atmospheric temperature measurements using a pure rotational raman lidar

Atmospheric temperature measurements using a purerotational Raman lidar

Yu. F. Arshinov, S. M. Bobrovnikov, V. E. Zuev, and V. M. Mitev

A Raman lidar technique for measuring atmospheric temperature using pure rotational Raman spectra ofN2 and 02 is discussed in detail. The use of a double-grating monochromator in the lidar for isolating twoportions of the pure rotational Raman spectrum (PRRS) of N2 and 02 and suppressing the line of aerosollight scattering is experimentally shown to be very efficient. The feasibility of the method is convincinglyillustrated by the results of laboratory experiments, as well as with measurements of air temperature carriedout in the atmosphere. The accuracy of temperature measurements using the ratio of intensities of two por-tions of PRRS of N2 and 02 was -+0.74 K in laboratory experiments. The accuracy of the atmospheric tem-perature profile measurements using the lidar varied from 0.8 K at altitudes up to 300-400 mto, and slightlyexceeded, +1.5 K at 1-km height. Lidar temperature data are in good agreement with radiosonde data.

1. Introduction

The advantageous features of lidar sensing tech-niques being actually remote attracted much attentionfrom investigators and led to the development of lasermethods and facilities for measuring various atmo-spheric parameters characterizing composition, opticalproperties, and meteorological situation. The greatvariety of interaction phenomena accompanying laserlight propagation through the atmosphere makes itpossible to obtain information about the most impor-tant meteorological parameters, i.e., temperature, hu-midity, and wind speed.

This paper presents a detailed discussion of a lidartechnique for measuring atmospheric temperaturebased on the use of a pure rotational Raman spectrum(PRRS) of N2 and 02 molecules. The method wassuggested by Cooney in 1972,1 and during the last dec-ade other authors have also contributed to its devel-opment.2-4 It should be noted, however, that somesevere technical difficulties hampered practical reali-zation of the method. It is for this reason that only afew papers5-8 presented experimental results demon-strating the feasibility of the method. The main dif-ficulties are adequate suppression of the spurious signal

V. M. Mitev is with Bulgarian Academy of Sciences, Institute forElectronics, Sofia, Bulgaria; the other authors are with U.S.S.R.Academy of Sciences, Siberian Branch, Institute of AtmosphericOptics, Tomsk, 634055, U.S.S.R.

Received 6 January 1983.0003-6935/83/192984-07$01.00/0.© 1983 Optical Society of America.

due to Rayleigh and Mie scattering, correct interpre-tation of the measurement data,and maintenance of thelong-term stability of lidar recording system parame-ters.

In recent years a detailed investigation of the methodand its lidar performance has been carried out at theInstitute of Atmospheric Optics, Siberian Branch,U.S.S.R. Academy of Sciences, and at the Institute forElectronics of the Bulgarian Academy of Sciences. Thispaper summarizes the results obtained in both insti-tutes.

11. Physical Grounding for the Method

Physically, the possibility of measuring air temper-ature using PRRS of N2 and 02 molecules is obvious,since the intensity of an individual pure rotationalRaman line depends, due to Boltzmann distribution,on temperature.9 For linear molecules the followingexpression can be written:

I(J,T) = IoiJgi BN (2J + 1)S(J) exp J(J + 1)] (1)

where J is the rotational quantum number, T is thetemperature, Io is the intensity of incident radiation offrequency vo (cm-'), B is the rotational constant of amolecule, and g is the statistical weight due to nucleusspin. The product of the S(J) function and the de-generacy factor has the form

(2J + 1)S(J) =(J + 1)(J + 2)

for the Stokes branch, and

(2J + 1)S(J) = (J-1)(2J - 1)

2984 APPLIED OPTICS / Vol. 22, No. 19 / 1 October 1983

4 12 60 108 156

0 4 8 12 16 - J

Envelopes of N2 pure rotational Raman spectrum at threetemperatures.

for the anti-Stokes branch. Here the number J is thequantum number of the initial state of a molecule in thetransitions obeying the selection rule AJ = =f2.

