1..

REPoRT AC-3 December 1969

~ AC - SEKR~~

CARBONDIOXIDE MEASUREMENTS FROM AIRCRAFT

-Walter BischOf

INSTITUTE OF METEOROLOGY UNIVERSITY . OF STOCKHOLM

INTERNATIONAL METEOROLOGICAL INSTITUTE IN STOCKHOLM

INSTITUTE OF METEOROLOGY UNIVERSITY OF STOCKHOLM (MISU)

REPORT AC-3 21/1163

1(14)

INTERNATIONAL METEOROLOGICAL INSTITUTE IN STOCKHOLM (IMI)

2.12.69

P. ~ .Box 19111 S-104 32 Stockholm 19, Sweden Tel . 08/340860/275

CARBONDIOXIDE ~ffiASUREr~N TS FROM AIRCRAFT

Walter Bischof

ABSTRACT

During 1962-68, 1482 air samples were collected from aircraft, partly from jet airliners, at both tropo­spheric and stratospheric flight levels. The sampling and analysis technique is described and the accuracy of measurement discussed.

This work has been supported by the Swedish Science Research Council as part of Contract No. 2065-16.

iUSU TlYli \.Ti3 1 s::

REPORT

2.12.69

AC-3 21/1163

CONTEJ'~TS

1 Introduction

2 Air sampling and analysis

2.,1 Air sampling technique

2.2 Analysis equipment

2.3 Description of the analysis procedure

3 Accuracy of measurement

3.1 Check of analyzer calibration

3 ~ 2 Field work

3.3 Comparison of data

3 , L:. Stor::..ng time

4 References

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14

~ - f ....... J,, 1 • .-. .. .... '-

REPORT

INJ.'RODUCTIO H

AC-3 21/1163

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t1ea:nrrements of co2

concentrations in air samples collected

from aircraft were be gun in 1957 at the Institute of Mete­

orolo gy j_n Stockholm as a complement to the Scandinavian

g:roe1d c::~~ tl!. -7' ·. on netNork, Data obtained during 1957-1961 from

fli f,ht l eve:!_s e<.bO V f; 1000 In ~ show that the irregular fluctua­

tic~s i n t~a con conte nt of the air decrease with elevation c.

a~1d - ~he sens'J·.::_aj_ vm:iations therefore become less obscured

(_~:i.:.9.~-:._~~~ ' 1960:. !.962) . The s e varia tions and the a nnua l mean

we:-:-e founcl. to be c::.o s'2 to those reported by Kee~ing_ (1960)"

Unfortnnate ly, a E n tt em9t to calculate an annual increa se fo:..~

th~_s pe r iod i:'e. iJ_e d. be c ause of insufficient accuracy in the

anaJ.ys j_ s me tl~:Jd 1.:.sed a t that time .o

In 1962, a projec t wc.. s started to collect air samples from

colllfficrcial j 8t a j_rcraf t on cruises over larger distance s and

o. t higher i'li::;ht lev-e l s . A new analysis technique was

deve loped t.c i.'Ujll' OV ~ the a ccuracy and gas standard were

established in coape r o. tion with Scripps Institution of

Gceano gr c::.plc.y, Fr..i v. of' California .

The re sults ob tn:i.ned d11ring 1963 at 5000 m are in good

agr cem8n -'; wi·~:~. d3 t c. :r.;; pc.rte d by ,l?_9lin and Keeling (1963)

f:rorJ. f li g'-l t.::: a~~ t !:8 5CO o.b leve l during 1958-1961 over the

Pacific~ c onfirm~i_ng 2. growth r ate of 0.6- 0.7 ppm/yr as

calculated by E8lin and Ke eling. The 1963 data also show

h ow releaec a nd abs~:rption of co2

at the earth 1 s surface are

~eason~l co2 variations at all tropospheric

lev2l s u p to the tropo9au sc, In contrast, no or only small

...-a r:::..a ; :ionrJ Y!e :!:' s .LO"Lmd in t~1e lower stratosphere (Bischof

l o _c:.::: \ -· ..... l.. ) ., ar .. d :Solin .. ---- ··-·' ~~~; i s shows how the vertical exchange of

co2 :..s d2.r:1:,>eu by the t r opopause, as already tentatively

(; onr~ } .ude d by !'~c:~S:9:'?~~ (1965 ) from data collected during flights

bet·-, •ee:n C:'p0nh9.2':en enrl_ Los Angeles in 1963.

