- Email: [email protected]
Remote monitoring of aerosols from space
Adv. Space Rae.
Vol.2, No.5, pp.87—93, 1983 Printed in Great Britain. All rights reserved.
0273—1177/83/050087—07$03.50/O Copyright © COSPAR
REMOTE MONITORING OF AEROSOLS FROM SPACE 0. A. Avaste and S. H. Keevallik Institute ofAstrophysics and Atmospheric Physics, Estonian Academy of Sciences, Tartu 202444, Estonia, U.S.S.R.
AB STRLLCT
Using the four—channel teleracliometer “Micron” aboard the Orbital Stations “Salyut—4” and tlSalyut_6!t the brightness profiles were determined in the near—infrared spectral region up to the height of 60 km (in case of nocti— lucent clouds up to 80—85 1m~). Proceeding from the data above we obtained information on the global and vertical distributions of atmospheric aerosol, water vapour concentration and the optical properties of the noctilucent clouds. INTRODUCTION The global aerosol distribution and its effects on the Earth’s atmosphere have been recently receiving considerable attention. The measurements carried out using the teleradiometer “Micron” aboard the Orbital Station “Salyut—4” in 1975 and “Salyut—G” in 1978 gave a number of vertical bright-
ness profiles
of the atmosphere in the near—infrared region over different
geographical areas for different heights of the Sun [1—4] . These measurements made it possible to determine the vertical distribution of the aerosol extinction coefficient and that of the water vapour concentration. TELERDIOMiTER “MICRON”
Teleradionieter “Micron” is a four—channel instrument. Its general characteristics are summarized in Table 1. The optical lay—out is given in iSig. 1. For more details see paper ES] The field of view for all the channels was circular and the electronic transfer function had Gaussian profile. Por the reduction of the off—axis scattered radiation internal baffling was used. Labora.tory absolute calibration was carried out using a tungsten ribbon lamp with imown brightness
temperature [6]
.
For the expansion of the dynamic range the amplifiers had
four outputs with 1:10:100:1000 gains. Under space conditions the optical lay—out and the rigidly fixed optical filters ensured a high stability of the characteristics of the radiometer. 1/
1/
The scientific team of the aerosol experiment was made up of: R.M.c~rech— ko, A.A.Gubarev, P.I.Klimuk, V.I.Sevastyanov (Pilot—Astronauts of the USSR), O.A.Avaste, K.A.Eerme, S.H.Keevallik, Yu.V.Kn~azikhin, R.I.R~m, G.M.Vainikko, U.K.Veismann, Oh. I.Uillmarm (Institute of Astroph~rsicsand Atmospheric Physics of the Estonian Academy of Sciences).
87
88
O.A. Avaste and S.H. Keevallik
TABLE 1
Optical Characteristics of the Rear—Infrared I~adioueter
Ch~nel o
Sensor
Centre eve— length Qim)
Mandwidth ~
Lastantaneous geo— Noise equivalent ~etrac feld of v~.e, ~ e_ ~ or~it Aperture imi tiove , ~ —2 —1 ~—1 mmci. horizon O~.i
I
PbS
1.35
0.21
3.49
7.3
2.1O_0
2
PbS
1.9
0.28
2.91
6.1
2~10~
3
PbS
2.2
0.25
3.49
7.3
6.1O~
4
PbS
2.7
0.34
3.78
7.9
3•10~
:~
~
‘•
I ~
—-—~t31’~t<1
i_ri
Li
1W
I
____
1111
1.
1~-~L-n~i
~1iT1-J1 ~1_7;4~
1.~
____
T9f~
Pig. 1 The block diagram of the four— channel near —infrared radiometer. 1 — objective lens; 2 — optical filter; 3 — light chopper; 4 — field diaphragm; 5 — photoresistcr~ 6 — selective preamplifier; 7 — amplifier with four selectable gainsettings; 8 — standard light source; 9 — temperature measuring system ThE EARTH’S AUREOLE LG~THOD In a lucid comparative critical review[7J D.Deirmendjian pointed out that while comparing different remote sensing techniques one must take into account the following four categories: (1) efficiency of coverage: global, geographical, vertical and diurnal or temporal; (2) information on aerosol loading; (3) reliability on the basis of theoretical justification (or scathe— matical inversion) and/or experimental checkout of the teclini— que; (4) overall rating or level of recommendation for implementation.
