Performance reduction of solar irradiance parametric models due to limitations in required aerosol data: case of the CPCR2 model

Summary Knowledge of the partition of global solar irradiance in its diffuse and direct beam components is required in different areas of applied meteorology. In the absence of solar irradiance measurements parametric approaches have to be used instead. In the present work, the parametric CPCR2 model has been analysed at Granada (37.18° N, 3.58° W, 660 m a.m.s.l), an inland location, covering a period greater than three years. Only cloudless conditions are analysed. Angstr?m’s α and β coefficients have been computed from measurements carried out with a sunphotometer. As the study reveals, the best performance of the parametric model is conditioned to the availability of appropriate information on aerosols, especially when the interest is focused on the direct and diffuse irradiance. Received October 18, 1999/Revised December 18, 2000     

Potential Role of Solar Variability as an Agent for Climate Change

Numerical experiments have been carried out with a two-dimensional sector averaged global climate model in order to assess the potential impact of solar variability on the Earth's surface temperature from 1700 to 1992. This was done by investigating the model response to the variations in solar radiation caused by the changes in the Earth's orbital elements, as well as by the changes intrinsic to the Sun. In the absence of a full physical theory able to explain the origin of the observed total solar irradiance variations, three different total solar irradiance reconstructions have been used. A total solar irradiance change due to the photospheric effects incorporated in the Willson and Hudson (1988) parameterization, and the newly reconstructed solar total irradiance variations from the solar models of Hoyt and Schatten (1993) and Lean et al. (1995). Our results indicate that while the influence of the orbital forcing on the annual and global mean surface temperature is negligible at the century time scale, the monthly mean response to this forcing can be quite different from one month to another. The modelled global warming due to the three investigated total solar irradiance reconstructions is insufficient to reproduce the observed 20th century warming. Nevertheless, our simulated surface temperature response to the changes in the Sun's radiant energy output suggests that the Gleissberg cycle (88 years) solar forcing should not be neglected in explaining the century-scale climate variations. Finally, spectral analysis seems to point out that the 10- to 12-year oscillations found in the recorded Northern Hemisphere temperature variations from 1700 to 1992 could be unrelated to the solar forcing. Such a result could indicate that the eleven-year period which is frequently found in climate data might be related to oscillations in the atmosphere or oceans, internal to the climate system.     

Variations and trends in global solar radiation for Turkey

Summary Since measured solar radiation data in Turkey have rather high random errors, sunshine duration data covering the period from 1960 through 1994 from 34 stations in Turkey were taken to derive estimates of monthly mean global solar radiation by a quadratic correlation. The least square linear regression method was applied for trend analysis. Significant negative trends of the annual means were observed with 71 percent of the stations A 3.44 percent decrease in global solar radiation was observed over the last 35 years in Turkey. The decrease in solar radiation is an indication of increased air pollution, as statistical parameters show that Turkey is rapidly expanding economically, and thus air quality has deteriorated correspondingly.With 3 Figures     

Bright Sunshine Duration in Relation to Precipitation,Air Temperature and Geographic Location

Summary  Bright sunshine duration (BSD) is of singular importance for estimating solar irradiance, and its data base is small in comparison. This paper reports a generic algorithm that captures global variation in monthly BSD data in relation to temperature, precipitation and geographic location. The algorithm depicts BSD in terms of reduction from daylength as a negative exponential function of standard station pressure, with the exponential reduction rate as proportional to the product of a series of multiplicative functions reflective of global generalities and regional idiosyncrasies. The algorithm is parameterized by regression fitting to monthly climate normal data for 729 stations worldwide. It accounts statistically for 85% of the variance in the BSD data, with a root mean square error of 1.0 hr, or 15% of the data mean. The data fitting tends to be least robust for tropical humid climates or for tropical and subtropical monsoonal Asia. The spatially-based algorithm projects with a reasonable accuracy 5-yr sequential monthly BSD data for five stations representative of the climate regimes in the conterminous United States: the absolute error is within ±1.5 hr for 70% to 93% of the 60 monthly mean BSD values for each of the stations. Received April 22, 1999     

