Stelios Pashiardis - Academia.edu (original) (raw)

Papers by Stelios Pashiardis

Solar Energy and Sustainable Development Journal

In this work, hourly measurements of global solar irradiances obtained from a pyranometer and dir... more In this work, hourly measurements of global solar irradiances obtained from a pyranometer and direct normal irradiances obtained from sunshine duration sensor are assessed through an extensive quality control procedure and statistical analysis on the measured and derived solar parameters for a semimountainous location using data from the last fie years (2016-2020). This information and the method suggested concerning the solar energy capture systems and energy efficiency is useful for engineers who can therefore take knowledge of the local radiation levels. Furthermore, the direct horizontal irradiance canbe easily calculated and the diffuse component can be estimated from the difference of global and direct horizontal irradiances. Monthly mean hourly values of the radiation components are also estimated and shown through isolines diagrams. Representative values of global direct and diffuse irradiances for different times of the year and different hour of the day can be easily read ...

The purpose of this paper is to compare daily sunshine duration (SD) measured by Campbell-Stokes ... more The purpose of this paper is to compare daily sunshine duration (SD) measured by Campbell-Stokes sunshine recorder (CS) with three automatic instruments (Kipp & Zonen pyranometers (CM6B), pyrheliometer (CHP1) and CSD3 sunshine recorders). The comparisons are essential, since in recent decades automatic sunshine duration sensors have been systematically replacing the manual measurements affecting therefore the continuity of the CS time series. The comparisons were applied to the daily SD data of three synoptic stations (Larnaca A/P, Pafos A/P and Athalassa) where parallel measurements of manual and automatic instruments are carried out during the periods 2009-2012 and 2012-2015. The CSD3 measurements were obtained from two automatic weather stations (AWS) (Mennogia and Pentakomo) which are closed to the synoptic station of Larnaca A/P. The comparisons cover the daily and monthly sums, their statistical distributions and their relationships. The daily differences of the pairs of the s...

SM journal of biometrics and biostatistics, 2017

A statistical analysis and inter-comparison of the Ultraviolet Radiation (UVR) at two sites in Cy... more A statistical analysis and inter-comparison of the Ultraviolet Radiation (UVR) at two sites in Cyprus representing two different climate regimes of the island (Athalassa-inland plain vs Larnaca-coastal location) covering the period 2013-2015 is presented. Mean annual and mean monthly daily totals of the UV irradiation and their frequency distribution at both sites are computed and discussed. The total accumulated UV irradiation along an average year reaches 398 MJ m-2 at Athalassa and 494 MJ m-2 at Larnaca. During summer, the daily UV radiation exceeds the value of 1800 kJ m-2 at Athalassa and 2200 kJ m-2 at Larnaca. Linear relationships were established between UVR and global solar radiation, with the coefficient of determination close to 1. These relationships indicate that UV irradiation corresponds to 5.9% and 6.8% of the horizontal global solar irradiation at the two sites, respectively. Four models were tested for the estimation of UVR and the best performed models were recalibrated according to the local conditions. Relationships between the clearness index (t k) and the UV hemispherical transmittance (tUV k) were also established. The annual tUV k is about 71% of t k. Finally, the dependence of the UV/G ratio values to the solar elevation angle and clearness index was also examined. It can be concluded that the presence of clouds reduces less the UV component rather than the global solar radiation, due to the strong absorption of water in the near infrared spectrum.

