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WORLD METEOROLOGICAL ORGANIZATION |
UNITED NATIONS ENVIRONMENT PROGRAMME |
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Abstract. The first total ozone measurements in Portugal were carried out in Santa Maria Island (Azores) in 195l with the Dobson spectrophotometer #13 borrowed by the IOC (International Ozone Commission) in the scope of the IGY (International Geophysical Year) activities. After that, regular total and Umkehr ozone measurements have been made in Lisbon since 1967 with the same instrument. Recently, three stations equipped with automated Brewer spectrophotometers were installed at Funchal (Madeira Is.) in 1989, Angra do Heroismo (Terceira Is. - Azores) in 1992 and Penhas Douradas (Portugal Mainland) in 1994. The Brewer instruments are equipped with UV-B option and perform daily measurements of global UV-B radiation. The actual monitoring program, some results and comparisons between these stations are shown.
1 Historical review
In 1950, the International Ozone Commission (IOC) asked to the portuguese National Meteorológical Service (SMN -Servico Meteorologico Nacional) for a collaboration in an observational program at Azores Is. In this way, Mr. L. Neves, one of the former meteorologists of the SMN. went to Oxford in order to learn how to operate the Dobson ozone spectrophotometer with Sir Charles Normand. After this short training period, Mr. Naves carried out the first total ozone measurements at Santa Maria Island with the Dobson spectrophotometer #13. However, due to technical reasons, the instrument was moved to Lisbon in 1958, were is operated until now. The total ozone observations at Lisbon began in 1960 with Prof. Mário Figueira who developed the most part of the scientific research on the Ozone Layer field in Portugal until 1991. The first years of operation had some technical problems and some irregularities can be seen in the record until 1975. The regular Umkehr observations started in 1967, and later in 1'978. some ozone soundings were made using Brewer-Mast ozone sondes. Continuous surface ozone measurements were also started in Lisbon and in other locations (Castelo Branco and Beja) using Max Planck instruments and then KWS 775 ozone-meters based in the KI method.
Later in 1987, the portuguese National Institute for Meteorology and Geophysics (INMG - Institute Nacional de Meteorologia e Geofísica), who replaced the first SMN, and the portuguese National Agency for Scientific Research and Technology (JNICT - Junta Nacional de Investigacão Cientifica e Tecnológica) supported the purchase and installation of two Brewer ozone spectrophotometers at Funchal (Madeira Is.) in 1989, and at Angra do Heroismo (Terceira Is. - Azores) in 1992. These instruments are automated and performs total ozone and SO2, Umkehr and UV-B measurements Surface ozone photometric UV analyzers were also purchased and installed in both places.
Also during 1983 to 1992, continuously measurements of erithemally effective UV-B global radiation was performed by Mr. C. Goncalves et al. using a Robertson-Berger detector. However, due to calibration problems, the data needs to be revised.
More recently in 1994, the portuguese Institute for Meteorology (IM - Instituto de Meteorologia). who replaced the last INMG, supported the purchase of a third Brewer spectrophotometer, that was installed at the Penhas Douradas meteorological Observatory in Portugal Mainland, as well as a surface ozone photometric UV analyzer.
All these instruments are located in meteorological observatories and are daily operated by the meteorological observer personnel of each one. The data is sent to she IM headquarters in a monthly basis, and then it is validated, processed and sent to she World Ozone Dana Center. Figure 1.1 shows the geographical location of the four portuguese ozone stations.
2 Objectives
The objectives of these stations are she following:
To match these objectives, a great effort is made by the IM in order to
purchase, to install, and to operate the instruments for long term periods. At
she same time, some of she records are processed, validated and stored and
can be available for scientific research. However. there is a lot of data that
needs to be processed, and/or re-evaulated according changes (purred in the
calibration levels of the instruments or in the absorption coefficients.
Unafortunately, due to personnel limitations, only few graduated people ( I -
9) are actually involved in this work and for this reason an international
cooperation is needed in order to match these objectives.
3 Location of the stations and the actual observing program
All stations are equipped with ozone spectrophotometers and other ancillary instruments. like surface ozone analyzers, carbon dioxide analyzers. and some of them also with high volume samplers (suspended matter) and automated precipitation collectors, integrated in the BAPMoN program. Table 3.1 shows the actual O3/UV-B Portuguese network characterization .
