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Transcript
Reproduced b.
1-)I)O C MM ENT SERVICE CENTER . ...-
'-ARMED SERVICES TECHNICAL-INFORMATION AGENCY•
--- U. B. BUILDIM.G, DAYTON, 2, O H I1O
£.TI I -IF I
"NOT.7CE: When Government or other drawings, specifications orothe' data are used for any purpose other than in connection witha defti.itely related Government procuremei.t operation, the U.S.Government thereby incurs no responsibility, nor any obligationwIwt'.t:oever; and the fact that the Government may have formulated,furaikE hed, or in any way supplied the said drawings, specificationsor other data is not to be regarded by implication or otherwise asin any manner licensirng the holder or any other person or corpora-tion, ':.r conveying any rights or permission to manufacture, use orsell awiy patented invention that may in any way be related therat0."2
_ ___ _ I
AWSTR 105-86AIR WEATHER F •RVICE TECHNICAL REPORT
TROPOPAUSE ANALYSISrC--
-u
AND lQ-%
FORECASTING
p os
MARCH 1952
DEPARTMENT OF THE AIR FORCE
ARWTEAWSTR 105-86A IR WEATHER SERVICE TECHNICAL REPORT
TROPOPAUSE ANALYSIS
AND
FORECASTING
MARCH 1952
D E P A R T M E N T O F T H E A I R F O R C
AIR WETHE S1VICZ TEHNICAL REFPORT UNo. 10546 Am WEATHER SEvIC
A=nR'rs AmR Foac3 BASEWaahlngton 25, D. C.
March 1952
Foreword
1. Purpose: Air Weather Service Technical Report No. 105-86,"Troppauae Analysis and Forecasting' is published for the informationand guidance of all concerned.
2. Scope: This report outlines a recommended procedure of construc-tion of tropopause charts and tropopause prognostic-char-t for guidanceof thoce forecasting detachme'ats which have a requirement for suchcharts. A discussion of the basis for the recommendations and illustrativeeamples are included, These procedures have been developed and testedIn Hq. Air Weather Service and are believed to be well adapted for theparticular present needs of this Servim They represent a combination ofcertain ideas proposed in the older literature and new conceptions growingout of recent experience with the expanded upper-air coverage nowavailable.
8, Supply: Additional copies of this report may be procured in accord-ance with provisions of AWS Letter 5-3.
By ORDER O COLONEL MOORMAN:
OMnC7AL: OLIVER K JOINTESColan, USAF, Chief of Staff
ROBERT B, EDWARDSLt. Col., USAFAdjutant Gene.ra
DISTRIBUTION:"A" plus "D"(Except 1 copy per Hq. and Det.)
ill
M limU AWM 105-M
: -Z
[4Contents
IN TRODUCTION .................................................... 1
STRUCTURE OF THE TROPOPAUSE ................................... 1
SkdN MIDEFINITION OF THE TROPOPAUSE .................................. .8
11win VVRELATION OF TROPOPAUSE HEIGHT TO THE HEIGHT OF
V 41.. 1 U M W IN D ..................................................... 4
CHOOSING A METHOD OF TROPOPAUSE ANALYSIS .................. a
RE FE R EN CES .......................................................... 81
2W No. PaoAnalyvis of the Tropopause in the Ascents at An, Feb 1935 .............. ITropopau.e T e .......... ........................................ 2 3
TWA rej~td ig," pool,Height DifferencM Tropopause and Maximum Wind ............... 1&.Height Diffeorces, Tropopause and Maximum Wind (Latitude Belts)- lb. 5Height Diffeences, Tropopause and Maximum Wind (Tropopouse Types) 1o. aCorrelation of Trapopause Height and Pressure at Various Levels ...... 2. 8Tropopause Chart for 0800, 20 March 1951 ........................ Sa. 9500-mb Chart for 0800, 20 March 1951 ............................. 8b, 10Tropopause Chart foar 0800, 21 March 1951 .......................... 3r 11500-mb Chart for 0300, 91 March 1951 .............................. ad. 12Tropopause Chart for 0300, 22 March 1951 ......................... Se. 1S500-mb Chart for 0200, 22 March 1951 ............................. 8f. 14Selected Soundings for 0300, 22 March 1951
(On Skew T-Lo*g P Dlagram) ................................. 4. 16Selected Soundinga for S030, 21 March 1951 ......................... 5, 17Selected Soundings for 0800, 21 March 1951 ......................... 6. 18Entry of 200-mb Isobar on Segment of Tropopause Chart ............ 7a, 19
V
AWl! 105,o M-A MUCH 198
Contnts-cont'dr4%"w POCe
Tropopausa Position In Veztical Crom Seetion ....................... 7b. 19Tropopause and Temprature Atslysis at 200-mb .................... 7e. 20Entry of 200-mb Isobar for Tvo Tropoiaus. Ieaves on
SegmenZ of Tropopaum Chart ................................... U•, 20Double Tropopause Position on Vertical Cron Section ................ 8b. 21Tropop•use and Tempemture A lyaim at 200-mb .................... Be. 22Tropopaume Break-Line 'on Sermett of Tropopaue Char' ...... 9m, 22Double Tropopause Poiltion on Vertical Cros Section ................ 9b, 28Tropopau" and Temperature Analysis at 200-mb ................... k, 2STropopauso Chart for 0800, 18 January 1931 ....................... 10s, 24200-mb Coitourm for 0800, 18 Jimuary 1951 .......................... 10b. 25400-mb rsotherm• for 08U, 16 hanuwTr 1951 ......................... 10e. 20800-mb Ibotherwo for 0800, 16 January 1951 ,... .....- -.......... 10d. 7200-mb Ihatherms for 0800, 16 January 1951 ......................... f0e. 2A150-mb Isothorrtu for 0800, 18 January 1951 ......................... 10f, 29
vi
MARCH IM5 AWIT 105-U
Soction 1. INTRODUCTION
This report is intended as a quide to the c. Upper Invel forecasting for air oper-construction and analysis of tropopause atlons..charts and the construction of prognotic The appl~ications of tropopause charts intropopause charts. forecasts for other meteorological elements
Th ,vlugL tropopause charts is demon. such aas cirrus clouds, turbulence, visibility,strated fn-connectlon with-
a. Determining the height at which the etc., will be covered in future technicl re-maximum wind will f found. ports and manuals to be prepared when suf-
b. Accurate analysis of the temperature fici ent experience and additional informa-field on constant-presure charts. tion have accumulated.
