An ozone lidar system was installed at the National Institute for Environmental Studies (NIES) in Tsukuba, Japan in March 1988 and has been measuring vertical profiles of ozone (15 - 45 km) since September 1988. The lidar system consists of a XeCl (308 nm) excimer laser, its deuterium Raman shifter (339 nm), a XeF excimer laser (351 nm), a 2 m telescope, a receiving system and a data processing system. The precision of the derived ozone concentration is about 10 percent of an altitude of 40 km for a 4 hr observation. Temperature profiles (30 - 80 km) are also obtained from the Rayleigh scattering signals at 351 nm. Approximate 50 ozone measurements are carried out in a year and variations of vertical profiles of ozone such as seasonal variations and shorter-term variations are observed. Systematic errors due to aerosols had been negligible until the arrival of the stratospheric aerosols injected by the eruption of Mt. Pinatubo. Effects of the volcanic aerosols on ozone measurements depend on the differences between wavelengths used as the on- and off-resonance

Hayashida, S.

Matsui, I.

Minato, A.

Nakane, H.

Sasano, Y.

Sugimoto, N.

English

NASA Technical Reports Server

N95-11109
LIDAR OBSERVATION OF OZONE OVER TSUKUBA (36°N, 140°E)
H. Nakane, S. Hayashida, I. Matsui, N. Sugimoto,
A. Minato and Y. Sasano
The National Institute for Environmental Studies
Onogawa, Tsukuba, Ibaraki 305 Japan
ABSTRACT
An ozone lidar system was installed at the National
Institute for Environmental Studies (NIES) in Tsukuba, Japan
in March 1988 and has been measuring vertical profiles of
ozone (15 - 45 km) since September 1988. The lidar system
consists of a XeC1 (308 nm) excimer laser, its deuterium
Raman shifter (339 nm), a XeF excimer laser (351 nm), a 2 m
telescope, a receiving system and a data processing system.
The precision of the derived ozone concentration is about 10%
at an altitude of 40 km for a 4 hr observation. Temperature
profiles (30 - 80 km) are also obtained from the Rayleigh
scattering signals at 351 nm. Approximate 50 ozone
measurements are carried out in a year and variations of
vertical profiles of ozone such as seasonal variations and
shorter-term variations are observed. Systematic errors due to
aerosols had been negligible until the arrival of the
stratospheric aerosols injected by the eruption of Mt.
Pinatubo. Effects of the volcanic aerosols on ozone
measurements depend on the differences between wavelengths
used as the on- and off- resonance.
1. INTRODUCTION
Recently, total ozone in both hemispheres at middle
and high latitudes have been decreasing significantly. These
decreases in the total ozone are especially large in late winter
and early spring at those latitudes, and there are longitudinal
inhomogeneities. Therefore, long-term measurements of
ozone and related species and parameters are important;
especially information on variations of the vertical profiles is
valuable. The Network for the Detection for Stratospheric
Change (NDSC) and related research activities will meet these
requirements.
Lidars (laser radars) are expected to play an important
role in NDSC because they can measure vertical profiles of
ozone, temperature and aerosols with high accuracy and
vertical resolution.
We, at the National Institute for the Environmental
Studies (NIES), installed an ozone lidar system in March
1988 (Sugimoto et al., 1989; Sasano et al., 1989) and have
obtained ozone profiles since September 1988. After
examining the distortions of the signals received and sources
of systematic errors, we archive the ozone profiles.
Comparisons with the data obtained by the SAGE II satellite
sensor show that there are in good agreement with our lidar
data and the SAGE II data (Nakane et al., 1992). As we use a
high power XeF excimer laser as the source of the off-
resonance radiation, we can also measure temperature profiles
utilizing Rayleigh scattering from the stratosphere and
mesosphere. We carried out an intensive observation of the
temperature profiles during the DYANA (DYnamicsAdapted
Network for the Atmosphere) campaign from January 1990
to March 1990 (Nakane et al., 1992).
In this paper, we will describe the ozone lidar system,
its performance and show the results of the first 2.5 years
data. Then, we will mention the effects of the stratospheric
aerosols injected by the eruption of Mt. Pinatubo.
2. NIES OZONE LIDAR SYSTEM