Renewable Energy, Oct 1, 2016

Routine measurements of irradiance are valuable for many research fields such as energy applicati... more Routine measurements of irradiance are valuable for many research fields such as energy applications. However, ground data of solar global radiation can present questionable values. In this study, a set of check procedures is used to test the quality of shortwave and longwave radiation measurements taken at two actinometric stations in Cyprus (Athalassa-inland location and Larnaca-coastal location), during the period November 2012eJuly 2014. The testing procedures include physically possible limits for all the radiation components and comparisons between global radiation and the sum of direct and diffuse radiation. The quality process is implemented to both the 10-min averaged irradiances, hourly irradiation and the respective daily values. This paper reviews the currently available procedures for quality assessment of the solar shortwave and longwave irradiation data. In the present study, the first level of test includes physical possible limits which are determined by the Daylight Research Group and the Baseline Surface Radiation Network of the World Meteorological Organisation (WMO). The second level of test is a semi-automated procedure that is based on the creation of an envelope in the clearness index and the diffuse to global irradiance ratio. The third level of test is based on the comparison of various radiation parameters including comparison of measured extreme values with theoretical estimations from clear sky-models. The fourth level of test of the quality control procedure refers to the analysis of daily and annual variations of the radiation parameters.

Renewable Energy, Oct 1, 2017

Statistical analysis of ultraviolet erythemal radiation.  Monthly and diurnal variation of ultra... more Statistical analysis of ultraviolet erythemal radiation.  Monthly and diurnal variation of ultraviolet erythemal radiation.  Statistical relationships between ultraviolet erythemal and other radiation components, total ozone column, relative air mass, clearness index and solar zenith angle.  Calculation of UV Index.  Estimation of the cumulative doses during an average year for the four skin phototypes.  Comparison of ultraviolet erythemal radiation between two sites.  It is the first time that an analysis of this type is performed in Cyprus.

SM journal of biometrics and biostatistics, 2018

A statistical analysis and inter-comparison of the reflected radiation at two sites in Cyprus rep... more A statistical analysis and inter-comparison of the reflected radiation at two sites in Cyprus representing two different climate regimes of the island (Athalassa-inland plain vs Larnaca-coastal location) covering the period January 2013-December 2015 is presented. Mean annual and mean monthly daily totals of the reflected radiation and ground albedo as well as their frequency distribution are computed and discussed. The monthly means of reflected irradiance range from 50 to 120 W m-2 at Athalassa, while at Larnaca they range between 50 and 140 W m-2. The mean annual albedo for Athalassa is 0.202 which coincides with the most common value given in the literature, while for Larnaca it is higher (0.221). The higher value at Larnaca is attributed to its alluvial (silty sandy) soil which has higher reflectivity compared to the calcarenite (calcium carbonate) soil at Athalassa. The lowest values of albedo at Athalassa, are observed around noon and the higher values in the morning and afternoon. The highest values are obtained in January and February and the lowest in May and June when global solar irradiance have its higher values. On the other hand, we observe an increasing trend from the morning towards the afternoon hours at Larnaca throughout the year. The maximum of daily reflected irradiation is about 6.5 MJ m-2 at Athalassa and about 7.5 MJ m-2 at Larnaca. The monthly mean daily values of albedo at Athalassa range between 0.175 to 0.224, while at Larnaca they are higher ranging from 0.198 to 0.239. As a result of the differences of the global and reflected radiation of the two sites, the net shortwave irradiation at Larnaca is slightly higher than that at Athalassa, almost throughout the year.

SM journal of biometrics and biostatistics, 2017

Measurements of Photosynthetically Active Radiation (PAR) and global solar radiation at Larnaca (... more Measurements of Photosynthetically Active Radiation (PAR) and global solar radiation at Larnaca (a coastal site in Cyprus) during the period 3013-2015 were used to investigate the seasonal characteristics of PAR and PAR/G ratio (PAR fraction or fFEC). PAR showed seasonal features with higher values in summer and lower values in winter. The annual mean values of PPFD and fFEC being 40.3 mol m-2 d-1 and 2.03 mol M J-1 , respectively. Monthly average daily PAR increased from 19.1 mol m-2 d-1 (in December) to 59.6 mol m-2 d-1 (in June).The monthly daily average of fFEC remained almost constant throughout the year at Larnaca. The spatial variability of PAR was also investigated using measurements from other four sites with different climate characteristics. The annual mean daily PAR value ranged between 31.7 to 40.0mol m-2 d-1. The highest values are recorded in the coastal stations (Larnaca and Paralimni). The annual average value of fFEC at the five observation sites ranged from 1.82 mol MJ-1 to 2.03 mol MJ-1 , in accordance to what is observed in most parts of the world. The highest appeared in the coastal sites of Larnaca and Paralimni due to the presence of high water vapour atmospheric concentrations. Elevation plays a significant role on the values of the above variables. As a general trend, fFEC followed the order Clear<Partly cloudy<Cloudy. In all cases fFEC was decreased with elevation but with a different rate. Three linear or multilinear and three power law models were tested and validated under all sky conditions. All the models showed high coefficients of determination (R 2) (close to 1), which indicates that the proposed models are suitable for predicting hourly PAR values. The linear and multilinear models (models 1 to 3) have the same coefficient of determination (0.996). The relative error values for the first five models ranged between 3.3% and 4.5%, while the sixth model showed higher relative error (8.4%).

