The WMO ozone sonde intercomparison was held at Vanscoy, Saskatchewan from May 13 to May 24, 1991. The purpose of the intercomparison is to evaluate the performance of various ozone sonde types used operationally in the Global Ozone Observing System and to ensure that the accuracy and precision of the measurements are sufficient to detect long-term trends in stratospheric ozone. The intercomparison was sponsored by WMO and hosted by the Atmospheric Environment Service (AES) of Canada. It was attended by scientists from six countries: Canada, Finland, Germany, India, Japan and USA. A total of 10 balloon payloads were launched each carrying 7 or 8 sondes for a total of 67 successful ozone sonde flights. The payloads were carried to altitudes between 35 and 40 km where the flights terminated by balloon burst. Results of the profile measurements made during the series of the profile measurements made during the series of flight are used to determine statistically meaningful evaluations of the different sonde types. A description of the payload and the different ozone sondes is given. Preliminary results of the profile measurements and an evaluation of the performance of the sonde types are presented

Claude, Hans J.

Fast, Hans

Kerr, James B.

Kohler, Ulf

Kyro, Esko

Lathrop, Jeff A.

Mcelroy, C. Thomas

Oltmans, Sam J.

Paukkunen, Ari

Sreedharan, C. R.

English

NASA Technical Reports Server

N95- 11095
THE 1991 WMO OZONE SONDE INTERCOMPARISON
James B. Kerr, C. Thomas McElroy, Hans Fast
Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Canada
Sam J. Oltmans, Jeff A. Lathrop
NOAA/Air Resources Laboratory, Boulder, Colorado 80303, USA
Esko Kyro
Finnish Meteorological Institute, Sodankyla Observatorio, Tahtela, SF-99600, Sodankyla, Finland
Ari Paukkunen
Vaisala, PL 26, SF-00421, Helsinki, Finland
Hans J. Claude, Ulf Kohler
Deutscher Wetterdienst, Albin-Schwaiger-Weg i0, D-8126 Hohenpeissenberg, Germany
C.R. Sreedharan
India Meteorological Department, Meteorological Office, Pune-411005, India
Toshinori Tako and Yoichi Tsukagoshi
Japan Meteorological Agency, 1-3-40te-Machi, Chiyoda-Ku, Tokyo i00, Japan
ABSTRACT
The ?NO ozone sonde intercomparison was held
at Vanscoy, Saskatchewan from May 13 to May 24,
1991. The purpose of the intercomparison is to
evaluate the performance of various ozone sonde
types used operationally in the Global Ozone
Observing System and to ensure that the accuracy
and precision of the measurements are sufficient to
detect long-term trends in stratospheric ozone.
The intercomparison was sponsored by WMO and hosted
by the Atmospheric Environment Service (AES) of
Canada. It was attended by scientists from six
countries: Canada, Finland, Germany, India, Japan
and USA.
A total of I0 balloon payloads were launched
each carrying 7 or 8 sondes for a total of 67
successful ozone sonde flights. The payloads were
carried to altitudes between 35 and 40 km where the
flights terminated by balloon burst. Results of
the profile measurements made during the series of
flights are used to determine statistically
meaningful evaluations of the different sonde
t_es. A description of the payload and the
different ozone sondes is given. Preliminary
results of the profile measurements and an
evaluation of the performance of the sonde types
are presented.
I . INTRODUCTION
A variety of types and manufacturers of
ozonesondes are currently used operationally in the
Global Ozone Observing System (GQOS) and there is
ccncern that the accuracy and precision of
measurements differ from one sonde type to another.
An ozone sonde intercomparison was held with the
goal of evaluating the various ozonesonde types to
ensure that their measurements are comparable with
each other and that they are of sufficient quality
to detect long-term trends in stratospheric ozone.
The WMO organized and provided financial
support for the comparison and the Atmospheric
Environment Service (AES) of Canada hosted it. The
comparison was held at Vanscoy, Saskatchewan from
May 13 to May 24, 1991. The participants included
scientists from six countries: Canada, Finland,
Germany, India, Japan and USA.
The intercomparison was held at Vanscoy,
which is the site that the AES has used for
launching large experimental payloads. The
facility was readily adapted for launching and
recording multi-ozonesonde payloads. The
intercomparison was held in May when the day-to-day
variability of ozone is large and, therefore, a