Secton 11, STRUCTURE OF THE TROPOPAUSE
The tropopause has always been defined layer are usually found in the vicinity ofsimply as the boundary between stratosphere strong wind currents in the high tropo-and troposphere. Early, ideas of the tropo- sphere.pause held It to be a surface of discontinuity The leaf.Uike structure of the tropopauseat which there Is a marked decrease of lapse has been studied In detail by Palm~n (see.rate. Detailed investigations of this boun- VII, ref. 9), and Ejerknes and Palmdndary with accurate and abundant data have (see, VIII, ref. 2). They found that eachindicated that the tropopause is not so much one of the tropopaus surfaces in a "bundle" '
a single surface as a layer. The term tropo- or layer is characterized by a' relativelypause layer has been proposed by Byers (ame constant potential temperature, although its.VII, ref. 3), and by Flohn and Penncdorf height varies. With the aid of a series of(Sec. VIII, ref. 7). In this layer the lapse- "swarm ascents" of balloon meteorographsrate changes from Its tropospheric value to they tabulated the changing values in spaceits stratospheric value by either a single and time for the various tropo~pause surfaceschange toward greater stability (sisr/ace of at several stations. Their table for As- inffta-biliatio~n) or by successive steps, giving Norway Is reproduced as an illustration (seeeither a single or mufttpe tropopause. The table 1).multiple tropopauses are often in evidence The mean values of potential tem~peratureIn the vertical cross sections as an overlap- for each of the four tropopause surfaaesping leaf -lie atrueturs. The tropopause observed at As for the 3-day poriod are-layer Is generally found at high elevations M IVand low temperatures in the low latitudes 294 S80i 815 828and at low elevations and relatively high esaetopue perdinsndtemperatures in high latitudes. The p-oten- Tesm rppuaapae nsudtial temperature in the tropopause layer is Ig rmajcn ttosfrtesmfar from constant laterilly, being highest in time.low latitudes and lowost In high latitudes. Palm6n (se, VIII, ref. 9) demonstratedThe greatest changes of height, temperature, that the variations of the tropopau-se layer
and potential temperature of the tropopause in time and space are acoi~plished by the
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MAICH 19M AWSU 105-"
disappearance of some individual troap•ouae ref, 8), and is amply supported by recent"leaves and the appearance of others, This synoptic experience,fact has also been demonstrated in many Palmdn (sec. VIII, ref, 9) and Flohn andlater studies, for example by Bjerknes and Penndorf (see, VIII, ref, 7) give three mainPalmnn (see, VIII, ref. 2), B6mont et al., types of tropopause structure, shown inlaec VIII, ref, 1), and Graves (sec, VIII, table 2.
2 LIFTING TYPE WARM.AIR ADVECTION,WARM-AIR ANTICYCLOGENESIS
3. SUBSIDENCE TYPE TROPOSPHERIC COLD-AIR ADVECTION;CORE OF STATIONARY LOW
The three types represent an oversimpli- isothermal conditions prevailing from thefied classification of the diverse lapse-rate ground to the top of the sounding, At othercurves encountered in the atmosphere but times there will be a slight but relativelyare useful in relating tropopause structure steady decrease of temperatur"e upwardto atmospheric proces-.A through the whole sounding (see Court (sea.
Under certain conditions at high latitudes, VIII, rf, 5)). In either case the tropopausethe recognition of a tropopause becomes Is a matter of arbitrary definition, In thevery difficult. Occasionally a lapse-rate curve latter case, one might say that there is nowill be observed where there are nearly tropopause at all,
Se~flon III. DEFINITION OF THE TROPOPAUSE
When the lapse rate changes from its tropopause definition is mori difficult. Duetropospheric value to its stratospheric value to the desirability of representing the tropo-by a single change towards greates stability, pause structure on a single map, it has beenthe tropopause Is taken to be Identical with found convenient to define a predominwttthis surface of stabilization. If there are tropopause in such a way as to give maxi-several tropopause leaves, or po-iWt of sta- mum upefulness to the single trpopo•4sebiization, In a sounding, the question )f clhrt.
