data are t~rea~d. ~Y a grouping of emr.1plea u.1.th atatiatical procedures being used w!1enqyer oond:t t1ons pel"£1i t. ~ta in the form of $00 lovol :r,ream.1.l"ea are not rM411Y adapt.able to the application of tho nUtWrous kinemtical and d,y!ntl!eal principles which my ~p:pl.y in the mocking Action ease. li:ny s ueh -a.pplioo.tion must be rnde by !nf'eNm.ce tror:1 the obs.~ soo level !)ressu.re distributions. 'l'he vn1ue ot the imrostie;iltion, the."l., lies in the reeoeni t1on of' some of the proecsses a.eaoeiated with Blocl-d.ng Action thrcmg}.1 a eonsiderution of n l'l'.llatively large num'bor ot ®.SOe. Theae 4 prooesaea may then be studied in more detail in: individual emnplee wliere a more adequate network of data ie available. Due to t~ character ot the availab1e data and due to tr..e oonp1.en ty or the interactions between va:riaus Bloolrlng Action high eel.la, it can hardly be expected that this study Will ha.vo :much semblance of eompj.etenese. . . It is hoped, hffl'l.-ver, that there have been a auttioient nu..'n'ber or nn ideas introduced to ~ t e interest, toward i'urther ~roh in this t"ield. 5 PART I. 'l:It::~ El?F.GC'.LU OF TIE! :rm,rm:rmrt.!ElIJT OF TIE ELOOr.n:ro IllCID The General Problem In Ol'der to visualize the ~ c e of the introduQtion of a semi-stationary high ~acu.re cell into the lat1 tudes nO?'l'i'ally occupied by o. westerly fltm the ettecte ot this 4ietur~ on the o11"Cttlation :i;nttEmls u;pstroom and downstream trom tho blocking lJigh will be dUcussed tmt. In tho later sections aor.1& of the details ot t.he ohe.nges in too circulation Jntterns a e ~ the torcntion c.nd diasi1X1-tion ot the blocldng h1eh oell will be investii;ated. Objective cntena ln order to se~te those cases which will be troe.ted from those which arc ot less :l.trportance eomo objective definition ot the oxiGtcnc~ ot llJ.ooking Action lm.lSt be t'ormulat.d. Using sea level :r,resSUl'O data this def'1n11:.1on can tolce many f'orroo depondine on the ~tude desired, the auount of r..overiont of the bign oonter pernittM, ote • Several er1 teria have been ttsed 1n the inwstit:llti on o.nd each will be discussed in the section to w11ioh it applies. Acewding to the oonoept of a blocld.ng high cell. the general orite~on that must ·1,o satisfied is the erlstenoe ot Pf)rs1stent, abno~ high preasui-e in the bolt usually ocoupied by otrong westerly nc.. 'Ibis belt un.4-r ' nve~e conditions extends betwotn latitu.4es 456 U and 5oO Nin the Fac,1:tto Ocean area, 'b$in,e 4iaplaeod ~ r d slightly in the 11'o:tth 6 Amerieen eontinenta.l area and rea~h1nc 55° to Go0 lil' in the eastern Atlantic ocean and 'i!-Jeotem ~ area.a. Persistent high :riresSUi"e 1n any pQll't1on ot tltis bo.nd then constitutes o. major illttlrru.ption in the normal ft1Jterly f1ov of the general eiroulation rJt the atmosphe~. Bl.ooking in the 1:Torthewttern Atla.ntie Area A oheck ot the ceosre»bieal distribution ot Bl~ldlig Mt.ion ah~ the highest ~u.noy of oe•~oe in the longitude• 1-U.d tro.m d' to z 0 W in the northeast A:tlantic Ocean. Thia. reeion is tollowed 1n impol;"tan<)$ by the eastern ~1t1c area. The nortlleMtem Atlantic area was th&l'efore $eleeted as the tint region to be 1nvesttS1te4• 'lbe objective ~1 terton in ttus case ia as tollmn,: "A bnnd tltteen decrees of leng1 tude wide and eovering 55° N and scP 11 latitudes must eX!)ertence preasure de3):lrtures of plu,s ro mb. or more for at least three conseettttve days.... Tbtt ~uirornent of plus 00 r.ro. or .more el1m:lnates all but the &xtret~e eases of Bl.oolnnc Aatioo., The oontinuo.tion for at loest three daye is Im- the ptl't'POSe of excluding the possibility ot the hie-,h eell beine; m.crat01'Y in nature wheJ:te the mean ~riod from one tl'OUgh «low-pres~ to the next is norrelly thl"ee dtl.ys. The • ~ s n'tietying this criterion have been divided into two el.asses designated by :t'dgh te.t1 tu.de and Low latitude Blooking when the distinetion 1s obrlouely tlle latitudinal position of the CtJnter ot the blocking high coll. '1l1e Ili&":.h tati tude eases are the more 7 extreme 4iatu1'bance bein8 ehe.mcter1M4 bya high pressuzre eell tu- to the norbh Md trapped low preesure ~ along its eoutbern ~Pl'Y• In term, ot the displacement ot the west w.tnd belt they r:a:r • eori... aid-,:-ed as disple.o~ tar to the north around the nortll&l"n limb ot the blooklng itt.gh or diaplao.nenta tat- to the eouth a.rotmd the aouthcQ!n 11.mb of the tl.'am;,ed lcw ~SSUl'e areas. h Lem Latitude •ses aft ol:lareoterize! by a northwal:'d extension or the sub-tropieal high eell , wh&N the oonn&otion W1 th this o:ell u, not b~ken; any ~pp&il 1.ow pre$SUJ"e oent.n a.re tormed •ll to the east ~ the blockS.,ne high eeU. In terms ot the atap;le.oement of the o&t wind belt these oases~ ... . . eent a lus extreme north'wal1d displacement ot tho belt. The ineeption c:late tor •oh eamp1e eat1&t'Y1218 the above o71wrlon is listed below; '1'h& tigun in pal!'«lthesea repreaenta the duzatlon ot the blooldng eddy in days. !le.IW1! ~1:ltttJldJ 1.ow latitude J'an. 50, 1902 (12) 1an. 13, 1902 (4) 1aa. 11, 1914 (5) .ran. 20, 1904. (3) Feb. 21 1 1916 {3) :ran. 19• 1906 (4) Feb. 25, 1928 (7) Feb• 4, 1900 (6) Peb. 7; 1900 (G) .ran. (5) JJ'eb. a•. 1ss2 (23) Feb. 12, 1934 (10) 2, 1922 8 .Q.M. Yee.1"$ .. p Jk\t&Iftli¥~ 'I' 1901 - Low Liettitude (16) Jan.. 26, 1905 (4) San. 15, 1900 · (7) Feb. 13, 1909 (3) Jan. 30 1911 (10) Jan • 15, 1911 (4) Feb. 16, 1913 (3) 1an. 18, 1925 (3) tan. 20. 1917 (5) Feb. 11, 1933 (4) a, 191'1 (4) .ran. 1.6, 1035 ($} Feb. • Feb. It is apparent i'rom this thnt the High l.ati tude tY.Pe is a conaidera'bly more stable develop!rJljnt wen t.r..augh 1t represents the r.a.ore extrer~e disturbanoe. It would therefore be expected to exert more intluen~e on the oireule.tion r,ntterns in other reeions of thf> Northern raw11isphere than the l•s:s extret.:'.l8, leas persistent tow latitude tYl)e. In order to eliminate some of the snail scale fl.uetuations caused by migratory- eyolones end anticyclones- t'l-am the larger scale tluotuatiens cs.used by the Blooldne Ae:tion process, three day mean pressure d~_!XU"tura charts have been pN:pared for eonseeutive: three day period# tollom.nc the in¢$]?tion ot $Sch type ot Atlantic bloold.ne. !Jhe use or sueh c ~ 1a ditO'Wi.sed in greater detail in Ibrt IV. 'Hi-en eharts e.re shown in Fi.gs. I to x. Solid 11,ruits 8Url'oun4 fU"(':ea for which the total de~rture {sum of the even year cases and odd year oases) during the gt ven thNe day period exC$9ded an ·average of+ 5 mba . per day. Dotted lines surround areas tor which 9 Fig. I .. 10 ...... /_ i I I i 0 0 f ... ! 0 \ , J I / ' '- . I ! ' / / ,.,. ' J ·/ / ·-. , / • f / '"i"--, I' :NT i. ~46 / I I / .................. / Fig. II ' -/ . / ;- 11 .___ - ' " . - - :. ✓ - - "'- - ~------~ - ;H. 1946 Fig. III 12 Fig. I.V 13 I - - Fig. V . I --u - - - - -- - --- 71 14 .I I t ~ .. \ \ . \ I \ I ·/ \\ Fig. VI 15 -j ' ! / f ..\ • \ \ \ / I I I ,,,/ / ; ; , I / ' I I ~'-- / ,J ~ 1E NT :H. ·1946 I '--.<_/ · ,~o , '---. " ._, I·• .. ! 16 I- - . I r j ~,. . I ~ I /"_ i 0 ); i--t---· ! ·• . - 'r \ -- \ '' - \ \ / ,·1946 Fig. VIII 17 / / / -1:, \ \ \ / / ' I ./· 'y~ EN T ' '. H. 194 6 Fig. IX \ _,· X 18 I I I I / I I I \ \ / '..