the stratification of the atmosphere (i) · 2013-03-17 · the stratification of the atmosphere . 1...

$: The Stratification of the Atmosphere (I) · 2013-03-17 · The Stratification of the Atmosphere . 1 (I) n. FLOHN" ami R. PENNDORF" /\RSTRACT . A suitable nomenclature for atmospheric$
[Reprinted fr0111 BULLETIN OF TilE AMERICA1 METEOROLOGICAL SOCIETY Vol 31 Nos 3 and 4 March and April 1950 pp 71-78 and 126-130]

Printed in U S A

The Stratification of the Atmosphere 1 (I)

n FLOHN ami R PENNDORF

RSTRACT

A suitable nomenclature for atmospheric strata as well as a clear definition of the boundaries is proposed The necessity of stich a new classification is stressed The atmosphere is dishyvided into an inner and an outer atmosphere from the latter particles may escape The inner atmosphere is divided into three spheres-troposphere stratosphere and ionosphere-with each sphere in ttlrn being subdivided into 3 or 4 layers The new classification is based upon the thershymal structure of the atmosphere Boundaries of each layer are fixed by a sudden change of lapse rate

The boltom layer the grollnd layer the advection layer anrl the tropopause layer are subshydivisions of the troposphere The arlvantag-es gainer hy defining a separate tropopause layer as part of th e troposphere are rlisCltsseri in detail Its upper b01lndary is assumed to be sittlshytted at 12 km over tempertte latitudes The strttosphere consisting of an isothermal layer a warm layer and an upper mixing layer extends frolll 12 to 80 km The atmosphere between 80 and 800 km is occupied by the ionosphere the suhdivisions of which are the E-Iayer the Fshylayer and the atomic layer Above that height the exosphere exists

1 THE NECESSITY OF A SYSTEM OF CLASSIFYING

THE ATMOSPHERIC LAYERS

AT AXONOMTC system should be a tool of

research Tts functions are twofold Firstly it gi Ies a COlll1l10n name to a conshy

cept so that semantic confusion may he avoided and secondly by its internal organization it structures the knowledge of an area of learning so that the relationships therein are clarified As long as basic investigations in a particular field prevail neither a unique nor a formal systcm seems necesshy

1 This article is based essentially on our paper Die Stockwerke der Atmosphare M eteorol Zeitschr vol 59 1- 7 (1942) However it has been completely reshywritten and changed to a very large extent We will be pleased if it opens a discllssion on this subject

2 Zentralamt fiir Wetterdienst (US-Zone) Bad Kisshysingen Genllany

3 Geophysical Research Directorate A F Cambridge Research Laboratories AMC Cambridge Mass

sary The present time however seems a good one for the presentation of such a system for the layers of the atmosphere Such a system must be adopted on a very wide basis to avoid the unshynecessary expenditure of energy in discussions which are purely nominal The need for a clear system of classification is esrecially great in closely aIJied sciences where conventional meteorological usage is not familiar

An example will demonstrate this During the recent years with the increase of radiosonde data available daily the recognition has been growing that the l1pper layers are of importance for foreshycasting Thus the expression stratosphere enshytered the synoptic weather service Esrecially in continental Enrope stratospheric steering has been used so frequently that a sound definition of the adjective stratospheric is necessary The

71

72

increase of knOdeclge 011 the steering layers necesshysitates a clear and specinc demarcation of its houndaries Unnecessary con troversies have arisen between several authors and schools beshycause the same word has been used for different layers To prevent a similar confusion and misshyunderstanding in thc future we propose a partly ncw nomenclature for definite slrata Tn doing 1his we alsn hopc to contrill1lte toard a l1niform tfrtninology Standardization of nQlllcnclatmc seems nrgently necessary

Teisserenc de Bort divided the atmosphere into to layers the troposphere and the stratosphere based upon the simple thermal structure of the atmosphere known at that time Tater on Sir Napier Shaw introduced the term traroraIS for the houndary hetween these to layers During the past 20 years this classification proved to be too simple 1middot10re and mnre suhdivisions were proposed Til Gcrman puhlications cg the exshypressions high troposphere (Hochtroposphare) l11d suhstratosphere ere used Several aushythors rather complicated the understanding of their ideas hy using the notation high troposhysphere for the lower layer of the stratosphere too whereas others applied the notation substratosphere inr the upper troposphere Furthermore the ionosphere was regarded as part of the stratoshysphere Such varying nomenclature necessarily leads 10 seeming mnl radictions

The expression houndary of 1he 5t ratosphere is al11higuolls Tmiddoto houl1(aries e~it an upper ltlno a loer one Up 10 lhe present only the lower boundarv has been important for forecasting purshyposes But in t his era of rockets the upper houndary will tmdouhtedly be of importance too

2 CLASSIFICATION OF THE ATMOSPHERE

The foregoing was in mind in proposing a new classification of atmospheric layers Based upon the best available knodedge of the thermal strucshyture of the atmosphere the scheme given in TABLE J was constructed Suhdivisions of the atmosphere are based best upon the lapse rate y = -dTdJ (CO100 m) because it characterized the meteoroshylogical properties of a layer in the simplest Nay (eg 111lxmg separation convection etc) Boundaries of a layer are easily fixed by its change of sign or by a sudden change in its abshysolute value

Thus our definitions arc based upon a charactershyistic vertical temperature distribution discussed hy one of the authors (r 1 I Fig 10) T t should he emphasized however lhat this cune is only valid for temperate latitudes Above polar regions

BULLETIN AMERICAN lfETEOROLOGICAL SOCIETY

the temperature of the upper layers may be different

In view of the fact that stratification occurs in the earth and atmosphere ie the horizontal exshytension of a uniform property is greater than the vertical extension it will always be sensihle t(l usc fixed strata as a guide to descrihe processes in the atmosphere However it is very frequently only a quasi-horizontal stratificalion hecause adshyditional accelerations occur ithin 1he atmosphere bending the boundaries of layers

First of all the atmosphere is divided into an inncr and an outer atmosphere Tn the outer atshymosphere the particles may escape from the gravishytational or magnetic field of the earth whereas in the inner atmosphere this does not occur In parashygraph 6 more facts about the outer atmosphere will be given

The inner atmosphere is subdivided iul0 three spheres and each sphere in tllrn into several layers A layer is characterized hy its uniforlll thermal structure if several layers llCiong together according to their meteorological state and heshyhaviour they form a sphere This definition closely follows the C01111110n use The word region is reshyserved for subdivision of a layer Tn choosing the names for the layers and spheres we accepted the names already in use as far as possible TARLE I shows the Ilolatiolls suggested and the lllctcorological characteritics

3 TilE TIWPOSPlIERE

lJinoc1illlatology and spot climatology Jre 1110Stly concerned with the study of the meteoroshylogical conditions adjacent to the earths surface ie within the first two meters above the ground It will be denoted bottom layer (bodennahe Luftshyschicht) r21 r3] Macroclimatology studies the conditions within the gronnd layer that is up to ahout 2000 meters 4 r41 AerolorJ) r studies the climate of the frce atmosphere ie within th advection layer and the tropopause la)er

(a) The Botom Layer

The conditions within the botlon~ layer are governed by physical constants of soil (absorpshytion and emission of radiation) species of plants their height and formation VIle shall not deal with this layer specifically (see [2])

bull We neglect mountain stations because they do not represent the climate of the undisturbed atmosphere

Co The term aerology is used as a subdivision of meteorshyologY the ~tudy of the free atmosphere throughout its vettie1i extent rlistinguished from studies confined to the layer~ adjacent to the earths surface (c Meteorologishycal Glossary)