基于EC细网格数值预报产品的太阳辐照度订正技术

太阳辐照度与光伏电站发电功率密切相关,其预报的准确性直接影响发电功率预报的准确性。根据光伏电站太阳辐照度实况、气象站实况、WRF(Weather Research and Forecast Model)模式辐照度预报、EC细网格数值预报以及太阳理论辐照度,利用逐步回归法开展太阳辐照度预报订正研究,得到以下结论:①太阳辐照度实况与太阳理论辐照度的比值与EC细网格数值预报中气象要素的相关性优于太阳辐照度实况与气象要素的相关性;②不同时刻影响太阳辐照度的气象因子存在差异,通过逐步回归法建立不同时刻太阳辐照度预报模型;③在非晴天情况下,回归预报辐照度相对均方根误差比WRF模式预报辐照度降低10%左右,减小了辐照度预报误差。该研究成果在光伏电站的新能源数值预报服务中有一定的应用价值。     

The influence of clouds on surface UV erythemal irradiance

The purpose of this study is to examine the effect of clouds on the ultraviolet erythemal irradiance. The study was developed at three stations in the Iberian Peninsula: Madrid and Murcia, using data recorded in the period 2000–2001, and Zaragoza, using data recorded in 2001. In order to determine the cloud effect on ultraviolet erythemal irradiance, we considered a cloud modification factor defined as the ratio between the measured values of ultraviolet erythemal irradiance and the corresponding clear-sky ultraviolet erythemal irradiance, which would be expected for the same time period and atmospheric conditions. The dependence of this cloud modification factor on total cloud amount, cloud type and solar elevation angle was investigated. The results suggest that the effect of cloud on ultraviolet erythemal irradiance can be parameterized in a simple way in terms of the cloud amount. Our results suggest that the same cloud modification factor model can be used at the three analysed locations estimating the ultraviolet erythemal irradiance with mean bias deviation (MBD) in the range of the expected experimental errors. This cloud modification factor is lower than that associated to the whole solar spectral range, indicating that the attenuation for the ultraviolet erythemal irradiance is lower than that associated to other solar spectral ranges. The cloud modification factor for ultraviolet erythemal irradiance presents dependence with solar elevation, with opposite dependencies with solar elevation for overcast and partial cloud cover conditions, a fact that can be explained in terms of the influence of reflection-enhancement of the ultraviolet irradiance in the last case. Concerning the influence of cloud type, a limited study of two cloud categories, low and medium level and high level, indicated that for overcast conditions, lower clouds presents an attenuation of ultraviolet erythemal irradiance 20% greater than that associated to high level clouds.     

On the use of a cloud modification factor for solar UV (290–385 nm) spectral range

Summary  Knowledge of ultraviolet radiation is necessary in different applications, in the absence of measurements, this radiometric flux must be estimated from available parameters. To compute this flux under all sky conditions one must consider the influence of clouds. Clouds are the largest modulators of the solar radiative flux reaching the Earth’s surface. The amount and type of cloud cover prevailing at a given time and location largely determines the amount and type of solar radiation received at the Earth’s surface. This cloud radiative effect is different for the different solar spectral bands. In this work, we analyse the cloud radiative effect over ultraviolet radiation (290–385 nm). This could be done by defining a cloud modification Factor. We have developed such cloud modification Factor considering two different types of clouds. The efficiency of the cloud radiative effect scheme has been tested in combination with a cloudless sky empirical model using independent data sets. The performance of the model has been tested in relation to its predictive capability of global ultraviolet radiation. For this purpose, data recorded at two radiometric stations are used. The first one is located at the University of Almería, a seashore location (36.83° N, 2.41° W, 20 m a.m.s.l.), while the second one is located at Granada (37.18° N, 3.58° W, 660 m a.m.s.l.), an inland location. The database includes hourly values of the relevant variables that cover the years 1993–94 in Almería and 1994–95 in Granada. Cloud cover information provided by the Spanish Meteorological Service has been include to compute the clouds radiative effect. After our study, it appears that the combination of an appropriate cloudless sky model with the cloud modification Factor scheme provides estimates of ultraviolet radiation with mean bias deviation of about 5% that is close to experimental errors. Comparisons with similar formulations of the cloud radiative effect over the whole solar spectrum provides evidence for the spectral dependency of the cloud radiative effect. Received November 15, 1999 Revised September 11, 2000     

Estimation of Hourly Solar Radiation at the Surface under Cloudless Conditions on the Tibetan Plateau Using a Simple Radiation Model

In this study,the clear sky hourly global and net solar irradiances at the surface determined using SUNFLUX,a simple parameterization scheme,for three stations(Gaize,Naqu,and Lhasa) on the Tibetan Plateau were evaluated against observation data.Our modeled results agree well with observations.The correlation coefficients between modeled and observed values were > 0.99 for all three stations.The relative error of modeled results,in average was < 7%,and the root-mean-square variance was < 27 W m 2.The solar irradiances in the radiation model were slightly overestimated compared with observation data;there were at least two likely causes.First,the radiative effects of aerosols were not included in the radiation model.Second,solar irradiances determined by thermopile pyranometers include a thermal offset error that causes solar radiation to be slightly underestimated.The solar radiation absorbed by the ozone and water vapor was estimated.The results show that monthly mean solar radiation absorbed by the ozone is < 2% of the global solar radiation(< 14 W m 2).Solar radiation absorbed by water vapor is stronger in summer than in winter.The maximum amount of monthly mean solar radiation absorbed by water vapor can be up to 13% of the global solar radiation(95 W m 2).This indicates that water vapor measurements with high precision are very important for precise determination of solar radiation.     