{' ' ,/ , , '-\> . • 'J '- '-·; . / / ~,, , / ',J~ I '/ I 'I; / \ I ✓ '. X / / i / / / I I i / I ', , I / / / '~""--, ,,_ !E NT : H, 19 46 / I -"-. I --·- - .· ,L ______ ll'L Fig. X I 19 the total de];)('~ure -exceeded. an a.vera~ ot - 5 mb$ • per day. Shaded ~ s are those arena where a..n a."V'fll'&fie ae:te.rture ot at lee.st 5 m.bs. per day was obser'fed inde:pendantly i.."l both odd nnd even years. 'il1ese area-s er$ eona1dered. partioulu'ly significant. Areas ahori.ng no large ano.~U•s were O!!'.i ttad '!or Clarity. A check has been !!lJ.d.e at the point so0 N. UQt) Wot the stat1st1eal. aigniticanae ot an a.vemge dmat1on from the normal presaUI"e sueh as is indicated by the sbaded areas ot the f'iguros. (S" Appendix A). This check lltlS indicated that at tl".nt ~~!cul.al" wint an avel"l!lge deviation or a bout 7 m'bs. per day oe.lcul.a,t.E)d from a total of ten inde-pendent tbfte day :Perio&I 1.s statistically s1gn1t1... cant at the five percent level. Since the standaro deviation (if the ;pressure t1.t tirl.s point is larger than t11at of most of the ;points in th~ area under oonsidce1"8.tion it is believed tr-l!.t most of the Bhaded areas represent sta:tist1cally sig:nit"icant dffia.tions from. thfll normal pressure. C~son of _the High nnd Low 'Latitude• el.asses in the Atlantic•i'uXi<>poan reg-lon shows the le.t.itude variation between the two claasee and the etteet of this 'Wirio.tion in producing a wi4eepreo.d low :pressure a.Nm in the vioinity of the Azores in Fig. n t in eont1"Ut to the above nornnl c-endi tion in the cornspQnding area. in Fig. VII. ln the west Atlilntic...southea.st United Ste.tea sector en tmportant d1t1"0:rence between the cls.s:aes may be noted. Fig. VJ! shews ~ long ea.st..,..s t belt ot abn.o.rna.lly hit.h pressure extending we-stwnrd from the vicinity of tl,e Briti.sh Isles to the Uisa1saipp1. Valley. l!rom a co:neiderat.ion· of the 1nd1Vid'Ual weather mi:,s involved and of same ot 20 the surface tempera.t.u.ree included on these .maps, it appears that the western portion of this belt is made up of a warn hip:,h pressure cell 1n tho initial sta.ces followed by cold polar outbJ1>eaka. This CC'l'Nsl)Onds to the p1oture al.read:, :tormod ot the distinction between the High and Law Latitude el.as-.e. The Lew latitude tnie being a less intense defomat1on of too nor.ma! pressure field extends its influence farther in a longitudinal direction than the more o.isturbetl !"dgh latitude type. l!!o further large s1gn1ticant aroaa are observed until Figs. IV and V. In the High latitude case only• tu1 exta.."lStvo low prea.sure area. beeins to develop in the east hl.cif1c and oontinu&S into Fig. v. Fro.."!l the cheek ot tm statistical siGOiftcanee at the point 600 U - 140° W ~nt1oned above. the peak average deviation or ~er 10 mbs. per day reached on Fig. V i.s considered h1(1')11y signifioent in a statistioo.l sense. It shotdd be not.ed tliat there is no evidence on the charts to show that this deviati<m is produced by any etteots acting u_pstream trorn the bl.oel..'1.ne liigh. The :pos&ible method.a ot tor.ma. ... tion then, a.ro P..n upstream effect fl-om the bloc}4ng High at latitudea north ot ao0 N or a. downst1'$S!!l effect thl'()O.Sh Siberia. E.1tlJS,: r.iethod eoUl.d lead to thi) development ot high pre-asu.re in the Al.uka."l c.rea (outside of the network ot available q.ate.} and a M.lbaequent t'lieplaee- ment of the west wind belt 1n. the ntcitie Ocean toward tho south. l1he emr.dnation of s.onie of the :Northern I!emisphere sea l•vel cl-iarts f'01" whioh an adequat-0 network of aata is available in Siberia has shcrml tl18.t t.he da.mstream f.'!Othod ot formation is the .raore probabl~. An emellent example ot this High latitude aervelOI,GE>nt 1a e.ttol'(}.ea in a ~oent & ~ which may serve as en 1.n de»endent illutration, Du.rt.ne mid....Tamw.,, ot 194? a high prese\ir!EI oell 4-veloped 1n the eastern Atlantic area reaching the High Latitude BlOQld.ng ACJtian stage over the Brit!sh Isles about J'anual""J l<J, 1947 with the pr&a6Ul"e ren»J.ning ~orninantly hieh int.bat o.rea· i n t o ~ . An txten&tive low pressure area subsequently developed in the eastern Incitio Ocean at low latitudu with the ~so-ure ~inina e.lmolnl.Uy low in that region b"om !rfbruary l thl"OUP')l February 14. A more norau ~ttem waa rMatabllahe4 ttJr a short period in the Pao1f1c but beg1n.nitlg a ~ about Februa.17 22 and continuing into the middle ot arch, ~ssuru ~ again predominantly low at·- low lati tudee in the eastern a.oU'1o. In ~ l terms• then• ono& the Bloold.ns Aotion eddy 1s established it oont:lm.-e to ftfft ita eontrol.llng intluenoe on the c:ivemll oh-oula• t1en pattern at least until ~ diaturbing eddy is d1UiP!t&d• 1'he 1nV$&Jtigatian rd Atle.ntio bloOldng «.ao2'ibed in the ~ ~ p h s has shown the probabllit1 of dorm.stream effects or:tstnated by the 1ntroduot1on ot a dlaturmnoe 1n the :f'orm of a blocld.1:1,a high presSU.1."9 eeU. In order to study this downstream •ttoct a roeton was selected tor 1nvest1au.tion tor whieh a larete downstream area t;,t de.ta was available. '!118 region selected 18 boun.4-4 by the lcmgitudea 1800 and 17d' w. '!he atr(mg west Wind belt n ~ 11ee I between 5o0 N an4 d ' ll latitude in this eeotor '01" thf> hemisphere ao that these latitudes tom tlle other bo\lndanes ot the ree1on. In the 22 Atlant1o ~~cm 'the :ttestrletifl ,-eq'ld,reme:ntlJ re~ing hish ~ d&!Xi~ baiS ~bl:y pelu4ed 4(&$ oaees which should be inolndGd 1n the n1.Mldng Aot1on o a . ~ . TneN restrictions ai-e ll$Ge8BfU7 in ~a- to p;roouce 4 i a ~ s or suttl~ient ~ h to ce.wy t ~ the blank aN&. ot data in Siberia Wl4 be 6ba$ne.ble in the .l:aoitio reg1.on where <la:ta are available. Vihen the &.!ilm&date dOWM~ ettecte ot ~ 41stur~ are Obse~ble the objeetiff criterion mllY be ~ned CO?lflidentbly and the 41Jturbanoe my etili ~ eXl)ectf.ld to produce ~ pressure deriatiO!!.e e.t last tor a sht>rt d!1rta.noe 40Wlllitrea,in. nu. toll.olr,ing objeotlw •1'1terion ._. thetrerore tOl'fflll• late4 f~ tho i.011'10 blO(tk:1.Del "b total pressure do~ure ot the tou:t inteNMttom i'"Ol"nlild b1180° an4 lvoO Wwt~ 5o0 U an4. 45° N muat e.'f'e~ 5 • • e,l>Qve n<a"mlll tf.Xr a two ky IJ$l"io4. be maintained t~ at leut three Oa~. tt .Thi• aftnge mu$t ~s 18 ob?iously an extNDely weQk 4-t1n1tto.o.. Iii oould 411• nesative d~ure• on any given day prcmd1ng the Poeittw 4 - ~ s Qi the :rneeding en4 tol.l.oring ds.711 averbltlanoe the ntBStive -values to the •xten.t ot a n • ~ r4 :pl.wt 5 .mbs. tor the two lay period. rue ia tor the :pupoae or allowtns e. minor t ~ pauege after which the S'U?'tace presaun is reestabliel:led. In t&1'ml ot the UMJer level tlow, the eontro.Uill6 waYO pattern ray still eurt 1w Wl.UiJl')l)e on the eiNUlation even though a minor low preuure ~baapuGGd. Another illustration ot th$ weakness ot the detini tion li&s in the -.11 area 1 t en.oCJm..I,a-3se.s. The center of the bloc.kins cell nar lie ~ r e outside ct the etwn Oll'8a and the detinition may atill ~ satisfied. An obviou,:s adwnta.e;e ot the de:fini tion is tr.at it allows the inclusion of a larger nU!'l.bar ~ cases so that some of the diaad... vantages .mentioned above tend to be smoothed out. <J:i!1e cases which ae.t1$i"Y this criterion are lit:1ted 1n !able I (the figure in ;a.renthost}s represents tlie total lE)ngth in days for ea.eh onse). '!he downstrea.'ll e:f'tects or this distui"bance are shown in Fi.gs. XI through XV. These figures are age.in presented in the f om ot th.rce day .IJ11!tan rnps. Solid lines enclose aree.s where the ave:rnB8 daily pressure during the t ~ da.y interval. is 2 rn.b., 4 mb., etc. above norrnel. a.nd whiah are cQ'!ln10n to both tho odd year and ovon year l sa..,"1l)les. Dashed litws enclose similar area.a r>t 'bolow normal presaure. In order that no extraneous influonces a.eeonpa.