S. Lykoudis

Comparison of methodologies for tmy generation using 20 years data for Athens, Greece

Abstract The need of accurate Test Reference Years (TRYs) for simulations has been well recognised over the years. Various methods for deriving TRYs have been developed, but their final results can be significantly different. In this paper, the major methodologies reported in literature were applied to 20-year hourly measurements of weather data from Athens, covering the period 1977 to 1996. Seventeen TRYs were produced in total. The basis to select the “best” performing TRY includes meteorological criteria (inherent in the selection process used by each method) and comparisons of results from various simulations for typical energy systems (i.e. a solar water heater, a building, a large scale solar heating system with interseasonal storage and a photovoltaic system). Based on the results of each simulation exercise, a scoring system was developed and applied. The best performing TRY was found to be the one produced by a modified Festa-Ratto method.

Generation of a typical meteorological year for Nicosia, Cyprus

The present study is concerned with the generation of a Typical Meterological Year for Nicosia, Cyprus. The above tool will be useful for the prediction and comparison of the performance and cost effectiveness of passive and active solar systems in the island. The Typical Meteorological Year was generated from available hourly meteorological data recorded during the period 1986–1992, using the Filkenstein-Schafer statistical method.

Spatial and temporal characteristics of the relationship between air quality status and mesoscale circulation over an urban Mediterranean basin

The objective of this study is to identify and establish the day-by-day relationship between mesoscale circulation and the air quality status over the Metropolitan area of Athens for a period of 13 years and to further investigate its temporal and spatial variability. Eleven distinct mesoscale patterns are identified using a formulated methodology based on surface wind measurements. The air quality conditions are classified into seven distinct classes according to . the method of the Air Quality Indicators for five main pollutants namely, O , NO , SO , CO and black smoke BS . 32 2 It was found that severe and bad air quality conditions over specific parts of the examined area are associated with the weak mesoscale patterns of southern direction or calm conditions. The good and moderate conditions are established mainly under northerly airflows. The most serious pollution problem favored even by intense northerly flow is attributed to O during the warm period in the northern zone. High concentrations of O , NO and SO in 3 32 2 the warm period are remarkably related to the pure sea breeze circulation, especially in the central and northern zone. Q 1998 Elsevier Science B.V. All rights reserved.

“Air-quality indicators” for uniform indexing of atmospheric pollution over large metropolitan areas

Abstract National and international authorities recommend a variety of air-quality standards that should not be exceeded in local and regional scales currently. With this work a uniform indexing scale is introduced which characterises several urban pollutants in a simple and comparable manner. The “indicators” proposed are implemented at the Athens Metropolitan Area (AMA) which is an area with serious pollution problems. Hourly data from all available monitoring stations are analysed during 1983 and 1995. This analysis demonstrates that the status of air quality in Athens can be characterised as acute with regards to photochemical pollutants while strong spatial and temporal variability is encountered for all pollutants.

Atmospheric Circulation Types and Daily Mortality in Athens, Greece

We investigated the short-term effects of synoptic and mesoscale atmospheric circulation types on mortality in Athens, Greece. The synoptic patterns in the lower troposphere were classified in 8 a priori defined categories. The mesoscale weather types were classified into 11 categories, using meteorologic parameters from the Athens area surface monitoring network; the daily number of deaths was available for 1987-1991. We applied generalized additive models (GAM), extending Poisson regression, using a LOESS smoother to control for the confounding effects of seasonal patterns. We adjusted for long-term trends, day of the week, ambient particle concentrations, and additional temperature effects. Both classifications, synoptic and mesoscale, explain the daily variation of mortality to a statistically significant degree. The highest daily mortality was observed on days characterized by southeasterly flow [increase 10%; 95% confidence interval (CI), 6.1-13.9% compared to the high-low pressure system), followed by zonal flow (5.8%; 95% CI, 1.8-10%). The high-low pressure system and the northwesterly flow are associated with the lowest mortality. The seasonal patterns are consistent with the annual pattern. For mesoscale categories, in the cold period the highest mortality is observed during days characterized by the easterly flow category (increase 9.4%; 95% CI, 1.0-18.5% compared to flow without the main component). In the warm period, the highest mortality occurs during the strong southerly flow category (8.5% increase; 95% CI, 2.0-15.4% compared again to flow without the main component). Adjusting for ambient particle levels leaves the estimated associations unchanged for the synoptic categories and slightly increases the effects of mesoscale categories. In conclusion, synoptic and mesoscale weather classification is a useful tool for studying the weather-health associations in a warm Mediterranean climate situation.