wide range of ozone conditions could be expected.
2. DESCRIPTION OF SONDES
An ozonesonde is a self-powered ozone sensor
which is usually used as a supplement to a standard
meteorological radiosonde. The ozonesonde samples
ambient air to determine its ozone content and
provides as output an electronic signal which is
related to the amount of ozone in the air sample.
The output signal from the ozonesonde is read
(often through an electronic interface) into the
radiosonde where the data are transmitted by radio
to the ground receiver along with the regular
meteorological data record.
Four different types of ozonesondes were
represented at the intercomparison: the
electrochemical concentration cell (ECC) sensor,
807
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the Brewer-Mast sensor, the Indian sensor and the
RSII-KC79 sensor. The ECC sensor was used by the
participants from Canada, Finland and USA. The
Brewer-Mast sensor was used by the participants
from Germany. The Indian sensor was used by the
participant from India. The RSII-KC79 sensor was
used by the participants from Japan and is
integrated into a combined radiosonde/ozonesonde
package. Most Of the ozonesonde profile data which
are reported routinely to the World Ozone Data
Center (WODC) are measured by these four types of
ozone sensors. The type of ozonesondes used by
each participant is summarized in Table i.
In operation the different types of ozone
sensors are linked to radiosondes, often through an
interface. The interface digitizes the signal from
the ozone sensor so it can be included as part of
the data record on the recently developed automated
digital radiosondes. There are many combinations
of ozone sensors, interfaces and radiosondes which
are used operationally. The primary objective of
the intercomparison reported here is the evaluation
of the performance of the ozone sensors. It is
also useful to compare ozone profiles derived from
data which are transferred through different
radiosondes and processed by different recording
and analysis procedures. Information regarding the
type of ozonesonde, radiosonde, data logging and
analysis used by each country is stur_arized in
Table I.
3. DESCRIPTION OF THE BALLOON PAYLOAD
The ozonesonde packages from all countries
were attached to a single balloon payload which is
shown schematically in Figure I. Up to eight
sondes were suspended with a minimum separation of
approximately one meter around the perimeter of an
octagonally shaped frame. The frame is
collapsible, light-weight (< 2kg) and sufficiently
robust. The command and telemetry package and
batteries were positioned at the center of the
support frame. The payload systems were designed
to be recovered after a flight and reflown with a
new set of ozonesonde/radiosonde packages. Two
payload systems were made in order to allow the
preparation and checkout of a second set of
ozonesondes while the first set was being
recovered. This minimized the time interval
between flights.
A special telemetry package was developed to
accommodate the requirement of simultaneously
transmitting the data from several sondes. This
package consists of an eight-channel voltage
controlled oscillator (VC0). A VCO channel reads
the voltage output from either a radiosonde or an
ozonesonde, transmits the information by telemetry
to the ground receiver which replicates the voltage
level at one of eight work areas. A test flight on
May I, 1991 demonstrated that the signals received
at the ground through the VCO system were identical
to those received in parallel through a regular
1680 MBz radiosonde and ozonesonde transmission.
The resulting ozone profiles derived from the
flight data recorded by both systems were
essentially identical.
The participants were given the option to fly
their ozonesonde either with or without a
supporting radiosonde. The capability to telemeter
the output from a radiosonde directly to the ground
station using the standard radiosonde frequencies
was available for only three sondes. The remaining
sondes on the payload used the VCO system. When an
ozone sensor was flown without a supporting
radiosonde the signal from the ozonesonde was fed
into the VCO. When both ozonesonde and radiosonde
were flown the output from the radiosonde was fed
to the VCO and the radiosonde transmitter was
disabled. The ozonesonde, interface, radiosonde
and telemetry configuration used by each of the
participating countries are summarized in Table ].
The 403 MHz radiosonde channel was used for