Journal of Atmospheric and Solar-Terrestrial Physics, Nov 1, 2017

In this study, three years of hourly longwave downward and upward irradiance measurements for two... more In this study, three years of hourly longwave downward and upward irradiance measurements for two sites in Cyprus representing two different climate regimes (inland vs coastal locations) are used to analyse and compare them. The quality control process was based on physically possible, extremely rare and climatological limits. Furthermore, comparison tests between the two longwave components as well as with air and ground surface temperatures were used to evaluate the hourly values of longwave irradiances. The annual mean daily downward longwave irradiation at Athalassa is 29.1 MJ m À2 and at Larnaca it is slightly higher (31.3 MJ m À2). On the other hand, the annual mean daily upward longwave irradiation at Athalassa is 38.2 MJ m À2 , while at Larnaca it is slightly lower (37.4 MJ m À2). The performance of various models in estimating the daylight downward and upward longwave irradiances under clear-sky and all-sky conditions was evaluated. Root-mean-square errors, mean bias errors, and linear regression correlations have been used to compare measured and estimated values. The results of this comparison for the station of Athalassa, showed that Idso's model perform well and it can be used to estimate downward longwave irradiance under clear-sky conditions. Furthermore, Idso's model was extended to estimate the daylight downward longwave irradiance under all-sky conditions by taking into account the ratio of global to the clear-sky global solar irradiance. The RMSE of the local calibrated coefficients scheme of Idso's model was 17.70 W m À2. For the estimation of the daylight upward longwave irradiance under all-sky conditions, the calibrated Dognieux and Lemoine model was used which performed well. The RMSE in this case was 12.75 W m À2 .

Agrometeorology of the Potato Crop, 1988

... in the cool temperate regions, the length of the growing season is usually limited by tempera... more ... in the cool temperate regions, the length of the growing season is usually limited by temperature, planting being determined by temperatures adequate for ... In order to quantify the effect of water stress on crop yield, Doorenbos and Kassam (1979) used the empi-rical relationship ...

Solar Energy, 1996

Six years of hourly global and diffuse irradiation measurements on a horizontal surface performed... more Six years of hourly global and diffuse irradiation measurements on a horizontal surface performed at Athalassa, Cyprus, are used to establish a relationship between the daily diffuse fraction and the daily clearness index. Two types of correlations-yearly and seasonal-have been developed. These correlations, of first and third order in the clearness index are compared to the various correlations established by Collares-Pereira

Regional Environmental Change, 2015

ABSTRACT This study strives to highlight the potential of flood inundation monitoring and mapping... more ABSTRACT This study strives to highlight the potential of flood inundation monitoring and mapping in a catchment area in Cyprus (Yialias river) with the use of radar satellite images. Due to the lack of satellite data acquired during dates flood inundation events took place, the research team selected specific images acquired during dates that severe precipitation events were recorded from the rain gauge station network of Cyprus Meteorological Service in the specific study area. The relationship between soil moisture and precipitation was thoroughly studied and linear regression models were developed to predict future flood inundation events. Specifically, the application of fully polarimetric (ALOS PALSAR) and data acquired over different dates for soil moisture mapping is presented. The PALSAR (Phased Array type L-band Synthetic Aperture Radar) sensor carried by the ALOS (Advanced Land Observing Satellite) have quadruple polarizations (HH, VV, HV, VH). The amount of returned radiation (as backscatter echoes) that dictates the brightness of the image depends on factors such as the roughness, size of the target relative to the signal’s wavelength, volumetric and diffused scattering. The variation in soil moisture pattern during different precipitation events is presented through soil moisture maps obtained from ALOS PALSAR and data acquired during different dates with different precipitation rates. Soil moisture variation is clearly seen through soil moisture maps and the developed regression models are used to simulate future inundation events. The results indicated the considerable potential of radar satellite images in soil moisture and flood mapping in catchments areas of Mediterranean region.