重庆山地区域气象要素空间插值方法对比

利用重庆地区1999年和2018年气象数据, 分别采用薄盘光滑样条、协同克里金、普通克里金、反距离加权4种方法, 从年和月两种尺度对气温、降水、太阳总辐射三个要素进行空间插值; 采取交叉验证方法, 用MAE、MRE、RMSE评估插值精度, 确定各要素最优插值方法。结果表明: 气温和太阳总辐射最优插值方法为薄盘光滑样条, 降水为反距离加权; 插值精度上气温、太阳总辐射高值月份优于低值月份, 降水则相反, 但三个要素均表现出年尺度优于月尺度。MRE检验表明, 插值精度为气温>太阳总辐射>降水, 1999年年尺度插值精度分别为1.86%、4.60%、6.87%, 月尺度插值精度分别为2.79%、5.82%、17.42%;2018年太阳总辐射年、月尺度插值精度分别为3.03%、4.88%, 区域站加密后气温、降水年尺度插值精度分别为2.03%、11.20%, 月尺度对应插值精度分别为3.20%、23.14%。     

Procedure of embedding biological action functions into the atmospheric transmittance

In order to perform calculations of biologically effective irradiance, the usual procedure is to modulate the ground-measured spectral solar irradiance with a specific biological action function. The inconvenience is that only a few meteorological stations worldwide are equipped to measure the spectral solar irradiance in the ultraviolet range. This motivates the search for a numerical substitute, which constitutes the subject of this report. An innovative approach based on generalized mean is used to infer the effective atmospheric transmittance. Its illustration resulted in a new parametric model for computing the biological dose under clear sky. The action spectrum for the growth response of plants, as a carrier of biological effects, is encapsulated into the atmospheric transmittance, leading to the calculation of the effective irradiance by simple algebra. The overall results indicate that the new parametric model performs accurately enough to be routinely used in practice. The procedure is general; therefore, it is described in detail to guide potential users in developing similar models incorporating other biological action spectra as needed. For speed-intensive applications, an executable file intended to run on any PC, which computes the effective irradiance with the proposed model, is provided.     

太阳辐射与我国降水的相关分析

本文通过对太阳辐照度与我国160个站降水量的相关分析,说明太阳辐射的变化对我国降水的影响,并对其影响机制进行了初步探讨。     

Solar irradiance during the last 1200 years based on cosmogenic nuclides

Based on a quantitative study of the common fluctuations of ¹⁴C and ¹⁰Be production rates, we have derived a time series of the solar magnetic variability over the last 1200 years. This record is converted into irradiance variations by linear scaling based on previous studies of sun‐like stars and of the sun's behavior over the last few centuries. The new solar irradiance record exhibits low values during the well‐known solar minima centered at about 1900, 1810 (Dalton) and 1690 ad (Maunder). Further back in time, a rather long period between 1450 and 1750 ad is characterized by low irradiance values. A shorter period is centered at about 1200 ad , with irradiance slightly higher or similar to present day values. It is tempting to correlate these periods with the so‐called "little ice age" and "medieval warm period", respectively. An accurate quantification of the climatic impact of this new irradiance record requires the use of coupled atmosphere–ocean general circulation models (GCMs). Nevertheless, our record is already compatible with a global cooling of about 0.5‐1°C during the "little ice age", and with a general cooling trend during the past millenium followed by global warming during the 20th century (Mann et al., 1999).     