Figure 1 illustrates the changes of the N2 PRRS en-velope with temperature. As seen from this figure andEq. (1), one can construct a number of techniques formeasuring air temperature based on various combina-tions of the individual line intensities. Omitting thedetailed analysis of all such possibilities here, let usconsider the temperature dependence of the intensityratio. For two individual lines such a ratio as a functionof temperature is expressed by a simple analytical for-mula [see Eq. (1)]:

R(T) I(ji) Ty+A (2)

where ae = [Erot(J2) - Eot(Ji)]/k and: = lnS(Jl) -lnS(J2).

It should be noted however that the isolation of in-dividual lines of PRRS would be inevitably followed bysignificant losses of scattered radiation received fromthe atmosphere in a lidar spectral device.

These facts make it necessary to analyze the tech-nique based on the use of two portions of PRRS formeasuring air temperature. In the general case ofportions involving several oxygen and nitrogen purerotational Raman lines the intensity ratio Ry, is writtenas

{ E [IN 2(JN2,T) + IO2 (Jo2,T)I}1N2,J02 1

I~~~~~~~~~~~~~ I

[IN 2 (JN2,T) + Io 2 (Jo 2,T)lj{1N2,Jo2 1where IN2,o2(JN2,o2 ,T) is the intensity of an individualnitrogen or oxygen Raman line. Indices 1 and 2 showthat summations in the numerator and denominatorrefer to different portions of PRRS. It is obvious thatEq. (3) does not allow the temperature dependenceR2(T) to be written in a simple analytical form. In thiscase the experimental performance of the methodshould necessarily require the temperature calibrationof R2(T) over the whole temperature range desired.

But taking Eq. (2) into account and assuming that theoverall intensity of a PRRS portion can be represented

by the intensity of an individual line corresponding toa transition from a level with energy equal to the valueof energy averaged in any way over the group of levels,one can approximate the function Ry,(T) by the sameexponential function as in Eq. (2), i.e.,

(4)

Such an approach has been discussed in Refs. 9 and 10.Constant values ac2 and 02; are represented in this casein terms of the mean rotational energies Eroti and Erot2and mean logarithms [lnS(J)]jnS(J)] 2 of corre-sponding PRRS portions. As shown in Refs. 9 and 10,the approximation (4) is in good agreement with theresults of direct computations made using Eq. (3) bysubstituting into it the line intensities described by Eq.(1).

I1. Spectral Separation of Parasitic BackgroundRadiation due to Aerosol Scattering and PRRSRadiation

It can easily be shown that in the atmospheric con-ditions characterized by the value of meteorologicalvisual range SM • 10 km, the volume backscatteringcoefficient of the aerosol atmosphere exceeds that forthe strongest pure rotational Raman line of N2 (J = 6)by 4 orders of magnitude. In view of this fact oneshould use' in the pure rotational Raman lidar a spectraldevice which can provide a 106, or greater, suppressionof the spurious signal due to aerosol scattering, to re-strict its contribution to the intensities of PRRS por-tions.

The difficulties in solving this technical problem aremainly caused by the fact that PRRS lines of N2 and 02are very close to the unshifted scattering line, see, e.g.,Fig. 1, but there are several solutions, e.g., Ref. 3 dis-cusses the possibility of suppressing the aerosol line witha selectively absorbing filter. In Ref. 5 the aerosol linebackground is monitored with an additional PMT andis then subtracted from the intensities of lidar returnsat pure rotational Raman frequencies. Obviously atechnique is preferable which allows efficient suppres-sion of the spurious signal from the unshifted line ofaerosol scattering to a negligible level.

Here we discuss the technique suggested in Refs. 11and 12. Based on the use of a double monochromatorwith two intermediate slits, this application is illus-trated schematically in Fig. 2. Curve 1 in Fig. 2(a)represents the distribution of parasitic background froma monochromatic spectral line of unshifted scatteringin the exit plane of the first monochromator. Curve 2shows the envelope of PRRS branches plus back-ground.

