A small optical ozone instrument has been developed for a rocket-borne dropsonde to measure the altitude profile of stratospheric ozone. It consists of a four-color filter photometer that measures the attenuation of sunlight as a function of altitude at four wavelengths in the middle ultraviolet. The ozone dropsonde is launched aboard a meteorological rocket MT-135, providing the altitude profiles of ozone as well as atmospheric temperature and wind. The rocket launchings have been carried out five times since August 1990 at Uchinoura (31 deg N, 131 deg E), Japan to measure ozone concentration from 52 to 20 km altitudes during the slow fall of the dropsonde. The ozone profiles measured in summer (August 27, 1990; Sep. 11 and 12, 1991) were very stable above an altitude of 28km. where as those measured in winter (Feb. 9, and 11, 1991) showed considerable day-to-day variations at the stratospheric altitudes. Ozone, temperature and wind profiles measured simultaneously by both rocket and balloon ozonsondes are compared with CIRA 1986 model atmosphere

Ogawa, Toshihiro

Watanabe, Takashi

English

NASA Technical Reports Server

N95- 11096
MEASUREMENTS OF STRATOSPHERIC OZONE BY ROCKET
OZONESONDES IN JAPAN
Takashi Watanabe
Department of Information Science and Electronics
Tsukuba College of Technology, Amakubo 4-3, Tsukuba 305, Japan
Toshihiro Ogmva
Department of Earth and Planetary Physics, Faculty of Science
University of Tokyo, Hongo 7-3-1, Bunkyo-Ku, Tokyo 113, Japan
ABS'IRAC'I"
A small optical ozone instrument has been developed for
a rocket-borne dropsonde to measure the altitude profile of
stratospheric ozone. It consists of a four-color filter
photometer that measures the attenuation of sunlight as a
function of altitude at four wavelengths in the middle
ultraviolet. The ozone dropsonde is launched aboard a
meteorological rocket MT-135, providing the altitude profiles
of ozone as well as amaospheric temperature and wind. The
rocket launchings have been carried out five times since August
1990 at Uchinoura (31°N, 131°E), Japan, to measure ozone
concentration from 52 to 20 km altitudes during the slow fall of
the dropsonde. The ozone profiles measured in summer (Aug.
27, 1990; Sep. 11 and 12, 1991) were very stable above an
altitude of 28km. where as those measured in winter (Feb. 9
and 11, 1991) showed considerable day-to-day variations at the
stratospheric altitudes. Ozone, temperature and wind profiles
measured simultaneously by both rocket and balloon
ozonsondes are compared with CIRA 1986 model atmosphere.
f_tlO 10[)IOI)E
FILTER DIFFUSER
tENS "
i il ,:,tTFR
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Fig. 1 Optical configuration of the radiometer
for the rocket borne drop ozonesonde.
1. INTRODUCTION
A sounding rocket is useful for the direct
measurement of vertical structures in the middle and upper
stratosphere. A rocket-borne ozonesonde has been used for
validating satellite measurements to detect long-term change in
stratospheric ozone on a global scale. It is important to
monitor ozone concentration in the upper stratosphere around
35-45km where long-term chemical perturbations occur most
significantly. An optical ozonesonde is most suitable to
measure ozone concentration accurately at those altitudes.
We developed an optical ozone dropsonde in 1987, and
modified a MT-135 rocket to accomodate the dropsonde in
1989. Since the first successful measurement was made on
Aug. 27, 1990 from Uchinoura (31°N, 131'E), so far we
obtained five altitude profiles of ozone, atmospheric
temperature and horizontal wind in the stratosphere.
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Fig.2 Altitude profile of the intensity measured by
a 290nm radiometer aboard MT-135-56 flight.
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MT-135-52 Aug. 27, 1990 IIIOJST
-- MT-135-55 Sep. I1, 1991 ll00JST
-- MT-135-56 Sep. 12, 1991 1100JST
Uchinoura (31N. 131E)
(a)
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-- MT-135-53
Feb. 9, 1991 1100JST
---- MT-135-54
Feb. 11, 1991 1100JST
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• 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Ozone Number Density (cm -3) Ozone Number Density (cm -3) Ratio of Ozone Density
Fig.3 (a) Ozone number densities measured on August 27, 1990, September 11, and 12, 1991,
respectively, at Uchinoura (31°N, 131°I/). (b) Same as (a) for data on Februay 9 and 11,
1991at Uchinoura. (c) Ratios of the three August-September profiles to their mean profile.
2. INSTRUMENTAL
The ozone sensor is based on the solar middle ultraviolet
absorption technique and its optics is quite similar to that of
ROC_Z and R(X2OZ-A (Krueger and McBride, 1968; Barnes
and Simeth, 1986). It is a multi-color filter photometer (Fig. 1)
to measure the attenuation of the solar ultraviolet 0dV) at the