73 VOL 31 No3 MARCH 1950

VI U

~ lt2 iii U of

x u

z ~ nx In I

In Q lt

Z c shy UJ C lt S ~ ~ VI C _ UU 0

V

= ~~~ f=gt ~~~ ~ 3

middot~~e ~o8

S -5 g c IIshyI _ ltIt

~~~~ lt1

8

aCg gt u

0 c OJ

Q) Q) -gt Il) gt gt~v v

~ ~ ~ r3middot5 ~middot50 iii ~ g1 ~ 0 ~ jj

8 ~ ~88 8

N

ltJ If)

0 1-0 111 001 0

o ltJ If)

8 o

~~ ltJ ltJ if) OJ OJ ~ ~ Egt shy E at

~ o ~~I~o++middotcmiddotc 0 0 +0 00

sect~ ~ B B ~ 0 0 000 -4 _

I I I I I o88 0 0 U ) o lr) 0 o __ t-OOQ

00 23++++ 1 I 1+ 00

+ ~BBBEB BEB pound

If) 00 o~ii5 ii5~~ N lt n ++ I I I I + I I

01000 1)0+ 1+111 1

(li) The Grolflld La)ler

Besides thermal structure variations of wind and 1ustausch with height are very helpful in subdividing the tropospheric layers The immedishyate effect of surface friction is to reduce wind speed and to change wind direction Surface fricshytion also causes the dynamic constituents of Ausshytausch a terl1l which will be used here in the sense of a turhulent mass exchange and which is generally accepted and well defined Solar energy ahsorbed and transformed to heat in the soil leads to unstahle lapse rates near the surface giving rise to uprlrafts which compose the convective conshystituent of Austausch The ground layer 6 is deshyfined as a layer in which a noticeable influence of the surface (by friction) on wind occurs (i e up to the heights where the wind vector first equals the gradient wind) and in which the Austallsch coefficient A undergoes characteristic changes 151 The upper boundary which extends up to I or 2 km in all climates is to a large extent deshytermined by an inversion Variations vill he disshycussed at the end of this paragraph The ground layer is more or less identical with Lettaus planeshytary boundary layer r51 Aerological investigashytions have recently clarified some of its behaviour r4 6 7 8 91 other than the already thoroughly studied influence of friction and Austausch [51 ft seems necessary to subdivide this ground layer into two regions a holloill frict-ional region and an Ifper frictional regiol In the bottom frictional region A increases with height reaching a maxishyll1um The height and value oi A nwx depends on Ao the roughness of the earths surface and the latitude with the height ranging from 2 to about 100 111 The upper frictional region is charactershyized by a decrease in A This subdivision fully discussed by Lettau r51 is especially important in regard to the explanation of variation of wind vector with height Its upper boundary is defined hy the lowest height where gradient wind and acshyt ual wind are practically equal That occurs at about 1000-1500 m over continental Europe and U S 1 r51 Over oceans it will be at lower heights than over continents and over polar reshygions as low as 400-600 111 (Schneider-Carius [6] ) The deeper the bottom frictional region the thicker is the upper one If the convective constituent of A becomes large this conception of a bottom and an upper frictional region breaks dmvl1

o Schneider-Carius [4] proposed this name or altemashytively the Greek term peplos Since we denote only spheres with Greek names bllt not layers it shall not be IIseo here

~ 0

~

3 ~

f

l5

~~ 0

~ E ~8shy ampu0 l

~ 1I 1-8i)Jta 0 gt- N

Igtl

8 0=gt ~

_05~ ~ -----r-+-~-shy VI OJ ~8 0100 10 0

~ o ~ gt 1 +jl1+ 1lt 3 iii 0 ~ =2

- 8 000l 00)00o~ OJ OJ5 117Z = gtc 000o be 0 o 0)00~ 0 D lt li I 0lt ~

~

iii l Q)ZIII gt~ 3~ j u1 sect ~ ~ s~~ ~~~

V OJ OJ OJ~ -= 0 -= 011 I) UJ0 o 0 ~ c

UJ

I ~ 0 -

~ OJ -= 0 ~

8 E =~ O~

N o o

~o00 0lr) Ir) IN_ 00 CI I I I I I I 9

OIJ)N CONN o lr)oI)_ 0

o o

I~gt 1 t3 OJ gt

be~3~ tL- 4)~Q) OJ

Q) - II) - gt gt

~~ sect3 3 E-L [ o~ ~ E ~ 8 a sect E

85o e62 o~~l f-lt~0 iQ

OJ OJ OJ cOJ o-= -= 0 000 g UJ 0 ltJ 0 ~ 2 5 b f-lt eorn

c 0 oj eo OJ1 Fgt~

Fgt 0 OJ

0

I ~ c E ltJ

5~

74

Tn the ground layer the temperature normally dccreases with height (but there may be at times a negative lapse rate as during the night or over Arctic regions) whereas the relative humidity inshycreases with height Jn the bottom frictional reshygion normally cloucls are lI1issing however if 1 hec01lles very small (and other conditions are favoralde) fog or haze Illay furn Thc upper frictional region is freqllcntly rdlcd with haze Imiddothere these two effects (increasing humidity and low A) combine Under the upper houndary of the grollnd layer turbulence clollds (f ractocllmulus or fractostratus) may form Convective cloudshyforms caused by high val11es of the convective constituent of A have a pronounced dailv period with a maximulll in afternoon The Pcr10pause Co

acts as a hlocking surface tu air coming rom above (eg the trade inversioll slIhsidence invershysions in allt icyc1ones)

(r) The ldu(doll lawl

[11 this [acr horiwntal Illotions exc(ed vertical llles hy a factor of 100-10000 Thc tcrlll advccshyti(m layer is preferred r41 since advection is far larger than convection In 1942 we suggested the term con vection layer or cloud layer but the new term proposed seems more appropriate HOshyever it is impossible to s11bdivide it into regions at this time without further aerologiral invcstishygations In this layer stratilied clollds prevail and distinct doud laCrs occur as shown Ily Illany statistical and acr()logiral studies Subsidence nrl lifting change the lapse rate in this layer and give rise to the weathcr Tn this layer the wind regillarly increases with height Thus the overrunning of warm air first occurs here anshynouncing the arrival of a warm front Overrunshyning cold air (voreilende Ka1tluft) frequently ocshycl1rs in this layer causing unstahle conditions Suhsidence must approach zero near the ground and therefore its effects 011 the ground layer arc normally expressed only il1directly as a modiflcashytiol1 of surface air lIIass properties through lIIixshying and cross-isobar flow greater radiatio~ etc

(d) The Troropallse Layer

(1) Earlier dasSifi~aliolls-Whereas the lower boundary of the troposphere given by the solid or fluid surface of the earth is dearly defined different defil1itions of its upper boundary exist Many textbooks state simply that the tropopausc separates the troposphere from the stratosphere Since the installation of a world-wide network of radiosondc stations in daily operation for ahout fllelast 15 years stratospheric conditions have

BULLETIN AMERICAN METEOROLOGICAL SOCIETY

been thorollghly studied They have shown that this conception of the tropopause is unsatisfactory In earlier years it had been already known that the tropopal1s~ grew higher and colder as one proceeded from the pole towards the equator H lYing that in milld J 13 jcrknes in I()12 reduced the explanalion of day to day and seasonal variashytiol1s in height of the tropopause 1(1 pllre kineshyllIatic effects of 1I1eridional horizontal displaceshyments of tropospheric air masses Iater on howshyever cases were recorded in which I he tropopause over middle Europe was much lower than the corshyresponding mean value over the polar regions Studying synoptic tropopause vaves more thorshyoughly Palmen rIO I came to the conclusion that vertical air motions contribute to its variations The height of the tropopause changes nearly twice as much as calculated from the horizontal displaceshyment o( air particles (Tn these calrulations changes of height of iscnt ropic s11rfaces hcle I)(en used) This discrepancy Illay hc explained by asshysuming processes other than adiabatic Ialmen mcntioned radiative cooling as such a process But he helivcd it more probable that a new troposhypause forms at another height and the older one dissolves Furthermore he showed a new low tropopause torms ill the later stage of cyclogenesis over deep cyclones Jn a similar fashion the for~ Illatjon of a high tropopause has been ohserved over areas of quasi-stationary Clnticydogenesis

) hservat iOlls have s(lOn IIl1mCr011S cxcct ions to the silllple static picture of the tropopa11se as well as to the simple pattern proposed hy I Bjerknes 111(1 Iropupalfsc is 101 a sillgle solid slIrace as formerly sllggested It is frequently illshy I) defined with wIIlI middotiplc tropopauses often in evishydence in sort of all overlapping lcaf-like structure In a new meridional cross-section through the atshymosphere at 80deg V Hess [26] showed that the tropopausc falls into a separate arctic and tropic tropopause Even in the mean the discontinuity appears very distinct

As early as 1909 alld 1912 Schmaus III I classified Ihe Irororallsc into 4 types Palillen r101 chose 3 similar types in 1933 neglecting Type IJI of Schmallss which-in the opinion of the authors-is mostly caused by instrumental crrors due either to lag or to absorbed solar radiashytion These classifications are essential to this consideration too and the esplanation of thcse types follows Palmens idea of the influence of vertical motion upon the formation of the troposhypause as mentioned above For comparison the various types arc grouped together ill TA IlLE 2 In the classification of the authors the Normal

- - -

-----

- - - - - - -

------

VOL 31 No3 MARCH 1950

Type N prevails during a 1110re or less stationary weather situation the Liiting Type H charactershyizes warm air advection as IIell as wtrlll-type anti shycyclogenesis and the Suhsicr-Ilce Tvpe S charshyact e rize~ tropuspheric cold air advection as well as the core oi statiunary (cold) lows In thes( latter two types l11ultiple tropopauses uccur freqllently Thus Schlllalls Type I as well as l-almen Type I corresponds to the Normal Type N Type II of hoth authors (with a strong inversion) to ollr Lifting Type H ancl Type IV (Schmauss) or Type III (Palmen) (with a thick transition layer) to Ollr subsiclence types