Pet1.•reen 1962 ~ n l968 , 837 ::; av.ples were collected from fli ghts

v:i +.h :r;c ... o o..Lr cn,.:Lt b,;:·.:i.nly ove r- Scandinavia, the North Atlantic

a n d ~he North Am~ricon contj_nent, but a lso on flights to

Tokyo, Rio de J 2."'.C-! i ro 8.nd Bombay.

REPORT

2.12.69

AC-3 21/1163

4

Furthermore i~ cooperation with other institutions, such as

?~vironmental Science Services Administration (ESSA) and

Wo~dG E0lR Oceanographic Institution (WHOI) in the U.S.,

air se..mples V'.'e r e collected on flight expeditions over t he

Ca r:!..bbean Sea, the eas t coast of North America , and the

Incian Ocean . Samples have also been obtained from airc~aft

be J. on~ing to t he Swedish Air Force and from small priva t e

plaDes . A to~al number of 1482 samples were collected

during 1962- 1968.

L da to. separa ti.on was made i n order to obtain a me an annua l

co2 cycl e f o::- t!:le tropospher e as well as for the stratospher e:­

and the ave:c'8.ge r ate of annual co2 increase for this pc:J:>ind

of -~ine. The YC'.r:i.abil i ty of data has a lso been studied,

An extensive present a tion of these studies is given i n a

oe:p c:.:-:a te 2.r "..; icle (.J?.<?.l"i_~ and Bischof, 1970).

In t~is article a description of the air coll ec tion and

s.nalys i s te cl:l:':lique i s pre sented and tlll:l the a ccuracy of the

MISU HII WJ3 1 mo

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2 ,1

REPORT AC-3 5 21/1163

2~ 12.69

AIR SAMPLING AND ~{ALYSIS

Air sampling techn~que

In spite of the most varying kinds of aircraft used in this

project 1 air samples were collected in the same type of

500 ml PyTex glass flasks with two stopcocks and 14 ~~ stan­

dard taper ~aint connections, see figure 1. Samples, in

general ar e collected by connecting the flasks to an air

v entilation system, for example$ using ram air from a Pitot

tube . The air is drawn t hrough the sample flask for oome time~

occas.:..onally a suc~ing pump is connected to the outgoing

stopcock, or a Ventury tub e is used 1 in order to increase the

air exchange in t h e sample flask. Usually, the flasks c.1.so a~e

evacuat ed before sampling, in order to ensure complete air

exchange in the f l ask .

To collect air samples from a DC-8, a surprisingly easy way

was found by connecting the f l asks to the fresh air v enti­

lation system in the cabin. Unlike other j e t airliners, the

DC-.. 8 is equipe~ with a separe..t e ram air intal<:e and turbo

compressor for c abin air conditiorirg. Pressurised and heated

r am air is brought to the cabin, while fresh air via a bypass

is brought to the fresh air outlets at the passangers seat.

Tests were made to check the contamination ri sk by conparing

the results from DC-8 flights during descent with r esults

obtained from a Piper plane shortly after':Vards 1 In addition,

c?.::::lpl c:J . .fJ:o!:l diffe~ent :DC-8 2.ircraft an:i from differ e1rc O'x(:

l e ts on the same c.irc r aft were compared and the r esul ~"' arP

found to b e identic al G

Wnerever air samples a:a::.-e t ak en, the s ampling time must be

long enough to en sure a comple t e air exch ange in the sampl e

fl ask. Tests with fl asks not being ev acua t ed before samplins­

show tha t a sampling time of~ ninutos . i s required •when

using an air flow of o, 6 1/min, which i s equal to abou.t three

time s the volmne of the sampl e flask .