central wavelengths of 265, 290, 300, and 310 nm, with a
pass band (full width at a half maximum) of 15-20 nm. The
photometer receives the solar UV with a UV glass diffuser
plate installed at the top of the instrument container. The
effective aperture of the diffuser is 3 cm diameter. The light
transmitted through the diffuser plate is then passes through a
beam splitter, f'dter wheel, and a lens used to limit the
convergence angle of the rays accepted by the phototube with
SbCs photocathode. Four pieces of filter plates are mounted
on a disk that rotates at a rate of about 3 Hz. Owing to the
diffuser plate we do not need any pointing device for the sun,
but the diffuser radiance depends on the incident angle of the
solar UV onto the diffuser plate. The light from the diffuser
plate is monitored at 420nm wavelength through the reflection
by the beam splitter. We use an interference fdter of 12 nm
passband width and a Si photodiode detector for this monitor.
Rationing the measured UV intensity to the reference 420nm
intensity eliminates the modulation due to the change in solar
incident angle. Fig. 2 shows the solar uv absorption measured
as a function of altitude by the 290rim band, which is corrected
for the attitude modulation of the instrument.
The dropsonde consists of the photometer, a temperature
sensor, and a radar transponder / telemeter along with a
parachute, and is placed in a airtight container that is installed in
the payload section of the rocket. The payload is separated
and ejected from the rocket at 95 sec after the launch. The
dropsonde is ejected out of the container which is opened at
112 sec after the launch. The temperature sensor is deployed
from the dropsonde at 117 sec after the launch. The single
staged rocket reaches its appex of 56 - 60 km at about 110 sec
after launch. The 6.8kg payload is hung from a parashute of
3.5m diameter and descends slowly through the stratosphere
and troposphere. The temperature sensor is a wire of Fe-Ni
alloy with a diameter of 20 ,u m and approximate length of 18
cm. The atmospheric temperature is obtained by measuring the
electrical resistence of the metal wire, as it depends on the
temperature of the ambient atmosphere. The data from the
photometer and the temperature sensor are converted in 40 bits
digital form with a 10-bit A/T) converter, and transmitted to the
ground every 4 msec using a 1687MHz PCM transmitter. So
the data rate is 10 k bits/sec. The transmitter also works as a
radar transponder and the positioning of the dropsonde is
possible by tracking it with the ground-based radar.
Positioning accuracy of the radar tracking system is about 50
m. The positioning data are also used to deduce horizontal
wind.
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Ratio to CIRA Ratio to CIRA Ratio of Number Density
Fig.4 (a) Ozone number densities measured on August 27, 1990, September 11, and 12, 1991,
respectively, at Uchinoura (31° N, 131° E). The values are normalized by CIRA 1986
average ozone model atmosphere for September at 30N. (b) Same as (a) for data on
Februay 9 and 11, 1991at Uchinoura and CIRA average ozone for February at 30N. (c)
Ratio of the mean February profile to the mean September profile. Thin curves show
ozone number denstity ratios of February to September CIRA average ozone for 30N and
40N, respectively.
The data received on the ground are processed using a
personal computer. The UV intensity data used for the data
analysis are only those for limited phase of the filter rotation, as
the filter wheel rotates continously. The effective data
sampling rate becomes about 0.3 sec with respect to an
individual filter. This sampling rate corresponds to an altitude
width of about 40 m at an altitude of 55km and less than 15 m
below 40 km. The modulation of the UV intensity data due to
aerodynamic disturbances during the descend is eliminated in
the data processing by taking the ratio of the UV intensity to the
420 nm intensity. In the retrieval procedure, we subtracted
small component of the solar UV extinction due to the Rayleigh
scattering.
The measured attenuation of solar UV due to ozone is
converted to ozone column density along the solar ray path as a
function of altitude using effective ozone absorption cross
section for the wavelength range of filter pass band. We use
the solar flux of Mentall et al. (1981) and the absorption cross
sections of ozone measured by Bass and Paur (1985). A
quadratic spline function is fitted to the derived column density
against altitude with every 1 km bin, and the number density is
derived as a derivative of this function. We got four ozone
number density profiles retrieved from the attenuation curves
measured at four wavelength bands for a rocket flight.
Evaluating the retrieval sensitivity in the altitude range for the