l’lbnitoring of Aerds~dis frbhi SparS
89
A comparison of the solar occultation method (see e.g. [8] ) with the so— called Earth’s aureole method (measuring the spectral brightness of the
Earth’s aureole) on the basis of the above categories for satellite—borne systems yielded the following results: the first method allows us to determine the extinction of direct solar rays up to the tangent height of 25 to 30 1~n, the second method enables us to measure the spectral brightness of the Earth’s aureole un to a height of 60—70 km (in case of noctilucent clouds up to 80—85 km~. The solar occultation method when the radiometer tracks the solar disk during each spacecraft sunrise or sunset with the aim of producing an atmospheric extinction profile down to an atmospheric vertical altitude of 10 lan, gives each day approximately 14 vertical profiles in each hemisphere, equally spaced around the latitude circle. The aureole method allows one to scan the horizon from the spacecraft practically continuously (see Fig. 2) and essentially increases the amount of information during a fixed time—interval (day, month).
/S
Pig.2
Orbital station scanning horizon, while ft #0
The aureole method yields also information on the mean scattering indicatrix: if the angle ft between the plane of scanning asia that of the satellite orbit (see Fig.2) ranges from 0 to 2~r, the scattering angle ~ varies from 0 to 2~r—o.. Here o~ is the depression angle of the ray directed from the satellite towards the horizon. An optimum measuring system may use two horizon—scanning radiometers: one having an angle ft 15-20°, another having an angle fi =180°. Thenwe measure6 . Then use only ments will be carried out for all scattering angles 1’~J one radiometer, e.g. for the satellite height H =300 1cm, we have scattering angles varying from 15° to 105°. It should be mentioned that the combination of these two methods (occultation method and the Earth’s aureole method) probably gives the most reliable and economical mode of indication of global particulate turbidity over long periods of time. It will be especially useful for the monitoring of unusual events, such as volcanic dust transport, etc. SOLUTION OF THE INVERSE PROBLEM Proceeding from simple geometrical considerations which take into account only first—order scattering, and assuming that the underlying surface reflects radiation according to Lambert’s Law, it is possible to present the aerosol extinction coefficient as a solution of Abel’s integral equation E2J , i.e. q
I
aI’(x) d
~Jh V~f—(R4~h)~1—aI(x)
(1)
90
O.A. Avaste and S.H. Keevallik
where =
~ceEq(T) ÷24&~]
const
(2)
ere 6~(h) is the ~erosol e~ctinction coefficiert at tne heght h, ~ flea ~he ~art’i’s~±ean radius, H c..eaotes tne dep~ of the atiiosp~ere (H = 100 in-i), 1(x) ann I’(x) determine tie measured brig~t’iess urofile and ~ts deriv~tnve, ~ ~ives the single scatterin~ albeao, c 0 indicates ire solar constant, g~r)as the scattering ix~aicatiiz at the scamteria. ~n~,le~ hale A is the cloedo of the underlyin~ surface ann ~ aeter~-iines inc cosine of the Sun’s zenith an~le 1~ in algor~t~-m for solva’ig bel’s integral equ~taonar aiscmete form ‘as used[2J The oocuiac~ of this aethoo. ‘as estarated b~r a corpa_izon ith tie lonte Carlo calcul~t_on[9,lO] It was shown that in case of an optically thin atmosphere ( D< 0.1) an approximate solution (1) yields an accuracy of 10 per cent. The above—mentioned method used an assumption that the atmosphere is horizontally (or in spherical layer) hompgeneous. Since the real aerosol dis— tributhon aiflers from tne assumption above, an anal~siaof the effect of tne aerosol aoataal innon-ogene_ties on the data obtained froa the Oroatal Stotao~-i as carried out This effect turned oit to ac ins~gniflc~ntan the stratosphere anc~ riesosphere (less than 1 per celt) RESULTS Aerosol extinction coefficient profiles were determined for the wavelengths X=1.35, 1.9 and 2.2~LLm. Pig.3 illustrates four vertical profiles of the aerosol extinction coefficient while 2~. =2.2gm in the latitudinal belt of 60—65°N. The longitude of the observing point varies 1O~°Etoll5°E . Prom Pig.3 curves with a geographical longitude 85°E and 100 E determi.ne definite aerosol layer at a height of 35 km. The extinction coefficient vertical de-
