Nikolaos Soulakellis

Socioeconomic Dimensions of Changes in the Agricultural Landscape of the Mediterranean Basin: A Case Study of the Abandonment of Cultivation Terraces on Nisyros Island, Greece

Agricultural landscapes illustrate the impact of human actions on physical settings, and differential human pressures cause these landscapes to change with time. Our study explored changes in the terraced landscapes of Nisyros Island, Greece, focusing on the socioeconomic aspects during two time periods using field data, cadastral research, local documents, and published literature, as well as surveys of the islanders. Population increases during the late 19th to early 20th centuries marked a significant escalation of terrace and dry stone wall construction, which facilitated cultivation on 58.4% of the island. By the mid-20th century, the economic collapse of agricultural activities and consequent emigration caused the abandonment of cultivated land and traditional management practices, dramatically reducing farm and field numbers. Terrace abandonment continued in recent decades, with increased livestock grazing becoming the main land management tool; as a result, both farm and pasture sizes increased. Neglect and changing land use has led to deterioration and destruction of many terraces on the island. We discuss the socioeconomic and political backgrounds responsible for the land-use change before World War II (annexation of Nisyros Island by the Ottoman Empire, Italy, and Greece; overseas migration opportunities; and world transportation changes) and after the war (social changes in peasant societies; worldwide changes in agricultural production practices). The adverse landscape changes documented for Nisyros Island appear to be inevitable for modern Mediterranean rural societies, including those on other islands in this region. The island’s unique terraced landscapes may qualify Nisyros to become an archive or repository of old agricultural management techniques to be used by future generations and a living resource for sustainable management.

Identifying geomorphic features using LANDSAT-5/TM data processing techniques on Lesvos, Greece

In order to delineate the geomorphic features of the island of Lesvos, Greece, fieldwork and digital satellite (LANDSAT-5/TM) data analysis were combined. The main image analysis techniques involved in this study were (1) principal component analysis (PCA) and (2) false color composite (FCC). These techniques led to the creation of enhanced satellite images with respect to the topographic and geomorphologic characteristics of the island. The final digitally enhanced LANDSAT-5/TM images have been used to interpret and map the geomorphic features of Lesvos. Ground-truthing of image data led to the identification of the following geomorphic units: dissected metamorphic terrains, lava plateaus, colluvial foothills, alluvial plains (including coastal and fluvial), and eroded regions underlain by ignimbrite and welded tuff. Lineaments detected in this study were coincident with: (1) mapped contacts or faults, (2) extensions of previously mapped faults or (3) previously undetected geologic features including faults, tectonic contacts or formational contacts.

Towards a semantics-based approach in the development of geographic portals

As the demand for geospatial data increases, the lack of efficient ways to find suitable information becomes critical. In this paper, a new methodology for knowledge discovery in geographic portals is presented. Based on the Semantic Web, our approach exploits the Resource Description Framework (RDF) in order to describe the geoportals information with ontology-based metadata. When users traverse from page to page in the portal, they take advantage of the metadata infrastructure to navigate easily through data of interest. New metadata descriptions are published in the geoportal according to the RDF schemas.

ICAROS: An Integrated Computational Environment for the Assimilation of Environmental Data and Models for Urban and Regional Air Quality

Integrated environmental management in urban areas is nowadaysconsidered a sine qua non objective of Community and nationalenvironmental and development policies. A large amount ofscientific information on the state of the environment is nowavailable from a large pool of data sources. This work presentsan innovative method for integration of these data sources andeffective coupling of environmental information with appropriatemodels and decision-support tools. State-of-the-art Earthobservation techniques, ground-based air quality measurements,atmospheric transport and chemical modelling, and multi-criteriadecision-aid systems are used in an integrated information fusionenvironment in support of environmental and health impactassessment and decision-making at the urban and regional scales. Results of the pilot application of the method in the area ofLombardy in Northern Italy demonstrate the validity andusefulness of this novel approach.

Fusing Landsat-5/TM Imagery and Shaded Relief Maps in Tectonic and Geomorphic Mapping: Lesvos Island, Greece

The significance of both solar elevation angle and azimuth are critical elements for examining Earth observation datasets. Illumination angle is a crucial parameter affecting the appearance of the topographically related and dependent features. Therefore, an improved methodology of data fusion for tectonic and geomorphic mapping is needed to augment the traditional false color composite analysis. A long-standing problem in such applications is the bias introduced by illumination geometry, specifically sun elevation and azimuth. A Landsat-5 image of Lesvos Island, Greece, was combined with digital elevation models to produce fused images with a wide range of illumination azimuths and elevation in a GIS environment. Sixteen combinations of sun elevation angle (using 15° and 30°) paired with azimuth (0° to 360° at 45° increments) were considered. This new technique compensates for local conditions such as generally cloudy winters which make it difficult to obtain images with low sun elevation or images of eroded landforms with subdued geomorphic expression. The resulting fused images combine the tonal information and high spatial resolution of Landsat with the strong topographic rendition of digital elevation models. Well-known faults, with more or less significant expression on the surface known from previous image interpretation and fieldwork, are more easily identifiable. Shaded relief maps produced by applying the lower illumination angle in combination with an azimuth perpendicular to the fault orientation produced the best results. Additionally, previously unknown linear and circular features, e.g., calderas, were represented in the low illumination angle image, independent of its azimuth. Fused images will be further combined with geologic and seismicity maps to study problems such as location of the Anatolian Plate’s boundaries and their nature (sharp or diffuse).