Journal of Exposure Science & Environmental Epidemiology, 2013

Atmospheric Research, 1999

Applied Sciences

In this work, hourly measurements of global solar irradiances obtained from pyranometers and suns... more In this work, hourly measurements of global solar irradiances obtained from pyranometers and sunshine duration data using either Kipp & Zonen CSD3 automatic sensors or Campbell–Stokes sunshine recorders were assessed through an extensive quality control procedure and statistical analysis on the measured and derived solar parameters for all the actinometric stations installed in various locations over the island of Cyprus, covering mainly the period 2019–2021. This information is useful for engineers concerning the solar energy capture systems and energy efficiency who can therefore take knowledge of the local radiation levels. Monthly mean hourly values of global radiation and sunshine duration are calculated and shown through isoline diagrams. During June or July, daily global irradiations ranged between 25 MJ/m2 and 30 MJ/m2, with the lowest occurring in the mountainous locations. On the other hand, in January or December, they ranged between 6.5 MJ/m2 and 10.5 MJ/m2. The total an...

Applied Sciences

Athalassa is the main actinometric station of Cyprus and is located in the center of the island a... more Athalassa is the main actinometric station of Cyprus and is located in the center of the island at a height of about 160 m. The station is equipped with shortwave and longwave radiation instruments. The time step of the measurements is 10 min, and hourly and daily values were derived for the period of June 2020–May 2021. The solar data underwent an extensive quality control process based mainly on the suggested tests of Baseline Surface Radiation Network (BSRN) for both the hourly and daily datasets. More than 98% of the data were within the limits recommended by the BSRN and other radiation networks. A statistical analysis of the shortwave solar radiation components was then performed. Linear and quadratic relationships were established between various radiation components, and their diurnal and monthly variability was assessed. The annual average daily global radiation amount was approximately 19 MJ/m2, whereas the amounts of horizontal beam and diffuse radiation were 12.9 MJ/m2 a...

Effect of climate variability and climate change on crop production and water resources in Cyprus

ABSTRACT: A multilayered artificial neural network has been used for predicting the mean monthly ... more ABSTRACT: A multilayered artificial neural network has been used for predicting the mean monthly wind speed in regions of Cyprus where data are not available. Data for the period 1986-1996 have been used to train a neural network, whereas data for the year 1997 were used for validation. Both learning and prediction were performed with adequate accuracy. Two network architectures of the similar type have been tried. One with eleven neurons in the input layer and one with five. The second one proved to be more accurate in predicting the mean wind speed. The maximum percentage difference for the validation set was confined to less than 1.8 % on an annual basis, which is considered by the domain expert as adequate.

Applied Sciences, 2021

In this study, two years of hourly longwave downward and upward irradiance measurements at Athala... more In this study, two years of hourly longwave downward and upward irradiance measurements at Athalassa, an inland location, are used to analyze and compare them. A detailed quality control process was followed according to the suggested tests proposed by the Baseline Surface Radiation Network (BSRN) group. The criteria involved are based on physically possible, extremely rare and climatological limits. Furthermore, comparison tests were also applied between the two longwave components as well as with air and ground surface temperatures. Additionally, time consistency and persistency tests were applied. All the suspect data were excluded from the analysis. The data showed that the frequency distribution of downward longwave irradiances follows a normal distribution function, while the upward longwave follows an almost normal distribution but with a long positive tail. The annual mean daily downward longwave irradiation is 27.3 MJ m−2 and the annual mean daily upward longwave irradiatio...