pendence can be roughly approximated by an exponential law. In Fig.4 the
dashed area presents the region of the aerosol extinction coefficient variation in the latitudinal belt of 65—70°R. For comparison the aerosol models of Shettle and Penn (see e.g. [4] ) (durve 1), McClatchey (curve 2), Toon and Pollack (curve 3) have also been reduced toX=2.2 ,L~.m, assuming that ~(x)~6cx)~/~. Here ~(x) is the aerosol extinction coefficient where X = .0=0.55~m. Tig.4 shows that the data measured from “Salyut—4” and from the model by Shettle and Penn are rather close in the layer of 10—50 km. In two other models ~(x) decreases withheight in the stratosphere more quickly than our experimental data show Ou~experimental data andicate a very 2yl..5 Ion) times smaller than those derived faint Junge layer (18—21 andat the height interval of from 10—25 paper km ourby TScClatchey data on ~ at al. are [11]. l. The mean values of the background aerosol extinction coefficients were in paper [4] approximated by the formula
(3) where
6’ (x) is the aerosol extinction coefficient at the height x,~ and
are constants in different layers: x(*crn)
~~(,.m’)
1
10—30
0.1382
1.259x103
2
30—40
0.1842
5.014x1O3
3
40—60
0 0691
5 O11x105
Monitoring of Aerosols from Space
91
80
60
0
fiT’
Pig.3
Pig.4
X=115°E
io~’
.
0 0 io~ ~(Y~~)
~o-~
10 ~
Calculated vertical profiles of the aerosol extinction coefficient in the latitudinal belt 6O—65°N
Vertical distribution of the
aerosol extinction coefficient at X the dashed latitudinal belt va1f =2.2.~tmin =65—70°N. The area shows riations in experimental data, curve 1 presents the model by Shettle and Penn (1965), 2 — by McClatchey et al. (1972), curve 3 — by Toon and Pol—
lack (1976).
h,~m 70~
I ———2
~‘
—-——3
\
50
\
~
N.,
N 3Q
\
10
io~ ib~ ib~ ~
iü~6’,Km4
The parameters in different layers are mean values, since for individual profiles they depend on the temperature regime which determines the vertical turbulent aerosol exchange.
In the case of noctilucent clouds (NLC) our radiometer was able to detect the brightness profile to a height of 8O~85km. (See Pig.5). The brightness of RIO at the height of 80 km was nearly by one order of magnitude higher than that of the twilight aureole. Depending on the structure and the optical thicimess of NLC the brightness varied within the limits of one order of magnitude. Figure 6 presents an estimate of the spectral brightness of NLC and of the hydro~rl emission in case the line of sight has a tangent
height of h —81 lan. The results of measurements have been entered on the same graph: it presents both average values and maximum deviations for the channels of 1.35, 1.9 and 2.2gm. For the channel of 1.35gm the eraission of O2(~g) was eliminated. The data at 2.7~rnturned out to be insuffi—
92
0.A. Avaste and S.H. Keevallik
ciently reliable and were omitted. The .ULC spec~ralbrightness was calculated for the optical thickness ‘~ =10’5 , 3x10~, i04 and for a scattering angle of ~‘ =800 since measuremen~s of. NLC were carried out at the scattering angles which lay close to 80
Ii~B~~
-3
~
~
~2
\i•” U
20
80
“-l
H0,Km
—3,
.
1 Pig.5 Brightness measurements of the horizon with NLC at a wave— length of 1.9~Lm
2
3
Pig.6 Spectral distribution of the RIO brightness at a scattering angle of 1=800:1 — calculated when ‘~ 5, = 1o~, 3 — calculated 2 — calculated when ‘v’=104, when r=3x1O 4 — OH emission (Shefov, 1968), 5 —sum of NLC brightness when ‘~‘ =3x1O~ and of Oil emission; • — .indicates the mean experimental values, vertical bars denote variations in NLC brightness.