~ng the breakdown of this proeea, would be introdue6d, ipdiTidua.1 e~les were ollmine.ted from consideration a.a soon as the ori terion was no longer satisfied although it 1s pro'IX\bl8 that the effect of' this breakdown is prop,.- gated down.str&eJU rather slow'ly and is not iv.mediately apparent at distenees tar downst~ !n th1.s sy the number ot eas-es considered 1.s g:i,a4\la.lly reduced from about twftnty for »"lg. XI to eight for Fig. rl t~ the even ~ em.mpl.es and simila:r:-ly for the Odd. year examples. Figs. n through XV show the ereu1ual establishment ot a eonsistent 1'111V8 inttem. d.om:-.stree.m beeom.1ng well established in the period twelve to tourteen days tollowine inception. 'f'n.e pres&Ul"e r i ~ obeened in ee.storo Oe.nadet in this perlod has been found to exist tc»: perto&J longer than twelve to fourteen days and represGnts th~ first downst1"8al:l crest ot the stable, nve pattern. The wave length 24 'lnble I Mid-1~cif'1c Bloakir.g Dates Even Years Odd Years San. 21, 1900 (6) J'an,. 18, 1899 (15} , 1904 (31) Jeb. 1, 1009 (4} :ran. 5, 1906 (5) '{6) 1an. 12, 1906 (12) nee. 30, 1900 :F&b. z, 1901 Feb. 23, 1908 (7) San. 2, 1905 (7} nee. 28 1 lf)09 (56) (9} 1an. 1, 1912 (9) 7, 1903 J'an. s, 1907 .Tan• • •• 1914 (5) 1an• 25, 1907 (12) :ru.. 19, 1914 (10) (52) Dec. 26, 1915 (S?) (37) Feb. 11, 1918 (7) :an. 5, 1909 J'nn. z, 19U :e.n. 1, 1913 Jun. a, 1920 (22) 1an. , lS:t.5 (5) Feb. 4., 1922 (25) J'an. 18, 1915 (8) .tan. oo, 1924 (19) :ran• 29, 1915 (22) Dec. 31, 1929 (6) Jan. 14, 1917 (G) 1an. oo, 1~ (20) Jan. 2, 1921 (24) :an. J"an. 29 Feb,. 9 (14) (12) (16) 9, 1932 J'an. 9, 1934 (7) Feb,. 10, 1921 (5) (0) ja.n,. 9, 1023 (19) Feb• l t 1936 ('7) Feb. 12, 1923 (12) J"an. 21, 1938 (25) Jan. 9, 1925 (15) Feb. 7, 1025 (13) , 1929 (5) u, 1933 {20) li'ebe 22, 1933 (24} San. 6, 1935 (15) Feb. u, 1935 (10) G, 1937 (15) J'an. 20. 1957 (26) lreb. 21 Jan. J'e.n. I I i /- / I I !-' I •·I · l \ . -,1 i o' / I . \ \ Fig. XI Fig. XII 0 IIENT CH. ·1946 Fig. XIII Fig. JCTV ~ \,_ ' o.., ••.'ti ""'~ • // \ \ 1/' Fig. X.V tor this .?;etter.n is about 100°. ·w1111e the :r,n,ssu.re abnorr.nlitiee observed a.?e not large, account should be to.ken of the extreme •akness ot the objective criterion. ~ r deviation.a could be produced With a more rigid dst1nition. An independent illust:t'ation of this process occurred L'l ~...il;pril 194.8. Boe;irmi.ng about l~ch 8 p,r,tssu.ras in the on tical area ~ gene~ above nor.ml a.Tld t.he wave pattem downstream resembled the pree.SUJ!'e d e ~ pattern ~hOWll With the pnnci]W. ditterenees OO(JUl'I'ing tollowing mar".€0d pressure tluQt'Uati ons in the c,ap.tr<>llil:I.G ~ . Degimtlng the latter ]:D.rt of ?Ju"Ch and eont.1nU1ng through the Bliddle of April, :rmessuroe 1n the mtieel area we:-e nll and com1st-ently ab.ove no?!M.l. ~ During \h1.s period the above 'PNf.S-$UM pattern was tollomJd c1ooel.y, 'breald.ne down only rollOWing the 'bl-eakdovm <>f the Paoifie bloold.ne msn. IJ.'be development ot tnre-e types ot ste.ble wave patte~ is shown 1n F!.g• .XV! thr~.J1 x.tx:. 'Ihese auiplas were chosen by a ca!Sidere.tion of' the tl"ecks or positive preaaure QD.cm'llies in the .A.tle.nt1¢ area. fO.ll<X"rs: 'nJ..e mteria tor eel.eot1on or these examples are. as only anomloua a..~e containing n center ot' plus 10 nba. m' r.iore were consid~rcd. Upon ohartinc the tracks of theae OO.."'lteri, thoy are• occasionally o'bsorved to have no ap~ciable eastward mt)Y&me?lt . for a period or t..11,ree days 0:r mot"e. These are the cases t~ted in Figs. XVI throueh XXX vrl. th a $&~ration being r-.:ado (>n t,.~ basis of 0 0 y ~ -~ • '-/_' 'j / / / '"··~ , .t'-- ' ' - - - - / . '-; •o ...... / ~--, __ ___ -l 0 / ' ,,$ ------ 6 Fig. X!lI \ / j ---- ..__ ! I I I i - rI ---L ' \ \ / / 7. / 0 lENT :H. 1946 Fig. MI Fig. XVIII Fig. XIX 0 :;H. ·1946 Fig. xx: 1 o,.~ 4·~ "-, / '\ . ,,, 0 0 c· \ \ CH. ~- 1946 Fig. m ·, ,--.; • · 1 , , ', · . ·, . ' -f' • ' ·. . ' ~ENT CH. ;•1946 . GASE B 0 Day~ reced1 I · I Fig. XXII P \ • ', ' •. ' ,:, -~ ✓ / ./ I -I .L ! I _j I ' - -♦ .., - \·· 0 ?· -; ", ~ \ l / ~, ./ I / ·..; / 'I~ H. 946 Fig. XXIII Fig. XXIV , I _"'<-_£._ : •··- ·,- -:rf:-d!"'"i p 0 - .. : ~ 0 .:~,., c,,, - ~ 0 (j ~ if'Pviu1 •O , , ..... L. . 0 ' I. \ o · lP!'l\~#14 -~; • o -•t ., d, o owtc 11;~a ~-- _; o o __ • , .,_o~-;_ .... I. 46 Fig. XXV Fig. xx:vr Fig. XXVII \;¼ ~i ·• . •. • . ' : \ o +'."'~ ~ .~+_;-~ /=t:1 ""~o ' o ' ' • y :. .!>-~o ·o •• !. ' -+~~ 0 +ot O .. IMOJ.0 0 \ .\ - \I I ~1 ''-.... :',1·"·-·.•_ ·.• " • • .·< . ~'>,. / - -~ ~.,., '· 'I CASE C v1ENT CH. - /- - - - + j--10------ 2 Days Prece i·l946 Fig~ X!VIII ' Fig. XXIX I ---f- ·- -1 I I ·sr -- 1 I r- I _J I 1- 1 i . . r ·· ··· · ··--·" ~ ' \ Fig. XXX the area in whioh the mcnne ~ center stopped. Zero <la:, is dater.mined °b'IJ th$ :fi1"$'t &ly during which the center had no aw.recia.ble move!ll8nt to the ••t• Oases A, Band O rep,:-esent averages Of sixteen, nill$ and twelve e:aun.ples reapectively. Each cue is seen te have at lee.st one stable wave crest upstream. For Case- A t.l1e we.ve length is 1000, tor Case B 00° and tor ~se C about 1700 al:t;hough tor this case this .uuy 'be a .rmltiph It u dittietll.t to interpret Fies. m through XXX 1n terms of a down.st room or o.n upat:rean o:f'tect. :tn Co.see A w..d. B t..is to:mation ot the two p~ssure cnsts appaers to be almost simUlte.neO'U.$. no turtber atter.i.pt will be .ma.de to delineate these ef:f'eete. ~ For the of th1$ investigation Figs. XVI through JcrX represent ~lea or stable wave patterns. Such stable wn:ve patterns have been studied by numerous invest1aators. Rossby (4} and o~rorkers have l'(>inted ou.t that tmder the asmun.pt1011 ot small horizontal divergence, the l'mW 16lU;tth ot stable long we.ves in the a~phere qhould be giTen by: where L is the wnve length, u the zonal wind s ;feed rul4 ~ the n<¢t..'1mrd. rate of oti.a.nee of the 001.'iolla ~~ter. In a l,"eoent paper Crt;iS$trml (5) has investigated a n1.m1oor of properties ct these long waves. lie has found an avenge wave hmgth ot about ~ty-eight degrees ot longitude tor the stationa.ry waves on the \nais of up~ ltvel tlow patterns. The etatio.llnrY wave lengths tound in the study 47 ot lllccldns Action processes are eonsid•mbly long$r, being o!' the order or ninety to one lmndred degrees ot longi tudo. These Blocking Action p.ttOCesses are norm.Uy e.s-sociated with closed cyclonic and anticyelonic centers in the upper level. f'low pattern o.nd as Cresmnan .has pOl,ntl.3d out, this cmmotertstic na.l."ea the use ot the above t ~ questionable due to t.J1e difficulty in the determination of the mean Z-o;Jal Wind si,eed u. Cress.man himself bu eliminated t...'liese upper le'vel tlm po.tterns from his study eo that no oonflict exists between t..1'ie two investi!'3-tions. ~• lnreer a.nplitucle, more extrer~ eta.ble 'fJaves in the atmosphere are np1nrently o't'.are.ot.e:r•ized by lonc;er wave i.engtbs than the less disturbed statione.