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Global Solar Radiation (global + solar_radiation)
Selected AbstractsStochastic modelling of global solar radiation measured in the state of KuwaitENVIRONMETRICS, Issue 7 2002S. A. Al-Awadhi Abstract Two stochastic models that capture the main features of daily exposure of global radiation in Kuwait are proposed. The development of these models is based on removing the annual periodicity and seasonal variation of solar radiation. Thus the daily radiation is decomposed as the sum of the trend component and a stochastic component. In many situations, there are dramatic changes in the radiation series through the year due to the condition of the weather, as is the case of the data from Kuwait. This would affect the accuracy of the model, and therefore the series is divided into two regimes: one corresponds to clear days where the value of the global radiation would be normal and the other to non-clear days where the value of global radiation would be very low. Then the trend component is expressed as a Fourier series taking into account such apparent breaks in the series. The stochastic component is first tested for linearity and Gaussianity and it is found that it does not satisfy these assumptions. Therefore, a linear time series model (ARMA modeling) may not be adequate and, to overcome this problem, a bilinear time series is used to model the stochastic component of daily global radiation in Kuwait. The method proposed considers first fitting an AR model to the data and then seeing whether a further reduction in the mean sum of squares can be achieved by introducing extra bilinear terms. The Akaike Information Criterion (AIC) is used to select the best model. Copyright © 2002 John Wiley & Sons, Ltd. [source] UV and global solar radiation in ,ód,, Central PolandINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2010Agnieszka Podstawczy Abstract With the overall aim of quantifying urban atmospheric effects on different parts of the solar spectrum, a multi year analysis of data collected at ,ód, was undertaken. UV (290,400 nm) and global solar radiation measured by means of a Kipp and Zonen CUV3 radiometer and a Kipp and Zonen CM11 pyranometer in the center of ,ód, between 1997 and 2001 are analysed. The mean annual sum of global and UV solar radiation equaled 3710.8 MJ m,2 and 154.1 MJ m,2, respectively. The minimum monthly total of solar energy occurred in December (48.7 M Jm,2,global; 2.1 MJ m,2,UV); however, the maximum monthly total occurred atypically in May (620.9 MJ m,2,global; 25.3 MJ m,2,UV). UV clearness index (Kuv) is approximately half of the clearness index of the global solar radiation, indicating greater attenuation of that part of the spectrum (Kuv 0.14 in December to 0.26 in May). A linear regression model was fitted to the daily values of UV and global (g) solar irradiation (Duv = a + Dgb). The slope coefficient b and the coefficient of determination equal 0.039 and 0.98, respectively. Cloudiness exerts an important control on the solar radiation flux at the ground level and for the relation between UV and global solar radiation. The convective clouds caused an increase of global and UV solar irradiance by about 10,20% compared to clear days, the enhancement resulting from reflections. On clear days, UV comprises 3.3,4% of global solar irradiance (10-min values) on average, while during cloudy weather it increases to 8%. The results presented have implications for understanding the radiative transfer of UV and global solar radiation in the atmosphere over an urban area and the influence of clouds on transmission of solar radiation flux. Copyright © 2009 Royal Meteorological Society [source] Comparison of solar radiation correlations for ,zmir, TurkeyINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2002K. Ulgen Abstract In this study, empirical correlations are developed to estimate the monthly average daily global solar radiation on a horizontal surface (H) for the city of ,zmir in Turkey. Experimental data were measured in the Solar,Meteorological Station of the Solar Energy Institute at Ege University. The present models are then compared with the 25 models available in the literature for calculating H based on the main percentage error, root mean error, the main bias error, and correlation coefficient. It can be concluded that the present models predict the values of H for ,zmir better than other available models. Copyright © 2002 John Wiley & Sons, Ltd. [source] Metabolic correlates of leg length in breeding arctic shorebirds: the cost of getting highJOURNAL OF BIOGEOGRAPHY, Issue 3 2005Ralph V. Cartar Abstract Aim, We test the hypothesis that tarsus length in all shorebirds breeding in the Canadian arctic shows an evolutionary response to average metabolic stress encountered across the breeding range, such that birds nesting in metabolically stressful environments have relatively shorter legs. Longer-legged birds living in colder environments will experience greater metabolic costs because their torsos are elevated farther away from the ground's wind-dampening boundary layer. Methods, We use weather data (temperature, wind speed, global solar radiation) from 27 arctic weather stations measured over 37 years, and a previously published model of heat transfer, to characterize the metabolic harshness over the breeding season of the ranges of each of the 17 shorebirds of the family Charadriidae nesting in the Canadian arctic. Results, After controlling for the lengths of two other body extremities (wing and bill), there was a significant negative relationship between tarsus length and mean metabolic harshness. This result was obtained whether species were treated as independent data points, or in a comparative analysis using standardized independent contrasts. Main conclusions, We support a unique extension of Allen's rule: body-supporting appendages of homeotherms may be shorter in colder environments so as to take advantage of a boundary layer effect, thereby reducing metabolic costs. [source] The accuracy of downward short- and long-wave radiation at the earth's surface calculated using simple modelsMETEOROLOGICAL APPLICATIONS, Issue 1 2004J. W. Finch Estimates of the downward global solar and long-wave radiations are commonly made using simple models. We have tested the estimates produced by a number of these simple models against the values predicted by the radiative transfer model used in a climate model in order to determine their suitability for global applications. For clear sky, two simple models were comparable, but under cloudy conditions a combination of a clear-sky model based on the Angstrom-Prescott equation (which deals with the downwelling solar radiation) with a cloud transmissivity utilising total cloud fraction proved best. The lowest root mean square errors were 27 W m,2 for clear-sky global solar radiation and 90 W m,2 for cloudy conditions. For downward long-wave radiation in clear-sky conditions, the model of Garratt (1992) performed best with a root mean square error of 24 W m,2. However, in cloudy conditions the model of Idso & Jackson (1969) performed best with a root mean square error of 22 W m,2, and, as it performs nearly as well as that of Garratt (1992) in clear-sky conditions, it is probably the best choice. Copyright © 2004 Royal Meteorological Society. [source] | ||||||||||