According to this scheme the light flux entering twointermediate slits [see Fig. 2(b)] contains radiation fromthe wavelength X0 of the unshifted line caused byaerosol scattering and radiation with the wavelengthsO + AX1,2 of PRRS intervals of N2 and 02- Conse-

quently, after the second monochromator run four im-ages of the intermediate slits are formed at the exit ofthe double monochromator, in two of which the radia-

1 October 1983 / Vol. 22, No. 19 / APPLIED OPTICS 2985

(4

0

12

/ 1\ 1 2

I I ilm 1

1L

Fig. 1.

Rv4T)

Ry,(T) n_� exr ay 0, -I� T ,

. 1I

i

( )10-6

I I..

(c)

(1,) ~~~X ( .) X ( )Fig. 2. (a) Schematic presentation of spectrum of backscatteredradiation in the vicinity of aerosol scattering line after one mono-chromatization. (b) Position of intermediate slits. (c) Positions ofimages of the intermediate slits at the exit of a double

monochromator.

tion with X = X0 is concentrated, while the other twoimages are formed by radiation with = o + AX, andX2 = XO + AX2 [see Fig. 2(c)].

As seen from this figure one can easily choose thepositions and widths of the two intermediate slits so thatthe images at X0, XI, and 2 do not overlap. Taking intoaccount the fact that ordinarily' 3 single-gratingmonochromators have a background level of -10-4 ofthe monochromatic line intensity, one can assume thatdouble monochromatization will result in a 107-108suppression of the aerosol scattering line.

As the measurements made with a Littrow double-grating monochromator have shown, the backgroundintensity sharply decreases with the increase of spectraldistance from the center of the monochromatic spectralline. The results of such measurements for a 514.5-nmargon-ion laser line are presented in Fig. 3. As seenfrom this figure the stray-light intensity is of the orderof 10-8 at a spectral distance -20 A from the mono-chromatic line. This is just the distance where themaxima of PRRS branches of N2 and 02 are located.Thus, the above results show that the use of a double-grating monochromator provides the possibility ofisolating the portions of PRRS with a negligible stray-light contribution from an aerosol scattering line.

IV. Results of Laboratory Tests of the MethodLaboratory tests of the method were carried out at the

Remote Sensing Division of the Institute for Electronicsof the Bulgarian Academy of Sciences.' 4

A block diagram of the laboratory experiments isdepicted in Fig. 4. A Spectra-Physics 165-08 argon-ionlaser was used in the experiments, and a Spectra-Physics 344 intracavity Q-switcher generated 20-nsecpulses at a 4-MHz pulse repetition rate. Mean powerof output radiation at X = 514.5 nm was 0.3 W. The gassample cell allowed the investigations to be carried outat the atmospheric pressure. Long-term stability oftemperature inside the cell was better than 0.4 K/h.The nitrogen and oxygen used in the experiments were

10-8

F

= .NU( )N AO)

'S

*

10-9 , I I I I I5 10 15 20 AX,A

Fig. 3. Spectral behavior of the stray-light intensity at the exit ofthe double-grating monochromator. Light source is the argon-ion

laser ( = 514.5 nm).

U2

M1

Fig. 4. Block diagram of the laboratory experiments.

99.9% pure. The gas cell could be filled with pureN2,02, or with ambient air.

The combination of lenses L1,L2,L3 and mirrors Mland M 2 shown in Fig. 4 forms a conventional opticalscheme used in Raman scattering experiments for il-luminating a gas cell and collecting scattered light. Theisolation of two portions of PRRS of N2 and 02 wasperformed using the Littrow double-grating mono-chromator with two intermediate slits. To illustratethe action of the double monochromator we simulta-neously illuminated its entrance slit by thermal radia-tion and argon-ion laser radiation. The continuousspectrum of thermal source mixed with monochromaticlaser radiation at = 514.5 nm recorded at the exit ofthe double monochromator is shown in Fig. 5. Twonarrow central peaks in this figure represent thestray-light lines of wavelength X = 514.5 nm, while thebroader peaks to left and right are the spectral intervalsof the continuous spectrum of the thermal source. Themonochromatic laser line is focused in this case onto anopaque screen between the two intermediate slits.Widths of the continuous spectrum intervals were 28± 2 cm-1 and 31 2 cm-' for right and left, respec-tively. The width of the entrance slit was 150 m.