Solar Energy and Sustainable Development Journal

In this work, hourly measurements of global solar irradiances obtained from a pyranometer and dir... more In this work, hourly measurements of global solar irradiances obtained from a pyranometer and direct normal irradiances obtained from sunshine duration sensor are assessed through an extensive quality control procedure and statistical analysis on the measured and derived solar parameters for a semimountainous location using data from the last fie years (2016-2020). This information and the method suggested concerning the solar energy capture systems and energy efficiency is useful for engineers who can therefore take knowledge of the local radiation levels. Furthermore, the direct horizontal irradiance canbe easily calculated and the diffuse component can be estimated from the difference of global and direct horizontal irradiances. Monthly mean hourly values of the radiation components are also estimated and shown through isolines diagrams. Representative values of global direct and diffuse irradiances for different times of the year and different hour of the day can be easily read ...

The purpose of this paper is to compare daily sunshine duration (SD) measured by Campbell-Stokes ... more The purpose of this paper is to compare daily sunshine duration (SD) measured by Campbell-Stokes sunshine recorder (CS) with three automatic instruments (Kipp & Zonen pyranometers (CM6B), pyrheliometer (CHP1) and CSD3 sunshine recorders). The comparisons are essential, since in recent decades automatic sunshine duration sensors have been systematically replacing the manual measurements affecting therefore the continuity of the CS time series. The comparisons were applied to the daily SD data of three synoptic stations (Larnaca A/P, Pafos A/P and Athalassa) where parallel measurements of manual and automatic instruments are carried out during the periods 2009-2012 and 2012-2015. The CSD3 measurements were obtained from two automatic weather stations (AWS) (Mennogia and Pentakomo) which are closed to the synoptic station of Larnaca A/P. The comparisons cover the daily and monthly sums, their statistical distributions and their relationships. The daily differences of the pairs of the s...

SM journal of biometrics and biostatistics, 2017

A statistical analysis and inter-comparison of the Ultraviolet Radiation (UVR) at two sites in Cy... more A statistical analysis and inter-comparison of the Ultraviolet Radiation (UVR) at two sites in Cyprus representing two different climate regimes of the island (Athalassa-inland plain vs Larnaca-coastal location) covering the period 2013-2015 is presented. Mean annual and mean monthly daily totals of the UV irradiation and their frequency distribution at both sites are computed and discussed. The total accumulated UV irradiation along an average year reaches 398 MJ m-2 at Athalassa and 494 MJ m-2 at Larnaca. During summer, the daily UV radiation exceeds the value of 1800 kJ m-2 at Athalassa and 2200 kJ m-2 at Larnaca. Linear relationships were established between UVR and global solar radiation, with the coefficient of determination close to 1. These relationships indicate that UV irradiation corresponds to 5.9% and 6.8% of the horizontal global solar irradiation at the two sites, respectively. Four models were tested for the estimation of UVR and the best performed models were recalibrated according to the local conditions. Relationships between the clearness index (t k) and the UV hemispherical transmittance (tUV k) were also established. The annual tUV k is about 71% of t k. Finally, the dependence of the UV/G ratio values to the solar elevation angle and clearness index was also examined. It can be concluded that the presence of clouds reduces less the UV component rather than the global solar radiation, due to the strong absorption of water in the near infrared spectrum.

Renewable Energy, Oct 1, 2016

Routine measurements of irradiance are valuable for many research fields such as energy applicati... more Routine measurements of irradiance are valuable for many research fields such as energy applications. However, ground data of solar global radiation can present questionable values. In this study, a set of check procedures is used to test the quality of shortwave and longwave radiation measurements taken at two actinometric stations in Cyprus (Athalassa-inland location and Larnaca-coastal location), during the period November 2012eJuly 2014. The testing procedures include physically possible limits for all the radiation components and comparisons between global radiation and the sum of direct and diffuse radiation. The quality process is implemented to both the 10-min averaged irradiances, hourly irradiation and the respective daily values. This paper reviews the currently available procedures for quality assessment of the solar shortwave and longwave irradiation data. In the present study, the first level of test includes physical possible limits which are determined by the Daylight Research Group and the Baseline Surface Radiation Network of the World Meteorological Organisation (WMO). The second level of test is a semi-automated procedure that is based on the creation of an envelope in the clearness index and the diffuse to global irradiance ratio. The third level of test is based on the comparison of various radiation parameters including comparison of measured extreme values with theoretical estimations from clear sky-models. The fourth level of test of the quality control procedure refers to the analysis of daily and annual variations of the radiation parameters.