LBLE 2 TROPOPAUSE TYPES

Chatacteristk WealherFlohn-Penndorf Schmallss Palmen tem peratureshy situationsheiglit curve

I stationary type Normal N I

weather l~ situation

varIn airLifting H II II I advectic)Iltype ( VarOl airshyanticycloshygenis

III I - - -

- I

trop()~p heric

type Subsidence S IV III l cold air

advectio n -

core of stashytionary low

bull In the opinion of the authors and Palmen this type does not exist

(2) F oliat ed structure alld proposal of a tro 10shypause layer-The presence of several invers ion~

or isothermal strata needs careful consideration I t demonstrates that the tropupause consists of several dynamically unlike (unequal) surfaces alternately appearing 1110re or less pronounced TIlliS the boundary between the tropopause and stratosphere becomes indistinct in middle latishytudes In such cases it is a matter of individual choice where the boundary between these two layers is placed

This foliated structure is frequently observed at the boundary between subtropics and temperate latitudes at about 30-4soN The upper apparent equatorial tropopause extends to 18- 20 kl11 or even higher as examples frol11 AJI1erican stashytions Italy and North Africa prove [12 261 During a voyage across the Atlantic irOI11 SOON to 30deg S radiosonde observations were carried out

75

The cross-sections prepared by V uorela [13 ] show this double polar and tropical tropopause on the poleward sides of the tropical anticyclones on IJoth hemispheres Contrary to conditions in tropical and temperate latitudes in high latishytucles and eSJ-lecially under extremely cold conshyditions at the surface the tropopause disappears entirely during the final months of the Antarctic winter (Little America III 194041) There is more or less a steady decrease in lapse rate [141 Under these conditions the tropopause should be classified as belonging to the Type S indicating sUJsidence helow 8 k111

These facts show that it is not always easy to define a tropopause even if single ascents an considered hy pllrc hycirostatics ie pressureshytel11perature relationship without regard to tillle I f there is but one sharp delineation between the tropospheric and stratospheric lapse rate the troposhypause is clearly defined y becomes either gt 0 (inversion) or = 0 (isothermal stratum) H OVshy

ever several inversions or isothe rmal strata ocshycur quite frequently instead of one Someti11les neither an inversion nor an isothermal stratum occurs hut an irregular lapse rate_ For these duhious cases no clear criterion for identifying til( tropopause has been worked Ollt This is a source of confusion wlIen fignres for the height of the tropopause for ditTerent stations are compared There exists a regulation in England which howshyever does not satisfy all requirelllents Criteria for tlte tropopause l1lay be hased according to omt 1141 on

I Level of minimum temperature (this is useshyless in the case of an isothermal stratum)

2 L evel at which the lapse rate tirst begins to decrease

3 Level at which the lapse rate first becomes less than SOl1le arJitrary value such as y ~

+ 02

The last criterion seems to be the hest and lJ) acoJting it a distinct value will he oJtained evell for the Antarctic data mentioned above

Fro111 careful consideration uf these facts it was concluded that it would be preferable not to try any new definition of the tropopause but rather to define a separate layer in which the tropopause oscillates up and clown and in which 11lultiple tropopauses occur vVe proposed itt ]CJ42 the name tropopause layer Byers in 1944 1151 dividing tlte atmus(Jhere into layers sepashyrates a specific tropopause layer too as a zone of lllult iple t ropopauses Since this proposal bears

76

some significance for meteorology we shall discuss it in detail

The troposphere ellds al lie IOiler lil1lil of lie isuthermal stmltl1ll and not at the inversioll Thus the upper boulldary of the tropopause layer is well defined This boundary is naturally situated above t he lower limit of the inversion

The lower bOllldary is harder to define Disshyregarding the subsidence type where it agrees fairly oell with a distinct change of the lapse rate only cOllventional assumptions (eg 6 or 8 k111 or perhaps the 300-l1Ib level) would be satisshyfying However it seems more suitable to choose a gradual instead of a distinct boundary since the thickness may vary with latitude and season

The values for the upper and lower houndaries of the tropopause layer for middle Europe are 8-13 k111 in rare cases 5-15 km for USA 10-18 1lt111 These may be regarded as first approximashytions for the tropopause layer ]n extreme cases the lower boundary descends to 4 kl1l over a cold dome eg Baltic (Riga) 24 Jannary 1942 or vVestern Germany (Iserlohn) 19 February 1948 and over an anticyclonic warm-air advecshytion it may ascend to 14 km or even higher 1 t may be mentioned ill passing that the meall values are higher over subtropical and tropical regions and lower over polar regions

Flolm 1161 drew maps for the mean heighl of the Iropopause layer over the northern hemishysphere in summer and winter The mean values for each parallel deduced frOI11 these maps show a mean height of 165-17 km uver the equator and -9 kill over the pole J ts mean telll) )erat ure

ranges frOlll - 4()o tu - ROue ill SUl11111er and from - 57deg to - 83 degC ill winter

Exalllpies of soundings will he Olllitted hecause they Illay be found in standard llleteorological text books For various parts of the earth not too much is knon so far concerning the troposhypause layer its structure deepness extreme valshyues or deviations from Illeall value as well as its role in atillospheric circulatioll and influence in tropospheric weather

The water content decreases very rapidly in this layer too as shown I)y reliable measurements over Europe [27 28J and USA l29J The relative humidity stays below 10 in the upper part of this layer

vVhen we speak of a tropopause layer and hear in mind the frequent occurrence oi lllultiple troposhypauses the classification of the tropupause as a Hadamard discontinuity loses its significance as do the theoretical conclusions drawn from this classification


N ow we shall discuss those [acts which show this definition of the tropopause layer is advanshytageous and vvhich establish the influence of nleteurological processes occurrillg in this layer un the lower troposphere

(3) A dvGntagcs of the new pro posat-Some of the temperature changes in the tropopause layer may be attrihuted to the long wave radiation of atshymospheric dust Considering dust as a grey body Moller [171 calculated large temperature changes at the upper boundary of a tropospheric dust layer Assuming a dust layer imbedded into the troposhypause layer 125 kill deep with a grey absorptivity of 2000 the atmosphere is heated hy 2Co I day beluw and cooled by ~Co Ida) above the upper boulldary of the dust layer The sharp decrease of both water vapor anel dust in this layer will intensify the inversion The lower temperature in this layer over the tropics has been attributed to the strong elllission of CO 2 (Moller l18 J )

The wind is mostly frolll the west with velocity increasing and reaching a very pronounced maxishymum in the tropopause layer all over the globe According to very valuable investigations by the Chicago Group a jet stream is imbedded in this layer too It consists of a nanow helt of very strong wind and a concentration of the isotherms within it The high tropical tropopause invershysiun ends directly above it the high tropical troshypopause and the lower )Jolar tropopause having no direct connection [26 30 31 J The jet stream is found llleandering through the vVesterlies all arollnd the glohe 132 J however it is more proshynOllnced on the east sides of the continents than un the west sides where difluence prevails Moreshyover its geographical position undergoes seasonal anel clay-to-day variations there are often two jets present Ol1e north of the other The forshymation and maintenance of the jet stream is explained by Rossby [331 on the basis of largeshyscale horizontal mixing which results in a lIet flux of vorticity frum high to low latitudes This Illixing is interrupted at a critical zone in middle latitudes thus producing a sharp peak around 35degN Namias l321 on the other hand thinks that it is caused by confluence of warm and cold air masses in the upper troposphere

A mountain barrier causes internal waves with large amplitudes even in this layer as theoretishycally investigated by Kuttner [341 Colson [35 J and Queney [36 J These waves are manifested by certltlin cloud forllls and already have been used for gliding

The Austausch A obviously is smaller here than below Having determined the values for A bemiddot


tween 14 and 28 kill Lettau p 91 aSSU1l1eu a linear decrease of A betveen 8-J 4 kill This decrease is very important The wrtical distriiJution of IJwne ill the tropusphere call he theord ically cal ndated anu is fuulld to agree Imiddotitll till I)servatiuns basic Huw uf ozolle COllles froill the stratosphere clown to the earths ~llrface where it is destroyed as proved by theuretical investigatiolls The distribution within the troposphere is largely due to Austallsch The strong increase of ozone conshycentration above the tropopause layer is caused iJy the sharp decrease in A according to Lettaus calculation r191 The height of increase of ozone concelltration is deterlllined hy the height at which the IIppC r boundary of the tropopause layer occurs The variations of this height with latitude deshypend on the variation of the tropopause layer with latitude The direct measurements of vertishycal ozone distribution carried out by V -2 ascents confirm this fact l37 381 Dtitsch [20J calcushylated A for different latitudes and his c1ata agree very well with those published by Lettau E Regener [211 stressed the relationship of ozone and turbulence by variolls examples