The recording system used in the experiments in-volved EMI-9789-QA PMTs and an EG&G PARC1112photon counting unit. The PMT photocathode cooling


10-7

tos

104

011O0

AR

0

on

i

103

Xeit

Fig. 5. View of continuous spectrum mixed with the 514.5-nmmonochromatic line at the exit plane of the double monochromator

having two intermediate slits.

R(T)

1.90

1.80

1.70

1.60

1.50

-. 't-,\'blo> 2 10. , ,O*_

2a.

air

& Qo

'01R ~ ~ °

303 313 323 T

Fig. 6. Temperature behavior of the R(T) function measured in pureN2 , 02, and air.

was used in our experiments to reduce the thermalphotopulse count rate along with the synchronouspulsed gating. The average count rate of the noisepulses of the system did not exceed 1 or 2 Hz.

Using the above experimental setup we investigatedthe temperature dependence of the intensity ratio fortwo PRRS portions of pure N2,02, and of ambient airwithin the 303-323 K temperature range.

The results of such measurements are presented inFig. 6. It should be noted that the data refer to the ra-tios of the light flux intensities since the data handlingprocedure used allowed the sensitivities of photocath-odes to be excluded. The gas temperature inside thecell was measured with a mercury thermometer. Theaccuracy of the thermometer data was '0.1C.

Dashed curves in Fig. 6 represent the approximatingfunction

Table 1. Parameters of the Approximating Formula Calculated fromExperimental Data Presented in Fig. 6

Gas species a[K] 0

N2 418.924 -0.703402 732.667 -1.9041Air 477.172 -0.9521

RZ(T)_ exp t +(2lTiwhose parameters a, and , were found from the ex-perimental data of Fig. 6 using the least-squares fittechnique. These calculations used the data obtainedduring a 600-sec measuring time interval (circles in Fig.6). The values of a, and /2; thus obtained are pre-sented in Table I.

The dots in Fig. 6 represent the data obtained in airfor a 120-sec measuring time interval. If the dashedlines shown in the figure are assumed to be calibrationcurves, the rms error of temperature measurements inair for a 120-sec time interval does not exceed -0.74 K,as seen from Fig. 6.

These results of the laboratory tests of the pure ro-tational Raman scattering technique for measuring gastemperature clearly demonstrate its feasibility as wellas the possibility of using the approximation formula(4) to describe R>(T). The usefulness of the doublemonochromator for the isolation of air PRRS portionsis also proved experimentally.

V. Results of Atmospheric Experiments

Atmospheric experiments to study the feasibility ofthe method were carried out in two stages. First wemeasured the temporal behavior of temperature of afixed atmospheric volume using the pure rotationalRaman lidar technique and a contact thermoresistorthermometer. At the second stage the data of lidarmeasurements of atmospheric temperature profileswere compared with the balloon-borne measurementdata.

The arrangement of the experiment for measuringtemporal behavior of temperature of a fixed atmo-spheric volume is shown schematically in Fig. 7. Thecontact sensor of the thermometer used for temperaturecontrol measurements allowed temperature averagingto be made over an atmospheric volume of the samelength as in lidar measurements. Spatial separationbetween the lidar sounding path and the distributedcontact sensor of the thermometer does not exceed

Fig. 7. Arrangement of the atmospheric experiment on measuringthe temporal behavior of temperature of a fixed atmospheric

volume.


-~~~~I :X

.^ @ w

* _4- : :-. ...... * .:

102

Table II. Basic Parameters of the Pure Rotational Raman Lidar

Transmitter:Copper-vapor laser:WavelengthMean powerPulse durationPulse repetition rateAngular width of the beam

Receiver:Two lens objectiveswith a diameterand D/fDouble-grating Czerny-Turner monochromatorReciprocal linear dispersionOverall transmission ofthe optical receiverData digital acquisition system:Photon counting system withthe maximum count rate

several meters. A block diagram of the lidar facility isalso shown in Fig. 7.

It should be noted that the atmospheric studies werecarried out in Tomsk, U.S.S.R.; the lidar setup used aCzerny-Turner double-grating monochromator and acopper-vapor laser as the transmitter. Basic parame-ters of the lidar are presented in Table II.