MI SU Ii·.li

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REPORT AC~3 6 21/1163

2 01 2. 69

Anc::lzsis egui:pment

A specie)_ fl<'.i:k sa'Jlp}..e anB.l;-isis equipment was developed ~-· C:.. , •

the Institute in Stockholm (Figure 1) .. By avoiding high

pressure technj_c~ue a:1d presE.'ure regulation it has been

pos::::.ible -~o co~3b~uct a portable equipment which is easy to

opere.te. The a ccu:::·a8y of measurement was found to be about

0, 2 :ppm, i ,. 8- c.bo·c_·c i~l1 e same as reported by K'?eling_ ( 1963).

A s imil ar eq_u;_p:-, 'lo a:::; ;;e en i:1st2.lled at the Insti tut .)

1s: 64) and at ESSA. APCL~ Boulder, Colorado~ USA. A detailed

In general: a some'f:-hat mc-dified infrared gas analyze::- of tyoe

UR1i.S~ mam-:.factu·: e d by I-:::-·.r tw:mn and Bl.'aun, Germany~ uas 1.'.sec ,

but also ot':l e:c- t~~e s U RGA I <:r'ld II, by Grubb Parsson~ JJon don) ,

S::.:.::>? 1966, 2n u:r JR of MAIHAK, Hc:mburg rerlaced the ea::·lio : ~

meas-:1remen t s on ai.:-~craf t.

Stano .-· '· gas was :prepQ.reG. by AGA, Stockholm, and stored in

50 1 : ':li c;h :.)re s sure g::::.s t e:c;:: :> , Standard gas calibratio:1 i ,s

annually macle 2gai~1st t:!:le ::;~_-'L J:l'~ s standard::.. We thereby obtain

·~ · --~' :primary s":: r.r.

~es_c_,Ii ption of _=(~h e anal:y__si£_:p_~edure

:Before cnteri:c1g the .0~J::Y~~.E. ( A )~ all gases have to pass a

."!~:~er_Y.§-J!.Or __ J;£~12. (5) , ~Cn :r::cinciple 7 trm different oper a.t:i.O:i.lS

e.:c:e made ,

a) _StanC.2-~d_E.~ .. . ~:?:!-:.~1? 2~ .'!-tior.?:_, by flowing standard gas -;:-li tl:.

we:i..L~nG TV!l co2

:;o :~.c-::,~ .. t2at ·.i.on through the anal:;rzer~

b) 2'.~.8.:?1~~- ~-~-~pJ ,-: ~"'~l£tl~: ?. j-_ ~ , by bringing sampJ.e a ir i'J.to the

a~1aly~~ er"

'S+. c::ndard cctlib~ca.":.i.on is ma(':.e be C'ore start.ing any flask

an::::.l;ys is -Go o b t c:.::.'1 <'~ c:J.l~_-b ration factor, i.e. recorder-

. r:c&1e fact::>r; r--,n rl to ch0ck the li'J.ea:d.ty of the ca~_ibratior

c·.Jrve< Ten stanc:r.n:-d :.;.J.s tan~cs are available~ conta i.n:i.ng gas

·:v5.th CO~ c;onc8n 'G..:.':J.t :Jms fro:n 30(1 ·i~ :::> 340 ppmo Standard gas i f~

brm .. '.ght into ::h e ec::-.c o. l;:.r~ ?~~ sanpl e cell wi t:h a flow rate o f

., , . .. ) '.)

i l -3 ' s~·

F

s

FILTER

220 v ..._

R

A

5

2 • . L2 . G':3

8

2

Analysis equ~pment.

A Analyzer S Voltage s t abil izer R Re corder F Recorder filter

;~ :.; - )

:2 1/1163

3

7

6

Sample flask 2 1 l H~ reservoir 3 2 l Hg reservoir 4 Vacuwn punrp 5 Water vapor tra p 6 Standard gas

connections 7 Vacuum meter 8 F low meter and

regulator

REPORT

2. 1 2. 69

AC-3 21/1163

8

Of 3 1/min controlled by a flow meter and re~ator (8). Cal5 ... bratio~ is made either with a conste.nt flow rate or ~

after flushing the cell, with air resting in the 3ample

cell (static air analysis).

