Ta' Gordan lighthouse: background trace gas monitoring station

The Physics Department of the University of Malta conceived the idea of setting up a background trace gas monitoring facility in the early 1990s; more specifically 1993 when Dr Raymond Ellul and Professor Paul Crutzen of the Max Planck Institute for Atmospheric Chemistry in Mainz, Germany, collaborated on questions of Climate Change and the pollutant trace gases responsible for this in the Mediterranean region.

In 1995 Professor Crutzen was awarded the Nobel Prize for Atmospheric Chemistry; he has visited Malta twice in connection with this work.

In 1996 the University allocated a sum of money to this work and with the kind consent of the Maritime Authority, who hold the title to Ta' Gordan lighthouse in Gozo, and the help of the Gozo Ministry, instruments donated first by the Max Planck Institute and later by the International Bureau in Bonn were installed.

These instruments comprised ozone monitors, a full set of meteorological instruments measuring wind speed and direction, relative humidity, temperature and atmospheric pressure and radiation intensity. Later another ozone monitor, designed to serve as a standard, and meteorological instruments were installed at the University's Gozo Centre. This centre, which had just been opened in co-operation with the Ministry for Gozo, serves as a base for the operation which cannot realistically be run from the main University campus.

The International Bureau in Bonn as well as the Institute for Climate Research in Karlsrühe continued to support the initial work with the further provision of carbon monoxide and sulphur dioxide monitors as well as annual calibration facilities for the ozone monitors which, since ozone is an unstable trace gas, cannot be calibrated in the normal way using "standard" gas mixtures but requires a special transfer standard technique related to a primary standard only available in a few of the larger European laboratories.

Over the years the collection of data has grown more sophisticated so that the standard procedure is now daily downloading of all the data to, as well as remote calibration of the instruments from, the Xewkija station. Weekly visits to the lighthouse are still, however, an essential part of the programme as these very delicate instruments need careful maintenance to be able to reliably and reproducibly detect the very low concentrations of ozone, carbon monoxide and sulphur dioxide.

In 2000 the Gordan lighthouse station achieved Global Atmospheric Watch Status with the United Nations Environment Programme of the World Meteorological Organisation.

The Global Atmospheric Watch programme (GAW) was set up in the 1980s and contains 22 "global" stations around the world in extremely remote spots away from direct man-made (anthropogenic) influences as well as another set of regional stations in geographically critical positions.

These stations record trace gas concentrations and meteorological parameters and annually pass their results to the World Data Centre for Green-house Gases based in Tokyo at the Japanese Meteorological Agency's headquarters. These results are worked into an annual publication showing all the greenhouse gas changes in the Northern and Southern hemisphere.

The Gordan lighthouse station (registration no. 16587) is located in a strategically important position between Europe and North Africa and can be found on the GAWSIS Website with all details necessary. The GAW network also works with and is slowly becoming interchangeable, with the EMEP network run from the Norwegian Institute for Atmospheric Research - Co-operative programme for the monitoring and evaluation of the long range transmission of air pollutants in Europe (NILU).

Dr Julian Wilson of the EU's Joint Research Centre in Ispra as well as other researchers at WMO, Geneva, and NILU, are presently engaged in unifying the two systems into one common database which can be used by Climate researchers worldwide.

It is interesting to note that as of April 1 Dr Slobodan Nickovic, formerly employed at the Euro Mediterranean Institute for Coastal Dynamics (ICOD) at the Foundation for International Studies, Valletta, has moved to join the team at WMO Geneva.

The Gordan lighthouse monitoring station has now been running for eight years and the sum of Lm250,000 from German and Maltese taxpayers' money has been expended in the setting up and running of this facility.

One of the main advantages of the Gordan lighthouse station is its location on the seashore and proximity to the main shipping lane between Gibraltar and the Suez Canal; it is estimated that a quarter of the world's shipping uses this route and hence measurement of the pollution from this "source" is a critical part of the programme.

Indeed it is possible that the high concentration of ozone measured here could partly be due to this shipping intensity.

The location of the station is also excellent when it comes to measuring aerosols which are thought to be a primary factor in climate change; put very simplistically the effect of aerosols is to change the reflectivity of the Earth's surface to the sun's radiation (albedo).

This results in trapping of the heat rays in the atmosphere leading to an enhanced greenhouse effect and lower precipitation (rain) in the Mediterranean. The overall effect is an increase in the surface temperature of the Earth and hence global warming.

The results from Gordan lighthouse show that the concentration of surface ozone in the Mediterranean is one of the highest in the world and very slowly but steadily increasing. In 2004 the mean concentration was 53 parts per billion by volume. A comparison of the data for Malta, Crete, Cyprus and Athens shows that differently originating air masses are measured by these stations; while the Gozo station measures air masses from the Atlantic modified by passage over Spain and France, the Greek stations measure air masses originating over Northern Europe and moving south via the Balkans.

In 2002 an atmospheric measurement campaign based on Crete and led by the Max Planck Institute for Airchemistry in Mainz (the MINOS campaign) resulted in clarification of some of the mechanisms that lead to pollution of the Mediterranean region. It is clear that pollution finds its way directly into the upper levels of the Mediterranean from both the American continent and as a result of the South East Asian regime.

A campaign planned for 2005-2007 and based on aircraft measurements from Malta has failed to materialise due to a shortage of EU funds in the VIth framework programme; however it is hoped that this will be remedied in the round due next year.

The results from the carbon monoxide and sulphur dioxide instruments enable us to pick out pollution episodes that effect the Maltese Islands. During the summer months we find many examples of locally recirculated pollution that comes back to affect us directly.

However the opposite is also true. Indeed one such episode occurred last year on August 15, when three very high peaks of ozone, carbon monoxide and sulphur dioxide were recorded.

Analysis of the origin of these air masses using the so called HYSPLIT-4 model available from NCAR, Boulder, Colorado, USA, showed a track directly from the North West. It is probable that a strong pollution event possibly illegal discharge of hydrocarbons took place and hit the Maltese islands in the afternoon of that day.

The facility has obviously proved its worth both in scientific terms as well as practical usage and the University hopes it can continue to grow in collaboration with the environmental and civil protection agencies as well as serving as a major and southernmost European and UN station for climate change monitoring.

ray.ellul@um.edu.mt

Dr Ellul and Mr Saliba are from the Physics Department, University of Malta.