~J stable waves. h r a :Pro1Beat1cn 1n the Atmooph&n The problem of the rate of P?'OI,a~tion of energy·tn atmoaphmo waves has reoently e0t1JG into aonsiderable prominence due to the wot'k ot Roasby (6) and others. some intorsnation on thls subject Qan be gained from t:t>.e preeedinc discussions ot Blocking Action process,s 'by c onoiderir--r; the intrusion ot a blocking Hie.h into the no:r!Inl. hsterly circulation as an energy a ~ . '11lb· use or thfte t'lay mean nape and the c;oosequent elimination ot the t1.onller scale P"SB'Ure 1"luetua.tions eervas also to ellrninate moat ot the erte.ots at propagation of ·energy downstream at a. speed greater than that ot the, 'Olave velocity sueh as al'e bypothuized by Rossby. '!!le tln'e$ day mean mps then show the })rOl'llS&tion. of enei'$Y With the a ~ ot the waves aasoo1atod with the Blooklne Aet1on i,rocess•• 48 Thia ie moot cleurl::t shm-m in Figs. n to 1.'V tor the mid-113.ci:fic bloold!t..g ca.ee where the disturbance reaches the north- eastern Car...e.dian c.roo twelve to fourteen da.3-"S after the inception o:t the disturbs.nee in the Iueitio. ru.s is a dieto..nce Cit about one hundred degrees of longi tUde t..~veled at the latitude of a bout 60° It ao that its velocity is ~:pp;i.Nnt,ly less tl'lf!in the mean zonal .flow. '.the Hi~ I.etitu4e Atlantic blocldn.G case i! less clearly de.fined ,1nce the lOill l)t'e.tilStire fOJ."1!11.ng in the l-1\oi:t'ic twelve to fourteen days toll~ng ineeption is as,B"1.t,".led to be a seeonanry effect ot the pro- duction of high :pNSS~ in Alaslm at'lat1tudesi outside of the network of data. IIowever, the rat~ or d0ffll8trea.'l :propaaation is COlll,Xl.rable to the Fc.cU.'ic en-l;l})le when consideration is given to th& nore nwt;herly lati ti.ide traversed thrOUt~ Siberia and. Alas bl. The introduction of a distur'l:anoe ot the form. shown in the llidson 1-y area ot Fig. fl' has been studi$d in .oore detail. The m:-ea considered was bounded by longitudes so0 and. 100° w a.nd by latitudes 5f30 and GOO u. Daya were selected for investigation on Which an aV&mge preB$Ul'e de).'nrtu.re of ?.5 n'bs. above~ for the tour corners ot the area was tirst realized. TI'$ effect of this rele.tively weak d1aturbance on the nessure r-atterns in the Atla.l"J.tie U"ea has been s-tudied by a considemtion ot the total disturbed state of the sector bou."lded by 500 W to 4tJO E longi t1.1dea n,.'1d 35o N to GOO N latitudes. A masure of the r:2.gnitude of this disturbed state, repre• sen.ting a .measure ot the turbulent energy in the eeotor. ie given by the sta.naaro. &wiation frre. the raeen or all the pressu.:re del)e.l'tUre&il within the sector. Thus the largest standa.1-d deviation is ~oouoe4 4,9 by the si.rmdtan.eous ~ n e e ot lal"ee poaitive a..•1d ne{11tive varia- tions trom the nortinl pressure field of the seotor. The avarace ste.."lda:rd deviation in mbs. -tor the sector tor a tote.l or •nty-nine om.m,p.lets 1ti shomi belcm as a t"lmvtio:n of the nunber ot days following the intJ!Oduotion ot the disturbance: 0 ~ 1 ~y 2 a.,a 3 d(iys 4 &,.ya 5 days 6 ~ya 7 ~ya 10.69 U.43 11.75 ll.51 11.45 11.49 10.00 10.44, \!lhew th& a,-mge standard deviation tor the eecto:r orrer u long pertod ot time it 11.00 mba. 7.bese •2amPles were tak&n regardless ot - ~ JgttEml on which the disturbanoee were supenmposed. The ald.mum o:rr.et is o'baerwa two days following the .int:roductioo of the 418.. turbance. By this time the ettoot o~ the disturbeuite has appe.rently been dittuaed tr..ro'UP',.hout the entire area although the titeeto:t ~inil oonsia..rably dist~ for the toll.Oiii.DS three day-a deoreas.ing rati.r rapidly •u: and ecmm days toll.awing the intl.90duotion of the disturbance. FrQl'a the •ta.ndpoint of energy !}l"OI'.6cnt1on the rapid ine.rease in the disturbed ,state frro zero to two days nus-t be teken ao an effect of en~ pro~ted mater than ~ ~ flow wldle the z:nintennnce of th& highly disturbed stat& from thr&e to tive days r:1ey be nplain.4 on the .beai• ot inertial ettects or by too slower rate o'f ene~ prolB8Qtio:o. lll0'9'ine with -velooi ties less than Ol" equal to the zonal ti.ow. Tli• •f'tects of e. generally dirturbed presaUi'e field 1n the Mm,th American Mei;or boundH by 600 Wtm4 100° w longitu.an and "b1' ~ 11 iUld e<fJ N latd.tu4e$ have also been considered. The standard 50 dn1e.t1ons obar&oter1stic er this seotor have bean correlated with those ot the atorementianed Atlantic aeotor for two so;pe:rate J'anUD.17• . F • ~ nseuans." These are shown 'below e.a ~latian ooeffieients w:I.th ~ . cm& &r two aay lags• the lag eorre11J)Onding to the r~l'th Aari.oa.n seotor 'ftlue o c ~ tint. (SM A~:z D). 0 lag l day lag 2 day lag 1914 .339 .485 .325 1988 .038 .016 ........ In the 1914 ceae, ~ e m with the results ot the preNa.ing pam-. ~r>h enaivs tbat the rna:rtmnm oonielation 'betW$en eeotON now mats for a one aay lag or the d i s t ~ 1n tu NOJ.'th American sector prc,duoing t1-ir CY\Xtmnm •tte4t one day later in the Atlantio sector. Thia r.iay be explained on the basis ot an O'f&rwtetshttne 1n ta~ at thoae d i ~ s whioh e:dat in the •-.torn po,.-tion or the Hoi-th Americal:l aeetor a."ld which will p.ooduce larger effects in the Atlantii than an:r eXiatine 1n t-oo centl"Sl or •stern portion (1£ the NOl"th Amerimn eeott1r. The ditterenco between the two years 19'14 and l.900 18 . ver--J SU!k:1-ne. 1900 1s Cbu'act.erized by la.Z'ge distortions tram the n0%'1'!¥il presllJlmG field in the Atl.nntie sector br(rusht about by lolle; D$r10ds ot Blocking Aet1on. In 1914 however, ml1y about tive days 4tt1'1ng the two month period may be denrlbed as having any sigm.f:tcant IilOOld.ne Action. One :m1s;ht inter ~m. this that oner{g 1• not u ew,117 pr~ted ~i"eam 0.urin(t l'-IRiOtla ot m.ookins Aoti~ al.thoueh a ~ t h o ~ 1-nveatiaa.tion 1a nef)ded to verify this point. 51 EAR': II. THE ~'!'Im OF TJ:m BLOCKING AC'l'!ON EDDY 1'he general ohamoteri■tiqe ot: the l)'»eeSUl'e field lee.4illg to the de'feloJ;1C1tnt ot a bloeldna High tn the nortbeulteri Atlantic area e.re aru..n in Fies. xxn to XXK.V1. Thee• t1su:,u •repre- sent the average pre&sUJ'le departures ror the even~ ae.aea- llete« in,Ivt I,. 1he tigul'f)S sh01r Olef.U!ily that the prinoitnl Origin of the Bloeldng .A ction ll1gh in th1a tegion io the Atlantic su'b-tropioel. high p~suro cell and thc.t the priru,ipal dynamic development 1s an a ~ high zonal tl.QW ·direc\ly to the north ot the eub-~eal. cell. Th1s h1sh zonal tlow increaaea throueh tll.6 eu1Y stages ot the d.evelo~t and is 4$fl.Geted gradually to a more nonlmesterly tlow thu8 repree.ent1ng a llftldual ohanae tr(n a strong zonal now to a s t ~ .r:erldional tlow •• 'ibe cmtio,olonio detleot1on and the su.bsequent t~tion ot the low preasu.N nree. 1n -...tern Europe 1a esplahiablA, 1n a quolitative sense by the zona:1 tlow acquiring ant1oyeion1o TOr'tieS.t1 ll'l the horii&Ontal divergent U"R ot extftme western~. Ma la not the m11 me&n8 by which the bl.ocldng High J!1lly tom. Anc>thff method Will be diffuNed bi-1etly 1n a later paragraph. an. intportant :taot lhould be l)Ointed out 1n oonneetian with th.18 caae. '.Ihe et.art of the development takes pla1.te at least twelve to fiftMn dQB -1or to the e.otual tonstion ot the high cell at high latttuaM. It one attempts an explanation at the toaiation on the be.sis ot ~tel/'l'e8trial radiation, the ohange in that radiation should MQU!I over a com.pu-able per10d. 