an omega navigation sonde to determine payload
position for calculations of winds.
The overall weight of the payload including
the support frame, ozonesonde/radiosonde packages,
telemetry package and power supply was about 20 kg.
The payloads were flown on plastic balloons ranging
in size from 140,000 to 500,000 cubic feet. The
relatively light-weight payload was easily hand-
] --
INTER- I RADIO TELEMETRY
FACE I SONDE CHANNEL
OZONE
SENSOR
CAN ECC
FIN ECC
GER Brewer
/Mast
IND Indian
JAP RSII-
KC79
USA ECC
TABLE
N/A VIZ 1680 MHz
(VCO # 7)
VaisalalVaisala 405 MHz
! (VCO # 7)1
N/A ! N/A VCO # 5
: _(VCO # 2)
I
N/A N/A |VCO # 6
(VCO # 7)
N/A N/A ,VCO # 5
(VCO # 7)
TMAX Vaisalai401 MHz
(VCO # 7)
Dig.
Ana,
Ana
Dig.
1: Summary of the ozonesonde, interface,
radiosonde and telemetry channel used by each
country. The type of the transmitted data signal
(analog or digital) and the data analysis procedure
(automatic or manual) are also indicated. The
telemetry channel in brackets indicates the channel
used by that country when a second sonde was flown.
CANADA
ECC SONDE !
Fig. I= Schematic diagram of ozone sonde payload.
808
launched by two people provided the surface wind
was less than 10 knots.
The transmitted radio signals from the
payloads were received at the ground and
distributed to the work areas of the participants.
This allowed the participants to display and record
their data with their normal operational equipment
and the data could be analyzed using their normal
methods and procedures. The data was recorded on
magnetic tape to allow playback of data for
reanalysis, if necessary. It also enabled the
participants to analyze data from their second
ozonesonde which was flown on some of the flights.
4. DATA ACQUISITION
The participants prepared their ozonesondes
using their normal pre-flight calibration and
preparation procedures. When a participant's ozone
sensor was ready for flight it was integrated on to
the payload. The signals were checked through the
telemetry and data distribution systems in order to
ensure that the proper signals were being received
at the appropriate work area. After signals had
been checked on an individual basis, they were
checked with all sondes on the payload operating in
order to test for interference and cross-talk.
When the all-up tests had been completed with
verification from all participants that their
sensors were operating correctly and the proper
signals were being received at the work areas, the
payload was ready for flight.
FLT JDATE
1991
1 14
2 15 21:431
05
3 16 04 : 55
4 16 21 .
9 _ 21 _:29
i
START FLIGHT MAX ITOTAL TWO GOOD
TIME LF_GTH HEIGHT OZONE SNDS PROS
(CST) (MIN) (KM DU)
22:16 99 37.0 346 Can 7
129 37.9 354 USA 7
120 39.8 331 Fin 7
ii0 37.0 321 * 3
122 36.0 325 Ind 7
116 37.2 334 Jap 7
115 38.8 374 6
112 38.4 365 Can 8
USA
114 36.1 367 Fin 8
Ind
t
118 38.8 374 Jap 77
|
TABLE 2: Summary of the ozonesonde flights during
the intercomparison. The date, time of launch,
flight duration, maximum altitude, total ozone, two
sonde assignment and number of successful profiles
are given. Time is in central standard time (CST)
which is six hours behind GMT. Total ozone is in
Dobson Units using the Bass-Paur absorption
coefficient scale effective January i, 1992. The
"*" denotes a flight during which the VC0 telemetry
system failed and for which profile data for those
sondes using the VCO system (Germany, India and
Japan) are unavailable.
The balloon payload was designed to
accon_odate physically up to eight sondes and the
telemetry system to accon_nodate up to eleven
sondes. This allowed the opportunity for two
sondes from one or two countries to be flown on
each flight. Two sondes were flown by different
groups on a rotational basis for different
flights.
A total of 10 balloon payloads were launched
between May 14 and May 22, each carrying 7 or 8
ozonesondes for a total of 67 successful ozonesonde
profile measurements. Most of the flights were
launched during the sunrise or sunset period when
low surface winds allowed good launch
opportunities. The payloads were carried to
altitudes between 35 and 40 km where the flights
were terminated by balloon burst. The payloads
were recovered, refurbished and prepared for re-
flight with unused ozonesondes usually within 24
hours. The launch times, flight durations, maximum
altitudes, number of good profiles and country
assignments for the two-sondes are summarized in
Table 2.
Data from the intercomparison were submitted