Trend analysis of rainfall time series for Sindh river basin in India

The main goal of this paper is to estimate a set of optimal seasonal, daily, and hourly values of atmospheric turbidity and surface radiative parameters Ångström’s turbidity coefficient (β), Ångström’s wavelength exponent (α), aerosol single scattering albedo (ω_o), forward scatterance (F_c) and average surface albedo (ρ_g), using the Brute Force multidimensional minimization method to minimize the difference between measured and simulated solar irradiance components, expressed as cost functions. In order to simulate the components of short-wave solar irradiance (direct, diffuse and global) for clear sky conditions, incidents on a horizontal surface in the Metropolitan Area of Rio de Janeiro (MARJ), Brazil (22° 51′ 27″ S, 43° 13′ 58″ W), we use two parameterized broadband solar irradiance models, called CPCR2 and Iqbal C, based on synoptic information. The meteorological variables such as precipitable water (u_w) and ozone concentration (u_o) required by the broadband solar models were obtained from moderate-resolution imaging spectroradiometer (MODIS) sensor on Terra and Aqua NASA platforms. For the implementation and validation processes, we use global and diffuse solar irradiance data measured by the radiometric platform of LabMiM, located in the north area of the MARJ. The data were measured between the years 2010 and 2012 at 1-min intervals. The performance of solar irradiance models using optimal parameters was evaluated with several quantitative statistical indicators and a subset of measured solar irradiance data. Some daily results for Ångström’s wavelength exponent α were compared with Ångström’s parameter (440–870 nm) values obtained by aerosol robotic network (AERONET) for 11 days, showing an acceptable level of agreement. Results for Ångström’s turbidity coefficient β, associated with the amount of aerosols in the atmosphere, show a seasonal pattern according with increased precipitation during summer months (December–February) in the MARJ.     

陆面模式中土壤湿度影响蒸散参数化方案的评估

本文将四个常见陆面模式CLM3.5（Community Land Model Version 3.5）、Noah_LSM（The Noah Land Surface Model）、VIC（Variable Infiltration Capacity）以及SSiB（The Simplified Simple Biosphere Model）中土壤湿度影响蒸散的参数化方案进行简化,并利用实验观测资料对不同参数化方案进行评估,探究不同陆面模式对土壤湿度与蒸散关系的模拟差异,从而为提高模式的模拟能力提供依据。结果表明,（1）CLM与SSiB中计算土壤湿度影响裸土蒸发的参数化方案较Noah_LSM和VIC更接近真实的物理过程,同时CLM与SSiB模式中土壤湿度对蒸发的影响程度较Noah_LSM和VIC大;而对于下垫面有植被条件下的蒸散而言,CLM中包含了植被光合作用、呼吸作用等生物物理学过程,与实际情况更为接近,并且CLM与SSiB中土壤湿度对植被蒸散的影响程度大于VIC,Noah_LSM最低;（2）根据干旱区、半干旱区、半湿润区以及湿润区各站点的分析可知,CLM、SSiB与Noah_LSM中土壤湿度影响蒸散的参数化方案的拟合效果较VIC好,同时在部分站点CLM与SSiB的参数化方案稍优于Noah_LSM。区域之间比较说明,四个模式对干旱半干旱区的模拟效果明显较半湿润区和湿润区好。     

Retrieving daily global solar radiation from routine climate variables

Solar radiation is an important variable for studies related to solar energy applications, meteorology, climatology, hydrology, and agricultural meteorology. However, solar radiation is not routinely measured at meteorological stations; therefore, it is often required to estimate it using other techniques such as retrieving from satellite data or estimating using other geophysical variables. Over the years, many models have been developed to estimate solar radiation from other geophysical variables such as temperature, rainfall, and sunshine duration. The aim of this study was to evaluate six of these models using data measured at four independent worldwide networks. The dataset included 13 stations from Australia, 25 stations from Germany, 12 stations from Saudi Arabia, and 48 stations from the USA. The models require either sunshine duration hours (Ångstrom) or daily range of air temperature (Bristow and Campbell, Donatelli and Bellocchi, Donatelli and Campbell, Hargreaves, and Hargreaves and Samani) as input. According to the statistical parameters, Ångstrom and Bristow and Campbell indicated a better performance than the other models. The bias and root mean square error for the Ångstrom model were less than 0.25 MJ m² day^?1 and 2.25 MJ m² day^?1, respectively, and the correlation coefficient was always greater than 95 %. Statistical analysis using Student’s t test indicated that the residuals for Ångstrom, Bristow and Campbell, Hargreaves, and Hargreaves and Samani are not statistically significant at the 5 % level. In other words, the estimated values by these models are statistically consistent with the measured data. Overall, given the simplicity and performance, the Ångstrom model is the best choice for estimating solar radiation when sunshine duration measurements are available; otherwise, Bristow and Campbell can be used to estimate solar radiation using daily range of air temperature.     

An evaluation of Arctic cloud and radiation processes during the SHEBA year: simulation results from eight Arctic regional climate models

Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project. The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions. Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages, many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic.     