'lb.is would appee.i, to wlA out ew,h short period ~ as solar tla.NS, ctrdl? huotuat:lona in fl'lllG!lStic numbers, etc. 52 Fig. XXJCT 53 Fig. XXXII 54 Fig. XXIlII 55 Fig. 56 57 Fig. XXXVI 'ale mean pressure gradient betwetm 50c, n alld 60Q :n tar the C&lies ~tioneA above is i1w•t1~ted 1n f<lO~ d.ts.11 in Fig. rnvIJ;.• 'ltle ~ Illtenitude ot thia. gl'!ldient ooi-.reapondin,g to the strong zO?Jal t'low ocourring 1n the Atlantic area 1• eleul.y ehOIR'l. The Oll1y •ueseat1on ot a eonsistent, mean1ngtul p.,.ttel.'ll upatnam :rron thia etrc:ne flow is that ooC'llrr1ng b i t ~ fifteen to seven days Fi,or 1n the neighbotl'hood ot longitude 1100 w. '1.hia 81.lggeste the exist4,nct ot a stable wave ot length ninety to one hUndNd de61"HB upatream trom . the sub-tropieal. high cell which r:ay aid in 1ts dn'elopnent into ti. blookins stage. The SUJ.-f'aoe tempe•ture antraaUes charaoteriatic of th-0 area occupied by the sub-tropieal coll dUl"ine the :t'ormtiff ate.sea of! bloold.ng lave been investitJatod with rewlt. depieted 1n rtg. xxxv.tn:. h 0 N end 40° N am bf 1one1tudea tll'e8 1a bounded by 1at1tudea eo 300 w an4 1(1) w. '1be temparat.ures nte takAm h'om ship rePl)J'ttJ in the 8.l'ea and are nee•S$$1"lly aubJeot to aOtil\l inaeeuraor. The values 'ftl'e averaged in ti'n degree sqwn-ee Oftr the entire area o.nd then a'f'e?e.8$4 tor tho various three &11 pel"lou prior to the inception at biocld.ng. While the total num'be'l'· ot r,..- Bloold.ng Action e:ampl.es used 1• a very m:all. sample the eonai""noY ot the reaul.te leads to the bel1$f that the eenere.l cho.rfteteriatiu ot t-he temperature tield are sat1ate.4tor1ly re~ted. F i g . ~ •hCIMJ the tempemture • ~ e.bCSYe nOJlrlJal. in the area eontinUOtWlY' in the tnnty-one days pri.~ to the inoepticm ot blocking. While the a'feraee o:t one to two deg?.'$ea is $mall in itself' it NPMBenta a considerable amount or exee,is heat \W'hltn -8UI!lllled over tho enti:re e.lNWl. 59 T \ l1 I ,' (. : -~oo-:~- ~---- 0 rr. . - - w • ••- i. I . •••- + - • - - - • •- • - ! 10-12 DAYS n 0 4-6 :r: .. DAYS : :1! ••• .. 1-3 DAYS 140°E 180° 140°w Fig • . XiCX.VIIaoow 20°w 40°E 60 -12 -6 0 +6 Fig. XXXVIII ( DAYS) 61 tor tri.e sa!."lts square for si.v.ilar periods prior to the inception of' the block:1.ns high eell. The pressure is aeen to~avera.ge abcwe not'llEl ·<lurine the fOl"f.'.'ative s~--es as has been discussed :previously. The slow d.o'Velo:pn.ent ot the Blocking Action ste,ge is again shown in tr1.J.e 'lwo SU&U&Stions have been ottered for the explanation of this d.~'!lafliaal d.e-velo:pment consisting ot the a.bnornnl extension of tho sub..tro:pical hieh cell into the region nor.rally oecupied by 0. westerly tla.w. The fililt explain$ too development as an instability phenomenon associated with the tntroduction of a pressure disturbance into an abnormally strong westerly flm. The exteneioll of the sub- tropioel high oell toward. the northwest in 1i'ics. xxmr and x:;::£J:V' , indicates th~ e:dstence of such e. disturbance. However, a eeneral investigation of disturbances sul,)8'ri.ffl;poaed on similar strong zonal flows shows many which are not unstable in the sense t,hat the disturoancf)s disappear rapidly. 'l'hese oases are mainly those where no .U o.eveloped sub-tropical high cell $xists. The cll0.l'8.cteristio tlow ~ttarn tt:Yr these cases ie n lal'ge low preasure ayst&.m in the hiG}1er latitudes which dominates the entire Atlantic sector. an predorninantly low throughcut the sector. Pressures The abnormally high ~nal gradiente exist but no abnormally high :pream1res dew1op suwequsntly e.t high latitudaa. Additional information in ree;ard to the thermal structure of the eireulo.tion appu-ently must be aaeum.ed and a pure 1:rwtability I>h$ncmenon similar to the breakdown of laminar tiow ha$ theretore been d!.S$.e.rded. The second suc;gestion ottered involves the acoumulation or heat in the ree;ion occupied by the $Uh- trt',p1.eal oaU. It the ohancteristios of the general circule.tion are such as to lead to an a.ocumu.1.ation ot heat in a given area. th$ ln.ocking Aetion p,.tocese is pcstule.ted as the mechanism by which the oirculation adjusts itself in ordei' to reMstribute this heat. The prooess may be rteuallzed a.a tol10111S: the aeeutWlnted heat in the 1u.b-U>opioal. hieh cell causes an ineree.se in the latitudinal tem.pe.rature gl"adient and c~quently an inoreGU:"Je 1n the 0011al tlow. Thia increased zonal flow is brought about 'by the tm!l$t"orr.ntion into kinetic $Il&l'B1 ot a amll :portion ot th$ Potential energy which aists tom of the abnormal latitudinal t&rlpemture m"adient. in the The meahsn1amt by which th1a ~ • s heat oan be transported northward end "distributed !e essumod to be the pressure disturbance superiL"'l)oSOO on the zor,..,al flow. Tbe add1tia:i:al twridional velocity com.p03Jent brought a.bout by this disturbance it& o.1~ntly su.ttie1ent to all.cm the flow ot h.$at northwG.rd a.'ld to lead to .the tormt1oo. of the hieh l)l'eSsure at the higher latitudes. The mintcno..nce ot the high :pressure at those high latitudee is not considered here. Fie. mvm, although not concl"uaive proot, indicates tliat this :postulate 1s a :poes1ble explanatiori. • . The exeeas beat is •een to re.main aensibly coll8temt tor a period ot about nine days being · • ~dually dissipated within the given o.ree. in the do.ye ir.v:1ediately ~ceding t.h6 1Meption of blookL"lB• A general .1nwstigation of all oe.see ot abnortlllly high !)l."ffmu"G in the area descrlbed by Fie • .axv1n. be.a. shtlfm that it the a b ~ t y eonti.llUtS ever a period of tive to aix 48.1$ an<t h$?10$ can be e<>naide-Nid as an excaJa accumulation of heat, 65 the eu~tropical. high 0$ll develops into high ~ssure o.t hieh lati- tudes TirtUAlly without exception.. The l.enst11 ct ti.rne involved in this Pl"()OeiJI• the longitudine.1 location and the peni#tentte ot the high pressure at .high latituu,s "VBey but the meohaniem. ot the tOlfflla• tion '1t the h i g h ~ at high latitudes seems to be a nec-eallal'7 4eTelormetnt after the tieNiatenQ of the abnormallJr hleh pressure• 1n the •~P1oiU. high cell. mi. ~ dePU'tures fr.tt three &1;7 intenala ~or to the i.nffptiOll ot the tftttty eYe year . . . . ot tdcl•PaCitiG blooklng sre •hown in F161!J,· :rm:x: term. h in Iert I• dates ot the oaau are llated . 1be origin ot the higll cell which subaequently beootiea ti. b l ~ lllgh is in Si1-r1a and movee out to the b1octk11l6 area in a __,1\'ll weGt to no1"t.llwe8t tlow, '!be~ 1a no tn'i4en~ tor t'he ~4Ual nort.l:aud extension ot :tho belt o:r the rrn~plf.Jell High ae 1l.1Wi tho oe.se 1n the Atlantic. 