The lapse rate in this layer largely depends on vert ical mot ions r unge 122] in vestigated the acshyceleratioll of souuding halloons Tt Jecreasecl lip tu 8 km however all increase was recorded from that height all the way up till the hursting altitude at 1S km The asccnsion rate of pilot Ialloolls measured carefully in Gerlllany (I illdenberg) as well as the experience conceming Ill1inpillCss ltlurshying stratosphere flight supports runges result This wOllld mean that the turhulence increases in the tropopause layer However his result is suhshyject to criticism because he assllllled a close corshyrelation between the acceleration of the balloons and the turbulence in the atmosphere Fluctuashytions of temperature as observed during the flight of flxplorer I 1231 may cause static variations of buoyancy and they in turn could resllit in an increase of accelerat ion of the balloons

Tropopause waves traveling in this layer may tend to steer the course of weather phenomena in the lower troposphere (but not the large-scale pattern for long-range forecasting) The strong vertical motions mentioned above in connection with Junges investigation are regarded as one of t he most important causes for the tropopause aves a~ el as for the temperature variations

SCvtral studies of intenliurnal pressure and klllperature variations in Europe and USA 241 showed that a maximum of interdiull1al pressure change occurs near 8 km without regard to the signs of surface pressllre and temperat lire changes

Pressure and Jensity changes are largest ahove 8 kill when the changes of sign are alike A zone of Jensity changes close to zero is found near 8 kill Thl temperature changes without regarJ to sigll show maxima at 6 and near 10 kill (lIlaxshyillia occurring at tile surface are disregarded)

These results indicate these maxima occur in the tropopause layer Up to now they have heen asshysigned partly to the lower stratosphere and partly tu the upper troposphere This apparent conshytroversy vanishes with the new definition of a tropopause layer Cumpensation 7 mainly resides in this layer yithin the tropopause ami isoshythermal layers the atmosphere tries to compensate the pressure contrasts of the lower troposphere the Illax imull1 contrast being reached at the troposhypause The tenll cOlllpensation means that a warm troposphere is coupled with a cold stratoshy~phere and vice versa Its importance to weather has been strongly emphasized by various papers of the Frankfurt School The average compenshysation and especially the deviations from it are fully described by Scherhag [39j who demonshystrates in many examples-using thickness charts - that the tropospheric temperatl1le distribution is normally already compensated between 225 and 9(1 m1gt

Studying processes in old cyclol1es and antishycyclones under the aspect of the compensation be shyt ween the lower troposphere and the tropopause layltr it is concluded that there exists a high layer where air is either flowing into the isobaric sysshytem or out (Thomas [25]) with strong vertical ll1otions ahove and below this level A similar conclusion is also dra VII by Palmen and ~ agler 131 Figure 16] That means in the upper-air circulation there may he in addition to the horishyzontal lTleridional advection effects either a conshyfluence or difluence depending on the position with respect to an upper trough or ridge llllshytherlllore some authorities believe the processes causing this in-and-out pumping component of thl upper-air circulation may originate in this layer 131 J

For these various reasons it is advantageous for synoptic meteorology to separate this layer frolll the advection layer as well as from the isoshythermal layer We classify it as part of the troposphere IJeCallSe its behaviour in regard to tropospheric yeat her is presllllla hi y more closel y OIlIH kd yith this sphtrt than ith the stratomiddotshysplwre

(o I C O(lIdy)

1itlljCII alld Zi stl er lise the terlll Gegelll~1ufigkeit

78

RFEINCES

[11 R Penndorf Die Temperatur der hohen Atmosshyphiire M ct Zeit 58 1-10 1941 Translation BIII A MS 27 331-342 1946

[2] R Geiger Das Klima der bodennahen Luftschichten 2 Edit Braunschweig 1942 (Trans to appear in 1950 Harvard U Press)

131 R Geiger and W Schmidt Einheitliche Bezeiclshynungen in kleinklimatischer und mikroklimatischer Forschung Bioklim Beibl 153-156 1934

[4] K Schneider-Carius Ocr Schichtenbau der Troposphare Met Rlllldsch I 79-83 1947

[5] H Lettau Atm sphiirische TllrblllclI3 Leipzig 1939

[6] K Schneider-Carius Der Inversionstyp der Grundshyschicht IVct Rlllldscz I 226-228 1947

[7] K Schneider-Carius Der Aufbau der Grundshysclicht illl mittelcuropiiischen Klimagebiet 111 ct Rilldsch 1 228-231 1947

[8] V Schwerdtfeger Stratocumulus-Inversionen Mel Rltndscll 1 150-152 1947

[9] H Flohn lum Klima der freien Atl110sphare iiber Sibirien II lWei [(lIIldsch 1 75- 79 1947

1101 E Palmen Aero10gi5che Untersuchungen der atmospharischen Storungen bei besonderer Beriickshysichtigung der stratosphiirischen Vorgiinge Soc Scienl Fellll Comment Phys-Math VII 1933

1111 A Schmauss Die obere Inversion M [I Z 26 241 1909 also Miinchener Aerologische Studien I Deulsch lvlet lalwb Bayerll 1912

112] H G Koch Ober Radiosondemessungen in der Cyrenaika im Sommer 1942 ZI f Met 1 385shy391 1937

1131 1 A Vuorela Contribution to the aerology of the tropical Atlantic 1 of Met 5 115-117 1948

1141 A Court Tropopause disappearance during the Antarctic winter BIIII A M S 23 220-238 1947

115] H R Byers Gellcral M elcorology New York 1944 p 45

1161 H Flohn Die mittlere Hbhenlage der Tropopause iiber der Nordhalbkugel M ct RWldsch I 26shy29 1947

117] F lloller Die Wiirmestrahlung des Wasserdal11pfes in der Atl11osphiire Gerl Beilr Geophys 58 51 1941

[181 F Moller Zur Erklarung der Stratospharentempermiddot atur NO1m 31 148 1943

1191 H Lettau lur Theorie der partiellen Gasentmisshychung in der Atmosphare Mel Rlflldsch 1 5-10 and 65-74 1947

120 I H U Dtitsch Photochemische Theorie des atm05shyphiirischen Ozons unter Berticksichtigung von N ichtgleichgewichtszustiinden und Luftbewegungen Thesis Ztirich 1947


1211 E Hegener Ozonschicht lind atmosphiirische Turshybulenz Met Z cit 60 253 1943

122] eh Junge Turbulenzl11essungen in den h0heren Atmospharenschichten A 1111 Hydr 66 104 1938

123] Nat Geogr Soc Tire Nal Geogr Soc U S 11111 Air Corps slralusphere flighl of 1935 ill tire hallooll Explorer I I Vashington 1936

12ol1 Th F Malone A stlldy of interdiurnal pressure and temperature variations in the free atmosphere over North America Pap PIrs OCIOIl a Met MIT alld Woods Hole Oc hlsl Vol IX Nr 4 1946

[25] H Thomas Zum Gegen1aufigkeitsgesetz insbesonshydere wr GegenJiiufigkeit zwischen der absoluten und relativen Topographie der 500-mb Fliiche Met Z 57 2151940 and 58 185 1941

126] S L Hess Some new mean meridional cross secshytions through the atmosphere 1 of Met 5 293shy300 1948

127] E Regener Akademie d Lrtflfalrrtfo-rschg p 22 1939

[28] G M B Dobson and A 1 Brewer Meteorology and high altitude aviation 1 Roy Aeroll Soc 50 787-810 1946

[29] E A Barrett and coIl A preliminary note on the measurements of water vapor content in the middle stratosphere r of Mel 6 367-368 1949

[30] E Palmen and K M Nagler An analysis of the wind and temperature distribution in the free at shymosphere over North America in a case of apshyproximately westerly flow 1 of Met 5 58-64 1948

131 I E Palmen and K M Nagler The formation and structure of a large scale disturbance in the westershylies 1 of Mel 6 227-242 1949

132] J Namias and Ph F Clapp Confillence theory of the high tropospheric jet stream 1 of Met 6 330-336 1949

[33] Univ of Chicago Dept of Iet On the general circulation of the atmosphere in middle latitudes BIIII AMS 28 255-280 1947

1341 J Klittner Zur Entstehung der Fohnwelle Beilr Phs b AltII 26 251-2991940

135] D Colson Air flow over a mountain barrier TrailS Am Geoplrys UII 30 818--830 1949

136J P Queney Theory of perturbations in stratified currents with applications to air flow over mounshytain barriers Dep Met UlIiv Chicago Misc Rep 231947 (also BIIII Amer Met Soc 29 16shy26 1948)

[371 E Durand and coIl in Upper almospheric middotresearch reporl No4 Naval Res Lab No 3171 1947

[38] J A van Allen Preliminary note 1949 Applied Physics Lab Johns Hopkins Univ

[391 R Scherhag WellerUwlyse Wid lVetterprogliose Springer Berlin 1948

126 BULLETIN AlI1ERfCAN METEOROLOGICAL SOCIETY

The Stratification of the Atmosphere I (II)

H FLOHN ~ and R PENNDORF

4 THE STRATOSPHERE

The stmtosphere is defined as the sphere sitshyHated between the troposphere and the ionoshysphere The stratosphere is subdivided into 3 layers whose thermal structure is essentially difshyferent The lowest is the isothermal lajler (cold) above that the 1tJar11l IOjler will be found with pershyhaps a more or less strong inversion and finally the upper IImiddotirillg layer exists where the temperashyture decreases again

