NATIONAL OBSERVATORY OF ATHENS

WEATHER FORECASTING

Operational weather forecasting is presented to the public through the popular web page www.meteo.gr (in greek) as well as through the English web page www.noa.gr/forecast. Meteo.gr provides 6-days weather forecasts for 500 cities across Greece, together with UV forecasts. Moreover, interactive map provides detailed wind and wave forecasts for the Greek Seas.

SOLAR ULTRAVIOLET (UV) INDEX FORECASTING FOR GREECE

The UV index is an internationally defined expression of the risk of solar ultraviolet radiation to humans and the ecosystem. The calculation of the UV index forecast is presented daily from the Institute for Environmental Research and Sustainable Development of the National Observatory of Athens. The methodology used includes a radiation transfer model with input parameters such as the solar zenith angle, cloud cover forecast, total column ozone forecasting (KNMI / ESA), the long-term climatology of aerosols from satellite measurements, ground albedo and altitude for each sub-region of the map below. Website: http://www.meteo.gr/meteoplus/uv.cfm Information related with the effects of UV radiation on health (dermatological effects, melanomas, cataracts, vitamin D), effects on plants (photosynthetic capacity) and marine ecosystems are also provided.

METEOROLOGICAL OBSERVATIONS

The extensive network of almost 260 fully automated meteorological stations, established by IERSD all over Greece, offers to the public, in almost real-time (data refreshment every 10 min), information about prevailing meteorological conditions. Meteorological parameters that are presented are the following: Air temperature (ºC) and relative humidity (%), Atmospheric pressure (hPa), Wind speed (m/s or Km/h) and wind direction (deg.), Total precipitation (mm) (rainfall, snow, or hail). In selected meteorological stations, the incoming total solar radiation (W/m²) and ultra-violet (UV) radiation (W/m²), incident at a horizontal surface, are also provided to the public. Real-time measurements of the above meteorological parameters are widely available to the public through the following WEB links: www.meteo.gr/meteosearch. All meteorological observations and measurements are automatically saved in the database for further statistical analysis.

ACTINOMETRIC OBSERVATIONS

The expanding network of radiometric stations includes two stations within Attica region, the historic radiometric station in Thissio and the newest in Penteli, but also six more stations scattered throughout Greece: in Klokotos (Trikala), in Larissa (Thessaly), in Methoni (Messinia, South Peloponnese), in Filotas (Florina), in Andros island (Cyclades) and in Antikythira island. Also included is another high altitude station (at 2340 m) in Neraidorahi site of Helmos mountain in Kalavryta (Achaia).

At all of the above stations, the intensity of the total incoming solar radiation (in W/m2) incident at a horizontal plane is recorded, in five of them the diffuse solar component (in W/m2) is recorded in parallel, while in four of them the duration of sunshine duration (in minutes) is also measured.

Both radiometric stations at Thissio and Penteli sites also record the intensity of the incoming Ultra-Violet solar radiation (Total UV, UV-A, UV-B, in W/m2) as well as the intensity of the natural daylight (in Lux) (Total and Diffuse components).

Furthermore, all basic meteorological parameters such as air temperature (oC) and relative humidity (%), atmospheric pressure (hPa), wind speed (m/sec) and direction (degrees) and total precipitation (mm) (rainfall, snow, hail) are recorded in parallel.

Real-time measurements of the above actinometric and meteorological parameters are widely available to the public through the following WEB link: www.iersd.noa.gr/WeatherOnLine.

For each parameter presented, the historic daily fluctuation is also available throughout the WEB-page for a period of 10 days.

All meteorological observations and measurements are automatically saved in the database for further statistical analysis.

SEVERE WEATHER MONITORING AND NOWCASTING

The Weather Radar Group operates unique equipment for the in situ measurement and remote sensing of rainfall, which includes a mobile weather radar, a 2D video and a Parsivel disdrometer and a network of rain gauges with data loggers. The system can provide monitoring and nowcasting of localized severe weather events (intense rain and hail storms, tornadoes) for distances up to 100 km.