The NIES ozone lidar system consists of two
subsystems; a stratospheric subsystem and a tropospheric
subsystem. As we are interested in the stratospheric system
here, we will describe it briefly. Table 1 is the specifications
of the lidar system. We use an injection-locked XeCI excimer
laser (Lambda Physik EMG160TMSC) as the light source for
the on-resonant wavelength (308 nm) and the same type
injection-locked XeF excimer laser for off-resonant
wavelength (351 nm). A Raman shifter with deuterium partly
converts the XeCI laser radiation to 339 nm radiation whose
intensity depends on the pressure of the gas beeing adjusted to
give comparable signal intensity to that of 308 nm around 40
km in altitude. The intensity of the signals at 351 nm is made
much larger than those of the others in the upper stratosphere
because temperature profiles in the upper stratosphere and
mesosphere are also important for studies on the dynamics
related to ozone variations.
A convex lens with a 60-cm focal length and a flat
window are positioned at the entrance and exit of the Raman
shifter, respectively. The diverging output beam from the
Raman shifter is collimated using an off-axis parabolic mirror
with a 200-cm focal length. A concave lens and an off-axis
parabolic mirror are used as a beam expander for the beam
from the XeF laser. Thus, the laser beams are expanded 3.3
times. The directions of the beams transmitted are the same
for 308 nm and 339 nm radiation and that of the 351 nm
radiation can be independently adjusted. As light absorption
by ozone both at 339 nm and 351 nm is negligible, the
signals received for these wavelengths are useful to check the
alignment of the beams transmitted and potential effects of the
aerosols on the lidar measurements of ozone.
The backscattered light is collected by a telescope with
a 2-m diameter, and then, focused on the chopper for cutting
the light scattered at a low altitude. Though the lenses placed
just before and after the chopper for focusing and collimation
had been single lenses before June 1990, they were replaced
by achromatic lenses. This improvement made the alignment
of the beams transmitted much easier. Dichroic mirrors,
interference filters and color glass filters are used for
wavelength separation. Monochromated light is then divided
863
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Table 1. Specifications of the NIES ozone lidar system
Transminet
Laser
Waveteagths
Oulpet energy
Pulse repetition rue
Ikam divetgmce
Receiver
Telescope d_unet_
Field of view
Filterbandwidth
Total optical efficiency
De_cmr
PboWmuRipliers
Gate width
P_amplifi_s
Signal processor
Photon counters
Damlm_ce_x
XeF excimer laser XeCI excimcr laser with deuterium Raman shifter
351 nm 308 nm 339 nm
75 mJ 140 nO adjustable
250 Hz (maximum)
94 Hz (typicg)
0.07 mrad 0.07 mrad
2m
0.6 nuad (typical)
2 nm 2 nm 2 nm
<20% < 10% <20%
750 Hz
Hamamatsu R3235 (6 channels)
1 - 200 tts
100 MHz
1 gs gate time, 2048 segments (6 channels)
PDP 11/53
into two by beam splitters (ratio: 95 to 5%) and is focused on
two photomultipliers for each wavelength. The signals from
the two photomultipliers with preamplifiers, we call those
channels high sensitivity (HS) and low sensitivity (LS)
channels, are sent to the discriminators, photon counters and
then the computers. The photomultiplicrs arc replaced with
those with a low signal induced noise (Hamamatsu R3235) in
January 1990. Data acquisition and control of the whole
system are carried out using a minicomputer (I:tDP 11/53).
The tropospheric subsystem has KrF excimer laser
(Lambda Physik EMG 201MSC) and Raman shiftcrs with
hydrogen and deuterium which generate 277,292 and 313 nm
radiation. The signal with a wavelength of 313 nm can be
used for the stratospheric ozone measurements because it has
a good signal-to-noise ratio up to 30 km. This wavelength is
quite useful in the presence of the volcanic aerosols.
3. DATA PROCESSING
The conventional DIAL equation is used for
calculation of the ozone concentration:
N(z)= 2_ 6_(T) 10of_T)l [ ddz ,[-lnn°n(z)t + B +Enof (z)' I
B = d lnl3on(z)
dz 13o (Z)
E = -2 {oo,_z) - O,oft(z)} (1)
where n(z) is the photoelectron number, _(z) the backscatter-
ing coefficient due to aerosols and air molecules at the altitude
of z, ct(z) the extinction coefficient due to aerosols and air
molecules, o (T) the absorption crosssection of ozone, T the