The lower two layers are sometimes named in connection with ozone However we do not reshyCOlllmend that Ozone determines only the thermal conditions in the warm layer where its concentrashytion is very small Its maximum concentration occurs in the isothermal layer but there its influshyence on meteorological processes is only slight The reasons for this are presented in [11

(a) The lsollzerlllal Layer

In poLar and middle latitudes isothermal condishytions are recorded in winter and a very slight increase in summer from the bottom of the stratoshysphere up to the maximum altitudes of sounding balloons and radiosondes (30- 35 Iltm ) This middotisoshythermal behavior characteries the lower stratoshysphere Records of the stratosphere balloon Exshyplorer II indicate fluctuations of temperature larger than 5degC between 18 and 22 km ([23J p 225) This temperature is not homogeneous Turbulence will be found because of these flucshytuations but to a lesser degree than in the troposhypause layer

)~eparatiol of gases has been found by E Regeshyner [40) and F A Panet 1411 above 14 km but this diffusion however is small The air samples laken during V-2 ascents are very doubtful beshycause air trapped within the vehicle-from lower levels or even the ground-may have entered the bottles It demonstrates that vertical motiolls within the isothermal layer are partly suppressed Stable thermal stratification weakens vertical moshytions From these measurements Lettau [19] calshyculated the Austausch coefficient A decreases hyshyperbolically Assuming A to be 2 g clll sec at a height of 14 km he calculated for IS km A = 0013 for 20 kill A = 0002 and for 28 km A = 00008

The values calculated by Dlitsch [20] agree very well with those Compared with the coefficient of viscosity p (000017 g cm sec for dry air at 0 deg C) A is still a multiple of p around 30 k111 Largeshyscale vertical Illotion and turbulence carry ozone from its source in the warm layer down into the isothermal layer and troposphere as pointed out by E Regentr [21 I and W ulf [57]

There occurs a marked change in viud direction and speed in this layer too [39 42] During summer the general westerly drift shiits into an easterly one at least over certain latitudes For the IS-km level this has been confirmed earlier from the temperature differences between tempershyate and polar regions [43]

Johnson and Murgatroyd [44] measured the wind direction and speed with smoke puffs proshyduceJ by bursting of smoke shells Over southern [ngland the wind is mainly easterly (NE to SE) with a mean velocity 44 k11l h (27 mijh) in sumshymer and a strong westerly component (SvV to NW) with a mean velocity of 134 km h (83 Ill ijh) in winter The change-over occurs about April and October

Bawin data in the USA also indicate easterly wiuds to prevail above 18 km between April and

ctober 145 2646 59 J Similar results have been fOllnd over Japan (Tateno Obsy) r47] and probshyably the northern Atlantic and Pacific areas r58]

The seasonal mean contour maps of the 41-mu level (- 22 km) show a prevailing easterly comshyponent over middle Europe in summer l39 J Over the southern hemisphere a similar wind ~hift--between an easterly wind in sLImmer and a westerly wind in winter- has been calculated reshycently by 1lohn [481 During the southern sumshymer the lower boundary of the upper-trade winds ascends to above 25 kill

in this layer there occur some of those changes which have a striking influence on weather (wetshyterwirksame U mstellutlg) by altering completely the large-scale circulation pattern (Grosswettershylage) vVhereas tropopause waves-or more generally speaking changes in the tropopause layer- rarely cause complete allerations of the cirshyculation pattern proof has been given that such large-scale changes are closely coupled with stratoshyspheric changes It has been confirmed lately that

Continued from March BULLETIN pp 71-78 part of the large-scale changes originate at the top

VOL 31 No4 APRIL 1950

of this layer or even higher (see nex t paragraph) Frequently such alterations involve poleward adshyvances of the upper-equatorial pressllre system ( Aeq uatorial Fron t as defined by Schmallss) Such an advance causes the isothermal layer over a stationary 11lid-Iatitude cyclone to become colder than normal Its temperature will be little influshyenced by air-mass changes in the troposphere durshying a persistent circulation pattern while the temshyperature of the tropopause layer umlergoes quick and extensive changes

(b) The Warm Layer

Until recently the measurements of tel1perashyture made above 30 km have not been reliable due to the effect of radiation on the instruments Various theoretical considerations however have been used to calculate a temperature of about ODe to + lODe at 40 km and of auout + 50degC at 50 km between 45-55 degN over Europe This is urought about by the strong absorption of solar radiation by a small concentration of ozone In view of this notably high temperature we propose the name warm layer Lately this temperature increase has been confirmed l)y means of V-2 rockets The temperature at 30 klJ1 is auout - 34degC at 40 kill - 14degC and at 50 km + 13 degC the maxi11lum is reached at 55 km with + 35 D e 1491 It is surmised that there exists an annual variation as well as a change with latitude The name oJonopause is proposed for the upper bounshydary of the warm layer (see paragraph 4c)

The strong thermal stability of the warm layer allows only a very small separation of gases by diffusion Extrapolating the formula proposed by Lettau [19) leads to A = p at 51 km Using an increasing separation with height Penndorf 8 calshyculated a value of 18 oxygen at 50 km This value presumably represents the lowest limit of oxygen content in the upper stratosphere since 11lixing prevails in the turbulent lIlixing layer ahove The concentration of a heavy gas can never increase with height it can only decrease or remain constant

The wind direction will remain easterly in sumshymer and westerly in winter In the winter time the warm layer is expected to be cooler over polar regions than over temperate latitudes because the heating due to solar absorption by ozone is missshying This leads to a normal horizontal temperashyture gradient over polar regions

Harmonic analysis of the pressure or the height of standard isobaric snrfaces showed the ampli-

S Taken from an unpublished report

127

tudes of long periods (29 days and over) to ue largest at the highest levels (41 mb) From such investigations 139 501 it seems possible to regarJ the warm layer (or perhaps the upper part of the isuthermal layer) as a seat of large-scale long steering waves To give an example a wave with a 29-Jay period has been investigated for the interval 1941-1944 in Germany and it was found that the maxima coincide with days where symmetrical points U or singularities 10 occur Thus it is concluded that these waves may be coupled with quasi-rhythmic alterations of the large-scale circulation pattern Moreover these a yes may play an important role in the formashytion oi the symmetry points (Veickmann) and of singularities (Schl11auss) observed in the troposphere

(c) The Upper Mixing Layer

vVhereas distinguishing phenomena characterize the layers treated auove no such characteristic phenomena are known to exist for the layer beshytween 50 and 80 km Therefore an appropriate name for the layer is difficult to choose No solar radiation is absorbed in the ultra-violet or visible part of the spectrum but rather the temperature is governed uy emission and absorption of infrashyred radiation The temperature of radiation equishylibriulll must be low and it will Jecrease with height in a similar iashion to its behavior in the troposphere A lapse rate of y = 04 (C O I00 111) has been previously assumed From the V-2 rockets the tell1perature has been calculated to be + lODe at 60 km and - 80degC at 80 km with a minimulII at 85 kill and a lapse rate of y = 045 (CO 100111) over New Mexico [49) Not much is known about its variation with latitude as yet However temperature decrease in this layer must exist all over the globe

Such a lapse in temperature will favor vertical Illotion Thus the turbulence in this layer is stronger than below The separation of air moleshycules will cease and the air is completely mixed the composition being the same as at the top of the warm layer Vmiddote therefore propose the name upper 11ILr-illg layer for the heights 50-80 km It is essential to give the boundaries of the upper mixing layer specific names on behalf of its im-

D Symmetry points discovered by L Veickmann are hose days to which the pressure course before and after is symmetrical They frequently occur near the solstices and are caused by persistent long pressure waves

I U Singularities are wcather types identifiable by cershytain prominent characteristics more or less bound to a certain day of the year

128

portance for the atmospheric structure For the lower bomldar) the term ozouopause is proposed and defined by the height where y becomes posishytive (temperature maximltlll around 50 km) Por the upper boundary the name upper tropopause is suggested and defined by the inversion at 80 kill where y becomes negative again This name seems to be appropriate since the upper mixing layer resembles the troposphere in various aspects Moreover it may be formed similarly to the tropopause

Meteor trails indicate that this layer is in a turbulent state This fact bears out our theoretishycal conclusions

