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OBSERVATIONAL NETWORKS OPERATED BY THE NATIONAL OBSERVATORY OF ATHENS V. . Kotroni - K. Lagouvardos Institute of Environmental Research National Observatory of Athens
NETWORK OF AUTOMATED SURFACE METEOROLOGICAL STATIONS • LIGHTNING DETECTION NETWORK
DESCRIPTION OF THE AUTOMATED SURFACE METEOROLOGICAL STATIONS NETWORK • Build a low-cost real-time surface observation network with the aim to: • support scientific needs for studies related to weather and climate over Greece • inform citizens for the present weather • support a variety of financial activities (e.g. tourism and leisure, agriculture, energy supply)
THE NETWORK • 250 stations: 210 are property of NOA, while the rest are property of municipalities, operated under the supervision of NOA • 20 stations are installed in elevation exceeding 1000 m, permitting thus the monitoring of weather in mountainous areas. • 35 stations measure total solar radiation
AVAILABILITY OF DATA • Real-time provision of data to all users through the web. • Provision of historical data through the web. • Provision of historical data / time series on request for scientific and/or technical applications.
HISTORICAL DATA www.meteo.gr/meteosearch
DESCRIPTION OF THE LIGHTNING DETECTION NETWORK A long-range lightning detection network with receivers located at six sites over Europe (Birmingham in UK, Roskilde in Denmark, Iasi in Romania, Larnaka in Cyprus, Athens in Greece and Mazagon in Spain). The network is operated by the National Observatory of Athens since 2005. The location of flashes are given in real-time at NOA’s web-site: http://www.noa.gr/forecast/lightning.gif
ZEUS NETWORK • ZEUS receivers record the radio noise (sferics) emitted by cloud-to-ground lightning discharges in the very-low-frequency (between 7-15 kHz). • The VLF signal is preamplified at each receiver site and the signal is synchronized to GPS time. • At each receiver site an identification algorithm is executed and is capable of capturing up to 70 sferics per second. • Then the lightning location is retrieved (at the central station of the network) using the ATD triangulation technique. • The ATD values represent positions between two outstations with the same time difference, and their intersection defines a sferic fix.
LIGHTNING METEOROLOGY • The ZEUS lightning detection network operated by the National Observatory of Athens is/has been used in order to study among others the : • relationship between lightning activity and physiographic characteristics • relationship between lightning and cloud microphysical properties • relationship between lightning and rainfall • use of lightning as a nowcasting tool • use of lightning for assimilation in NWP models.
LIGHTNING AND PHYSIOGAPHIC CHARACTERISTICS • during spring and summer there is a positive relationship of lightning activity with elevation while this feature is not evident during the rest of the year. • the lightning activity was found to be positively correlated with the elevation slope throughout the year except winter.
LIGHTNING AND PHYSIOGAPHIC CHARACTERISTICS • over bareground the lightning “yield” is low during the whole year while the inverse is true for woodland areas. • during the warm period of the year, due to drying of the Mediterranean surfaces, the forested and wooded areas that keep soil moisture present increasedlightning “yield” in contrast with the shrubland areas that for the same period present a decreased lightning yield.
LIGHTNING CLIMATOLOGY Thunderstorms and the accompanied lightning activity might be dangerous for : • human life (loss of 1 person/year) • the physical environment (forest fires) • the economic environment (damages to infrastructure, cultivations, …) when heavy rain rates / rainfall produce severe flood events. • The knowledge of the spatial and temporal distribution of lightning activity is important for public authorities and for the design of the lightning protection of infrastructure.