'llle ~ diet~ state ot the cmt:b• ~ iattern dur11'l.s the fitteen da:vt leacUne ~ to iuapid.on ahoul.4 be noted, 'lhis suggests that the circulation 1- ~ d y in a · h1gh1y disturbed state priOl" to the inception ot W• type ot blockill6 and that a al1sht readjustment of the l q n f f patterns suoh all 18 ~ in Put Ill ftsulte in the destrw:rtion ot the blocking in one area and tu re•tM!lB.tion in the nn area. Thie type ot tornet1on would then be oonaide"4 ae a eeconda.ry erteot :ra~her than as the introduotio.u ot a ~ Y diatm-bent.to. It should 1)e mentioned. he~ toot e. trim ot the Elgh Lllt1tu4• Atlrmt1e ca.see are a~ntl.y- tomed 1n tM• *"• the ·h lgb oell oomi.ng down h'oJn the ~ ._ urea. 9-:, ahow little relation to thtt Atlantio s u ~ o a l h1eh eell .ana ab.oul.4 be oansidered as aeoondary 1n origin. / . . .. . Fig~ XXXCX . ... ' • ~ 6·1946 ' • . . MENT :CH. . ; · ~ "--- -~ i:·-1 ·o ~ I . ~ ~~-r-~~~%- • \ 0 ,0 • • \ " .,.. ~ .: 0 ~ 0 ' 0 .A""· - - \ - · ~ 'c)~O • {' • ~ ~ 0 - ....,,,._, " 0 \ : O .•.,-.o ' , ...., : 0 . ',, I / I ' / ~~~'.,_ / . ., . ". MENT :CH. 6·1946 Fig. XL . . ·-/ ------ /~--,1N • , I ·,"/ ~., / '- . y. -y K -- .,o ~-- ,..., . ·-, • "" -"'.I . • " '\ r-· 0-170W BLO A ::r. t' 6 Days I ,I.'--.. P , I Even 'Years - -I :E'ig. xr..I • . ,)1' < , • \ , ~~- 0.··h 0 ~1·- -+ 0 • ,.. I ,c ~ l.. -f.:.-~ •• 61 ~-\ ~ -•---l - -- ~ "- ''.*'t&o /":! / • 0 ••1.1,,.1o1i1_. 0 ~ 00 4 O 0 ::,. ,,blo,1.0 0.•4,o -· '----- 0 0 "'so 0 ~-~ 0 ' MENT :CH. 6·1946 Fig. XLII 68 PJI.R1i lll. 't'fl"r<? D!SSIPATTON OF 'fl!f1 :m...ocm~ ACTlOO EDDY only a &:ia.ll atwunt of in:t'or.untion hes been o'btaillad a.a yet on th~ :n&eha.11:lsm ot the d:J.asi~tion ct the blocking W.&h cells. . Asid\lJ trara the natural degradA tiQll to a zonal type flow: tl~)l tr.e disaipitive action of nic;ro.tory systens. intemction between 'Bloo1d..n$ m.ghs 1n two different regions r:tl.ght lead to the destruction ot tlle weaker 1f 1t 't':ero not loeated e.t the cor.rset wave length trot.\ the stroncor. 'lliia r,rooess is shown in :?:lgs. XLlII to ml and :t"a~@nt,, the d<Jterioration of about w...e halt of th<l oases of mid.-Inoifte blo-okine f'or the eve11 years. Althoug.11 it ntl.St be considered. as orJ.y 011e breakdmm prpcoBs • 1t 1r.!ust represent one of the most 'eenmon t1:!,')8e. '!!le pressure de:pnrturee are aeeiin .~esented in gro'Ul:8 ct throe days. ?'ig. nm shcms the ave:re.ce daily d~~u...~s for the rtnal three days of blocldng 1n the nid-Pacitio. In the Atlantic the aub-tropical high cell is eonsidembly above n ~ l in pressure with a.'1 a b n ~ high zonal flow to the north, a eO?ldition strildnelt analoeoua to that lead1nc: t!) the fortl'l.ation ot tl:lb bloolc\.Ilg Hieb :t.n the northeastern .A.tl.antic 1 altJlO'I.J.&h displaced slightly to tlle nat. '!be Atlantic sub• tropical eell eont~ its analcgous develop:aent in Fig. xt.rr while the mid~mci:f'ic blooki11g cell det-eriorates eonsiderably in intensity. 'll:u!,. Atlantic high cell does not ~min as nn i t l ~ t bl.coking eell in Figs. XLV :-iruid :xr.vI but a new, 1.!!i;portent hig.ri oell appai,ently d.evelol'S in n~est Ce...ri.ade.. The mechrurl.sm "V'iJ.iit1ali2$.d in thie t1Janeition ia as foll..mm: Afl shown in Part l the first stable wave crett downo-tremn \ ~ • 0, Yb; . ,)', ·-·•····i- -- -0 -;"• 0 ' • - -~ - ~ ;H. 1946 ➔. i46 ... '-1ENT CH. >"1946 Fig. :xr.v Fig. JCT.VI from the f:114,..'Dicitie blocking High is located in northee.st•m Co.mda. Dile to ti. mechanism su~sted i n ~ II a blocking cell developa in the mid-Atlantic region tor reasons tnde:pe,!ldent of the action of the lueitic bloeld.nc. 'lhe position ie out of p.baae with the stable wav-e l)t'lttel'n tOJ:"lned downstream :rrom the I-aeitie blocld.ne eell. The m.d... Atle.ntic oell tends to set up its own stable •ve pattern indel)endent ot that formed by the Pae1f1o cell. It there is greater energy associated with the Atlant1o disturbance tmn with the Iaeitio. then the Atlantic i:attern Will dominate in the general eireu.lation and the original wave ~ttern will be destro1Ud• 74 PART IV. Tim OPl'IMUM USE 01" L~"1 PRfS.JU?J; crm.R'.rn It has beoor.ie ap~rent in the preeedinc sections that a large nw::mer of discrete processes oan be considered as taking place in the at.'l'losphere at various ti.r,w s. T'nese :processes r~.a.~,r be thought ot as contilllJOUSlY w.riable in length be~nning with the short term fluctuations caused by the InSsa.ge of miCTntorr cyelones and anticyclones and continuing throtl@')l the long period Blocking Action processes ct a month or .m.ore. With the reality of these long period processes established by this and other investic;nticns it would seem that ace.me thought should be given to the probleri1 of the length C1£ pe;dod for m ich a. mean pressure cha.rt should. be constructed in order to obtain the opti!ml!'!l benefit fron it .. Thia problem has been consid- ered. at so.me length and the prlnc1:r;e.l results are given .below. 'lbe uses to which mean pressure charts r~y be put can be classod. into two general categories; 1. They r:a y serve as en extre.;polation a.id such t.bat a series or nea.11 charts re::," be used in an attempt to foretell the L'leall pressure distribution during aom.e future period. 2. 'llley nay be used to describe• in averaee tel"mB, a distinct process wh1eh llas taken plaoe w1 thin too aw""°s:phere. In the firet category, neglecting any relationships between individual yrocesses. the best ertre.pol.e.tion :p.rocedure would involve short segments of the irulividua.1 ~ s s while the second. category would involve a nee.n chart made up or tha.t portion (?t the ent.ire process which contributes pressure d.ere.rt,U!t"es of the oome C\l.sebraie aign.. The results of this study Will be discussed in ter.rns • of these two oc.teeoriea. 75 '.Oecause of the gr,eat n'Ut!lber of calculations involved the mean pressure chart in t..l:l1s investigation bas been considered as ' rnde up ot a single _point at 6o" N and l7o0 w. All eom.putations havt> been carried out for that point alone but the results may be generalized to apply to the nee.n pJ"essuN cha.rt aa a whole with only slight mOd:itioations in the r~tude of the resw.ts. Data used in th& study were daily pressure de~ures tram normal at the point ao0 N and 170¢ w tor the winter season ot Hover.i.ber th.rcuel1 l&u-ch and for too imenty even yeara 1900 tlU"OuGll 1938. The study ns restricted to th~ winter season in order to obtain as homogeneous a Sali'l.l)le as poeai ble on-J. tti:nc the smller standard deviations eheraeteristie of the sumr..er pressure tield. Tr..1, individual dnily presG1.ll"G d e ~ s were added a.lc,,-.braica:ll;y in 'consecutive two day periods, three day periods, tour day :periods etc. u:r;, to and ineluding thirty-nine de.y pori ods. 