Renewable Energy, Oct 1, 2017

Statistical analysis of ultraviolet erythemal radiation.  Monthly and diurnal variation of ultra... more Statistical analysis of ultraviolet erythemal radiation.  Monthly and diurnal variation of ultraviolet erythemal radiation.  Statistical relationships between ultraviolet erythemal and other radiation components, total ozone column, relative air mass, clearness index and solar zenith angle.  Calculation of UV Index.  Estimation of the cumulative doses during an average year for the four skin phototypes.  Comparison of ultraviolet erythemal radiation between two sites.  It is the first time that an analysis of this type is performed in Cyprus.

SM journal of biometrics and biostatistics, 2018

A statistical analysis and inter-comparison of the reflected radiation at two sites in Cyprus rep... more A statistical analysis and inter-comparison of the reflected radiation at two sites in Cyprus representing two different climate regimes of the island (Athalassa-inland plain vs Larnaca-coastal location) covering the period January 2013-December 2015 is presented. Mean annual and mean monthly daily totals of the reflected radiation and ground albedo as well as their frequency distribution are computed and discussed. The monthly means of reflected irradiance range from 50 to 120 W m-2 at Athalassa, while at Larnaca they range between 50 and 140 W m-2. The mean annual albedo for Athalassa is 0.202 which coincides with the most common value given in the literature, while for Larnaca it is higher (0.221). The higher value at Larnaca is attributed to its alluvial (silty sandy) soil which has higher reflectivity compared to the calcarenite (calcium carbonate) soil at Athalassa. The lowest values of albedo at Athalassa, are observed around noon and the higher values in the morning and afternoon. The highest values are obtained in January and February and the lowest in May and June when global solar irradiance have its higher values. On the other hand, we observe an increasing trend from the morning towards the afternoon hours at Larnaca throughout the year. The maximum of daily reflected irradiation is about 6.5 MJ m-2 at Athalassa and about 7.5 MJ m-2 at Larnaca. The monthly mean daily values of albedo at Athalassa range between 0.175 to 0.224, while at Larnaca they are higher ranging from 0.198 to 0.239. As a result of the differences of the global and reflected radiation of the two sites, the net shortwave irradiation at Larnaca is slightly higher than that at Athalassa, almost throughout the year.

SM journal of biometrics and biostatistics, 2017

Measurements of Photosynthetically Active Radiation (PAR) and global solar radiation at Larnaca (... more Measurements of Photosynthetically Active Radiation (PAR) and global solar radiation at Larnaca (a coastal site in Cyprus) during the period 3013-2015 were used to investigate the seasonal characteristics of PAR and PAR/G ratio (PAR fraction or fFEC). PAR showed seasonal features with higher values in summer and lower values in winter. The annual mean values of PPFD and fFEC being 40.3 mol m-2 d-1 and 2.03 mol M J-1 , respectively. Monthly average daily PAR increased from 19.1 mol m-2 d-1 (in December) to 59.6 mol m-2 d-1 (in June).The monthly daily average of fFEC remained almost constant throughout the year at Larnaca. The spatial variability of PAR was also investigated using measurements from other four sites with different climate characteristics. The annual mean daily PAR value ranged between 31.7 to 40.0mol m-2 d-1. The highest values are recorded in the coastal stations (Larnaca and Paralimni). The annual average value of fFEC at the five observation sites ranged from 1.82 mol MJ-1 to 2.03 mol MJ-1 , in accordance to what is observed in most parts of the world. The highest appeared in the coastal sites of Larnaca and Paralimni due to the presence of high water vapour atmospheric concentrations. Elevation plays a significant role on the values of the above variables. As a general trend, fFEC followed the order Clear<Partly cloudy<Cloudy. In all cases fFEC was decreased with elevation but with a different rate. Three linear or multilinear and three power law models were tested and validated under all sky conditions. All the models showed high coefficients of determination (R 2) (close to 1), which indicates that the proposed models are suitable for predicting hourly PAR values. The linear and multilinear models (models 1 to 3) have the same coefficient of determination (0.996). The relative error values for the first five models ranged between 3.3% and 4.5%, while the sixth model showed higher relative error (8.4%).