The spectral intensities of the hydroxyl emission in the direction of the line of sight with perigee of ~ =81 km at 60°Nwere calculated, taking into account the increase of OH when NLC occurred according to Shefov (see E12J ). The solid line characterizes the total effec~ of both the hydroxyl emission end the radiation scattered by NLC (r =3x10 ). As can be seen from Pig.6 the calculated values and measured brightness have rather close values. Hp— droxyl emission at A. =2.2 p.m is comparable with the radiation scattered by NLC, while at 7~=3 /~inthe former exceeds the latter by one order of magnitude. CONCLUS IONS 1 • The measurements carried out on board the Orbital Stations “Salyut—4” and “Salyut—6” enabled us to determine several characteristics of aerosol layers at heights of 18—25, 35—40, 50 and 80—82 km. 2. The simple inversion method based on Abel’s integral equation gave an accuracy of 10—15 per cent.
3. The so—~alled “Earth’s aureole method” enabled us to determine aerosol extinction profiles up to a height of 60—70 ion (in case of noctilucent clouds up to 80—85 lan). 4. The most reliable and economical data on the global distribution of atmospheric aerosol will give a combination of the Earth’s aureole method and the solar occultation method.
—
Monitoring of Aerosols from Spare
93
REFERENCE S 1. O.A.Avaste, U.K.Veismann, No.2, 60 (1980)
Ch.I.hillmann
and K.A.J3erme, Vestnik AN SSSR,
2. O.A.Avaste, V.S.Antyufeyev, G.M.Vainikko, U.K.Veisniann, Ch.I.Willmann, G.M.Grechko, A.A. Gubarev, G.A.Mikhailov, S.H.Keevallik, P.I.iclimuk, V.I.Sevastyanov, R.I.Room and K.A.Eerme, in: Invest~Zations of the At ~g!.pheric—Qp~cal Phenomena Aboard the Scientific Orbital Station ~al-~ut—~”, Tartu, 1979, p.146. 3. O.A.Avaste, V.S.Antyufeyev, G.M.Vainikko, TJ.K.Veismann, Ch.I.Willmann, O.M.Grechko, A.A.Gubarev, P.I.Klimuk, J.V.Knyazikhin,~.Ii.Keevallik, 3.A.Mikhailov, M.A.Nazaraliev, V.I.Sevastyanov, R.I.IToom and K.A.Eerme, in: Atmos~eri~QpticalPhenomena According To the Observations Carried Out 7~~d ~ Sci~r’I~~ital ~tations”Salyut”, Tartu, 1981, p.9l.
4. O.A.Avaate and P.N.Vainikko, in: Volume of Extended Abstracts, Interna-ET1 w341 572 m511 5 tional Radiation S~~sium,August 11—1~ l9ffO, Fort Collins, Colorado, ~ 5. T.V.Bamnaulova, M.I.Valov, U.K.Veismann, Ch.I.Nillinonn, G.Z.~~anelin, V.V.Demidov and N.A.Ohichkin, Teleradiometer for Remote Sounding of the Atmos aere in the Near Infrared_~p~iral Re~j~, Eatonian Academy of Sciences, Tartu, 1980. 6. U.K.Veismenn, in: ~
TechniuesinAstrono
,
No.5, Publishing House
“Science”, Moscow, 1975, p.70. 7. D.Deirmendjian, Rev. Ceophys. Space 2bps. 18, 341 (1980) 8. J.M.Russell III, Pure Appl. Geophys. 118, Nos. 1/2, 9. Yu.Enyazikhin, Izvestia All ESSR 10. Yu.llnyazikhin,
616 (1980)
Ps.—Math.
30, No.2, 140 (1981)
Izvesti~,,~l’T~SSR Ser._Phys.—Liath.
30, No.3, 239 (1981)
11. R.A. McClatchey, hN.Fenn, J.E.A.Selby, P.E.Volz and J.S.Garing, cal Properties of the Atmosphere (3rd Edition), AF CRL, Environm. Res. Papers, 411, 1972.
~—
12. O.A.Avaste, A.V.Fedynsky, G.M.Grechko, V.I.Sevastyanov and Ch.I.Willmarin, ~Pure Appl. Ceophys.118, Nos.1/2, 528 (1980)
Vol.2, No.5, pp.87—93, 1983 Printed in Great Britain. All rights reserved.