'Ihese consecutivo values tom groups or da.t.a J.'Elpreeenti.ne oonse.crutive two day mee.ns. thN-e day mee.ns, ete. F.aeh grou.:p has been treated in two ways• a.s a aroup of conset)U .. t1''NJ mean :p-r&ssure de:rnrt-urea f-or e given period end as e grou.p at oonseautiff u:ital pressure de:rnrtures tar the given period. The individual elef!'ants of tho total preseure departure group -are stmpl.1 the length of the period multipli.e d by- the correspending individ:ual he.a et mean value and a standard devtntio.'ll e.bout that ~ . The 4tEL"ldard deviation moo.aures the 1:,0,itni tude of flu~tuation or the 1nfil... vid'Ual elements in the sr:oup. It the individual element of the group 7G is assumed te btl representative or the process taking place during that tir,te interval the st.P.ndard dertation 1s a measure ot the vari.ation between the ditterent proceesea represented by the 1ndivi4ual. elements ot the~• These standard deviations have been pl.ott.4 as• tulio• t1on ot the ~ ot the pe~od in Fies. xtv.rI and XLVIII tor the two Fig. nm i-epresenta t.'1.e metl>.ods Qt tree:tment mentioned above. standard dm.at1ona ot the .mean :pressun de}l.U'"tUJies. The general ebape ot the OUl"ft 1• 4eter.r:rl.nad by the rather obr.l.oua taot that rnetQil8 taken over a longer :per1 od ot time tend to amooth out •ome ot tlw erratie tluotuatioru, 1n the press\U'e OUl'V9 and oonsequentl;J- the etan4utd deTiation ot the group ot mea.ns tor the longer period ia oonaidffably a.mall.er. In terms or the two uses ot mean preasun clla.r1;$ _little a@ be ae.14 in ~ to the uae 1n the fim eate€10Z'J' • namaly, extal)Ola- tion, since the standard dtrriation botwftn the individual elements ~ the group does not neeessar1J.y :,1.el4 any 1n/ol"I!lltion about the nlation be-tween successive values in the group. Fw the eeeond category, w thfJ delineation ot indirtdual processee, a a.irall stan4ard deviation implies small differenoea between the individual elenen;ts and mean ftlues which ue not auttieiently distinct trOI11 one another te give good delin~~ tion between the individual 'Wnl.uea. Consequently it mee.n wlu.,s are used 1t would appear t.t-w.t the lett hand portion ot Fig. tr.VII wou14 give the beet re!)ftsentation tat' individual l)l'Oee&Ha. the standard deviations ot the total pre,,SlU/'e 4ere.rt'.UlNl8 are plotted in Fig.- nvm. 'l1le pa.ral!olio tom ot the oune ehon 1~1nelY l.arge d1tterence11 b«ttwNn intUTidual •lemmte t>t a given :period length a, the length inoreases. It the t o t a l ~ • ~ 77 -- I '! I ' ' I I -- ----· r··---l--. :. ' I --.l.I --t---·--· ' I . t:Lt· --l -1- ' I • '. ·! ; ---'-I ----+-i l - --~l'I '' --r-__,..__1 l ' ....;.... l 1-·· I r: • - ~ Fig. XLVII 78 - ! I 1 ' ' I - 'I -~--... _:_ _'4----1---f----+---+---+! ]!_ ; : 3 I I-----+--+-----+- .....---+----+---+----+-- --+----'--I----+--+--+---....;..-+---+-- -1-'--''-+-'-+----+-----+--..+-.:.....---4---+-;...~------l 0 -L~ . - 'I' f------+-- +------'--+---+----+---+-·----+--+~-+-+--+--t---r--'--'-t-----'-'--+-'--t-'---4--+~+--+~'-i7t-----,r-'-'--!..c-:,-44'--f-~:+-i--+-+...-!N _ ; • • j '------~---'------....:L~~-·~'----'--'----'---'-'--~-'--'----'---.i.-_•.:_.:__.:_,__- : ,: , r , ::__:_::...-~·:_-:!~:_,__-~-'-......-'--.....~ ---J'------'----'-............~ = ~ -...... =..c.;.....;..............u W C\J 0 0 0 0 O 00 C\J C\J C\J ~ C\J 0 c.o O ~ Fig. XLVIII O 0 C\J 0 0 00 0 0 (.0 C\J 0 '79 for a given period is assu..,"'liSd to represent the pro<Jess tal.'i.ne place within that interval th$ best delineation between :proeesses oceu.rs for the longtlr 11$:rlods. Thie ie more representative of the o!-..a.roet-enstic teaturos of the individi1al process than the use of the mean proastu,e d1eo.ussed in the pre-cedi:ng :paragraph. It hns been assumed that the .mea"l or total :pressure d.ep.u-ture for a single period is representative of the process taldng ple.CHt within that interval. A cheok of the standard deviations ot the &:ily preasure depi.,.rtures which are added tocetber to f'orr:i the mean or total. pressure d-eP"JrtU1"0 shO!lls that these etaI1&a:cd deviations have the same shape our9'e ae F3,g. x:rmn when :plotted a@:l.inst the length ot pa1"iott. This may be V181l4ll~d as the prob1.em o'f fitting an e.rra.tic c ~ by mean ,m.lues taken over varying lengths. '!he best tit u obtained by mean& taken over ehort e~nte ot the curve. Th& ou:rve is parobolic• hmfflVer. so that the increase in standard deviation for the longer periods is ·not sroot. Np great error is introduee(i, then• by U8i..T.1€ mG111n values taken over tlleae longer periods. More quantitative in:t'crt18.t1on can be o\:>te.iood by conatdering ~ ~orrelation ooe:rtioients be.tween sucC&Htve individual ele.ot>nts o'f.' each e_rou:p. ThOf?e eorrelntion coefficients heve heen pl.otted ns o. tunotion of the length of the period in Fig. Xflr1 X. . For uso in extrapoatian., mean char.ts should have a.a lar&-e a correlation as :possible with the preceding ehart. 'l"!lis 1a clearly se.ttatied only for l)Ett'iods ot three to four da~1a or shorter. ~"10r perl9ds where the eo~la.tion co&tticienthe.s dropped to .5 or lower can haJ:dl;r be $Xpa-cted to yield .muoh when u9$d eonsiatentl.y for 80 R+t:~r •~T~c-1+~:1 ·L.!~F 1~n:rr+ .~ ' I :I I : l I- • . ··, . .l i . · 1 I .' { •• • -+-~--+--+- -· . ' t - - + -- 1-: i_:·1~_._ I 1 i ~~ :_~_ ::'.·_:1 ;1::: . :__ ! :. co / <'. : :;-+ : ~~1,_:_.-:+_;_;;_'.,. ._h•·- ----T: . . . CI . PJ i +--+--+--+-----lf--+--+---+<:j" r<) i• I ' 0 r<) i -j : I I • ___ I f I ' : ~j--+ : i t ' I ! j ! • • j - ~!- + - - ; - - + -........ ! • =iJi_ . : • • -. + =--;-!---~--:·--+-,- - + - - , - - - . . •. i ·. ·.. I ! ... ·:~: . l I _,__+--+- __JD_ N N :--- ·I--+--+--·..,," · ·- 0 N <.D Fig. XLIX 81 EJXtre.polation purposes. For use in dellMating individual prooeeses, ~ cherts should have as small a correlation as possible with the ~ i n g chart. 'Ihle minimum. correlation is best satisfied for r,enodo ct tmlmty days or mo1'9. Tho effeet of the m!gi,a.toey cyclones and ant1cycl~s on the form ot the pressure dei:e,rture e-urve l:iaa be$n eonsid.eJ"ed 1n 11g. L. Thie figu:re gives the t'reqU$ncy d1s~ibution of: t.he numb$r of days between peak :pressures for the point so(> lT - l7r:f' w. ~ val.ue at three days r9PJl'$stnta the :most frequent lfile 1ntel"Val between succes&ivc pressure ridges passing the gifln point where these r i ~ a.re the effects ot the alternate ~saaee or tho migre.tcnnJ $~"<slone,s and anticyclones. Little can be done to- represent these .short term. l,Y.t'Ocesses on a IDN.n :prest'An'e oh.a.rt. ~ delineation would be obtained using one half cyc1e ot the entire p.roeesa trM one nod.al point, to the next or a er,.sl."t; of about one ruid one half' days · in length. needed. For extrapolation even shorter length charts would be Since these period$ are of the order of nngnitude of the time between daily syneptic wather charts, these daily charts repre- sent th~ short term tluet.uations of the .PlSsace of tho miel'Q.tOry cyclones and anticyclones without the need tor any additional r1&an e..'la.rta. ~e r.'.IOst ootisfaetory representation of any longer tem wocess Wlll involve the eli.!'!lillB.tion ot these short term t'luctuat1ottS by the uatt ot some multiple of the moat tr.quent period ot three days 'bet'ween au.Qcessive pressux-e crest ~ssages. This will allow the l'el)Ntl$nte.t1an ot the longer pe:riod process with a mi.rd!1Um ot eontri ... button from t.he pNSsure cha..~s caused by the rntgratory o.:,,lOllfts and 82 :·~r~ ~ I -t T../- l •• :t •..,..••· ------- I • • ,- - : • -+--+---;--+---+-·-+---+~-~--+--·-r- .. ·•--·-· ··--· I ~ -.i ..