Journal of Atmospheric and Solar-Terrestrial Physics, Nov 1, 2017

In this study, three years of hourly longwave downward and upward irradiance measurements for two... more In this study, three years of hourly longwave downward and upward irradiance measurements for two sites in Cyprus representing two different climate regimes (inland vs coastal locations) are used to analyse and compare them. The quality control process was based on physically possible, extremely rare and climatological limits. Furthermore, comparison tests between the two longwave components as well as with air and ground surface temperatures were used to evaluate the hourly values of longwave irradiances. The annual mean daily downward longwave irradiation at Athalassa is 29.1 MJ m À2 and at Larnaca it is slightly higher (31.3 MJ m À2). On the other hand, the annual mean daily upward longwave irradiation at Athalassa is 38.2 MJ m À2 , while at Larnaca it is slightly lower (37.4 MJ m À2). The performance of various models in estimating the daylight downward and upward longwave irradiances under clear-sky and all-sky conditions was evaluated. Root-mean-square errors, mean bias errors, and linear regression correlations have been used to compare measured and estimated values. The results of this comparison for the station of Athalassa, showed that Idso's model perform well and it can be used to estimate downward longwave irradiance under clear-sky conditions. Furthermore, Idso's model was extended to estimate the daylight downward longwave irradiance under all-sky conditions by taking into account the ratio of global to the clear-sky global solar irradiance. The RMSE of the local calibrated coefficients scheme of Idso's model was 17.70 W m À2. For the estimation of the daylight upward longwave irradiance under all-sky conditions, the calibrated Dognieux and Lemoine model was used which performed well. The RMSE in this case was 12.75 W m À2 .

Agrometeorology of the Potato Crop, 1988

... in the cool temperate regions, the length of the growing season is usually limited by tempera... more ... in the cool temperate regions, the length of the growing season is usually limited by temperature, planting being determined by temperatures adequate for ... In order to quantify the effect of water stress on crop yield, Doorenbos and Kassam (1979) used the empi-rical relationship ...

Solar Energy, 1996

Six years of hourly global and diffuse irradiation measurements on a horizontal surface performed... more Six years of hourly global and diffuse irradiation measurements on a horizontal surface performed at Athalassa, Cyprus, are used to establish a relationship between the daily diffuse fraction and the daily clearness index. Two types of correlations-yearly and seasonal-have been developed. These correlations, of first and third order in the clearness index are compared to the various correlations established by Collares-Pereira

Regional Environmental Change, 2015

ABSTRACT This study strives to highlight the potential of flood inundation monitoring and mapping... more ABSTRACT This study strives to highlight the potential of flood inundation monitoring and mapping in a catchment area in Cyprus (Yialias river) with the use of radar satellite images. Due to the lack of satellite data acquired during dates flood inundation events took place, the research team selected specific images acquired during dates that severe precipitation events were recorded from the rain gauge station network of Cyprus Meteorological Service in the specific study area. The relationship between soil moisture and precipitation was thoroughly studied and linear regression models were developed to predict future flood inundation events. Specifically, the application of fully polarimetric (ALOS PALSAR) and data acquired over different dates for soil moisture mapping is presented. The PALSAR (Phased Array type L-band Synthetic Aperture Radar) sensor carried by the ALOS (Advanced Land Observing Satellite) have quadruple polarizations (HH, VV, HV, VH). The amount of returned radiation (as backscatter echoes) that dictates the brightness of the image depends on factors such as the roughness, size of the target relative to the signal’s wavelength, volumetric and diffused scattering. The variation in soil moisture pattern during different precipitation events is presented through soil moisture maps obtained from ALOS PALSAR and data acquired during different dates with different precipitation rates. Soil moisture variation is clearly seen through soil moisture maps and the developed regression models are used to simulate future inundation events. The results indicated the considerable potential of radar satellite images in soil moisture and flood mapping in catchments areas of Mediterranean region.

