The ENVIBASE-Project

Documentation / Online Handbook

Climate

Description of the Problem

Athens enjoys a pleasant Mediterranean climate, although conditions have changed dramatically in the post-war period. Nearly half the Greek population have gathered in the Attica area, burdening the environment with buildings, roads, and traffic-induced smog. Climatic conditions such as bright sunshine and lack of winds favour the concentration of photochemical pollutants.

The horizontal velocity of the wind is the most important factor in the dispersion of the pollutants.

Data Sources

In the Municipality of Athens, there is one complete first-class meteorological station, operated by the Institute of Meteorology and Physics of the Atmospheric Environment (IMPAE) since 1858. Until 1931 IMPAE was the main meteorological establishment in the country, but in 1932 the operation of all stations was undertaken by the newly founded National Meteorological Service (NMS).

In the area of Attica, there are six meteorological stations operated by the NMS:

• Ellinikon Airport;
• Municipality of Philadelphia;
• Tatoi Military Airport;
• Municipality of Elephsina;
• Municipality of Spata;
• Municipality of Marathon.

Methods, Results

The climatic data concerning Athen’s Station are in the form of a database. The data are annually published in the Climatological Bulletin, which contains summaries of meteorological observations gathered at the Institute of Meteorology and Physics of the Atmospheric Environment of the National Observatory of Athens (NOA) on the Hill Nymphs (height of 107 m above MSL) near the centre of Athens. Continuous observations of standard meteorological parameters have been carried out at this location, the close surroundings of which have remained unaltered since 1858.

The bulletin includes tables of mean hourly, daily, and monthly values of:

• Air temperature;
• Soil temperature at a depth of 0.15 m;
• Relative humidity;
• Atmospheric pressure;
• Wind speed and direction;
• Rainfall amount and duration;
• Evaporation, dew-point, saturation deficit, and vapour pressure;
• Sunshine duration, cloudiness and cloud type;
• Direct total and diffuse (without shadow ring correction) solar radiation;
• Global and diffuse luminance;
• Visibility;
• Miscellaneous phenomena.

Since the first of January 1991, the solar temperature station has been completely automated and therefore the temperature recording is now continuous.

Details of Instruments and Observing Practices

Total precipitation is measured with standard rain gauges. The total amount as well as the highest recorded value is obtained for a nominal 24-hour day that starts and ends at 0800 LST.

Since May 1995, air temperature (dry and wet) has been measured with electronic thermometers (August psychrometer). The thermometers are housed in a Stevenson screen 1.50 m above ground level. Ground level temperatures and soil temperatures at various depths are measured continuously with electronic thermometers (Campbell Scientific Ltd, model 107).

An electronic anemometer is used for wind observation. Mercury barometers and barographs are used for the pressure readings. The characteristics of pressure tendency during the 3-hour period before each observation is determined from the barograph placed beside the barometer at 0800, 1400 and 2000 LST at the NOA actinometric station. Evaporation is measured with Wild and Piche evaporimeters, which are also housed in the Stevenson screen. Sunshine duration is recorded with a Campbell-Stokes sunshine recorder; global and diffuse components are measured with Eppley pyranometers and direct component with a Kipp-Zonen actinometer.

Uses

The use of the above mentioned system is also for public information and planning.

Addresses for responsible Agencies