A complete calibra+,ion includes the use of at least three

different standard8~ e:tch one referr ed. to ·cen tinec, A

me2.n value is obta::_ned and a ~onparison made n j th two of

our primary ::;t8..nda.rds . w:;_ ~;h the equipment in good condition,

no de-viation larger than~ 0 ~ 2 :ppTI a r e accepted. Otherv:ri8 e

the calibration h as to be rechecked . Part of the error s are

due t o hysteresis and non-linearity in the membrane r;onden-·

sator c::.1 a.r acterictic s. By th e proced1..'.re we ensure that + these errorf1 a r e less than - 0 1 2 ppm.

In performing the f!_~ sop.,:ele_~na~_ysis the flask is

con::1ected to ~he equipmen·t by a 14 mro standard t aper join

connection. Th e s2Jll:ple ai r i n brought into the sample cell

by using a mercury pump 2ys tem containing two mercury

l;'.§.~~~~Q_~rs ( 2), ( 3 L which are connected to a .YE;9~~-J:~'!!..P..

(4). The vacuum pump is also u sed. to evacuate all remaini!l8'

air i n stopcocks <Jld connection lines b etween the sampl e

flack and -!;he 1 1 - Hg reservo~-~0 The vacuum is checked by

a 2~92-~!!! .... __I.!!e~_£?;. ( 7) ,..

A:.:ter evacuati:<r.: the connection lines, the flask stopcock

is open c--~ and the sample 11ir is brought i n to the 1 l .. Hg -·

reservoir by pumping the mercury into the 2 1 - Hg r eser-

voir 1 '..lsing th e ·;,racuuB:rmmp. In reverse order, the De::CG-:Iry

is used to push the sa1JJ.ple air from the 1 1 reservoi -c :i ... nJ.;o

che anoJ ... ~rzer and through the sample cell. To have complc·ce

gas cxchanze in the sample cell, about ·150 ml sample air at

room pressure is ::- eq_-J.ired (static air analysis). The a..Ylo.lysis

result is obt.ained on t~1e recorder (R) a.""ld is coli'.pared wi th

one of the standarc. gases. While preparing a new sample fo r

analysis, a comp2.rison bet i7een th e standard j ust us e d and

one of t he o the~ stRndards is performed~ ~his procedure

allows an an:'clysi s cap acity of about ijC:en samples per hour,

i ncJ.-r.c1.:i...ng s·~ ::mdard g ;.,s comparison fo r each sz.mpl c .

REPORT

2.12.69

AC·-3 21/1163

9

in order to 8heck the analysis reliability, :C'Jask samples

containing standard gas usually are analyzed at the

beginn~cg and also occasionally during routine analysis

l\USU IMI WB,mo

3

REPORT

2.12.69

ACCURACY OF THE l\'lEASURID/IENTS

AC-3 21/1163

10

Investigations w·er e m.o,de to check the reproducibility of

the an~lyses, i.e. the sum. of possible errors caused by the

infrared gas analyzer itself and the rest of the analysis

equipment resp ecti"lrely.

Check of a.-'1alyzer c alibration

An analyz er characteristic is found by flowing standard

gases of well--Y::no;m conc entrations through the sample cell

as describ ed in 2.1. A maximum deviation of~ 0,2 ppm

between :;__ndividual :a:casurements and a standard deviation oi" + - o, 1 ppm is found, 1rhich is equal to the accuracy of the

recorder. Part of those errors are due to the hysteresis of

the membrane condensator and lack of linearity of the

calibration. The results are SUL~arized in Table 1.

Table 1

Analxz~r_calibratiQn

deviation from average ~ 0 o, 1

number of cases

percent of total

standard deviation:

59

39

0,08 ppm

0,2

5

5

0,3 ppm

0

0

107

100

By analyzing samples of standard gas filled in flasks, we

can asses how repro ducible the measurements are. From Table

2 it can be soon, t hat almost the same accuracy is attained

in this way.

MISU I MI WB/mo

REPORT

2 . 12 . 69

AC- 3 21/1163

12

i n Stockholm and a t Scripps Institution respectively .

The result is show1 in Figure 2 .

]2oub}-_c_ana_!y~i~.