0273—1177/83/050087—07$03.50/O Copyright © COSPAR
REMOTE MONITORING OF AEROSOLS FROM SPACE 0. A. Avaste and S. H. Keevallik Institute ofAstrophysics and Atmospheric Physics, Estonian Academy of Sciences, Tartu 202444, Estonia, U.S.S.R.
AB STRLLCT
Using the four—channel teleracliometer “Micron” aboard the Orbital Stations “Salyut—4” and tlSalyut_6!t the brightness profiles were determined in the near—infrared spectral region up to the height of 60 km (in case of nocti— lucent clouds up to 80—85 1m~). Proceeding from the data above we obtained information on the global and vertical distributions of atmospheric aerosol, water vapour concentration and the optical properties of the noctilucent clouds. INTRODUCTION The global aerosol distribution and its effects on the Earth’s atmosphere have been recently receiving considerable attention. The measurements carried out using the teleradiometer “Micron” aboard the Orbital Station “Salyut—4” in 1975 and “Salyut—G” in 1978 gave a number of vertical bright-
ness profiles
of the atmosphere in the near—infrared region over different
geographical areas for different heights of the Sun [1—4] . These measurements made it possible to determine the vertical distribution of the aerosol extinction coefficient and that of the water vapour concentration. TELERDIOMiTER “MICRON”
Teleradionieter “Micron” is a four—channel instrument. Its general characteristics are summarized in Table 1. The optical lay—out is given in iSig. 1. For more details see paper ES] The field of view for all the channels was circular and the electronic transfer function had Gaussian profile. Por the reduction of the off—axis scattered radiation internal baffling was used. Labora.tory absolute calibration was carried out using a tungsten ribbon lamp with imown brightness
temperature [6]
.
For the expansion of the dynamic range the amplifiers had
four outputs with 1:10:100:1000 gains. Under space conditions the optical lay—out and the rigidly fixed optical filters ensured a high stability of the characteristics of the radiometer. 1/
1/
The scientific team of the aerosol experiment was made up of: R.M.c~rech— ko, A.A.Gubarev, P.I.Klimuk, V.I.Sevastyanov (Pilot—Astronauts of the USSR), O.A.Avaste, K.A.Eerme, S.H.Keevallik, Yu.V.Kn~azikhin, R.I.R~m, G.M.Vainikko, U.K.Veismann, Oh. I.Uillmarm (Institute of Astroph~rsicsand Atmospheric Physics of the Estonian Academy of Sciences).
87
88
O.A. Avaste and S.H. Keevallik
TABLE 1
Optical Characteristics of the Rear—Infrared I~adioueter
Ch~nel o
Sensor
Centre eve— length Qim)
Mandwidth ~
Lastantaneous geo— Noise equivalent ~etrac feld of v~.e, ~ e_ ~ or~it Aperture imi tiove , ~ —2 —1 ~—1 mmci. horizon O~.i
I
PbS
1.35
0.21
3.49
7.3
2.1O_0
2
PbS
1.9
0.28
2.91
6.1
2~10~
3
PbS
2.2
0.25
3.49
7.3
6.1O~
4
PbS
2.7
0.34
3.78
7.9
3•10~
:~
~
‘•
I ~
—-—~t31’~t<1
i_ri
Li
1W
I
____
1111
1.
1~-~L-n~i
~1iT1-J1 ~1_7;4~
1.~
____
T9f~
Pig. 1 The block diagram of the four— channel near —infrared radiometer. 1 — objective lens; 2 — optical filter; 3 — light chopper; 4 — field diaphragm; 5 — photoresistcr~ 6 — selective preamplifier; 7 — amplifier with four selectable gainsettings; 8 — standard light source; 9 — temperature measuring system ThE EARTH’S AUREOLE LG~THOD In a lucid comparative critical review[7J D.Deirmendjian pointed out that while comparing different remote sensing techniques one must take into account the following four categories: (1) efficiency of coverage: global, geographical, vertical and diurnal or temporal; (2) information on aerosol loading; (3) reliability on the basis of theoretical justification (or scathe— matical inversion) and/or experimental checkout of the teclini— que; (4) overall rating or level of recommendation for implementation.