4 Some results
The ozone stations are equipped also with personal computers that can be used to punch data from manual instruments or to store the data collected from automated instruments and data loggers. Then, the data is saved in Poppy disks and sent by mail to the IM headquarters (Lisbon) in a monthly basis. After that, the data is stored properly and processed. The processing consists in a simple control quality program to find and eventually correct some wrong data that can occur. In addition, this processing performs statistical computations for hourly, daily and monthly scales. The following section shows some of the daily results in graphical form.
4.1 Total ozone
The Figure 4.1.1 shows the daily total ozone averages (dots) and 365 days moving averages (solid line) for Lisbon station obtained with the Dobson #13 spectrophotometer from AD/DS measurements. It should be need that this data needs to be re-evaluated, mainly before 1972, however it can he seen the annual variation and a marked negative trend from 1972.
In the same way. Figures 4.1.9 and 4.1.3 shows the daily DS results for Funchal and Angra do Heroismo stations respectively, obtained with Brewer spectrophotometers.
| Station | Lisbon | Penhas Douradas | Funchal | A. do Heroismo |
|---|---|---|---|---|
| WMO Nr. | 08579 | 08568 | 08522 | 08511 |
| GO3OS Nr. | 082 | 288 | 287 | 327 |
| Latitude | 38.77°N | 40.42°N | 32.64°N | 38.66°N |
| Longitude | 9.15°W | 7.55°N | 16.89°W | 27.22°W |
| Altitude | 105 m | 1380 m | 49 m | 74 m |
| Site type | Portugal mainland: coastal region, moderately polluted site close to the airport and to the Tejo river. | Portugal mainland: Mountain region far from pollution sources and with near clean air conditions. | Madeira Is.: Moderately polluted site at the surroundings of the town very close to the sea shore (100m). | Terceira Is. (Azores): Lightly polluted site at the surroundings of the town, close to sea shore (1 km). |
| Instrumentation | Dobson #13 (IOC) since June 1960; Brewer MARK II #047, since July 1989 to June 1992; Robertson Berger sunburn UV meter, since 1983 to 1992. | Brewer MARK II #102, since October 1994. | Brewer MARK II #048, since October 1989. | Brewer MARK II #047, since July 1992. |
| Observing program | Daily AD/DS1 measurements at µ2 = 3.0, 2.5, 2.0, 1.5 and at noon; Daily Umkehr observation (mainly p.m.) | Daily DS1 measurements at Z3 < 79.5° Daily ZS4 measurements at Z3 < 69.5° Daily Umkehr observa-tions (a.m. and p.m.); Daily Global UV-B spectral irradiance measurements at Z3 < 69.5°. | Daily DS1 measurements at Z3 < 79.5° Daily ZS4 measurements at Z3 < 69.5° Daily Umkehr observa-tions (a.m. and p.m.); Daily Global UV-B spectral irradiance measurements at Z3 < 69.5°. | Daily DS1 measurements at Z3 < 79.5° Daily ZS4 measurements at Z3 < 69.5° Daily Umkehr observa-tions (a.m. and p.m.); Daily Global UV-B spectral irradiance measurements at Z3 < 69.5°. |
5 Future developments
The negative trends observed in global total ozone suggests that the UV-B levels at surface could be changing. However, the available UV-B data is some times inconsistent, probably due to different instrumentation and methods used, non calibrated instruments, etc. In other hand, there is a strong public interest to know how are and how will be the UV-B levels in the future. In this way, the IM is planning to install an extended UV-B network over the mainland territory, using broad-band or multi-filter instruments. This network will consist in 4 to 6 stations covering mainly the coastal and south regions with interest for the tourism in summer time and other activities. This monitoring could be complemented also with UV-B daily forecastings, using the available ozone and meteorological information. However, the development of this network will depend partially on an international definition of standard instrumentation and methods that are currently matter of discussion.
Figure 4.1.2. Total ozone at Funchal station, measured with Brewer #048. Dots: daily averages of DS measurements; solid line: 365 day moving averages.
Figure 4.1.3 Total ozone at Angra do Heroismo station, measured with Brewer #047. Dots: daily aveages of DS measurements; solid line: 365 days moving averages.
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