AW Ih U416 MA"C 1912
Aviation requirements for the tropopause follows: The predom(innt trompuse ischart vary from year to year, and it is not found at the lowest point in the soundingpossible to predict future requirenzents with where the 14p8e rate deoreaeee to #o C. peraccuracy. During the last few years, meteo- kilometer of pressure altitude or te18, dndrologists have come to regard the most avrgeo C. per kikmettr or Ws for theimportant characteristic of the tropopaumeas its association with the maimume-wind r two kiometer8 of presure altitudel
*•n the vertfzaL In view of thiis, six er~ent above the point of 8tabAiation (frontal and
L definitions of a predominant tropopause other middle-o-r low-tropocphoric stablehavo been studied in an effort to determine layers excepted).
V their suitability with respect to giving the 1 m ,o 1, =W s a x tg tw.V best "fit" to the maximum-wind in the verti. 6"p' to d• to enmja~ m• t 'amnumba• of k~gkt *=zmutu am fte to itu otabmtyior an
cal. The beat definition appears to be as in fo to t...i ,f1
Sotlon IV. RELATION OF TROPOPAUSE HEIGHT TO THE HEPIGT OF MAXIMUM-WIND
L The relation of the predominant tropo- is probably due to the small number of windpause, at dofned above, to the height of the ascents reaching very high levels.) Themaximum-wind is shown In figures la, Ib, frequency graph for the stations north ofIc, whicli were compiled from all available 400 N. shows a much better.develtped maxi-rawinsonde data from the United States and mum in the first kilometer below the tropo-its Caribbean stations for 1950. pause. The diagram for the belt 80-890 N.
The results from all the data are shown In apparently shows a combination of the dig-figure Is, Indicating that the maximum- tributions for lower and higher latitudes,wind in the vertical is found most frequently When the data are separated accordingjust below the predominant tropopause, to the tropopause types of table 2, resultsThere is, however, a considerable spread of are obtained as shown in figure Ic, Forthe individual tropopause-height values tropopauses of type I or type IN, the mW-d-about the most frequent (modal) height, due mum.wind Is found close to the troMpause.to the inclusion of all values regardless of For tropopauses of type I11, the maximum-wind speed, location of the station, or type wind occurs most frequently about 2 kmof tropopause, (The spread of values about below the tropopause, possibly in associationthe modal height Is significantly reduced if with the occurrence of lower secondaryonly cases of high winds are examined). tropopauses in this type of situation. How-
In figure lb the data are shown a"ter ever, caution must be exercised In the use ofi separation into different latitude belts. tropopause types, since many soundings do
Below 800 N. the maximum wind is found not conform well to any of the commonlyabout 8 km below the tropopause, with a accepted types. Also the type of tropopauserelatively small number of maximum-wind observed often depends on how high theobservations at the tropopause, In agreement sounding extends, Therefore, the practicewith a recent study by Coldn (sec. VIII, ref. of typing tropopauses should be limited to4). (The fail-are of Colfn's wind-maximum studies of a statistical nature and is notabove the tropopause to appear in figure lb recommended for daily analysis work.
4
715
HEIGHT DIFFERENCHI IN KILOMETERS-
wxmmw,i-te*A Dat& for all ntatiouclU aU uomanoid aU tropop~ause tym cf sr NoladoS
40N AND ABOVEtole SOUNDINGS
a.1
- 30-39 INOL1450 SOUNDINGS
w
101
BELOW 30 N705 SOUNDINGSah
.10
5
S 5 4 -3 -2 -1 0 I 2 3 4 5 6 'T S
.4!ICHT DIFFERENGES IN KILOMETERS
Fioum lb. Same Daft ew in Fig. la W~t the dczto Aous bees ,ib-divided aceff4big ta 1a~tiut& baU&.
AWMT 1C~-C MAACH 1911
TYPE Ito
________________________
ILAý_7 ý_ 0 a
0.1
1192 SOUJNDINGS
10 h
-a * 6 .5 .4 -3 -2 -1 0 1 2 3 4 5 5 8M9IGHT DIFFERENCES IN KILOMETERS
Fiatxn. 1c. Sawe Data wa iR Figue'e la bu~t Grousped Awrding to tha Troipopaule Types Given~ in Table 1
Section V. CHOOSING A METHOD OF~ TROPOPAUSE ANALYSIS
Owing to its complicated structure, the perattute gradient in the tropopause layertropopause presents a difficult analysis prob- are associated with sloping surfaces of sta-lenL A method of tropopause analysis should bilization.sere several purposes, as follows: b. The location of contrails, upper hame
1. It should enable the analyst to deter- layers, cirrus clouds and turbulence,mine the general distribution in space of the 8. The method of analysis used should beboundary btween troposphere and strato- simple enough to permit a generalized fore-sphere. cust of the above features,
2. It should give the location in the ver- Requirements 1 and 8, and to atica] of pronounced changes in hydrostatic cert~dn extent requirement 2 can be satissledstability. This information is significant for by the analysis of a chart of the predominantdetermination of: troý,!opause, Such a chart will show the geo-
a, The elevation at which the large- graphiceal distributi on of the ti-opopause layer,scale meridional temperature gradient re- from which the approximate geographicalverses and therefore the elevation at which distribution of the mawlmum-wlnd in thethe maximum-wind in the vertical is found, vertical Is In~ferred. Also it haa been demon-Odnce the strong changes In horizontal tern- strated that the height of the predominant
6
MARCH 1952. AWMT 105-44
tropopause can be forecast for a .24-hour tinuous tropopawee conto-ura can be drawnperiod with a skill significantly greater than in the region between the major breaks,persistence, A chart of the predominant tropopause,
Major interruptions of the tropopauae however useful, fails in certain respects.involving elevation changes of as much as Potential temperature, although conserved20,000 feet or more can occur in certain in space and time along the individual tropo-places, particularly in the vicinity of strong pause leaves, is not necessarily constantuind-mazima in the ho-wontaZ (jet streams) along the predominant tropopause, A plot-(for example, see Riehl (sec. VIII, ref. 12) ting of the intersectims of the predominantor Palm6n and Nagler (see. VIII, ref. 10)). tropopause with constant-pressure surfacesIt seems desirable to show these major will not aid the analyst in an analysis of thebreaks on the tropopause chart (an analysis temperature field. The details of the severalincluding all the smaller breaks would pre- surfaces of stabilization, or leaves, "An notsent an unduly complicated picture). Con- be readily shown on a single chart.