four wavelength bands, a synthesized ozone number density
profile is obtained by taking with a weighted mean of the four
ozone profiles. The retrieval error in the derived ozone density
is estimated to be about 3-10% at altitudes between 25 and
50km.
3. RESULT AND DISCUSSION
Figures 3 (a) and (b) illustrate the altitude profdes of ozone
concentrations observed by five MT-135 rocket flights. Also
the observed number density values are normalized by that of
the CIRA 1986 model atmosphere and shown in Fig.4 (a) and
(b). Three summer profiles exhibit less variable ozone
concentrations in the upper stratosphere than the February
profiles. Indeed, as seen in Fig.3 (c), the variance of ozone
density of the summer profiles is only 3% above 25km, and
this is close to or less than the estimated measurement error.
This may indicate the possibility to detect the long term ozone
trend in the upper stratosphere by the dropsonde observations
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Ozone Density (1012crn3)
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180 220 260
Ratio of Ozone Densily Temperatu re, K
c)
Observation ClRA
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Temperature Difference, K
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Wind Speed (In/s)
Fig.5 (a) Altitude profiles of ozone concentration measured by MT-135-56 on September 12,
1991 at II00JST (closed circle), balloon ozonesonde (thin curve), CIRA 1986 model
atmosphere September at 30N (broken curve). (b) Ratio of ozone concentration obtained
by the rocket ozonesonde to CIRA. (c) Atmospheric temperature measured at flight
MT-135-56 (thick curve), balloon ozonesonde at Uchinoura (thin curve), and CIRA 1986
September 30N(broken curve). (d) Deviations of temperature measured by the rocket from
CIRA. (e) Northward wind component measured by the rocket. (f) Eastward wind
component measured by the rocket (closed circle). CIRA 1986 zonal mean wind of
September at 30N is shown by thin line.
extending in summertime for several years. On the contrary,
two February ozone profiles show considerable day-to-day
variations. ALso ozone concentrations are smaller than ClRA in
most of the stratospheric altitudes. They are partly due to the
planetary wave activities, as intense westerly winds were
observed from the radar data of the both flights. And they are
partly due to the seasonal variation apppeared in CIRA model
shown in Fig 4 (c), which would be explained by chemistry.
Balloon ozonesondes were also flown from the rocket
launching site on the same day of the rocket flight to obtain
ozone and temperature profiles in the altitude range of 0 - 30
km. Fig. 4 (a) - (d) show the ozone and temperature profiles
measured by both rocket and balloon ozonesondes together
with CIRA. Ozone profiles by both rocket and balloon
ozonesonde observations agree well between 22 and 27 km.
Measured ozone by the rocket agrees with that of CIRA
within + 10% in the altitudes of 28 - 52 kin. Both rocket and
balloon temperature measurements agree well. They show
similar structures in the stratosphere. The temperature deviation
from CIRA is the magnitude of about +IOK. The atmospheric
wind components are shown in Fig. 4 (e) and (f). Although
IR model atmosphere provides only the zonal wind
components, measured westward component generally agrees
with the model. The ot_erved easterly winds in the middle and
upper stratosphere prevent planetary waves propagating
upward from lower atmosphere. This would support the stable
ozone profile in the upper stratosphere in September over
Uchinoura.
ACKNOWLEDGEMENTS
The authors are grateful to the Staff of the Institute of Space
and Astronautical Science for their hard work during the
successful rocket experiments. They also thank to K. Kita for
his ozonesonde analysis and I. Naito for his temperature and
wind analyses.
REFERENCES
Barnes, R.A. and Simeth, P.G., Design of a rocket-borne
radiometer for stratospheric ozone measurements, Rev.
Sci. Inst., 57, 544-551, 1986.
Bass, A.M. and Paur, R.J., The ultraviolet cross-sections of
ozone: I. The measurements, in Atmospheric Ozone,
Pro<:. Quad. Ozone Syrup., D. Reidei Pub. Co.,
606-610, 1985.
COSPAR International Reference Atmosphere: 1986 PART
II: Middle Atmosphere Models, edited by D. Rees, J.J.
Barnett and K. Labitzke, Pergamon Press, 1990.
Krueger A. J. and McBride, W. R., Rocket ozonesonde
(ROCOZ) design and development, Tech. Pub1. 4512,
Naval Weapons Cent., China Lake, Calif., 1968.
Mentall, J. M., Frederick, J. E. and Herman, J. R., The
solar irradiance from 200 and 330nm, J. Geophys. Res.,
86, 9881-9884, 1981.
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Measurements of stratospheric ozone by rocket ozonesondes in Japan

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