On a DC- 8 flight , both l/2-l and 2-(. fl a sks were u sed and

analyzed in Stockholm. Due to the larger volume , double

analysis could be made of the 21 samples . From the r esult

shovm in Table 3 i t can be seen that no devia tion l a r ger

than 0,15 ppm occured and that 87 % of all deviations wer e

found wi thin a 0,1 ppm range .

Table 3

Doub_!e_a~aly~i~ f r£m_ 2l sa~_!e_f_!a~k~

devia tion from 0 0~01- o , o6- 0' 11- 0 , 15 average 0,05 0, 10 0, 15 ppm

number of cases 15 29 17 9 0 70

percent of total 21 42 24 13 0 100

s tandar d deviation: 0,04 ppiil

3 . 4 Storing time

Samples wer e c onsistantly analyzed within a few days af ter

collection because i t ha d been found (by analyzing standard

gas samples ) tha t a con~ination risk exists after a few

weeks which is different for different flasks. This i s

proba bly due t o dj.ffu sion th.."":'ough s topcocks in the presence

of an ext erna l excess pressure and concentration differ ence

botween sample and room air, and depends of course also oYJ.

the quality of the individual flask .

;~a su I t<!I .VB , sf

"CO 2

AG- 2 13 21/1 16 3

2.12.6:J

ppm 325 0 Stotkholm I 324

323

322

321

----

~

~

t-

t-

320~ 319 t

+ Scripps

I ++ 0

+ coo 0 + 00

0 ocf +

d*oo +~ o·,- 0

0

25~ 20 15 10 5 0 Latit~\,~:if:

Fi g . 2. Comparison between flask samples analyzed in Stockholm and at Scripps Institution respectivelyo (HFl'' fligh t ( ESSA ) of April 27-29, 1966, ov e r the Caribbean Sea and s outh of Panama,the samples we re collected at 1.600 m. )

. -

MISu IMI WB , sf

4

REPORT

2 .12 . 69

REFERENCES

AC- 3 21/1163

14

Bischof, w, 1960 : Periodi cal variati ons of the atmosphe r ic co2 content in Scandinavia . Tellus 12 : 2 , 216- 226 .

Bischof, w, 1962 : Variations in concentr ati on of carbon di oxi de in the free a t mosphere . Te l lus 14 : 1 , 67- 90 .

Bischof, w, 1965 : Carbon dioxide concentration in the upper tropo sphere and lower stratosphe r e , I . Te llus 17:3, 395-402.

Bischof, Wand De Maio , A, 1964 : Ueber die Installa tion einer Apparatur fur di e Analyse des atmosphari schen Kohlensauregehal ts . Pure and Applied Geophysics 58 , II, 204-207 .

Bischof, W and Bolin , B, 1966 : Spa c e and time variations of the troposphere and lower stratosphere . Tellus 18 : 2, 155-159 .

Bolin, Band Bischof, w, 1970 : content of the atmosphere . Tellus vol. 22 .

Variations of carbondioxid0 To be published in

Bolin, B and Keeling , C D, 1963 : Large- scale atmospheric mixing as d8duced from seasonal and meridional varia­tions of carbon dioxide . J Geoph Res 68:13, 3899-3920 .

Ke eling , C D, 1960 : The concentTation and i s otopic a bundances of carbon d~oxide in the a tmosphere , Tellus 12 : 2, 200-203 .

Keeling, C D, Har~is, T B and Wilkins , E M, 1968 : The con­centration of a tmospheric carbon dioxide a t 500 a nd 700 millibars . J Geoph Res 73:14 , 4511-4528 .

INSTITUTE OF METEOROLOGY UNIVERSITY OF STOCKHOLM (MISU)

INTERNATIONAL METEOROLOGICAL INSTITUTE IN STOCKHOLM (IMI)

Atmospheric Chemistry (AC)

REPORTS l 1186

1969 -

l Rodhe, H, On the residence time of antropogenic sulfur in the atmosphere (in Swedish),

2

3

Bolin, B and Bischof, W, Variations of the carbondioxide content of the atmosphere~

Bischof, w, co2

measurements from aircraft,