l’lbnitoring of Aerds~dis frbhi SparS
89
A comparison of the solar occultation method (see e.g. [8] ) with the so— called Earth’s aureole method (measuring the spectral brightness of the
Earth’s aureole) on the basis of the above categories for satellite—borne systems yielded the following results: the first method allows us to determine the extinction of direct solar rays up to the tangent height of 25 to 30 1~n, the second method enables us to measure the spectral brightness of the Earth’s aureole un to a height of 60—70 km (in case of noctilucent clouds up to 80—85 km~. The solar occultation method when the radiometer tracks the solar disk during each spacecraft sunrise or sunset with the aim of producing an atmospheric extinction profile down to an atmospheric vertical altitude of 10 lan, gives each day approximately 14 vertical profiles in each hemisphere, equally spaced around the latitude circle. The aureole method allows one to scan the horizon from the spacecraft practically continuously (see Fig. 2) and essentially increases the amount of information during a fixed time—interval (day, month).
/S
Pig.2
Orbital station scanning horizon, while ft #0
The aureole method yields also information on the mean scattering indicatrix: if the angle ft between the plane of scanning asia that of the satellite orbit (see Fig.2) ranges from 0 to 2~r, the scattering angle ~ varies from 0 to 2~r—o.. Here o~ is the depression angle of the ray directed from the satellite towards the horizon. An optimum measuring system may use two horizon—scanning radiometers: one having an angle ft 15-20°, another having an angle fi =180°. Thenwe measure6 . Then use only ments will be carried out for all scattering angles 1’~J one radiometer, e.g. for the satellite height H =300 1cm, we have scattering angles varying from 15° to 105°. It should be mentioned that the combination of these two methods (occultation method and the Earth’s aureole method) probably gives the most reliable and economical mode of indication of global particulate turbidity over long periods of time. It will be especially useful for the monitoring of unusual events, such as volcanic dust transport, etc. SOLUTION OF THE INVERSE PROBLEM Proceeding from simple geometrical considerations which take into account only first—order scattering, and assuming that the underlying surface reflects radiation according to Lambert’s Law, it is possible to present the aerosol extinction coefficient as a solution of Abel’s integral equation E2J , i.e. q
I
aI’(x) d
~Jh V~f—(R4~h)~1—aI(x)
(1)
90
O.A. Avaste and S.H. Keevallik
where =
~ceEq(T) ÷24&~]
const
(2)
ere 6~(h) is the ~erosol e~ctinction coefficiert at tne heght h, ~ flea ~he ~art’i’s~±ean radius, H c..eaotes tne dep~ of the atiiosp~ere (H = 100 in-i), 1(x) ann I’(x) determine tie measured brig~t’iess urofile and ~ts deriv~tnve, ~ ~ives the single scatterin~ albeao, c 0 indicates ire solar constant, g~r)as the scattering ix~aicatiiz at the scamteria. ~n~,le~ hale A is the cloedo of the underlyin~ surface ann ~ aeter~-iines inc cosine of the Sun’s zenith an~le 1~ in algor~t~-m for solva’ig bel’s integral equ~taonar aiscmete form ‘as used[2J The oocuiac~ of this aethoo. ‘as estarated b~r a corpa_izon ith tie lonte Carlo calcul~t_on[9,lO] It was shown that in case of an optically thin atmosphere ( D< 0.1) an approximate solution (1) yields an accuracy of 10 per cent. The above—mentioned method used an assumption that the atmosphere is horizontally (or in spherical layer) hompgeneous. Since the real aerosol dis— tributhon aiflers from tne assumption above, an anal~siaof the effect of tne aerosol aoataal innon-ogene_ties on the data obtained froa the Oroatal Stotao~-i as carried out This effect turned oit to ac ins~gniflc~ntan the stratosphere anc~ riesosphere (less than 1 per celt) RESULTS Aerosol extinction coefficient profiles were determined for the wavelengths X=1.35, 1.9 and 2.2~LLm. Pig.3 illustrates four vertical profiles of the aerosol extinction coefficient while 2~. =2.2gm in the latitudinal belt of 60—65°N. The longitude of the observing point varies 1O~°Etoll5°E . Prom Pig.3 curves with a geographical longitude 85°E and 100 E determi.ne definite aerosol layer at a height of 35 km. The extinction coefficient vertical de-