Estimations of lidar return intensities have beenmade for the lidar parameters in Table II, using the lidarequation written in terms of a number of photocountsrecorded at a PMT anode:

n(r) = T ° Sry(r)am(r) ArT2(r), (5)hvRam r2

where n(r) is the number of photopulses at the PMTanode produced by photons scattered at the distancer by a scattering volume of the length Ar; q is the pho-tosurface quantum efficiency; is the overall trans-mission of the receiving optics; Wo is the laser pulseenergy; Sr is the receiving area; y(r) is the geometricalfunction of the receiver; "m(r) is the Raman back-scattering coefficient; T(r) is the atmospheric trans-mission; and ham is the energy of a scatteredphoton.

The ratio of two Raman lidar returns measured at twoportions of PRRS of N2 and 02 during the same timeinterval Atm can be written as

R[T(r)] = (r) -T(r)Atm (6)N2 (r) nT2 (r)Atm

where n, 2(r) are the mean numbers of photocounts persecond produced by the photons arriving at the photo-cathodes from the scattering volume of the atmosphereat a distance r from the lidar.

Assuming the validity of Poisson statistics for anumber of photocounts in both channels, one canreadily assess the value of relative error of R[T(r)]measurements according to the formula:

JR 1 + R(r)6Rt =-~F\// X(7)

?= ~Nl

510.6 nm5-10 W10 nsec6.7 kHz0.3 mrad

(with unstable resonator)

0.3m1/3

10 A/mm0.01

100 MHz

time, h

-7

-8

-9

T°C

R

1.50

1.48

1.46

(a)

. , (b)

: --t'_ __J1 time, h

Fig. 8. Experimental results illustrating the stability of the lidarrecording system: (a) temporal behavior of the atmospheric tem-perature; (b) values of the PRRS intensity ratio measured with the

lidar.

where R is the standard deviation of random value R (r)from its mean value R(r).

Then taking into account the desired accuracy oftemperature measurements one can estimate the re-quired numbers N1 and N2 of photocounts to be storedusing (7) and provided that the ratio temperature sen-sitivity dR/dT is known. It should be noted, however,that except for statistical errors, the errors due to short-and long-term instabilities of the photocathode ef-ficiencies can also contribute to the total measurementerrors. This, in turn, requires additional conditions tobe imposed on the short-term and long-term stabilitiesof the ratio of the PMTs' quantum efficiencies. It isdesirable, of course, that the instability of this ratio bemuch lower than the statistical errors. In practice thisrequirement is met by the proper selection of the PMTpair.

This is illustrated, for example, with the data pre-sented in Fig. 8. Figure 8(a) shows the temporal be-havior of the temperature of a fixed atmospheric volumerecorded with the contact thermometer. The values ofthe intensity ratio for two portions of PRRS of N2 and02 measured with the lidar at the same time interval are


,

,

1

presented in Fig. 8(b). Since, as seen from Fig. 8(a), thetemperature is practically constant within this interval,the intensity ratio should also keep a constant valuewithin the limits of measurement error. Dashed linesin Fig. 8(b) show the confidence-interval corridor of ±2standard deviations calculated using the experimentaldata according to (7). As seen from Fig. 8 the statisticalerror in this case is the main source of measurementinaccuracy.

Thus it can be expected that all the variations of R (T)exceeding R8t are caused by changes of atmospherictemperature. Obviously for a narrow interval of tem-perature difference AT << T as, e.g., atmospherictemperature profiles up to 1-km height, the functionR(T) can be written as

R[T(t)] - R[T(to)] + d AT(t)i.dT I

TIC U) I-

1 2 3 time, h

Fig. 9. (a) Comparison, between lidar temperature data (dots)and a contact thermometer (solid line). (b) The same as in (a).

H, X

1.0

0.5

1.0

o.5

2

April 16, 19E

3:30 LT

H, km

I 4 8 12 TIC

12

4: 00 LT

Fig. 10. Profiles of the atmospheric temperature obtained with thelidar (-.-) and radiosonde (solid lines). The lengths of bars in thelidar profiles denote the value of standard deviations calculated as-suming the Poisson statistics to be the only source of errors in mea-

surements of lidar returns.