"blindly" to a "data custodian" who served as an
objective recipient of the data and who had no
direct involvement in the preparation of the
ozonesondes or the analysis of the ozone profile
data. The participants were asked not to compare
or discuss their data with other groups during the
intercomparison. Shortly after each flight the
data were submitted to the data custodian together
with a rating as to whether the data were thought
to be good, average or poor. The data custodian
reviewed the data as they were submitted in case
there were severe problems (e.g. gross differences
from the other data sets or extremely noisy data)
so that the problem could be corrected for
subsequent flights.
The participants analyzed their flight data
using their normal analysis procedures. To reduce
the effort involved in comparing sonde results, the
participants submitted their data as floppy
diskette files.
Ground-based ozone measurements were made
with the Brewer and Dobson instruments to support
the ozone profile measurements made by the
ozonesondes. The ground-based measurements
consisted of both direct sun total ozone
measurements and Umkehr profile measurements. The
total ozone measurements were required to normalize
the sonde profile measurements using standard
correction procedures. The Umkehr profile
measurements were compared with the sonde profile
measurements. The ground-based total ozone values
valid for the ten flights are listed in Table 2.
These values are on the Bass-Paur absorption
coefficient scale. During the campaign the weather
was not very favourable for Umkehr measurements
which require clear zenith sky condltions over a
three hour period after sunrise or before sunset.
5. RESULTS
Results for flight #I on May 14 are shown in
Figure 2. This example shows the nature of the
variations of the vertical profile of ozone (top
diagram) as well as the variations between the
different sondes (bottom diagram).
809
The profiles were evaluated using a common
pressure and temperature profile as measured by the
Canadian radiosonde using a hypsometer measurement
for pressure. The profiles were then normalized
using the ground based total ozone measurements.
For all ten flights there were 3 or 4 ozone
profiles measured with the ECC sonde (used by
Canada, Finland and USA). On each flight the
simultaneous data from the other three sonde types
were compared with the mean ECC profile. The
average ratios of the other measurements to ECC
measurements and the standard deviations for the
ten flights are shown in Figure 3.
6. CONCLUSIONS
Ten intercomparison flights were made between
May 14 and May 22, 1991. Data from these flights
are analyzed for evaluation of the quality of ozone
profile measurements. Preliminary comparison
indicate that the profile measurements show
agreement of the order of 10% to an altitude
corresponding to i0 mb in pressure. Possible
systematic differences were observed. A thorough
analysis of the results from the comparison are to
be reported in a WMO publication.
-60 -40 -20 0 20 40
VANSCOY Ms 14, 19U91
100 - q, • i
_, Z _NNISll DATA ( )
Cld,lA.1)tAN DATA 2
: _ GlXI_24 DATA
,ooo. I +J¢-
i ..................... TT:,,_',.?'/,".......
0 25 50 75 100 125 150 175 200
PARTIAL PRESSURE OZONE (nbar)
'1 '_o ,4c,h ; .............
VANSCOY Ms 14, t99t
I TOTAL OZONE_ 346 DU
1000 ALL ? SOffiDiS NORM)/ - 4 ZCC SONDES (NORI_)
+ , , , I I J _-_3 0.40.0 0.[ 0.2
RELATIVE STANDARD DEVIATION
I , , + , r , , , , , , , , ,
10 SONDES (B-M)
NORMAUZED DATA
:+
too
+oool
[at'_ .... ::::7: - i
0.7
AVERAGE
...... STANDARD DEVL_TION
.2: 2::-: ::.. .....
.,::,---"
+?+
...
0.8 0.9 1.0 I.I 1.2 1.3
OZONE(:; ..... y/OZONEEcc
_ NORMALIZED DATA --.-_ _'['E._/_R_)._D DEVIATION
.----. I0 " ' _n"" :'
 ,ooo"
o._ o.a 0.9 ,.o ,., i._ i a
OZONE,.aLJOZONE_cc
I 1 SONDES (KC79) _ AVERAG!e
NORMALIZED DATA STANDARD DEVIAT[ON
0,7 0,8 0.9 1.0 1,1 1.2 1,3
OZONE.,,.p+./OZO NEEcc
Fig. 2: The measured profiles for flight 1 of May
14, 1991. The top diagram shows the profiles of
the individual ozone and the mean of four
temperature measurements.
Fig. 3: Ratios of measurements made by the Brewer-
Mast sonde <top), the Indian sonde (middle) and the
Japanese KC79 sonde Ibottom) to the flight-averaged
simultaneous ECC sonde measurements. Means and
standard deviations of the I0 flights are sho,_.
810


The 1991 WMO ozone sonde intercomparison

The 1991 WMO ozone sonde intercomparison

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