A software tool for the creation of a typical meteorological year

Abstract The generation of a typical meteorological year is of great importance for passive solar architectural applications. In this context, within the PASCOOL project, a software tool has been developed, utilizing the Filkenstein-Schafer statistical method for the creation of a typical meteorological year. Using this software tool, a typical meteorological year was generated for Athens, Greece. The data used were from the National Observatory of Athens and cover a period of 17 years (1977–1993).

Estimation of the Linke and Unsworth–Monteith turbidity factors in the visible spectrum: application for Athens, Greece

Abstract Expressions for the Linke, TLvis, and Unsworth–Monteith, TUvis, turbidity parameters in the visible region of the solar spectrum are derived. They are based on new determinations of the visible transmittances for the various atmospheric constituents obtained by spectrally integrating the wavelength-dependent atmospheric transmittances. Application of the TLvis and TUvis expressions for Athens is made for the first time; this is done from measurements of direct solar irradiance in the period 1992–1995. A linear interdependence between TLvis and TUvis is derived, as in the case of their broadband counterparts. The seasonal, monthly and daily variations of these turbidity parameters are also investigated.

Comparison of performance and cost effectiveness of solar water heaters at different collector tracking modes in Cyprus and Greece

Abstract The present study is concerned with investigation of the thermal performance and cost effectiveness of thermosyphon solar water heaters with different solar collector tracking modes under the weather and socioeconomic conditions of Nicosia–Cyprus and Athens–Greece. The tracking modes are the traditional configuration with the collector surface fixed to 40 degrees from the horizontal, the single-axis tracking with vertical axis, fixed slope and variable azimuth and the seasonal tracking mode where the collector slope is changed twice per year. The investigation is conducted through computer simulations using the trnsys program. The results of the simulations indicate that the traditional thermosyphon solar water heater with fixed collector surface is the most cost-effective configuration as compared to single-axis tracking and seasonal tracking. For Nicosia, the best performance is obtained with the single-axis mode, which results in a yearly solar fraction of 87.6% as compared to 81.6% with the seasonal mode and 79.7% with the fixed surface mode, while the corresponding figures for Athens are 81.4%, 76.2% and 74.4%, respectively. The payback time of this mode, however, is 10–11 years as compared to 5 years with the fixed collector surface tracking mode.

Relationship of Air Quality Indicators and Synoptic Scale Circulation at 850 hPa over Athens During 1983–1995

The daily relationship between synoptic circulation in the lower troposphere and air quality conditions is demonstrated over the Athens Metropolitan Area (AMA) for the period between 1983 and 1995. This approach utilises eight distinct synoptic categories at the isobaric level of 850 hPa and air quality indicators with respect to O3, NO2, CO, SO2 and black smoke (BS). It is demonstrated that high concentrations of photochemical pollutants and SO2 are closely related to the synoptic scale circulation while CO and BS show a weaker correlation. The most favourable synoptic pattern for the accumulation of high concentrations is the open anticyclonic circulation and for the occurrence of extreme events the closed anticyclone. NO2 and BS present the highest frequency of severe events. The seasonal analysis reveals that the bad and extreme air quality conditions due to O3 and NO2 prevail in the warm season while during the cold season CO and SO2 events prevail. The synoptic category representing a combination of...

Noise levels in primary schools of medium sized city in Greece.

This study presents and evaluates noise levels recorded at 15 school complexes in order to describe the indoor as well as the outdoor acoustic environment of schools and gain insight on controlling factors. Noise levels at the roadside in front of the school, the schoolyard, and 41 classrooms, both occupied and unoccupied, were simultaneously and continuously recorded through the course of a daily timetable (08:20-13:10). The average speech noise level of teachers was separately measured for 1min periods. Indoor noise levels, in all cases, were much higher than internationally recommended values: LAeq,5min averaged 69.0dB in occupied classrooms, and 47.1dB in unoccupied ones. Average speech-to-noise ratio (SNR) was estimated to be 12.0dB(A) during teaching, whereas both indoor and outdoor noise levels were significantly elevated during break time and outdoor physical-educational activities. Corresponding measurements of indoor and outdoor noise suggest that noise from the outside (road and schoolyard) affects the background noise level in the classrooms, however in varying degrees, depending on the specific layout and road traffic characteristics. Using double glazing diminishes this effect.