. ... Setion VI, TROPOPAUSE ANALYSIS
A fairly complete tropopaust, analysis can Analyzing the Trrpopause Chart, Inbe obtained as follows: the analysis of the tropopause chart, one
1. A Tropopause Chart is plotted. Poten. needs to wnsider the plotted values for thetial temperature and pressure for each predominant tropopause, which are obtainedstabilization surface at each station are by the procedure described above. Theplotted on a map, The particular point cor- analysis is usually made in terms of pressureresponding to the definition of the predomi- altitude as mentioned earlier, for convent-nant tropopauso ic indicated by a symbol ence in translating the analysis into a(e.g., underlining). In the event that a doscription or forecast for aircraft opera-large number of stabilization points is ob- tions. A 8,000-foot contour Interval isserved on a particular sounding, it Is advis- sufficient to give a good description of theable in the Interest of simplicity to limit the tropopause,number of points plotted to three-the Since tropopause Interruptions or bTva k.spredominant tropopause and the nearest of many sizes can be observed in the data,stabilization point above and below it. some sort tof selection is dbslrable. The
2, The preasrre (or presmire-atitude) entering of all the breaks which could bevalues of the predominant tro-pause are found would result in a chart which wouldanalyzed, Since it Is not possible to forecast be too complicated to use, On the otherdetails of the tropopause, this serves as the hand if no breaks were entered on the chart,basic type of prognostic as well as analyzed the drawing of elevation lines would be verytropopause chart, The forecast tropopause difficult in places where the tropopauseis useful In this form for determining the height differs by 15,000 feet or more atheight at which the maximum wind will be adjacent stations. A criterion for trope.adjacen sttins Ah crieronfore.pfound I n the future. pause breaks which does not lead to incon-
3. The intersections of each lef areWeTed on the approprsec teo ofeah eafare venient complications is to draw a breakentered on the apporae constant-'press-Ure
surfaces. Since each leaf 13 characterized only where the difference in potential tern-by nearly constant potential temperature, its perature of the tropopause between adjacentintersection will be characterized by a cor- radiosonde stations exceeds 15 to 20 degrees.responding temperature. This fact aids in The more extensive brcaks thus obtainedan accurate analysis of the temperature will usually parallel the direction of high-field on the constant-pressure surfaces. tropospheric flow, and will often be found
AWlmR I-4" M 2 9
in close proximity to wind-speed maxima in Example&. An uxmple of tropopausethe horizontaL analysis is shown with ac~ompanying 500-
Portig (sew VIII, ref. 11), following the mb charts in figures 8a, 8b, 8c, Id, Be, St.type of statistical analysis first made by In order to eliminate unnecessary detailDines (see. VIII, ref. 6) and by Schedler only the data for the predominant tropo-(sec. VIII, ref, 13), has shown the corre- pause points are plotted on the tropopauselation between height of the tropopause and charts, The problem of intersections withthe pressure at various levels at Munich, constant-pressure surfaces will be discussedfigure 2. (Many similar studies are avail- In the next section.able in the literature.) The relations given Broadly speaking the tropopause over theby a graph of this type can be used in a United States in this example can be divided
general way to check the tropopause analysis, into three general sections. The most ex-"partioularly in areas where data are miss- tensive section is characterized by potentialIng. One expects to find a high tropopause temperatures of from approximately 550 C.associated with upper-air ridges or highs, to 75' C. and Is located near 200 mb (38,700and a low tropopause associated with upper: ft. pressure altitude). A second section, lair troughs or Iowa. This simple and we. north of the maximum-wind (from the 500-known principle will often serve to avert mb chart), is characterized by potentialinconsistencies in the analysis. temperatures of from 850 C. to 450 C. and
is located near 800 mb (80,100 ft, pressureZ altitude). A third section appears over
-() Florida on 21 March and moves northward_0 (110) during the following 24 hours. This is a
(1O9) characteristic tr•po•ia troo'pauee with tem-
16 (192) peratures of from -750 C, to -800 C. andpotential temperatures near 1200 C., located
(232) a little below 100 mb (58,200 ft. pressure14 (282) altitude). There are two principal break-
-(339) linm between these general sections. The2I P-(370) break between the middle and lower tropo-
Mean -(394) pause sections conforms approximately toTropopause the maximum-wind at 500 mb. The southern
10 break corresponds to a secondary wind max-(405) Imum in the horizontal, which is located
8 (404) along the Gulf Coast of the United Statep.-(403) This maximum is somewhat more prominent
6 (404) at 200 mb than at 500 mb.In the major ridge, where the 500-mb
( 406) wind-maximum is much weaker, there is no4 (407) abrupt or pronounced change in elevation of
-(408) the tropopause such as can be found near2 (408) pronounced Jet streams. Since the tropo-
-(408) pause breaks depend to a certain extent on(I 408) the strength of the wind at the core of the
S0 0.2 0,4 0.6 0,8 I.Or (HC pZ) jet stream, it is to Le expected that a bre-ak.00(line will not extend interminably across the
FioUR 2 Corr, elat4n coeffieient (r) betwteen te map, but will gradually disappear towards4air Pum, (P,) at the surfae s and h e*iht regions of weak wind.(H,) of the• o•ft'eaeust at MSuniah a# a On 20 March, the tropopause is low in theof Weght. The msumbei'a in paren~imee are Mhe%u•mber of aawsa rewahing the given level, (After region of the major trough at 500 mb andSPort•) over the tropospheric cold air mass. An
Si
NAMIP 195 AWM' 1054A
140 ISO i 110 t t
7Q
44
38
50 A
442
FZouu Sx. Tropopau" Chart for 0100 GCT, W March MDIl. Oy the data for the predominant tropopauaeare reproduced (underlined), The potential temperaunur of the tropop~auae ýn degree. oentigradle is plotted tothe left of the station viTCZ anid the preuisres of the trop.opauee f4 tmilbars is plotted to the ri~ght, Thepreehtls altitude of the tropopauee in hundreds of ft tis i parena.me. The mItoi• are drmwn inthree-thoumnd foot Wervals, tolid un., laat two di$ta omitted Break-46ee are indl.'aod by the heavyd4Wed Unes.
