Three years of experience with the SoDa Web service delivering solar radiation information : lessons learned and perspectives.

Information on solar radiation is a critical issue in several environmental domains as well as for sun-powered sys-tems. The present means for accessing information by users present several severe drawbacks. Three major problems were identified and should be solved to supply users with relevant information: improved access to information, improved space and time description / knowledge of the radiation field and related quantities, improved matching to actual user needs. The SoDa project was launched (2000-2003, IST programme of the European Commission) to bring solutions by an efficient use of advanced information and communication technologies. An integration of information sources of different natures was initiated by the SoDa Intelligent System (see online at http://www.soda-is.com). These sources include databases containing solar radiation parameters and other relevant information; several of them originate from the processing of images taken by satellites. The sources! also include user-oriented applications. The successive prototypes of the SoDa Service were validated through users trials. The outcomes of the project SoDa represent a significant step forward beyond the current state of the art and include substantial original work. The main innovations of SoDa are to offer a smart access to diverse networked sources of information that are geographically dispersed, and to supply users with information of high quality. Surveys of users demonstrated that large gains in terms of efficiency, costs, etc. were expected by engineers, companies, agencies and research institutes if relevant information were more easily available for virtually any geographical location at any time. Accordingly, it was decided in 2003 to create the SoDa Service and to operate it. During these past three years, the SoDa Service underwent several improvements, all aiming at consolidating it with respect to access by users. Improvements were made on the SoDa Intellig! ent System, including works on the user interface and on the p! resentation of the services. Promotion efforts were made towards media, including TV. The effective use of the SoDa Service is increasing from year to year. In 2003, 2000 requests for information were satisfied; in 2004, 20 000 requests; 35 000 are expected in 2005. This communication presents the lessons learned from the past and the perspectives of the SoDa Service. We discuss the sustainability of the SoDa Service, the technologies used and the approach to customers, in the perspective of developing a B2B merchant site

Testing several models describing the change in surface solar irradiance with solar zenith angle in cloud-free skies

International audienceSeveral models aim at estimating surface downwelling solar irradiance (SSI) and are based on fast parameteri-zations of the radiative transfer in the atmosphere. This communication deals with the parameterization of the changes in SSI with solar zenith angle in cloudless conditions. It focuses on the total SSI and its direct and diffuse components. Several published and new models are tested against detailed calculations performed by the means of the radiative transfer model libRadtran in order to establish figures of merit. A methodology has been adopted whereby a large set of atmospheric properties (gas content, aerosols.. .) in cloud-free conditions is built by Monte-Carlo procedures and libRadtran is ran for each case of the set for solar zenith angle every 0.1 •. The selected models are tested against each case serving as reference and the discrepancies are computed and then summarized. The models comprise simple ones such as interpolation every 5 • of the irradiation itself or the clearness index, up to more complex ones such as Modified-Beer-Lambert model (MLB) or piecewise kernel-based functions. The accuracy of each model is assessed and compared to the accuracy currently achieved by the 5-piecewise MLB proposed by Qu et al. (2011). This 5-piecewise is made of five MLBs for five intervals (0 • , 60 •), (60 • , 75 •), (75 • , 80 •), (80 • , 85 •) and (85 • , 89.9 •). It exhibits satisfactory performances at any angle and outperforms standard linear interpolation techniques. 95% of errors in total SSI are less than 5 Wm-2. Conclusions on the respective performance of each model are drawn from this comparison. Finally, the strengths and weaknesses of each model are discussed having in mind their operational constraints. Reference: Qu, Z., Blanc, P., Lefevre, M., Wald, L., and Oumbe, A.: Study of the MLB parameterisation for change in surface solar irradiance with sun zenith angle in clear sky, Adv. Sci. Res., 6, 233–236, doi:10.5194/asr-6-233-2011, 2011

Production and Dissemination of Marine Renewable Energy Resource Information

International audienceThis paper investigates the capacity of appropriate Earth Observation Systems (EOS) – in situ and satellite measurements, numerical models – to deliver basic variables from which high level information relevant for Marine Renewable Energy (MRE) resource assessment can be generated. In addition, an operational solution for the production and dissemination of such information is proposed and set up. First, the parameters expected by end-users for accurate MRE resource assessment are identified. It turns out that a combination of appropriate spatial coverage and resolution, duration of time series and accuracy has to be met for the EOS data set to be relevant for the production of such parameters. Consequently, long term, high resolution hindcasts of sea states are identified as offering the best compromise over in situ and remote sensing measurements, which are best suited for models calibration and validation. Based on this analysis, a 19-year sea-state hindcast, Homere, has been selected. Homere accurately delivers relevant basic variables at appropriate time and spatial scales, over an area covering the south of the North Sea, the Channel, and the Atlantic coast of France and has been used to produce high level, end-user oriented information for the characterization of marine energy resource. Finally, dissemination tools, respecting international standards of interoperability, have been developed with a user-oriented state of mind in order to deliver the information

An OGC Web Processing Service for assessing the quality of solar radiation measurements

International audienceA service is presented that assesses the quality of measurements of daily global irradiation or means of global irradi-ance acquired by a ground station. Measurements are checked against models resulting in a measure of plausibility. This on-line service obeys the WPS (Web Processing Service) standard of the Open Geospatial Consortium. It is free of use and can be integrated into routine operations and Web portals thanks due its interoperability capability