The wind direction is mostly easterly as mea~shyured from meteor trails and noctilucent clouds

S THE IONOSPHERE

The ionosphere is defined as that part of the atmosphere in wh-ich the number of molecules and atoms to be found in an ionized state is sufficient to affect propagation of radio waves and where the cOllcentration oJ iOllized particles (positive and negative ions electrons) is essentially larger thall within the tro posphemiddotre and stratosphere Ionizashytion not only determines the electrical behavior bnt likewise the meteorological conditions of this sphere The electrical conditions have been largely explored It consists of several layers distributed regularly over the globe The concentration of ionized particles within each layer naturally varies with latitude season and hour of the day NIany of these distributions overlap one another but some are well separated There is some diffusion of ions from the heights at which they are proshyduced and the recombination is faster at a lower level than above Ve accept Appleton s classishyfication because it is very useful from the meteoroshylogical viewpoint too

The lower layer is called the E-Iayer (or Kennelly-Heaviside layer) the second the F -layer (or A ppleton layer) F or the third we proposed the notation atomic layer since the molecules are dissociated to a very large extent Purther subshydivisions like Fl and F~ have already been proshyposed from results of ionospheric investigations but as yet they have not been shown to have any sign ifican t meteorological importance II

It should be mentioned here that the Vave Propagation Commission of the American Tnstishytute of Radio Engineers defines

II The D-layer is not of any meteorological importance so far at any rate it is thermally ineffective Situated around 70 km it is not considered as part of the ionoshysphere The D-layer is primarily of importance because it absorbs energy from radio waves


Region-A region of the ionosphere is a portion of the atmosphere in which there is a tendency ior the formation of definite layers

Jayer-A layer of the ionosphere is a regularly strati~led distribution oi ionization which i~

formed in a region uf the ionosphere

Firstly the definition of the terms region and layer is restricted only for the special case of the ionosphere secondly it has not yet found many followers Thirdly it is very vague for it is very difficult to define boundaries of a region according to this proposal The entire ionosphere is more or less equivalent to the IRE definition of a region Therefore we are of the opinion that Ollr definitions of a layer and a region are still prefershyable because they are valid for the entire atmosshyphere and they agree with the general use in ionospheric research The terms E-layer and F-layer are generally accepted For subdivisions the term region is very suitable eg to speak of the region of nwximrtmiddotm ionization

The lower boundary of the ionosphere is situshyated at 80 k111 Generally just the stratum around the maximum of ionization is called the E-Iayer but this definition is rather limited For meteoroshylogical purposes the lower boundary of the E-Iayer lllust coincide with the height where ionization due to solar radiation begins to increase even if the actual number oi ions and electrons lIlay be small In the lower region of the E-Iayer the increase is very weak but becomes larger between 100 and 110 kl1l It has ueen shown in an earlier investigation 11 J that an essential change in the atmospheric structure takes place at 80 km noctishylucent clouds dust clouds from the eruption of Krakatoa vokano and the fall of the great Sishyberian lieteor meteor trails lower boundary of aurora a shift from easterly to westerly wind All these phenomena are localized near the 8O-km level for which the term upper tropopause has been proposed A temperatllre of - 70degC has been assullletl for 80 km and +60 to + 100deg C for 110 km The figures derived from V -2 measshyurements over New Mexico are - 80degC and - 3rc respectively [49] The temperature inshycrease is due to absorption of solar radiation by oxygen molecules and it is more or less steady within the layer as far as the calculations from the V-2 show Nevertheless the possibility of a strong inversion does exist

The compositioll of this layer is fairly well known The nitrogell (main constituent of the air) is completely molecular in the Ii-layer but atol1lic nitrogen must be present in an increasing

129 VOL 31 No 4 APRIL 1950

amount above say 150 1lt111 Oxygen is dissoshyciated into atoms between 90 and 110 km Soshydium atoms radiate between 90 and 105 kIll ami several more or less complicated processes IJetween neutral and iunized particles take place Tilt electron density is about 10 cc in the E-layer at 120 kIll during the night increasing to ahout 15 X

10cc during the day For the F-Iayer the night value for 250 km is about 25 X 1O cc and 106cc at 300 km during the day

A predominant westerly flow has been indicated by meteor trains occurring in this layer [42] Likewise Hoffmeister [5l1 evaluated his obsershyvations on Leuchtstreifen (glowing stripes) to finel Ollt the flow pattern over Germany and Southshywest Africa at 120 kIll At SooN a steady SSWshySV flow at 110 mi h (180 k1l1 h) is observed in summer however two different flow patterns occur in winter One is identical with the sumshymer type The other one is an advection of polar air from NV to NE Direction and speed vary 1110re than in SUlllmer and the air seems 1110re turbulent the mean velocities are higher 140 mi h (230 kmh) for the SV flow and 200 mijh (320 km h) for the N flow If Illore reliable observations from other latitudes were available a scheme for the general circulation at this height llIight be found For earth-magnetic quiet clays Bartels r52 1 believe5 there exists a rather conshystant wind field with a pronounced diurnal period (solar and lunar diurnal period) superimposed From the temperature gradient between 50 and 70deg N Penndorf r431 calculated a mean westerly wind of 225 l11i h (360 km h)

Very recently S N Mitra 1601 measured winds by a radio method at about 70-115 km over Engshyland Idid-day observations showed a predomishynant SE wind of about 112 mijhr (180 k1l1hr) thoLlgh all directions and a range of speeds occur (90-225 llIi hr ) II e finds a semi-diurnal period also

M ihran r53] summarizes the investigations on the existence of a correlation between surface eather conditions (mostly pressure) and E-Iayer or F 2-layer ionization or height of these layers However since the clata given by the various authors are limited the correlations found may be accidental Up to now no convincing evicience has been brought forward

The lower boundary of the F -layer presllmably is situated at 150 km The temperature at the IIIaximum electron concentration is assumed to be between + 600degC and + 2200degC Variolls values differing widely have IJeen calculated and the actual value is still doubtful 154 j Nothing is

known about the change of temperature with height between the maxima of ionization at the E- and F -layers All temperatures calculated so iar are questionable because the temperature difshyfers irom that defined by kinetic theory of gases with each constituent having its own temperature II I [II the future the track of ionic clouds lIIay give JIIore information on the air flow in this layer Subsidence of an ionic cloud from 250 to 140 km has been descri becl [55]

Jn the uppermost part of the ionosphere the particles are mostly in an atomic state Oxygen already undergoes a practically complete dissociashytion within the E-Iayer Auroral spectra prove that nitrogen atoms exist in the ionosphere too and it is aSSllmed that above the F-Iayer N is disshysociated ina large degree bu t not completely Therefore the highest layer is called the atomic layer Exploring this layer is still a project for the future since our knowledge is rather scanty

Naturally the lower and upper boundaries of these layers may undergo extreme daily and anshynual variations However from material known to us it is not possible to draw unique meteoroshylogical conclusions Vertical motions may be call sed by changes of temperature or degree of ionization and also by changes in the composition Tt seems necessary to warn against bold assumpshytions of very strong vertical motions (100 km h or more) Such observations may also be exshyplained by changes in the amoLlnt of ionized parshyticles at the particular heights without any vertical movement of particles The figures presented in T A PL I may be regarded as mean values for temperate latitudes

6 THE EXOSPHERE

The earths atmosphere gradually thins out into space Nevertheless a boundary may he defined as the lower height where the velocity of a gas particle equals the critical velocity Particles with velocities higher than the critical may escape the earth descrihing hyperbolic orbits The name exosphere-as the outerll1ost sphere-is proshyposed The critical velocity largely depends on the temperature of the gas which is rather uncershytain for the heights in question In addition to that the atmosphere will certainly have no unishyform temperature but each kind of gas in the lIIixture will possess its individual temperature Presumahly the att1losphere is lI1ixed but the composition changes with height hflIce the height

Since this manuscript has been written Spitzer [541 published an excellent article on the exosphere He also proposed the same name

130