9
AWtUU 104 M-"19
140 130 Ito 11 o0 to 0 0 to 56
100
SIS
184,30
1920
Ito 110 100 to 40
S~10
MAECI IM5 AWS?! 105-"
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ion4 91 AW I II-1
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Flow 8e. Fropepatu*. Chart for 0*00 OCT, 81 Mweh 1951.
13
AWM~ 105-M MANN4 IM5
140 130 ISO 110 go so 704 50
1%6
MAAcHiNs AWST 10&-46
interesting feature is the small area of very pause leaves, each leaf being characterizedhigh tropopause over the Great Lakes. This by a nearly constant potential temperature.area does not appear on the maps for the The representation of such a zone as afollowing two days, possibly due to Insuffi- break-line is justified by the necessity forcient data. The region of low tropopause maintaining a simple and feasible procedure,moves eastward with the major trough In contrast to the above case; we can ex-during the next 2 days, On 22 March a very amine a situation in which the predominantlow tropopause is reported at Buffalo, N. Y., tropopause slopes gradually. Such a situa-
and at the same time a very high tropopause tion is shown in figure 5.at Hatteras, N. C. This difference of 17,000 Here there is 9, stabilization point on allfeet pressure altitude in the tropopause at three soundings tt a potential temperaturethese stations is associated with an intensi- of 591 C At Nantucket this is the lower of
* ficatlon of the major trough at 500 mb and two tropopause surfaces. At Albany, It iswith the beginning of low-level cyclogenesis proiiounced, and is the only tropopauseoff the east coast of North America. present. At Rome, the 591 C. surface is the
In the vicinity of the 500-mb major ridge higher of two equally pronounced tropopausethe tropopause is high and flat It is charac- leaves, which are relatively close together.terized throughout the 8-day period by a The tropopause chart therefore shows theremarkably constant potential temperature predominant tropopause sloping continu-of about 62'0 C., indicating that only one ously down toward the westnorthwest.surface of stabilization it involved here. A third type of situation is found In the
Another area of low tropopause moves in vicinity of the major ridge The soundingsover the northwest part of the map on 22 is figure 6 from three widely-separated sta-March 1951, following a fresh low-level cold tions on 21 March 1951, show the same well-air outbreak in that area and in association developed tropopause surface, which Is foundwith another major trough at 500 mb. over a large area. Although the tempera-
In figure 4, the details of the tropopause ture in this tropopause varies considerably,structure over part of the map on 22 March the potential temperature Is very nearly1951 are shown by the upper portions of constant.the soundings for four stations. lIerseectglo of the Tropo"sue with
At Swan Island several srbihlization Conatant-Preaaure Surface. At the presentpoints are shown, with a pronounced tropo- time the analysis of the tropopause intersec-pause leaf at a potential temperature of tions with constant-pressure surfaces ap-1271 C. This same leaf marks the point of e,-Ars to have its chief value as an aid in theminimum temperature on both the Browns- drawing of isotherms on the constant-pres-ville and Burrwood soundings. A weakening sure charts. The basic principle of thisof this leas toward the north is shown by application is illustrated in figures 7a-c.comparing these soundings with the Dodge Figure 7a is a section of a tropopauseCity sounding. On the three northern sound- chart on which the potential temperatureIngs a lower tropopause leaf characterized and pressure at the tropopause are shownby potential temperatures near 650 C. is for four stations, A, B, C, and D. The solidindicated. Although this leaf does not appear line Indicates the intersection of the tropo-at Swan Island and is weak at Burrwood, pause with the 200-mb surface. Figure 7bit is pronounced at Brownsville and coincides is a vertical cross section from A to C. Anwith the minimum temperature at Dodge abrupt change of the gradient of potentialCity. The break at which the lower tropo- temperature (and consequently of tempera-pause became predominant, was drawn ture) on the 200-mb surface is clearly re-therefore just north of Burrwood and just vealed, The 200-mb chart for the same areasouth of Brownsville. However, there was as the tropopause chart (7a) is shown innot a sharp break in the tropopause, but figure 7c. Without knowledge of the tropo-rather a broad overlapping of two tropo- pause intersection, one would ordinarily
space the Wsthenns evenly between the eta- perature of -6V~ C. at 200 nib. A miuchtions. However, the tropopause itrsection, better picture of the 20O0.mb isotherms isobtained from the tropopause chart in azuare then obtained by aceepting the tropopause7a, ta characoterized by a potential tempera- intersection aa the -680 C. isotherm, whichture, of 800 C., which corresponds to a tem-. leads to different temperature gradients
GO0a210 60 @210
A B
200 Mbh
so 185 60* IS18
C D
Pin= UT. PO~tW ftdt~a ~ 'ure OW'i Presturv of MeS Tr~,opapaw, Susrface NlOW~ on a Tropopsues Chart.TA. IOO-mb isobar on Owe tropopaiue ruirfaws Ac been r~er'etd
0~-11 -10 A-o ooo
-A- -170 Mb
90 - A
75
65
605
030 Mb
Finnu 7b. Vertica4 Crocs-Section fro-n A to C. Dwhed2 lint ai-e iaentropic rurfacee,The heavyj U e iste trowo*'Uae.