The HelioClim Project: Surface Solar Irradiance Data for Climate Applications

URL : http://www.mdpi.com/2072-4292/3/2/343/International audienceMeteosat satellite images are processed to yield values of the incoming surface solar irradiance (SSI), one of the Essential Climate Variables. Two HelioClim databases, HC-1 and HC-3, were constructed covering Europe, Africa and the Atlantic Ocean, and contain daily and monthly means of SSI. The HC-1 database spans from 1985 to 2005; HC-3 began in 2004 and is updated daily. Their quality and limitations in retrieving monthly means of SSI have been studied by a comparison between eleven stations offering long time-series of measurements. A good agreement was observed for each site: bias was less than 10 W/m² in absolute value (5% in relative value) for HC-3. HC-1 offers a similar quality, though it underestimates the SSI for latitudes greater than 45° and less than −45°. Time-series running from 1985 to date can be created by concatenating the HC-1 and HC-3 values and could help in assessing SSI and its changes

Twelve monthly maps of ground albedo parameters derived from MODIS data sets

International audienceThe National Aeronautics and Space Administration (NASA) of the USA is making available to anyone worldwide maps of ground albedo parameters that are derived from the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument. The first parameter fiso describes the isotropic part of the bidirectional reflectance distribution function (BRDF); the two other parameters fvol and fgeo are linked to the viewing and illuminating geometry and describe the anisotropic part of the BRDF. These maps exhibit missing values. This communication describes a series of 12 monthly maps of the BRDF parameters with no missing values available on the Web. In addition, a method for computing the ground albedo is proposed that does not require the a priori knowledge of the ratio of the direct to the global irradiance

Converting a successful research project into a sustainable service: the case of the SoDa web service

International audienceInformation on solar radiation is a critical issue in several environmental domains. The means for accessing information suffer from severe drawbacks. The SoDa project was launched (2000-2003, IST programme of the European Commission) to bring solutions by an efficient use of information and communication technologies. Integration of information sources of different natures was realized by the SoDa Intelligent System. Surveys of users demonstrated that large gains in terms of efficiency, costs, etc. were expected by engineers, companies, agencies and research institutes. The SoDa Service was created in 2003. During the past three years, it has undergone several improvements, including works on the user interface and on the presentation of the services, all aiming at consolidating it with respect to access by users. Promotion efforts were made in the media, including TV. The use of the SoDa Service is increasing from year to year: in 2003, 10000 requests were satisfied, in 2004, 17000 requests and 27000 in 2005. This article presents the lessons learned from the past years and the perspectives of the SoDa Service. We discuss the sustainability of the SoDa Service, the technologies used and the approach to customers, in the perspective of building a B2B merchant site

The performances of the HelioClim databases in Mozambique

International audienceThis paper deals with the solar irradiance observed at ground level on horizontal surfaces and integrated over the whole spectrum (total irradiance), also called surface solar irradiance (SSI). The HelioClim project is an initiative of MINES ParisTech / Armines launched in 1997, to increase knowledge on SSI and to offer SSI values for any site, any instant within a large geographical area and large period of time, to a wide audience. It covers Europe, Africa and the Atlantic Ocean. The HelioClim-1 database, abbreviated in HC-1, offers daily values of SSI for the period 1985-2005. It has been created from archives of images of the Meteosat First Generation (MFG). The HelioClim-3 database, abbreviated in HC-3, began in 2004 and is updtaed daily. It exploits the enhanced capabilities of the series of satellites Meteosat Second Generation (MSG) to deliver values of SSI every 15 min with a spatial resolution of 3 km at nadir. These databases are available on the SoDa Service (www.soda-is.com). Their performances have been already assessed by a comparison with SSI measurements made at a number of meteorological stations. However, most of these stations are located in Europe, a very few are available in Africa and very often for a limited period of time. This communication focuses on the specific case of Mozambique. Owing to the World Radiation Data Center, data from several stations are available though the period of measurements is often limited to a few years. We discuss the quality of the ground-based measured daily means of SSI. Then, we perform a comparison between these measurements and the HC values, using standard procedure and performance parameters. We quantify the quality of the SSI retrieved from HC-1 and HC-3. We conclude that the HelioClim databases are a good means to assess the SSI in Mozambique and that the close-to 30-years period covered by HelioClim helps in depicting the change in SSI

Validating Meteosat-derived surface solar irradiance in Mozambique

International audiencehe solar radiation reaching the ground level on horizontal surfaces is of interest to many domains. The database HelioClim-1 contains daily values of radiation for 21 years: 1985-2005. It has been derived from Meteosat images and covers Europe, Africa and Atlantic Ocean. It is compared to ground-based measurements in Mozambique collected from the World Radiation Data Center. The quality of HelioClim-1 is good: the root mean square difference is approximately 30 W/m², and the correlation coefficient is greater than 0.85. These results are similar to those obtained by previous studies for Europe. HelioClim-1 is freely available through the SoDa Service and offers a reliable and accurate knowledge of the solar radiation and its daily, seasonal and annual variations over recent years

Test of several approaches for the composition of web services in meteorology.

International audienceComposition of web services is a powerful means to answer user needs in many domains. This communication focuses on applications in meteorology. This domain presents several particularities which are discussed. We present an overview of three main types of approaches in composition of web services: static plan, IA-plan and theorem proof. We confront these types of approaches to the specific case of meteorology which is not well studied by the research community in web services. We design a test bed that is capable of handling the key issues in meteorology. We have selected three approaches. We adapt them to our case and build three prototypes which are used in the test bed to point out weakness and strength of each approach. We find that current approaches do not fulfill needs in meteorology. We recommend an hybrid approach that combines the three in order to obtain an automatic and adaptative composition