A simplified but accurate spectral solar irradiance model

Summary ¶The paper deals with the computation of solar energy available in a specific location. First, a new formula describing the relation between global solar irradiation and the duration of bright sunshine is established. The analysis of its use shows that global solar clear sky irradiance models are essential tools for daily computation of global irradiation. An integrated spectral atmospheric transmittance model is presented, it can be used to compute beam and diffuse clear sky irradiance for all applications where broadband solar energy input is needed. Since it is desirable to use simplified estimation methods for many applications, a parametric global solar irradiance model, derived from the spectral model, is also presented. This model needs only surface meteorological data as input. The influence of the averaging method used for the input parameters on the model accuracy is evaluated. Comparison of model results with the measurements shows an acceptable level of accuracy with the new model. Finally, an application of daily global solar energy computation is presented.Received May 17, 2002; revised October 14, 2002; accepted February 11, 2003 Published online September 10, 2003     

Accuracy of CM-SAF solar irradiance incident on horizontal surface

The Climate Monitoring Satellite Application Facility (CM-SAF) provides estimates of global solar irradiance incident on horizontal surface at Earth surface. Measurements performed in 2010 at five Romanian meteorological stations are used to test the accuracy of the CM-SAF irradiance data. The dataset contains null solar global irradiance values, which cannot be explained by very large values of the zenith angle neither by overcast sky conditions. Sub-databases have been created. The database Z85 consists of irradiance data, without filtering and processing. The database Z85SIS+ remove all null irradiance values. For a given database, the root mean square error (RMSE) with respect to the ground-based measurements is rather similar for all stations, i.e. around 35 % for Z85 and 24 % for Z85SIS+. On average, the database Z85SIS+ has smaller mean bias error (MBE) than the database Z85, independent of the degree of cloudiness. For the database Z85, MBE (RMSE) ranges, depending on station, between ?9.4 and ?1.2 % (35.3 and 39.1 %). For database Z85SIS+, the MBE (RMSE) ranges, depending on station, between ?4.0 and 0.1 % (23.0 and 29.1 %). On overcast sky, we found for some stations MBE?=??0.1 % and RMSE?=?46.4 % when the database Z85SIS+ has been considered. The accuracy of the database Z85 is lower; we found MBE?=??7.0 % and RMSE?=?58.8 % as extreme cases.     

The Diffuse Fraction of Global Solar Irradianceat a Tropical Location

Summary The annual and monthly mean diurnal variations of the diffuse fraction of global solar irradiance arriving on the ground at a tropical station in Sub-Sahel Africa is here been reported. The monthly mean hourly values of the diffuse fraction (K _d ) for such clear-sky months as February, March and November at this location, which approach a minimum at about local noon, are observed to lie generally below 0.50 during the period from 11:00 to 15:00 hrs (LST). Consequently, solar concentrators utilising parabolic mirrors are expected to have high performance during these months in this region. Like the mainly-cloudy and wet months (June to August) in which monthly mean hourly values of K _d higher than 0.62 have been recorded, the corresponding diffuse fraction for dust-haze months (mostly December and January) with high turbidity coefficients were generally above 0.50. Monthly mean hourly values of K _d for less cloudy months (April, May, September and October) ranged between 0.48 and 0.77 during the period from 11:00 to 15:00 hrs (LST). The effects of atmospheric dust-haze, clouds and albedo on the monthly mean diurnal variation of the diffuse fraction has been discussed. Also reported are the characteristic values of K _d for sets of months with relatively similar atmospheric and sky conditions at this location. The annual variations of the monthly mean daily values of K _d which exhibit strong seasonal dependence showed a peak in August for both years. Except for the months of February and March, the monthly mean daily totals of K _d exhibited similar annual marches during both years. The major discrepancy in the values of the monthly mean daily totals of K _d in both years were recorded in the months of February, November and December, with the corresponding K _d values for these months in both years agreeing only to within 32.9% in February, 15.4% in November and 16.2% in December. Apart from the aforementioned months, the corresponding monthly mean daily totals of K _d for the remaining nine months in both years agreed mostly to within less than 8.4%. The least monthly mean daily ratios of K _d were obtained in the relatively clear month of November for both years being 0.43 in 1993 and 0.49 in 1994. On an annual average, the diffuse component was found to constitute 59.6% of the global solar irradiance arriving on the ground at this region in 1993 and 60.9% in 1994. The results been reported here have been compared with a few others emanating from other tropical stations. Received February 5, 1998 Revised May 12, 1998