pendence can be roughly approximated by an exponential law. In Fig.4 the
dashed area presents the region of the aerosol extinction coefficient variation in the latitudinal belt of 65—70°R. For comparison the aerosol models of Shettle and Penn (see e.g. [4] ) (durve 1), McClatchey (curve 2), Toon and Pollack (curve 3) have also been reduced toX=2.2 ,L~.m, assuming that ~(x)~6cx)~/~. Here ~(x) is the aerosol extinction coefficient where X = .0=0.55~m. Tig.4 shows that the data measured from “Salyut—4” and from the model by Shettle and Penn are rather close in the layer of 10—50 km. In two other models ~(x) decreases withheight in the stratosphere more quickly than our experimental data show Ou~experimental data andicate a very 2yl..5 Ion) times smaller than those derived faint Junge layer (18—21 andat the height interval of from 10—25 paper km ourby TScClatchey data on ~ at al. are [11]. l. The mean values of the background aerosol extinction coefficients were in paper [4] approximated by the formula
(3) where
6’ (x) is the aerosol extinction coefficient at the height x,~ and
are constants in different layers: x(*crn)
~~(,.m’)
1
10—30
0.1382
1.259x103
2
30—40
0.1842
5.014x1O3
3
40—60
0 0691
5 O11x105
Monitoring of Aerosols from Space
91
80
60
0
fiT’
Pig.3
Pig.4
X=115°E
io~’
.
0 0 io~ ~(Y~~)
~o-~
10 ~
Calculated vertical profiles of the aerosol extinction coefficient in the latitudinal belt 6O—65°N
Vertical distribution of the
aerosol extinction coefficient at X the dashed latitudinal belt va1f =2.2.~tmin =65—70°N. The area shows riations in experimental data, curve 1 presents the model by Shettle and Penn (1965), 2 — by McClatchey et al. (1972), curve 3 — by Toon and Pol—
lack (1976).
h,~m 70~
I ———2
~‘
—-——3
\
50
\
~
N.,
N 3Q
\
10
io~ ib~ ib~ ~
iü~6’,Km4
The parameters in different layers are mean values, since for individual profiles they depend on the temperature regime which determines the vertical turbulent aerosol exchange.
In the case of noctilucent clouds (NLC) our radiometer was able to detect the brightness profile to a height of 8O~85km. (See Pig.5). The brightness of RIO at the height of 80 km was nearly by one order of magnitude higher than that of the twilight aureole. Depending on the structure and the optical thicimess of NLC the brightness varied within the limits of one order of magnitude. Figure 6 presents an estimate of the spectral brightness of NLC and of the hydro~rl emission in case the line of sight has a tangent
height of h —81 lan. The results of measurements have been entered on the same graph: it presents both average values and maximum deviations for the channels of 1.35, 1.9 and 2.2gm. For the channel of 1.35gm the eraission of O2(~g) was eliminated. The data at 2.7~rnturned out to be insuffi—
92
0.A. Avaste and S.H. Keevallik
ciently reliable and were omitted. The .ULC spec~ralbrightness was calculated for the optical thickness ‘~ =10’5 , 3x10~, i04 and for a scattering angle of ~‘ =800 since measuremen~s of. NLC were carried out at the scattering angles which lay close to 80
Ii~B~~
-3
~
~
~2
\i•” U
20
80
“-l
H0,Km
—3,
.
1 Pig.5 Brightness measurements of the horizon with NLC at a wave— length of 1.9~Lm
2
3
Pig.6 Spectral distribution of the RIO brightness at a scattering angle of 1=800:1 — calculated when ‘~ 5, = 1o~, 3 — calculated 2 — calculated when ‘v’=104, when r=3x1O 4 — OH emission (Shefov, 1968), 5 —sum of NLC brightness when ‘~‘ =3x1O~ and of Oil emission; • — .indicates the mean experimental values, vertical bars denote variations in NLC brightness.
