On the effect of land use change on the meteorological parameters above the greater Athens area

The rapid land use changes that took place in the Greater Athens Area (GAA) the past decades, due to the expansion of the urban grid, have changed the landscape of Attica significantly. Areas that were covered by low vegetation in the past are now replaced by roads (e.g. Attiki Odos) and new towns. On the other hand, accurate and updated data of land use are necessary for simulating the meteorological fields above urban areas, which in turn are given as input to photochemical models in order to study the dispersion of pollutants above urban areas. The purpose of the present work is to study the effects of land use changes on the meteorological parameters, such as wind speed profiles and temperature. For this reason, the meteorological mesoscale model MM5 was applied, using updated land use data. The model ran with the grid nesting method using two grids, the fine one covering the GAA with a spatial resolution of 5 × 5 km2. Results showed that the land use changes affected wind and temperature fields. Wind velocities decreased above areas covered by urban grid that were previously characterised as shrub land, while above the rapidly developing eastern suburbs of Attica an increase in velocities appeared

Synoptic environment related to rapid cyclogenesis in the Eastern Mediterranean

International audienceThis paper presents first results on the investigation of the synoptic conditions that led to the rapid development of a low-pressure system over the Aegean Sea. Indeed, during the period 21?22 January 2004, a very deep cyclone was observed over the Aegean Sea with a minimum central pressure of ~972 hPa, a value which is among the lowest observed over the entire Mediterranean Sea during the last 40 years. The rapid development was associated with a two-trough system that, under the influence of a very intense upper-level jet, was merged in one and then acquired a negative tilting. Additional information on the mesoscale organisation of the system is given, based on lightning data and space borne microwave and infrared observations

A model-based study of the wind regime over the Corinthian Gulf

The Corinthian Gulf is a narrow sea-level passage surrounded by a steep complex topography that consists of high mountains as well as elevated and sea-level gaps and straits. The complex terrain is expected to affect the wind flow in the area that often experiences high winds, with important consequences on the commercial and recreational activities over the gulf's maritime area. For that reason, a model-based study of the wind regime over the Corinthian Gulf has been created, as observational data over the area are recent and spatially sparse. Analysis of 5 yr of data from the fifth-generation Penn State/NCAR mesoscale model (MM5) model reveals that the wind regime of the gulf is greatly influenced by the topography. Easterly winds occur more frequently and are stronger in the maritime area in the western edge of the gulf, with a frequency of occurrence on the order of 70%. Moreover, the most intense wind events at this area occur during the winter season (December, January, and February). Finally the paper also provides a discussion on the synoptic patterns, which lead to the strongest wind events in the studied area

Effect of the land use change characteristics on the air pollution patterns above the greater Athens area (GAA) after 2004

The Attica Peninsula has experienced the rapid expansion of the Athens urban area, prior to the Athens 2004 Olympics. As a result, the distribution of pollutant sources and emission patterns has changed with a subsequent effect on the distribution of photochemical pollutants and aerosols. The purpose of the present work is to perform a comparative study of the land use changes in the rapidly developing Attica Peninsula including the Greater Athens Area (GAA) before and after 2004, the year that the Olympic Games took place, as well as of the effect of these changes on the respective pollutant distribution profiles. The land use data were provided by USGS Global Land Use/Land Cover version 2.0 Database and the updating process was fulfilled with the help of a satellite image. The area was divided into cells using a spatial resolution of 5x5 km2. Results showed that the urban grid has expanded considerably the past fifteen years while a great shift of population has been made to the eastern area of Attica. Also, new towns were created while others expanded and many factories moved out of the center of the city of Athens. Moreover, the forest land has decreased considerably in the Attica Peninsula either by continuous and extended fires or by the residential burst. The Comprehensive Air Quality Model with extensions (CAMx) was used in order to estimate O3 distribution during a recorded pollution episode. Results revealed that land use changes affected slightly the O3 concentrations and the development of a new emission inventory related to the new LULC field is necessary