T(h) = Tc 0nt(ho) + ATiid(hi), (10)

where hi is the height of the ith pulse gate; Tcont(ho) isthe temperature measured with a contact thermometerat the lowest atmospheric layer, and ATlid(hi) is de-termined from lidar data on R (hi) using (8) in which theargument t is substituted by hi. It should be noted thatthe value of dR/dT entering Eq. (8) can be found be-forehand in the experiments monitoring the temporalbehavior of temperature of a fixed atmospheric volume,or during the altitude profile experiments using thecontact thermometer data.

-19-20

-21

TIC

-10

-15

(8)

Using Eq. (8) one can easily obtain AT(t) from lidarmeasurements provided that dR/dT is known and isconstant within the temperature-change region AT <<T. To obtain the absolute temperature values we usedthe data on temperature of a fixed atmospheric volumemeasured at the moment to with a contact thermometerTcont(to). The atmospheric temperature is then

T(t) = T:ont(to) + ATIid(t)- (9)

The temporal behavior of a fixed atmospheric volumetemperature recorded with the lidar is then comparedwith that obtained using a contact thermometer. Thedata presented in Figs. 9(a) and (b) illustrate the resultsof such a comparison. Since the time required formaking one lidar measurement was -20 sec we used amoving average of the lidar data over ten measurementsto equalize time constants of the lidar and thermometer.On average the results of lidar and thermometer mea-surements agree well enough. The most significantdiscrepancies between them are observed in the regionsof rapid temperature changes where the differencesexceed the confidence interval by a factor of 2 or more.Experimentally assessed rms deviation of lidar tem-perature measurements is - ±0.8 K. The accuracy ofthe contact temperature measurements is within ±0.1K. Such disagreement between the two methods maybe due to the fact that the distributed contact sensor ofthe digital thermometer and the lidar sounding path donot quite coincide.

VI. Temperature Profile Measurements Using theLidar

The experiments on lidar temperature profile mea-surements were carried out using the same lidar (see Fig.7) except for the photon counting system. The systemused in these experiments allowed the data acquisitionto be made simultaneously at 32 range gates each 30 mlong beginning from a 30-m distance. The maximumcount rate of the system is 100 MHz. Since the tem-perature changes in the ground atmospheric layer upto -1 km are within the 10-20° range, by analogy withthe above one can write the following expression for thetemperature profile measured with a lidar:


3 time, h

The results of lidar measurements of atmospherictemperature are presented in Fig. 10. Solid lines in thefigure indicate the balloon-borne temperature mea-surement data, while the horizontal bars represent thelidar temperature measurement data. The lengths ofthe bars denote the rms errors of lidar temperaturemeasurements calculated assuming statistical uncer-tainty to be the only source of error. The launchingsof the balloon were made from a platform near thebuilding where the lidar was installed. The time re-quired for measuring one profile was -20 min in theseexperiments, this time has now been shortened to-10min.

The data presented in Fig. 10 show quite goodagreement between the data of both methods.

VII. Concluding Remarks

Results of the experimental study discussed aboveclearly demonstrate the usefulness of the method forstudying the formation of the atmospheric temperatureinversion layers. The possibility of measuring tem-perature profiles in the ground atmospheric layer usingthe same lidar technique can be of some importance instudies of industrial smog formation in temperatureinversion conditions. Many other applications of thetemperature Raman lidar technique to atmosphericphysics and optics can also be mentioned. In thisconnection we should like to note that the experimentallidar unit described in this paper is not sophisticated,by which we mean that its parameters (such as, e.g.,transmission of the optical receiver and spectrometer)can be drastically improved. The anticipated effect ofthis improvement is a threefold or fourfold increase ofthe sensing range. On the other hand, there are certainpossibilities of making the pure rotational Raman lidartechnique an efficient instrument for measuring thecharacteristics of atmospheric aerosols. A combinationof such pure rotational Raman lidar technique possi-bilities with those of vibration Raman lidar methodsmakes such a combined Raman lidar facility a uniquetool for atmospheric research.