The spectral intensities of the hydroxyl emission in the direction of the line of sight with perigee of ~ =81 km at 60°Nwere calculated, taking into account the increase of OH when NLC occurred according to Shefov (see E12J ). The solid line characterizes the total effec~ of both the hydroxyl emission end the radiation scattered by NLC (r =3x10 ). As can be seen from Pig.6 the calculated values and measured brightness have rather close values. Hp— droxyl emission at A. =2.2 p.m is comparable with the radiation scattered by NLC, while at 7~=3 /~inthe former exceeds the latter by one order of magnitude. CONCLUS IONS 1 • The measurements carried out on board the Orbital Stations “Salyut—4” and “Salyut—6” enabled us to determine several characteristics of aerosol layers at heights of 18—25, 35—40, 50 and 80—82 km. 2. The simple inversion method based on Abel’s integral equation gave an accuracy of 10—15 per cent.
3. The so—~alled “Earth’s aureole method” enabled us to determine aerosol extinction profiles up to a height of 60—70 ion (in case of noctilucent clouds up to 80—85 lan). 4. The most reliable and economical data on the global distribution of atmospheric aerosol will give a combination of the Earth’s aureole method and the solar occultation method.
—
Monitoring of Aerosols from Spare
93
REFERENCE S 1. O.A.Avaste, U.K.Veismann, No.2, 60 (1980)
Ch.I.hillmann
and K.A.J3erme, Vestnik AN SSSR,
2. O.A.Avaste, V.S.Antyufeyev, G.M.Vainikko, U.K.Veisniann, Ch.I.Willmann, G.M.Grechko, A.A. Gubarev, G.A.Mikhailov, S.H.Keevallik, P.I.iclimuk, V.I.Sevastyanov, R.I.Room and K.A.Eerme, in: Invest~Zations of the At ~g!.pheric—Qp~cal Phenomena Aboard the Scientific Orbital Station ~al-~ut—~”, Tartu, 1979, p.146. 3. O.A.Avaste, V.S.Antyufeyev, G.M.Vainikko, TJ.K.Veismann, Ch.I.Willmann, O.M.Grechko, A.A.Gubarev, P.I.Klimuk, J.V.Knyazikhin,~.Ii.Keevallik, 3.A.Mikhailov, M.A.Nazaraliev, V.I.Sevastyanov, R.I.IToom and K.A.Eerme, in: Atmos~eri~QpticalPhenomena According To the Observations Carried Out 7~~d ~ Sci~r’I~~ital ~tations”Salyut”, Tartu, 1981, p.9l.
4. O.A.Avaate and P.N.Vainikko, in: Volume of Extended Abstracts, Interna-ET1 w341 572 m511 5 tional Radiation S~~sium,August 11—1~ l9ffO, Fort Collins, Colorado, ~ 5. T.V.Bamnaulova, M.I.Valov, U.K.Veismann, Ch.I.Nillinonn, G.Z.~~anelin, V.V.Demidov and N.A.Ohichkin, Teleradiometer for Remote Sounding of the Atmos aere in the Near Infrared_~p~iral Re~j~, Eatonian Academy of Sciences, Tartu, 1980. 6. U.K.Veismenn, in: ~
TechniuesinAstrono
,
No.5, Publishing House
“Science”, Moscow, 1975, p.70. 7. D.Deirmendjian, Rev. Ceophys. Space 2bps. 18, 341 (1980) 8. J.M.Russell III, Pure Appl. Geophys. 118, Nos. 1/2, 9. Yu.Enyazikhin, Izvestia All ESSR 10. Yu.llnyazikhin,
616 (1980)
Ps.—Math.
30, No.2, 140 (1981)
Izvesti~,,~l’T~SSR Ser._Phys.—Liath.
30, No.3, 239 (1981)
11. R.A. McClatchey, hN.Fenn, J.E.A.Selby, P.E.Volz and J.S.Garing, cal Properties of the Atmosphere (3rd Edition), AF CRL, Environm. Res. Papers, 411, 1972.
~—
12. O.A.Avaste, A.V.Fedynsky, G.M.Grechko, V.I.Sevastyanov and Ch.I.Willmarin, ~Pure Appl. Ceophys.118, Nos.1/2, 528 (1980)