where the critical velocity is reached differs for each component It is also natural to assume that the atmosphere rotates with the earth so long as there is appreciable collision between atoms

Tithin the inner atmosphere molecules and atoms are bound to the earth by the gravitational tield There (xists a continuous flow of lighter gas particles from the inlier into the outer atmosshyphere where they move arouml practically withshyout collisions descrihing orbits of large diameters Frolll the outer atmosphere particles can steadily escape the earth atmosphere into the interplaneshytary space if they surpass the critical velocity Collisions between He or H with metastable atoms (oxygen nitrogen) middotvould impart to the former non-thermal velocities higher than that of escape If the particles are ionized they do not describe any arbitrary orbit-on the contrary the orbit is prescribed by the earths magnetic field and they may not escape the earths atmosphere even if their velocities are sufficient to overcome the gravishytational field of the earth The escape of ionized particles into interplanetary space will be much smaller than for neutral particles Thus the exoshysphere gradually changes into interplanetary space and no fixed limit can be given

The value 800 km enteren in TABLE 1 has been adopted just to show the order of magn itucle withshyout placing much confidence ill this value It is presumably the level of escape of oxygen atoms Grimminger [561 puts the lower limit of the exoshysphere in latitude 45 0 to 650 km He also calcushylates the pressure density etc up to 70000 kill This is the first successful attempt to get reasonshyable values for the exosphere The columns in TABLE 1 are empty because hardly anything is known about this part of the atmosphere

That is the atmospheric structure as seen by the authors the reader however has doubtless observed many gaps and shortcomings in this picture of the stratification of O1r atmosphere and further discussion is invited

ACKNOWLEDGMENT

The authors are deeply indebted to Mr Jerome Pressman for his valuable comments and suggesshytions as well as for editorial assistance


REFERENCES

(ConcUded)

[40] E Regener Messungen des Sauerstoffgehaltes der Stratopharenluft LlIftfahrtforsch 13 361 1936

[411 1 A Paneth and E Gluckauf Helium content of the stratosphere NatHrc 136 717 1935

[42J E Ekhart Zur Kenntnis der Vindverhaltnissc in der oberen Stratosphare Reichsamt f Vettcrshydienst Bcrlin 1940

r4middot1 It Pcnndorf Die vVintertcmperaturen der Nordshylichter libel Tromso 1I-fet Z 58 429-433 1941

[44] N K Johnson Vind mcasurcmcnts at 30 kill llahltc 157 24 1946

[45] B Gutenberg New data on the lower stratosphcrc BIlII Amer Mct Soc 30 62-641949

[46] E Ekhart Neue Beitrage zum Aeroklima Nordshyamerikas Gcofts pllra e appl 12 Nr 5 6 1948

r47] H Flohn Zur Rolle des Oberpassats in der allshygemeinen Zirkulation Mct Rlmdsch I 23-24 1947

[481 H Flohn Grundziige del atm Zirkulation iiber del Siidhalbkugel Arch Geophys Jly[ ecorol fliokl (in pres) F Locwc and U Radok A meridional aerological cros scction in thc Southshywest Pacific 11 of Mct v 7 no I Feb 1950 pp 58-65

[491 A Nazarek Temperature distribution of the upper atmosphere over New Mexico BIIII Amcr M ct Soc 31 44-50 1950

[50] H Flohn Stratospharische Vellenvorgange als U rsache der Vitterungssingularitaten E~perishyClztia 3 319-322 and 464 1947

[51] K Hoffmeister Die Stromungen der Atmosphare in 120 km Hohe Z f lIJet 1 33-41 1948

[521 J Bartels Geomagnetic data on variations of olar radiation Part I-Wave radiation Terr Magn 51 181-242 1946

IS~I T G Mihran A notc on a new ionospheric-meteoroshylogical correlation Proc hZI Rad Hng 16 IOQ1-I095 1948

1541 T Spitzer in G Kuiper The atmospheres of thc eurth aHd planets Pp 213-249 Chicago 1949

[55] Carnegie Inst of Washington Y carbook No 38 60 1939

[56] G Grimminger Analysis of temperature pressure and density of the atmosphere extending to exshytreme altitudes Rand Report R-I05 1948 Rand Corp Santa Monica Calif

[57] O R IT ulf The distribution of atmospheric ozone Proc 8th Amer Sci Congrcss Vol VII pp 439shy446 1942

[58 U S vVeather Bureau NorlILal Monthly Weather jyups Northern H emispherc Upper Levels Wash 1944 (See charts for 19 km level)

[59] C J Brasefield Winds and temperatures in the lower stratosphere In of Met v 7 no I Feb 1950 pp 66-69

[60] S N Mitra A radio method of measuring winds in the ionosphere Yroc InSII Electr Eng Pt III V 96 no 43 Sept 1949 pp 441-446

72

increase of knOdeclge 011 the steering layers necesshysitates a clear and specinc demarcation of its houndaries Unnecessary con troversies have arisen between several authors and schools beshycause the same word has been used for different layers To prevent a similar confusion and misshyunderstanding in thc future we propose a partly ncw nomenclature for definite slrata Tn doing 1his we alsn hopc to contrill1lte toard a l1niform tfrtninology Standardization of nQlllcnclatmc seems nrgently necessary

Teisserenc de Bort divided the atmosphere into to layers the troposphere and the stratosphere based upon the simple thermal structure of the atmosphere known at that time Tater on Sir Napier Shaw introduced the term traroraIS for the houndary hetween these to layers During the past 20 years this classification proved to be too simple 1middot10re and mnre suhdivisions were proposed Til Gcrman puhlications cg the exshypressions high troposphere (Hochtroposphare) l11d suhstratosphere ere used Several aushythors rather complicated the understanding of their ideas hy using the notation high troposhysphere for the lower layer of the stratosphere too whereas others applied the notation substratosphere inr the upper troposphere Furthermore the ionosphere was regarded as part of the stratoshysphere Such varying nomenclature necessarily leads 10 seeming mnl radictions

The expression houndary of 1he 5t ratosphere is al11higuolls Tmiddoto houl1(aries e~it an upper ltlno a loer one Up 10 lhe present only the lower boundarv has been important for forecasting purshyposes But in t his era of rockets the upper houndary will tmdouhtedly be of importance too

2 CLASSIFICATION OF THE ATMOSPHERE

The foregoing was in mind in proposing a new classification of atmospheric layers Based upon the best available knodedge of the thermal strucshyture of the atmosphere the scheme given in TABLE J was constructed Suhdivisions of the atmosphere are based best upon the lapse rate y = -dTdJ (CO100 m) because it characterized the meteoroshylogical properties of a layer in the simplest Nay (eg 111lxmg separation convection etc) Boundaries of a layer are easily fixed by its change of sign or by a sudden change in its abshysolute value

Thus our definitions arc based upon a charactershyistic vertical temperature distribution discussed hy one of the authors (r 1 I Fig 10) T t should he emphasized however lhat this cune is only valid for temperate latitudes Above polar regions

BULLETIN AMERICAN lfETEOROLOGICAL SOCIETY

the temperature of the upper layers may be different

In view of the fact that stratification occurs in the earth and atmosphere ie the horizontal exshytension of a uniform property is greater than the vertical extension it will always be sensihle t(l usc fixed strata as a guide to descrihe processes in the atmosphere However it is very frequently only a quasi-horizontal stratificalion hecause adshyditional accelerations occur ithin 1he atmosphere bending the boundaries of layers

First of all the atmosphere is divided into an inncr and an outer atmosphere Tn the outer atshymosphere the particles may escape from the gravishytational or magnetic field of the earth whereas in the inner atmosphere this does not occur In parashygraph 6 more facts about the outer atmosphere will be given

The inner atmosphere is subdivided iul0 three spheres and each sphere in tllrn into several layers A layer is characterized hy its uniforlll thermal structure if several layers llCiong together according to their meteorological state and heshyhaviour they form a sphere This definition closely follows the C01111110n use The word region is reshyserved for subdivision of a layer Tn choosing the names for the layers and spheres we accepted the names already in use as far as possible TARLE I shows the Ilolatiolls suggested and the lllctcorological characteritics

3 TilE TIWPOSPlIERE

lJinoc1illlatology and spot climatology Jre 1110Stly concerned with the study of the meteoroshylogical conditions adjacent to the earths surface ie within the first two meters above the ground It will be denoted bottom layer (bodennahe Luftshyschicht) r21 r3] Macroclimatology studies the conditions within the gronnd layer that is up to ahout 2000 meters 4 r41 AerolorJ) r studies the climate of the frce atmosphere ie within th advection layer and the tropopause la)er

(a) The Botom Layer

The conditions within the botlon~ layer are governed by physical constants of soil (absorpshytion and emission of radiation) species of plants their height and formation VIle shall not deal with this layer specifically (see [2])

bull We neglect mountain stations because they do not represent the climate of the undisturbed atmosphere

Co The term aerology is used as a subdivision of meteorshyologY the ~tudy of the free atmosphere throughout its vettie1i extent rlistinguished from studies confined to the layer~ adjacent to the earths surface (c Meteorologishycal Glossary)


VI U

~ lt2 iii U of

x u

z ~ nx In I

In Q lt


V

= ~~~ f=gt ~~~ ~ 3

middot~~e ~o8