-,~-r; •• . ·_I -.r-··-(· - 1----l . !. I ---r--.-•.....·- • - !. 1 -)- J l---r +-r~ I r ---- ' ' I I ' -_;-i --le-----+----+--+-'--+--+--+- , - - - - - t - · ' I -1·.. ~ ~-••.· ! -; l /+-:__j_-- j- -:- --[---: - L -~----1 ---:-·------,1- ' -~,-- r·--- --+--~-+-----r-----1 -+·•:+-----~ -· •___ -~ - - i j i I -··7'-__;1--:--·--r-- i . . -~- 11• ~1~< r i -i ••, ,-4-l~ .•.•r.iL •· ;-~-----j-~-- r - 1-- C : ·t···· -=3 !",.: .. :· L--l--1 · -- ---•··· · ' - - - --- -- ---• · - ----.-.~--+------. : • ._ , - - + - - ! ____ I ' ·····•··-·-·• -- ---· J ______ ·--·-+--+'--+----'----! I I l · - -·-····' ·- --- --·i--· •· ·- · r i • : -- - •1--- - - ·-ia=;al---t--i-- ; 1___ _ --- _ , ____ _ _ _ __ i I l ____ l I ' -· --· - . _1 ' 1 .. .L. j. ·- - - - - - - - - - --1-·--t:-. - r~~- ::i_.-_-~7. . ~----- ·-------- 1- , I. i. . . . ; . . ': · i i: ·· ' :~-~:➔- - ---·-··-t -------- - - - ·--·- I -! j (lj;-t~ _---~~----~1 -:·~• ·'.-· i I - - k • ! I• .·•.i+ '------+--- :-----\--_,__ _, ___ )... +---+ ; • j I 2 4 Fiti. L ·i : Afi anticyo1ones. The wae of three day rriea.n oh.arts in the pre.oedinG eootions is thtls an attempt to elloinate the e:f'tects o'f these nic;ratory oyclones and nn~1cyclonee and to :ppeeent only those :pressure e ~ characteristic of the loneel-" period Illooldng Action :procese;es. !t is of interest to ocnpare the shepe of Figs. :xLVIll and ·n.1x. with c'Ul"'VGs obtained in the stat1stioo.l theory of turbulence as 41EH)USS$d by G. I. 'Jhy1'()%t ( 7} • Taylor ha$ treated the probler:1 ot turbulon:t now by considerine t.P.e ata.>ida.rd <lf,V1atioo. of the dista.--ioe traveled by a particle as a :function of' the tir.i..e of travel and by . cmu1i&i>rinc; tho correlation betmwri the velocity of the ~icle and its velocity at some later time. In c. later work (e} h.- has extended this id&e. to the oc.:n-relation bet,~,een th• velocity a.t a fixed :point and - the velocity at the ea..~ point e.t e-orae later tine. The standard dffia.tiO:r."t ourve and the oorrela.tion cUl"V'Ds which he obte.i:r..s are o:t e:ractl:, the form of lN.Ga• XI.\"'IlI and XIJ:X.- In terms ot turl>Ulent t'lOfl 'ihylor has used the velocity ot the tlow as the cha:raeterlstio tun-c,tion dea~rtbtng the ohara.oter ot th-e tlll!'"bul.6nt notion. Sinoe the mean presSl'.U'le over some interval is e.lso e. chara.ctenstie function of the turbulent flow one may choooe to relJ,l'Gsent the r.wtiM 1n terms at this charaeter1st1o tuu~ion. InterpNting Fie. 7.LVIII arid lLIX in the lieht of TaylOX"•a results one my e.s1:i-u.rne that they re;prese.."'l.t the :i;e,ssage ot turbulent eddies of varying sizes 1X3,st tbe f'ixed :x»int. In terms· ot the processes discussed in the preceding seetions tli...e t,uitbulent edil.1$8 begin w1 th the srrall s~le eddies a.a.s ooiated w.l. th th$ pass~~ ot migratory cyclones end anticyclones a...?J.d inc~se in siz.e Tc summarize tr...e preceding paragraph$, the most satis ... te.etory short per-iod mean pressure oh.art to US$ consistently Will be , th.et coiteril'.g a three day interval. This will eive the snoothest Npresenta.tion of sh.ort segments of a longer p e r i o d process with a mi.n1.mUm of emtriWtion from the a.mall see.le cyclones e.nd e.nti- eyelones. For the beat delineation of, tho lone period ~eesses, a mean prasou.rc ohart over a ~onsistently give the b e s t p e r i o d of twenty er more results with due d a y s will e o n s i d e r a . t i o n b e i n g c;ivon to the elimination of the short term JJJ."ossure tluotua.tions associated with rrJ.grator.1 csro1ones and anticyclones. Various expet'Ulentally obtittred tacrts in regard to the Bl.OQld.ng Action process have been p.t'esente<i in this study and Bot» attempt bas been made to otter tentative expla.natiOM for these tacts. An adequate thtOl"Y is not · yet ava.ile.bl.$ but the observations prat;en-d here r:lU.St be tal:en L'1to acoount in the formation of any future theory. It is hol)Od that enough intormation hns b$en presented to demonstmte the ~ ilnportanoe of these proces!"3es 111 the anticir.x:i.tion ot wea.the:r trends eove~ne periods of a rew days to three to f01.U' weeks a.."ld that thia information will serve to eti..inulate f'u.rth~r i-aeea.rch in this field.. 86 .A..T1.P.ifilID!X A The eta.tistiea.1 signifiea:n.o~ ot an average ::;irft8Slll19 a.~ure of Plus five nbs. for a. three day period has been • ~ by- adding the daii? preaaui:-e de!)lrlures at the point 601) M .. 1400 W in overla.:ppins thre<i!i day pcrl.O&I tor the 1a.nuary-F¢bruary n.onths ~ the twenty fhen yea.m 1900-1938. ~is giv$8 all possible oori.seout!ve three day total pressure de]'l(:lrt·u.i•es for the J"rmua:ey-Fe'blNary interval ot these yea1'S • • TJ:t.e c~eteristiea ot t.l-iis aet of &lta. are t11e P()I.nl.lat1on oharacterlstics and al"8 ~ ven ey: Mean stm1dard amatian 1149 Tot.al~ ~om. t.his data it is assumed t-1--.e.t u sar:iple of ten tr..ree day periods is drawn a.11d it is to bEl det-ermined wh.ether this sample .may be considered as a randnm sanpl.e drawn tr<m the original population. The oharaoteristics o-r the $W!1.I)le data are: The mean 'ftll.ue is to be auttieiently high to al.low ane ohw-ioe in twenty tor the SSJllPl.e to be a rnndom. sam»l• of the original. population. Total. lium.ber 10 F.ronl the concept of a :p;rresSUN dl.,pe.~ :f':rom no~. the ~sure deipart;ures ms be 1:onsidert'd as nol'!llally distributed about the mean value o:f' 2.21 mbs. 87 '!he usual statistical test for deviations from a nOl:mll distribution is: t • {i - x} rn fj whe-re t -is distributed norr:nlly with a mean of zero and a standard deviation of' one. i is the mean of the sample.~ 1s the mean ot the popula.tion 1 ff 1s the total nun'ber in the eample and (I'" ts the stan.&lrd dev1at1on of tho population. t • 1.84 corresponds to a probability of lese than ~ equal to .05 that the sample is a ra.'11.dan sample drawn tram the population. For this case: X ) .. 7.2 m.bs. An average of 7.2 mbs. over a period of three &lye is theretON statistically signiticant at tl'l.e five pel"Unt lavel. A sirdlar check at the point &oO N • 1'100 \Y ahon that ru.1 average dei:arture Of 5.Z r.100. tor a sample of ten is ste.tistieally s1cnifioant at the f'i't'e percent level. h corr.1.ation coe:f'f1c1.e:nt between the lZorth A-:ieri®.n sector ar.d the Atlantic seetQr' l$ oomputoo tra,,s stan<Jard (lor:t'elation formulae round in any standard statistics reference. In its simplest Oamptttational fOl'Il the eonelation coeftioient is c;iven b;r: 1" • For the 1914 case of one day lag: i-:/- • 6979.71 nbs. 2 i xy • 5772.54 moo. 2 11 • • 4:re 80 (1) Elliott, R. D. rrocreae Report no. 3 on mocklne Action l'rojeot submitted to Ottioe of Naftl Research hbrua.?"/ 10, 1948 (2) Detant, A. Die Zirkulation dm.- AtmQaphai-e in dtm Gemasa1gten Breiten ·der Erde-Goografiam Annal.er (1921) 3 1 p. 209 (3) L&ttau, :F,.. 1tAtroospharieche •'rurbUlenz," AledemiJehe Verla@igesellscha.tt, Leipzig (1959) Chap. 12 Rossby, c. G. . J. W .erine 1~ (1939) 2 1 P• 38 :r. Meteorology (1948) 5, P• 58 (5) Cressam, o. P. (G) Rossby, c. a. (?) Taylo.:r, G. l. Proc. London lib:th. Soc. (1922} 20, :p. 196 (8) 'Jhylor, G. I. J. Mete~ol.0('.3 (1945} 2, P• l.87 Proc. Roy. s oo. A (1935) 151, P• 421