The creation of realistic gridded precipitation fields improves our understanding of the observed... more The creation of realistic gridded precipitation fields improves our understanding of the observed climate and is necessary for validating climate model output for a wide range of applications. The challenge in trying to represent the highly variable nature of precipitation is to overcome the lack of density of observations in both time and space. Data sets of mean monthly and annual precipitations were developed for Greece in gridded format with an analysis of 30 arcsec (∼800 m) based on data from 1971 to 2000. One hundred and fifty-seven surface stations from two different observation networks were used to cover a satisfactory range of elevations. Station data were homogenized and subjected to quality control to represent changes in meteorological conditions rather than changes in the conditions under which the observations were made. The Meteorological Interpolation based on Surface Homogenized Data Basis (MISH) interpolation method was used to develop data sets that reproduce, as...
In this study long-term wind data obtained from high-resolution hindcast simulations is used to a... more In this study long-term wind data obtained from high-resolution hindcast simulations is used to analytically assess offshore wind power potential in the Aegean and Ionian Seas and provide wind climate and wind power potential characteristics at selected locations, where offshore wind farms are at the concept/planning phase. After ensuring the good model performance through detailed validation against buoy measurements, offshore wind speed and wind direction at 10 m above sea level are statistically analyzed on the annual and seasonal time scale. The spatial distribution of the mean wind speed and wind direction are provided in the appropriate time scales, along with the mean annual and the inter-annual variability; these statistical quantities are useful in the offshore wind energy sector as regards the preliminary identification of favorable sites for 269 AIMS Energy Volume 5, Issue 2, 268-289. exploitation of offshore wind energy. Moreover, the offshore wind power potential and its variability are also estimated at 80 m height above sea level. The obtained results reveal that there are specific areas in the central and the eastern Aegean Sea that combine intense annual winds with low variability; the annual offshore wind power potential in these areas reach values close to 900 W/m 2 , suggesting that a detailed assessment of offshore wind energy would be worth noticing and could lead in attractive investments. Furthermore, as a rough estimate of the availability factor, the equiprobable contours of the event [4 m/s ≤ wind speed ≤ 25 m/s] are also estimated and presented. The selected lower and upper bounds of wind speed correspond to typical cut-in and cutout wind speed thresholds, respectively, for commercial offshore wind turbines. Finally, for seven offshore wind farms that are at the concept/planning phase the main wind climate and wind power density characteristics are also provided.
... The coloured lines represent the score of the members where the tur len parameter is perturbe... more ... The coloured lines represent the score of the members where the tur len parameter is perturbed. The effect of these perturbations is generally reasonable, but the run driven by NCEP with the small tur len value shows high MAE values during daytime. ...
A case of an intense snowfall in the Greater Athens Area (GAA) between 16 and 18 February 2008 is... more A case of an intense snowfall in the Greater Athens Area (GAA) between 16 and 18 February 2008 is investigated. The physical processes that forced the snowfall event are identified and analysed. The main factor causing the event at its start was the entrainment of arctic air masses from NorthEastern Europe. At a second stage, the Aegean Sea acted as the Great Lakes of Canada and NorthEast USA and in association with the existing extremely cold air masses aloft and the enrichment of the air with humidity and heat led to the enhancement of the snowfall in the GAA. In the final stage of the event, the local meteorological conditions associated with the topography of the area resulted in the occurrence of very intense snowfall event on the leeward side of the GAA. The available operational observations and forecast tools were used for accurately predicting the intensity, duration and evolution of the event.
California faces some of the most serious air quality problems in the U.S., with motor vehicles a... more California faces some of the most serious air quality problems in the U.S., with motor vehicles a leading source of ozone forming precursors, carbon monoxide, and other toxic species. One of the control measures designed to reduce mobile source emissions of these species was the introduction in mid-1996 of California Phase 2 Reformulated Gasoline (RFG). Compared with California Phase 1 RFG (introduced in January 1992) and California Transitional Gasoline (introduced in January 1995), California Phase 2 RFG was designed reduce even further emissions of hydrocarbons, oxides of nitrogen, carbon monoxide, and toxic species, among others. An opportunity to evaluate the impact of California Phase 2 RFG was presented by the completion in October 1995, prior to the introduction of the new fuel, of an experiment measuring on-road motor vehicle emissions in the Sepulveda Tunnel of Los Angeles. Results of the 1995 study provided a benchmark with which were compared to mid-1996 or later emissio...
This project was aimed at consolidating the COSMO ensemble forecasting systems for the mesoscale.... more This project was aimed at consolidating the COSMO ensemble forecasting systems for the mesoscale. The operational ensemble COSMO-LEPS and the experimental COSMO-SREPS system, both running at 7 km horizontal mesh-size, have been designed for different forecast ranges (day 3-5 and 1-2, respectively) and with different perturbation strategies. The aim of the project was to propose a solution for a unique multi-perturbation-strategy" COSMO ensemble system, benefiting of perturbations which can produce appropriate spread for the entire forecast range (i.e., day 1-5), including a set of model perturbations which should guarantee a good description of the COSMO model error. Both perturbations of the mode physics parameters and perturbation of the soil moisture field had been considered. Furthermore, a calibration strategy was developed and applied to the QPF issued by the COSMO-LEPS ensemble. The project lasted for 3 years.
The project focused on building an ensemble system for the short-range using the COSMO model, cal... more The project focused on building an ensemble system for the short-range using the COSMO model, called COSMO-SREPS. During the first phases of the project, the ensemble was designed and implemented, then it was tested over long periods, in order to derive a robust statistical assessment of its features. In particular the system was running during the whole DOP of the MAP D-PHASE project (June to November 2007). The analysis of its performances was carried out over two COSMO regions: an alpine area and Greece.