Satellite Image Processing for Haze and Aerosol mapping (SIPHA): code description and presentation of results

The monitoring of aerosol concentrations becomes a high environmental priority particularly in urban areas. The aerosol optical thickness in the visible spectrum is a surrogate for fine aerosol concentrations, especially under pollution conditions with low mixing height, and can be measured with high ground sampling density with the help of satellite sensors. The SIPHA code was developed for such application on high-resolution satellite images and allows quantification of the aerosol optical thickness over land, snow and sea. The code compares multitemporal satellite data sets and evaluates radiometric alterations due to the optical atmospheric effects of aerosols. A novel feature of this code is the decoupling of the radiometric alterations due to optical atmospheric effects from those due to ground temporal variations. A real-scale application of the code on time series of Landsat data was carried out over European urban sites.

A GIS tool for the evaluation of the precipitation forecasts of a numerical weather prediction model using satellite data

In this study, the possibility of implementing Geographic Information Systems (GIS) for developing an integrated and automatic operational system for the real-time evaluation of the precipitation forecasts of the numerical weather prediction model BOLAM (BOlogna Limited Area Model) in Greece, is examined. In fact, the precipitation estimates derived by an infrared satellite technique are used for real-time qualitative and quantitative verification of the precipitation forecasts of the model BOLAM through the use of a GIS tool named as precipitation forecasts evaluator (PFE). The application of the developed tool in a case associated with intense precipitation in Greece, suggested that PFE could be a very important support tool for nowcasting and very short-range forecasting of such events.

Three-Dimensional Ground-Based Measurements of Urban Air Quality to Evaluate Satellite Derived Interpretations for Urban Air Pollution

Urban air quality and meteorological measurements were carried out in the region of Brescia (Italy) simultaneously to the acquisition of satellite data during winter and summer smog conditions in 1999. The main objectives of the campaigns were: delivery of data for the validation of air pollution interpretations based on satellite imagery, and determination of the aerosol optical thickness in spectral ranges similar to those used by satellites. During the winter campaign the ground-based network was complemented by local stations and by SODAR, DOAS, and FTIR remote sensing measurements. Size distributions of aerosol particles up to 4,000 m a.s.l. were measured by means of an ultra-light aircraft, which was also equipped with meteorological sensors and an ozone sensor. During the summer campaign an interference filter actinometer, an integrating nephelometer and an ozone LIDAR were operated additionally. The satellite images acquired and processed were taken from SPOT. Optical thickness retrieved from interference filter actinometer measurements were compared with the retrievals from the satellite imagery in the same spectral intervals. It is concluded that remaining aerosols in the reference image yield an off-set in the satellite retrieval data and that information about the vertical structure of the boundary layer is very important.

Estimation and Mapping of Aerosol Optical Thickness over the City of Brescia - Italy Using Diachronic and Multiangle SPOT-1, SPOT-2 and SPOT-4 Imagery

Abstract In this paper we process diachronic SPOT satellite images acquired with different viewing angles in order to assess the aerosol optical thickness (AOT) spatial distribution over Brescia. This urban area, located in Northern Italy, is subject to frequent visibility‐reducing smog episodes. AOT was calculated by using the Differential Textural Analysis (DTA) code on a satellite data series consisting by one pollution‐free and various pollution‐loaded SPOT images. The resulting maps showed the horizontal distribution of AOT with a resolution of 500 metres. These maps can be readily integrated with the results obtained by mesoscale modelling, ground measurements, and respond to local scale application requirements. Satellite AOT retrieval compared successfully with available AOT ground‐based measurements and with pollution measurements in the ambient air. In this study the use of diachronic multiangle SPOT imagery allowed us to analyse the effect of the viewing angle variation on AOT retrieval accuracy based on the contrast reduction method.

THE IMPORTANCE OF MIXING HEIGHT IN CHARACTERISING POLLUTION LEVELS FROM AEROSOL OPTICAL THICKNESS DERIVED BY SATELLITE

In the present study the horizontal distribution of columnar aerosol optical thicknessderived at high spatial resolution from Earth observation satellite data in the Lombardy area (Italy) was converted to the horizontal distribution of optically effective aerosols concentration at the ground level. This was achieved by incorporating information on atmospheres mixing height, at which pollutants released at ground level are vertically dispersed by convection or mechanical turbulence. The resulted fields compared favourably to pollutant concentration measurements provided by the ground stations. These results show that it is possible to calculate mean concentration fields by using the spatial distribution of aerosol optical thickness (AOT) measured by satellite normalized by the atmospheric mixing height. The advantage of satellites in measuring AOT is that they can capture all actual emissions compared to the models, which are based on inventoried data.