19
AWMT 101-U m~H1
-5 57' -57 5
B5 -58
-63 6
-64 -64 -64-64 - -
c D
Fiqum 7e, TFopopaw sW ~mtw .. # tto-The AftVV 6 isa Wat ttvpopows hae ne
Ezopl Showing the Intersection of Two Tropopause Leaveswith the 200-mb Surface (FIgures ga.Se).
s0 210 -
G0O 210 s0o 255 50' 255
A BC
2000mb 1
60o 185 60 * I8! 50,* 21550 215
D E F
200 mb60 170 60 170 50.195
50 195
G H
Fiatii Sa. Potontial To pe,'usre anid Pre-mwe of Mhe Tro-popaue Loame Pta tte4 on a Trppw Chart,Vahmu for the predomimmnt ropopauaC are underlUmed. Tht 200-mb itobar on eaech lea/ hu been mt~erwd.
j220
MAC ion AW-i 15•,-
Snorth and south of the tropopause, as Lmdl. curred in tho southern U. S. on 22 Marchcar in the crou sectiou. 1951, as shown by the soundings in figure 4.
A more complicated example is shown in Here a flight from south to north at 150 mb"curea Sac. would give the desired result,
#,.•.The tropopause chart for this situation, The above examples, although slightlyfifure 8, indicates two separate leaves of idealized, illustrate a use of the generalthe tropopauso, characterized by potentialtemperatures of 500 C. and 600 C, These principle that the {ne uecti'u of the tropo-
aapause surfaces (leaves) with cinstant-ffudam of stbillIation are shown as over- r" elapping leaves In the vertical cror -secton pressure surfaces are charact•aized bySthrougrh stations B, E, and H, f 8b, Tr e ~nearly constant potential temperatures and
200-mb intersections of these two leaves are consequently by nearly constant tempera-ture. Oi a co.stant-presaure surface is.obtained from figure 8a, and transferred to term. cn extendfmrops phere to•-° therms =a extend from troposphere tothe 200-mb chart, flgure Be, They are charac-•-. ~terized by temperatures of -- 680 C, and srtshr:()b rsigtooasr yuCleaves at wide intervals, or (b) more com.-- 69O C. at 200 mb. The resulting 200-mbS~monly by. extending between intersectionsisotherm picture is fixed by the reported of individual leaves, as shown in fiure 8.200-mb temperatures and by the tempera.tures eorresponding to the tropopause inter- A situation frequently is seen where ansection& It is interesting to note that an oxtensive tropopause break-line is found be-aircraft flying at 200 mb from G to E to C tween tropopause leaves which do not inter-[ could pass frum troposphere to stratosphere sect a constant-pressure surface, e. g,, 200without penetrating a tropopause. An actual rob, similar to the 22 March 1951 analysisal stuation in whicb this could be done oc- ahowt in flgures 8e and 4.
-- 75 - /50mb-" .- -- --- 70
S• 26060- 20mb
7- 0
so 45 - ... . ." 4550 E H
Fintim 8b. Vorftcs, Cr Sa"I fn Do s to S tfo R, D•shd liý. ae tsurfame& Necmti Ina" are the traoaomus teavmi
21
AWMIUh10-1 OAXC4 19U,
-57 -57
0606- 2
-630 - 0-
-62 4 -66a
-63 -6
- 66
-66 \--9
-669
-66 (6 6
A B
70 150 70 170
50 260 50 250
C D
Y'zaUIM ga, Tropopauae Data I"r Four Sta,.on. PloWte on a Tropopma~e Chart,
The heatT line is th4 tropopaiae break-Une.
22
MARCH 1952 AWMTI 1,5-3
70707
50so- 55.• --
50
A C
Fiam~ 9b. VertieWa C oe-Seelto% from A to C. D~a8.d Zia" ane iwitre$ mir/am..Hsaiy Wust W1 t" tropopeut leavee,
-58/
/-5 - -60 .-
- TROPOPAUSE BREAK-60 ""
-62 -6l-62 ... . .--...
C D
""- 62
FIGaUi 9t. Tr.opopause and Temperature An4a2jtis at £00-mb. Ths heavyi Uns indiecate the tioao~auu break.