The creation of realistic gridded precipitation fields improves our understanding of the observed... more The creation of realistic gridded precipitation fields improves our understanding of the observed climate and is necessary for validating climate model output for a wide range of applications. The challenge in trying to represent the highly variable nature of precipitation is to overcome the lack of density of observations in both time and space. Data sets of mean monthly and annual precipitations were developed for Greece in gridded format with an analysis of 30 arcsec (∼800 m) based on data from 1971 to 2000. One hundred and fifty-seven surface stations from two different observation networks were used to cover a satisfactory range of elevations. Station data were homogenized and subjected to quality control to represent changes in meteorological conditions rather than changes in the conditions under which the observations were made. The Meteorological Interpolation based on Surface Homogenized Data Basis (MISH) interpolation method was used to develop data sets that reproduce, as...
In this study long-term wind data obtained from high-resolution hindcast simulations is used to a... more In this study long-term wind data obtained from high-resolution hindcast simulations is used to analytically assess offshore wind power potential in the Aegean and Ionian Seas and provide wind climate and wind power potential characteristics at selected locations, where offshore wind farms are at the concept/planning phase. After ensuring the good model performance through detailed validation against buoy measurements, offshore wind speed and wind direction at 10 m above sea level are statistically analyzed on the annual and seasonal time scale. The spatial distribution of the mean wind speed and wind direction are provided in the appropriate time scales, along with the mean annual and the inter-annual variability; these statistical quantities are useful in the offshore wind energy sector as regards the preliminary identification of favorable sites for 269 AIMS Energy Volume 5, Issue 2, 268-289. exploitation of offshore wind energy. Moreover, the offshore wind power potential and its variability are also estimated at 80 m height above sea level. The obtained results reveal that there are specific areas in the central and the eastern Aegean Sea that combine intense annual winds with low variability; the annual offshore wind power potential in these areas reach values close to 900 W/m 2 , suggesting that a detailed assessment of offshore wind energy would be worth noticing and could lead in attractive investments. Furthermore, as a rough estimate of the availability factor, the equiprobable contours of the event [4 m/s ≤ wind speed ≤ 25 m/s] are also estimated and presented. The selected lower and upper bounds of wind speed correspond to typical cut-in and cutout wind speed thresholds, respectively, for commercial offshore wind turbines. Finally, for seven offshore wind farms that are at the concept/planning phase the main wind climate and wind power density characteristics are also provided.
... The coloured lines represent the score of the members where the tur len parameter is perturbe... more ... The coloured lines represent the score of the members where the tur len parameter is perturbed. The effect of these perturbations is generally reasonable, but the run driven by NCEP with the small tur len value shows high MAE values during daytime. ...
A case of an intense snowfall in the Greater Athens Area (GAA) between 16 and 18 February 2008 is... more A case of an intense snowfall in the Greater Athens Area (GAA) between 16 and 18 February 2008 is investigated. The physical processes that forced the snowfall event are identified and analysed. The main factor causing the event at its start was the entrainment of arctic air masses from NorthEastern Europe. At a second stage, the Aegean Sea acted as the Great Lakes of Canada and NorthEast USA and in association with the existing extremely cold air masses aloft and the enrichment of the air with humidity and heat led to the enhancement of the snowfall in the GAA. In the final stage of the event, the local meteorological conditions associated with the topography of the area resulted in the occurrence of very intense snowfall event on the leeward side of the GAA. The available operational observations and forecast tools were used for accurately predicting the intensity, duration and evolution of the event.
California faces some of the most serious air quality problems in the U.S., with motor vehicles a... more California faces some of the most serious air quality problems in the U.S., with motor vehicles a leading source of ozone forming precursors, carbon monoxide, and other toxic species. One of the control measures designed to reduce mobile source emissions of these species was the introduction in mid-1996 of California Phase 2 Reformulated Gasoline (RFG). Compared with California Phase 1 RFG (introduced in January 1992) and California Transitional Gasoline (introduced in January 1995), California Phase 2 RFG was designed reduce even further emissions of hydrocarbons, oxides of nitrogen, carbon monoxide, and toxic species, among others. An opportunity to evaluate the impact of California Phase 2 RFG was presented by the completion in October 1995, prior to the introduction of the new fuel, of an experiment measuring on-road motor vehicle emissions in the Sepulveda Tunnel of Los Angeles. Results of the 1995 study provided a benchmark with which were compared to mid-1996 or later emissio...
This project was aimed at consolidating the COSMO ensemble forecasting systems for the mesoscale.... more This project was aimed at consolidating the COSMO ensemble forecasting systems for the mesoscale. The operational ensemble COSMO-LEPS and the experimental COSMO-SREPS system, both running at 7 km horizontal mesh-size, have been designed for different forecast ranges (day 3-5 and 1-2, respectively) and with different perturbation strategies. The aim of the project was to propose a solution for a unique multi-perturbation-strategy" COSMO ensemble system, benefiting of perturbations which can produce appropriate spread for the entire forecast range (i.e., day 1-5), including a set of model perturbations which should guarantee a good description of the COSMO model error. Both perturbations of the mode physics parameters and perturbation of the soil moisture field had been considered. Furthermore, a calibration strategy was developed and applied to the QPF issued by the COSMO-LEPS ensemble. The project lasted for 3 years.
The project focused on building an ensemble system for the short-range using the COSMO model, cal... more The project focused on building an ensemble system for the short-range using the COSMO model, called COSMO-SREPS. During the first phases of the project, the ensemble was designed and implemented, then it was tested over long periods, in order to derive a robust statistical assessment of its features. In particular the system was running during the whole DOP of the MAP D-PHASE project (June to November 2007). The analysis of its performances was carried out over two COSMO regions: an alpine area and Greece.
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