High-resolution wave model validation over the Greek maritime areas

The increasing maritime activity can be seriously affected by severe weather and sea conditions. To avoid serious damages to ships, marine structures and humans, a good weather and wave forecast is of primary importance. In general the meteorological and the wave models are used to produce forecasts at large scale like the global or the medium-size inner seas. For much smaller environments like the Greek maritime areas, characterized by complicated features like the orography and the presence of islands, the modelisation becomes a not simple task. <br><br> This study is devoted to the validation of the performance of the WAM wave model over the Ionian and Aegean Seas. The period of validation refers to the first 12 months of operational use of the model at the National Observatory of Athens. The wave model is applied at a resolution of 1/16 degrees and is driven by the 10 m wind, produced by the BOLAM meteorological model operationally run over the same area. Two different sources of data have been used for the verification of the model results. The first dataset is provided by a network of buoys deployed over the Greek maritime areas and the second consists of altimeter data, provided by the OSTM/Jason-2 satellite platform. Although the study area is characterized by complex topography and a large number of islands, the implementation of the WAM model provides very encouraging results. In general, with the exception of the two buoys located in the Ionian Sea, the WAM model tends to underestimate the wave energy in the region of the Aegean Sea. The comparison with the altimeter data shows that the model has a tendency to overestimate the height for waves lower than 2.5 m and to underestimate the waves higher than 3 m

Assimilation of numerical study of the distribution of ozone above the greater Athens area (GAA)

Air pollution is considered to be a critical environmental problem of large urban areas posing a threat to human health because of elevated concentrations of pollutants such as O3, NOx, VOCs and PM. In the past decades the GAA has experienced rapid expansion of the urban grid. Thus, the current study aims to examine the distribution of ozone above the GAA, with the help of the photochemical model CAMx, and assess the contribution of multiple geographical source areas, boundary and initial conditions to ozone formation. Results showed that the transport of primary and secondary pollutants can affect the air quality of the receptor area. Many pollution episodes reported to ground stations are often due to the development of a local circulation system (sea breeze) that disperses intense pollutant emissions. Moreover, the boundary and initial conditions used in numerical studies play a significant role to the ozone formation

© Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License. Natural Hazards

Relationship between lightning and model simulated microphysical parameters over the central and eastern Mediterranea

Impact of the assimilation of conventional data on the quantitative precipitation forecasts in the Eastern Mediterranean

International audienceThis study is devoted to the evaluation of the role of assimilation of conventional data on the quantitative precipitation forecasts at regional scale. The conventional data included surface station reports as well as upper air observations. The analysis was based on the simulation of 15 cases of heavy precipitation that occurred in the Eastern Mediterranean. The verification procedure revealed that the ingestion of conventional data by objective analysis in the initial conditions of BOLAM limited area model do not result in a statistically significant improvement of the quantitative precipitation forecasts

Relationship between lightning and model simulated microphysical parameters over the central and eastern Mediterranean

Aubert Marcel. Lejeaux (Jeanne). Sculpture religieuse (Bibliothèque catholique des sciences religieuses), 1934. In: Bulletin Monumental, tome 93, n°2, année 1934. pp. 267-268

Development of Grid e-Infrastructure in South-Eastern Europe

Over the period of 6 years and three phases, the SEE-GRID programme has established a strong regional human network in the area of distributed scientific computing and has set up a powerful regional Grid infrastructure. It attracted a number of user communities and applications from diverse fields from countries throughout the South-Eastern Europe. From the infrastructure point view, the first project phase has established a pilot Grid infrastructure with more than 20 resource centers in 11 countries. During the subsequent two phases of the project, the infrastructure has grown to currently 55 resource centers with more than 6600 CPUs and 750 TBs of disk storage, distributed in 16 participating countries. Inclusion of new resource centers to the existing infrastructure, as well as a support to new user communities, has demanded setup of regionally distributed core services, development of new monitoring and operational tools, and close collaboration of all partner institution in managing such a complex infrastructure. In this paper we give an overview of the development and current status of SEE-GRID regional infrastructure and describe its transition to the NGI-based Grid model in EGI, with the strong SEE regional collaboration.Comment: 22 pages, 12 figures, 4 table