~~~~ lt1

8

aCg gt u

0 c OJ



8 ~ ~88 8

N

ltJ If)

0 1-0 111 001 0

o ltJ If)

8 o



sect~ ~ B B ~ 0 0 000 -4 _


00 23++++ 1 I 1+ 00

+ ~BBBEB BEB pound


01000 1)0+ 1+111 1




~ 0

~

3 ~

f

l5

~~ 0

~ E ~8shy ampu0 l

~ 1I 1-8i)Jta 0 gt- N

Igtl

8 0=gt ~

_05~ ~ -----r-+-~-shy VI OJ ~8 0100 10 0

~ o ~ gt 1 +jl1+ 1lt 3 iii 0 ~ =2


~


V OJ OJ OJ~ -= 0 -= 011 I) UJ0 o 0 ~ c

UJ

I ~ 0 -

~ OJ -= 0 ~

8 E =~ O~

N o o



o o

I~gt 1 t3 OJ gt

be~3~ tL- 4)~Q) OJ

Q) - II) - gt gt

~~ sect3 3 E-L [ o~ ~ E ~ 8 a sect E



c 0 oj eo OJ1 Fgt~

Fgt 0 OJ

0

I ~ c E ltJ

5~

74











- - -

-----

- - - - - - -

------








III I - - -

- I

trop()~p heric


advectio n -






75







+ 02



76

























(o I C O(lIdy)


78

RFEINCES












































4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)























VI U

~ lt2 iii U of

x u

z ~ nx In I

In Q lt


V

= ~~~ f=gt ~~~ ~ 3

middot~~e ~o8


~~~~ lt1

8

aCg gt u

0 c OJ



8 ~ ~88 8

N

ltJ If)

0 1-0 111 001 0

o ltJ If)

8 o



sect~ ~ B B ~ 0 0 000 -4 _


00 23++++ 1 I 1+ 00

+ ~BBBEB BEB pound


01000 1)0+ 1+111 1




~ 0

~

3 ~

f

l5

~~ 0

~ E ~8shy ampu0 l

~ 1I 1-8i)Jta 0 gt- N

Igtl

8 0=gt ~

_05~ ~ -----r-+-~-shy VI OJ ~8 0100 10 0

~ o ~ gt 1 +jl1+ 1lt 3 iii 0 ~ =2


~


V OJ OJ OJ~ -= 0 -= 011 I) UJ0 o 0 ~ c

UJ

I ~ 0 -

~ OJ -= 0 ~

8 E =~ O~

N o o



o o

I~gt 1 t3 OJ gt

be~3~ tL- 4)~Q) OJ

Q) - II) - gt gt

~~ sect3 3 E-L [ o~ ~ E ~ 8 a sect E



c 0 oj eo OJ1 Fgt~

Fgt 0 OJ

0

I ~ c E ltJ

5~

74











- - -

-----

- - - - - - -

------








III I - - -

- I

trop()~p heric


advectio n -






75







+ 02



76

























(o I C O(lIdy)


78

RFEINCES












































4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















74











- - -

-----

- - - - - - -

------








III I - - -

- I

trop()~p heric


advectio n -






75







+ 02



76

























(o I C O(lIdy)


78

RFEINCES












































4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















- - -

-----

- - - - - - -

------








III I - - -

- I

trop()~p heric


advectio n -






75







+ 02



76

























(o I C O(lIdy)


78

RFEINCES












































4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















76

























(o I C O(lIdy)


78

RFEINCES












































4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)































(o I C O(lIdy)


78

RFEINCES












































4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















78

RFEINCES












































4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)

























4 THE STRATOSPHERE
















(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)
























(b) The Warm Layer






127







128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















128




S THE IONOSPHERE












129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















129 VOL 31 No 4 APRIL 1950










6 THE EXOSPHERE



130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















130





ACKNOWLEDGMENT



REFERENCES

(ConcUded)






















the stratification of the atmosphere (i) · 2013-03-17 · the stratification of the atmosphere . 1...

Documents