temperature and N(z) the number density of ozone molecules.
864
When no aerosol is assumed in the range of interest, terms, B
and E, are estimated from the air molecule profile which is
given by meteorological measurements using upper-air sondes
or by .atmospheric models.
Though we do not describe the details of the data
processing here, we would like to mention the method for
differentiation in Eq. (1). The differentiation is carded out by
applying a kind of numerical filter which gives the third order
polynomial fitting and differentiation simultaneously. At first
we applied the second order polynomial fitting, however, it
was found to give systematic deviations in the ozone
concentration in the upper stratosphere when we assume
realistic vertical resolution.
Temperature profiles are calculated with the algorithm
proposed by Chanin and Hauchecorn (1984).
4. EXAMPLES OF OZONE AND TEMPERATURE
PROFILES
As three wavelengths are used for measurements of
the stratospheric ozone profiles with the NIES ozone lidar,
ozone profiles can be obtained from the two pairs of received
signals; 308 nm - 351 nm (A-) and 308 nm - 339 nm (B-)
signal pairs. Figure 1 shows an example of the ozone profiles
obtained from A- and B- signal pairs. The agreement is very
good and it is difficult to distinguish the two profiles. This
means first that the effects of the stratospheric aerosols on the
ozone lidar measurements are negligible within the error bars
in this case. This means second that the alignments of the laser
beam transmitted are probably good because laser beams with
a wavelength of 339 nm and 351 nm are independently
aligned. This is a typical example for ozone profiles measured
under good atmospheric conditions before the arrival of the
stratospheric aerosols due to the eruption of Mt. Pinatubo.
Comparison of ozone profiles obtained with the NIES ozone
lidar and SAGE II showed good agreement (Nakane et al.,
1992). Therefore, data obtained with the NIES ozone lidar
under good conditions have sufficient accuracy.
E
v
"O
m
4O
30
2O
1017
III
IIII
IIII
IIII
IIII
IIII
I111
IIII
IIII
IIII
IIII
III1,
III1!
III1'
IIII
IIII
IIII
IIII
IIII
IIII
I IIII
IIIII
IIIII
I IIII
I III1
II
February 20, 1991
-- 308-351 nm
-- 308- 339 nm
IIII
IIII
IIII
!III
IIII
IIIii
IIII
I 111
lllll
t111 !
IIII
I III
IIII
IIII
I
I
I
I
I
t
I
lOle 10,9 102o
number density of ozone (molecules/m3)
Fig. 1. Ozone profiles with random errors observed with the
NIES ozone lidar using two wavelength pairs.
E
_Q
O
8
o
i,n
E
r,
1.0
0.5
1.5
1.0
3.5
3.0
2.5
2.0
i i
5.0
4.0
3.0
6.0
50
4.0
3.0
2.0
, 40 km
o g. °,_*
o o o o o
_5 km
oo_ . °
° o ° )_; :
° _o o o _ °o
i , _ o i o
30 km
o: °
o o o o 'i_
o ot ° o
o o_ ° Oo --_°
o 00 8 o
o
o 25 km
o o
° ° _ -_l_"_'_"x_°o Oo o o o°
o
a , i i i
20 km
o
oo °o o
8
o o°
o
o,o_ o
o °IPo _o ° °°
o
* 9
i , i
SNJ MMJ SNJ MMJ SNJ MMJ
1988 ! 1989 I 1990 I 1991
Fig. 2. Ozone concentration observed with the NIES ozone
lidar for 2.5 years at 20 - 40 km.
Figure 2 shows the results of the lidar observation for
2.5 years. Different seasonal variations are shown at different
altitudes, ozone concentration is high in spring and low in
summer and autumn at 20 kin; and high in summer and low in
winter at 30 km and 35 km. The former is the typical seasonal
variation controlled by dynamical processes and the latter by
photochemical processes.
Figure 3 shows temperature profiles observed during
DYANA campaign (Nakane et al., 1992). Rapid increase and
decrease in the temperature can be seen around 55 and 70 km
in attitude, respectively.
5. EFFECTS OF VOLCANIC AEROSOLS ON OZONE
LIDAR MEASUREMENTS
In the presence of heavy volcanic aerosols like those
from Mt. Pinatubo, the wavelength dependence of the
extinction and backscattering coefficient of the aerosols may
cause systematic errors. The behaviors of the systematic
errors were simulated by Sasano et al. (1989) and also by
Browel et al. (1985). The systematic errors due to the
aerosol backscattering, B in Eq.(1), usually give the negative
(positive) error above (below) the peak of the aerosol layer.
The systematic errors due to aerosol extinction, E in Eq.(1), is
usually small and gives positive errors. These systematic
errors should be larger for the larger wavelength differencies
between the on- and off-resonant wavelengths.
Figure 4(a) shows the ozone profiles obtained from
the different wavelength pairs carried out from 10 UT to 14