This type of situation is also shown in in figure 9b. According tn the definition uffigure 9a where the tropopause data for four the predominant tropopause given earlier,stations Is shown, together with a break-lhne. 200 millibars at stations A and B is In theThis corresponds to the cross section shown stratosphere, while at stations C and D it Is
23
AWITA 105-14 MAICH 1MIn the troposphere, The resulting termpera- constant-pressure surfa~e and their ruls-ture an-slysis at 200 millibars Is shown In tion to the Isotherms. The complete tropo-figure 9c. pause chart is Ahown In figure 10a. The
The entering ot the break-IUne on the high-level flow pattern for the &&Mie time i's200-mb chart frorni the tropopause chart Is illustrated by the 200-mb contocurs in figuremerely a matter of convention, and has no 10b, and the tropopause intarme~tion~s andvalue for the temperaturro analysis, In'this Isothierms on the succesive coast~ant-pres.
tyeof situation the Isotherm analysis has sure charts from 400 mb to 150 r~b are givenno relation to the line separating strato- in figures 10^,1 0d, 10,c, and 10f.sphere from troposphere on the constant- The 400-mb and 150-mb chartsa representpressure surf am, the two extremes -of tropopause height for
A final example of tropopause analssls is most of the map. At several Aaces in'theshown in figures loa-f in order to Illustrate northeastern States the tropopau,"iseI foundthe tropopause intersections with suctessive as low as, but not lower than, 400 mb. The
400-mob chart is then the highest constant- tures in the north, giving a cold ridge and spressure surface which lies entirely in the warm trough.troposphere on this da.te. Here one can see Occasionally forecasters attempt to aria-the typical tropospheric pattern of isotherms lyze the tropopause intersections with con.nearly parallel to the flow pattern with a stant-pressuxe surfaces from the horizontalwarm ridge, a cold trough, and tempera- temperature field alone, by drawing thetures in goeneral decr~asing northward. With intersections through lines of minimumthe exception of part of Florida, the highest. temperature. The 150-mb chart from thispoint on the tropopause chart is at 150 mib series illustrates the fallacy of this approach.at Oklahoma City. The 150.rob chart is There is a line of minimum temperaturetherefore completely in the stratosphere over extending from Little Rock, Ark., throughnearly all of the map. The isotherms here Ely, Nev. This is associated not with atend to parallel thse at 4100 rob, but with an tropopause intersection, but with a generaloppositely directed gradient, cold tempera- regilon of high tropopause well below thetures being in the south arnd warm tempera- chart, at about 180-200 rob.
at~ ~ ~~F~RE1c 400 mb ecptathegd Iensofter-sher e o at0 200, 18 theure isvey itleh,
arT mle. t20m he tropopause wellsetios on thi 0- sie n som charts these sthen gradient sntrsebind ism wellt markedno shownI fimucyespoteay weraksTheri unsuaintue of thenescion
schageion the temperature gildradentmbln the rppueI eryfat fend overy closeal dph. nte trop2t00-mb surfcept frat theiyw gradie enofta.speea 200 mb ovthonierabe dis vr itale, ascanonteaturoposdpherampsitde of the Isothermectonbe seenpfromthre grppauienI chneart, fiur
tempreaturel strngmaones on th straosphneri sitatinI osbydet h atta h
26
PAMC IM! AW IU111
140~ l13 * 0i~ o)e o 0 100 90T TO Gel~u sD1 obel~ r too.u treio~
Duhed double LM~~~ Mdw.te as ra-u~ 0-bieaUuddii t~cpeefo v~eieaa
100-b bit were o trp~~~ae RtE~~ei0% oeso
'10 40
AWMT log-" MANN4 HO
44
1100so0so
Fwu10c. too-mb Iaoth.dwme for Ono0 GO, 1$ Jm.?V~ 1951.
28
"MARC4 M3S AWMT 109--"
400FO 5 0 40
Fiv~10, 18-M ZotelG oqOOGC 16J uzd18.