References1. J. A. Cooney, J. Appl. Meteorol. 11, 108 (1972).2. J. A. Salzman and T. Coney, "Measurements of Atmospheric

Temperature by Raman Lidar," Fifth Conference on Laser RadarStudies of the Atmosphere, Williamsburg, Va., 4-6 June 1973,Conference Abstracts, pp. 71 and 72.

3. T. Kobayasi, H. Shimizu, and H. Inaba, "Laser Radar Techniquefor Remote Measurement of Atmospheric Temperature," SixthConference on Laser Atmospheric Studies, Sendai, Japan, 3-6Sept. 1974, Conference Abstracts, pp. 49 and 50.

4. Yu. F. Arshinov and S. A. Danichkin, "Rotational Raman Spectraof Nitrogen and Oxygen and Use of Them for Measuring AirTemperature," in Optical Waves Propagation Through the At-mosphere, V. E. Zuev, Ed. (Nauka, Novosibirsk, 1975), pp.169-173.

5. A. Cohen, J. A. Cooney, and K. N. Geller, Appl. Opt. 15, 2896(1976).

6. R. Gill, K. Geller, J. Farina, J. Cooney, and A. Cohen, J. Appl.Meteorol. 8, 225 (1979).

7. Yu. F. Arshinov and S. M. Bobrovnikov, "Lidar Measurementsof Temperature Dependence of the Intensity Ratio for TwoPortions of N2 and 02 PRRS," Sixth All- Union Symposium onLidar and Acoustic Sensing of the Atmosphere, Tomsk (1980),Abstracts, pp. 242-245.

8. Yu. F. Arshinov and S. M. Bobrovnikov, Izv. Akad. Nauk SSSRFiz. Atmos. Okeana 19, 431 (1983).

9. G. Placzek, in Handbuch derRadiologie, Vol. 6, Part 2, E. Markx,Ed. (Akademischer Verlag, Leipzig, 1934).

10. Yu. F. Arshinov, S. M. Bobrovnikov, V. E. Zuev, and I. V. Samo-khvalov, "Atmospheric Temperature Measurements Using PureRotational Raman Spectrum and Lidar Calibration," Ninth In-ternational Conference on Laser Radar Studies of the Atmo-sphere, Munich, 3-5 July 1979, Conference Abstracts, pp. 21-25.

11. Yu. F. Arshinov, S. M. Bobrovnikov, and S. V. Sapozhnikov, Sov.J. Appl. Spectrosc. 32, 725 (1980).

12. Yu. F. Arshinov and S. M. Bobrovnikov, "Spectroscopic Sepa-ration of the Pure Rotational Raman Spectra and BackgroundRadiation due to Rayleigh and Mie Scattering," in Lidar Facili-ties and Techniques for Remote Sensing of the Atmosphere, V.E. Zuev, Ed. (Nauka, Novosibirsk, 1980), pp. 47-53.

13. A. N. Zaidel, G. V. Ostrovskaya, and Ya. N. Ostrovskii, Spectro-scopic Devices and Their Use in Practice (Nauka, Moscow, 1972),p. 375.

14. V. M. Mitev, V. B. Simeonov, and T. V. Grigorov, Sov. J. Appl.Spectrosc. 38, 338 (1983).

The authors greatly appreciate the assistance of V.V. Burkov, A. I. Nadejev, K. D. Shelevoy, and I. M.Shevchenko from the lidar systems group at the Insti-tute of Atmospheric Optics, who made the lidar datadigital acquisition system including the software for theon-line computer processing of the data. The authorsare also grateful to their colleagues V. B. Simeonov andI. V. Grigorov from the Institute for Electronics of theBulgarian Academy of Sciences for their help in thelaboratory experiments described in this paper. Andfinally we should like to underline that only the use ofthe copper-vapor laser manufactured at Special Con-structing Bureau Optika, Siberian Branch, U.S.S.R.Academy of Sciences, made it possible to carry out allthe atmospheric experiments discussed.


atmospheric temperature measurements using a pure rotational raman lidar

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