Journal of Exposure Science & Environmental Epidemiology, 2013

Atmospheric Research, 1999

Applied Sciences

In this work, hourly measurements of global solar irradiances obtained from pyranometers and suns... more In this work, hourly measurements of global solar irradiances obtained from pyranometers and sunshine duration data using either Kipp & Zonen CSD3 automatic sensors or Campbell–Stokes sunshine recorders were assessed through an extensive quality control procedure and statistical analysis on the measured and derived solar parameters for all the actinometric stations installed in various locations over the island of Cyprus, covering mainly the period 2019–2021. This information is useful for engineers concerning the solar energy capture systems and energy efficiency who can therefore take knowledge of the local radiation levels. Monthly mean hourly values of global radiation and sunshine duration are calculated and shown through isoline diagrams. During June or July, daily global irradiations ranged between 25 MJ/m2 and 30 MJ/m2, with the lowest occurring in the mountainous locations. On the other hand, in January or December, they ranged between 6.5 MJ/m2 and 10.5 MJ/m2. The total an...

Applied Sciences

Athalassa is the main actinometric station of Cyprus and is located in the center of the island a... more Athalassa is the main actinometric station of Cyprus and is located in the center of the island at a height of about 160 m. The station is equipped with shortwave and longwave radiation instruments. The time step of the measurements is 10 min, and hourly and daily values were derived for the period of June 2020–May 2021. The solar data underwent an extensive quality control process based mainly on the suggested tests of Baseline Surface Radiation Network (BSRN) for both the hourly and daily datasets. More than 98% of the data were within the limits recommended by the BSRN and other radiation networks. A statistical analysis of the shortwave solar radiation components was then performed. Linear and quadratic relationships were established between various radiation components, and their diurnal and monthly variability was assessed. The annual average daily global radiation amount was approximately 19 MJ/m2, whereas the amounts of horizontal beam and diffuse radiation were 12.9 MJ/m2 a...

Effect of climate variability and climate change on crop production and water resources in Cyprus

ABSTRACT: A multilayered artificial neural network has been used for predicting the mean monthly ... more ABSTRACT: A multilayered artificial neural network has been used for predicting the mean monthly wind speed in regions of Cyprus where data are not available. Data for the period 1986-1996 have been used to train a neural network, whereas data for the year 1997 were used for validation. Both learning and prediction were performed with adequate accuracy. Two network architectures of the similar type have been tried. One with eleven neurons in the input layer and one with five. The second one proved to be more accurate in predicting the mean wind speed. The maximum percentage difference for the validation set was confined to less than 1.8 % on an annual basis, which is considered by the domain expert as adequate.

Applied Sciences, 2021

In this study, two years of hourly longwave downward and upward irradiance measurements at Athala... more In this study, two years of hourly longwave downward and upward irradiance measurements at Athalassa, an inland location, are used to analyze and compare them. A detailed quality control process was followed according to the suggested tests proposed by the Baseline Surface Radiation Network (BSRN) group. The criteria involved are based on physically possible, extremely rare and climatological limits. Furthermore, comparison tests were also applied between the two longwave components as well as with air and ground surface temperatures. Additionally, time consistency and persistency tests were applied. All the suspect data were excluded from the analysis. The data showed that the frequency distribution of downward longwave irradiances follows a normal distribution function, while the upward longwave follows an almost normal distribution but with a long positive tail. The annual mean daily downward longwave irradiation is 27.3 MJ m−2 and the annual mean daily upward longwave irradiatio...