629
AWMY ft-a MMKI
Sectlon VIi. CONSTRUCTING THE PROGNO)•ic TROPOPAUSE CHARTTo date only a limited amount of infor- of the change patterns can be modlte(i ac-
rmation is available on methods of forecasting cording to the following rules:the tropopause height. The correlation be- In a particular locality, the discontinuitytween pressure in the high trop-ophere and of tropopatrse height at a break-line willthe height of the tropopause offers a fore- increase if the speed of the associated windcasting possibility. However, Portig (sec, maximu at 200-mb increase& Ifthere is aVIII, ref. 11) points out that the (sec Jet stream forming or increasing and nioo thsrelat11)poionts not that the o date- rasoclaed tropopause break, a break-lire canof this correlation does not lead to a -hor be expected to form in the vicinity of the
rly high correlation between the 24-hour wind-maximum, If the speed of the jetchunges of these quantities, It can be seen stream Is forecast to decrease, the tropoe.from inspection of thft daily charts that the pause discontinuity at the associated break.relation between height changes at e, surface line will also decrease. Extensive rmidlatitudesuch, as 800 mb and height changes of the break-lines not closely associated with prom-tropopaute is not dependable, being some- inant 200-mb wind.maxima will disappear.times definite and sometimes very dou'otful. If there is a distinct northward shilt of
In preparing 24-hour forecass of the the Jet stream (or more generally a shift totropopause-height distribution a few pre- the left as one looks downstream) in a par.liminary indications of some value hAve ticular area, tropopause rises moving intobeen found, The first step is the plotting and that area will increase in extent and inten.analysis of the 24-hour changes of the trolo sity. Tropopause falls moving into the areapause for the last several days. In doing will decrease or disappear.this suff•cient accuracy is obtained by plot- If there Is a distinct southward, shift ofting the change values at each station and the Jet stream (or sbift to the rig~ht as onethen drawing continuous lines connecting looks ,downsteam) in a particular area,equal values. This Is not a strictly correct tropopause rises moving into the area willprocedure In view of the fact that break. decreRse or disappear, Tropopause fallslines are drawn on the tropopause charts. A moving into the area will increase in sizemore exact method of obtaining the changes and intensity,would be the graphical subtraction of. a On 'ertain occasions contradictory resulttrpopausa chart from the previous one with seem to arise from application of the variousall discontinuities bting entered correctly, indications given above. Thul the rules maybut the extra effort involved does not sbem lead to surprising forecast patterns whichnoticeably to improve the results. are often actually observed, such as tropo-
The next step in the forecast procedure is pluse change centers of oppoalte sign mov.the preparation of a 24-hour 200-mb or Soo- ing along on opposite sides of a tropopausemb prognostic chart. For beat re-ults this bre•k-linc.should be done very carefully, using all avail. The above forecasting indications wereable aids. The present and forecast velocity derived mainly from analysis of the numer.fields should be represented by isotach ous vertical cross sections published in recentanalysis (see AWS Manual 105-23). years relating the thermal atructure of the
The height changes of the tropopause can atmosphere to the wind field. In practicethen be forecast to mov,. in paths extrapo- they have given results which have beenlated along the 200-mb fow, and traveling a useful in forecasting, and if applied prop-distance equivalent to the previous 24-hour erly will enable the preparation of a forf..travel of the change centers, their speed cast considerably better than persistence.being increased or decreased by an amount They should, however, be regarded as pre-proportional to the increase or decrease of liminary indications until better ones arethe 200-mb winds. The intensity (and size) developed.
MAXCN 1952 AWU 105-4•2
Sedton VIII. REFERENCES
1. Bimont, H., Van Mieghem, J., Dufour, Lhe subtropics (PuerWo Rico)." Bulletin ofL, and Descamps, A., "Analyse synoptique the Ameticn Met orologi"al Saoiety, vol. 82,et a6rologlque de Is situation atmosphtrique No. 2, 1951, pp. "-60.sur l'Europe du 16 au 19 Mars 1987, A l'aide 9. Palm6n, E., "Aerologliche Untersuch-d'une sdrie internationals des sondages." ungen der Atmosphd.risehen Sthrungen belInatitut Royal M~tdorologique do Belgique, besonderer Bertickslchtlgung der strato-Mdmoiree, vol. 17, Brussels, 1944. sphirischen Vorgainge." Sooietam Sc-entic-
2. Bjerknea, J. and Paimdn, E., "Investi- rum Fenro, Commtntatione8 Phyiuo-gation of selected European cyclones by Jatthemticae, vol. 7, 1988 (Also Mitt. d.
means of serial ascents, Case 4." Geofysiake Met. Im. d. Unt', Hesngfora, No. 25,Publikauaoner, vol. 12, No. 2, 1987, p. 6 2. 1988).
: &Byers, H. R., General Meteorology 10. Palm6n, E. and Nagler, K. M., "The.ew or, H.Raw-l, ) formation and structure of a large-scale
(New York, McGraw-Hill, 1944, 645 P.) dtU.b int weeie."Juw op. -45. diaturbance in the westerlies." Journal o~fp45. ,. A., "n the wind structure Meteorology, vol. 8, No. 4, 1949, pp. 227-
above the tropopause over Puerto Rico," 11. Porti,, W., "Beltr~ge zur KentnIsButletin of the American Meteorological der Tropopause." Beitrtge air Physi derSociety, vol. 82, No. 2, 1951, pp. 52-•8. freien Atmnohd*re, voL 23, No. 2, 1938, pp.
5. Court, A,, "Tropopause disappearance 8-594.during the Antarctic winter." Buletin of ig. Riehl, H., "Jet stream in upper tropo-the American Meteorological Soet 1', vol. 28, sphere and cyclone formation." TrawactionsNo, 5, 1942, pp. 220-288, of the Ameorfn Geohyslca• Unto, vol. 29,
6. Dines, W. H., "Total and partial corre- No. 2, 1948, pp. 175-186.latlon coeffcents between sundry variables 18. Schedler, A., "Die BezIehungen zwl-in the upper air." Air Ministry, London, schen Druak und Temperatur in der frelenMeteorological Office, Geophysical Mem,, Atmosphire." BSetrdge zur Phys derivol 1, No. 2, 1912. 50 pp. frelen Atmosphdre, vol. 9, 1920, pp. 181-
7. Flohn, H, and Penndorf, R., "The 201. (Earlier study, i&d, vol. 7, 1917, pp.stratification of the atmosphere." Btsetin 88-102.)o!NoU An eAtmeive bibiagrspby on the tropopaMco31, No, 8, 1950, pp. 71-78. woe an shortly. In the Men the m lto pop Abe
& Graves, M. E., "The relation between ind BiRiapa•h•/, puabliaed by the Amerikan Meteor.the tropopause and convective activity in olociwal soiety.