UT and Fig. 4 (b) is an aerosol profile measured by the large-
scale aerosol lidar in NIES on the same day. There is an
ozone profile obtained from an additional wavelength pair
(308 nm - 313 nm pair; C-pair). An ozone profile was
obtained from the ozonesonde observation carried out by
NIES and Tateno Aerological Observatory (TAO) at 6 UT at
TAO about 500 m from NIES. As there is a time difference of
about 6 hr between the lidar and sonde measurements, the
ozone profiles may not behave the same especially in the
lower stratosphere. The three ozone profiles with different
wavelength pairs agree well in the altitude region with
negligible aerosols. However, those profiles change
systematically as described above where there was the aerosol
layer. Taking the wavelength differences into account, the
correct ozone profile should be close to the C-pair profile.
This profile is not so different with that obtained from the
ozonesonde measurement. This result may suggest the
possibility of the correction of aerosol effects (Sasano, 1988)
if the lidar signals have enough signal-to-noise ratios.
6. CONCLUDING REMARKS
The stratospheric subsystem of the NIES ozone lidar
system is described. The measured vertical profiles have
good accuracy. The observed seasonal variations at 20 - 40
km show ozone variations related to typical dynamical and
photochemical processes, respectively. The effects of the
volcanic stratospheric aerosols on the ozone lidar
measurements are discussed.
ACKNOWLEDGMENTS
The assistance of Mr. F. Sakurai and Mr. H. Sato
with the lidar measurements are gratefully acknowledged.
865
Fig.3. Temperature profiles changing from
January 24 to 26, 1990 during DYANA
campaign (Nakane et al., 1992).
A
E
v
"O
40
30
20
February 26, 1992
-- 308- 351 nm
---308 - 339 nm
....7o ::oo;7
, i ll,llll i t., _,,1 I _ ,,Jl
101" 10 TM 1019 1020
number densityof ozone(molecules/m3)
Fig. 4(a). Ozone profiles obtained from 308 nm - 351 nm (A-),
308 nm- 339 nm (B-) and 308 nm- 313 nm (C-)
wavelength pairs of the NIES ozone lidar system on
February 26, 1992. Ozone profiles observed by NIES
and TAO on the same day is also shown.
9O , L ' ' I I J +
74
8O
"t<40 _ii , , + , __! I I I- /_ I I
_80 190 _00 Zl0 _0 230 Z40 _S0 2S0 ZT0 28O Zg0
T,mper.lurC (K)
-=
<
3O
2O
February 26, 1992
18: 43:32
\
Jf
5 10 15
Scattering Ratio
Fig. 4(b). Aerosol profile of the volcanic aerosols due to Mr.
Pinatubo measured with the NIES large scale Mie lidar
on February 26, 1992.
REFERENCES
Browell, E. V., S. Ismail and T. Shipley, 1985: Ultraviolet
DIAL measurements of 03 profiles in regions of
spatially inhomogeneous aerosols. Appl. Opt., 24,
2827 -2836.
Chanin, M.-L., and A. Hauchecorne, 1984: Lidar studies of
temperature and density using Rayleigh
scattering, MAP Handbook.13, edited by R.A
Vincent, pp87 - 99, SCOSTEP, Urbana,Illinois.
Nakane H., S. Hayashida, Y. Sasano, N. Sugimoto, I.
Matsui, and A. Minato, 1992: Vertical profiles of
temperature and ozone observed during DYANA
campaign with the NIES ozone lidar system at
Tsukuba. J. Geomag. Geoelectr. in press.
Nakane, H., Y. Sasano, S. Hayashida-Amano, N. Sugimoto,
I. Matsui, A. Minato, and M.P. McCormic, 1992:
Comparison of ozone profiles obtained with NIES
DIALand SAGE II measurements, submitted to
J, Meteorol. Soc. Japan.
866
Sasano, Y., H. Nakane, S. Hayashida-Amano, N. Sugimoto,
I., Matsui and A. Minato, 1989: Multiple-wavelength
DIAL and a new analysis technique to deduce the
ozone profile without systematic errors due to aerosol
effects. Pro¢. of the Ouadrennial Ozone Symposium
1988 and tropospheric ozone workshop. 743-746.
Sasano, Y., N. Sugimoto, H. Nakane, S. Hayashida-Amano,
I. Matsui, A. Minato, 1989: Multiple-wavelength
differential absorption lidar (DIAL) for measuring
the ozone profiles in the stratosphere and the
troposphere, Abstracts of First Tsukuba Workshop on
Ozone DIAL. Tsukuba. Japan. December 6 and 7.
Sasano, Y., 1988: Simultaneous determination of aerosol and
gas distribution by DIAL measurements, Appl. Opt.,
27, 2640 -2641.
Sugimoto, N., Y. Sasano, H. Nakane, S. Hayashida-Amano,
I. Matsui, and A. Minato, 1989: Multiple wavelength
laser radar for measuring the stratospheric and
tropospheric ozone profiles, Oyobutsuri, 56, 1385 -
1397 (in Japanese).


Lidar observation of ozone over Tsukuba (36 deg N, 140 deg E)

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