Intercomparison of spectroradiometers for global and direct solar irradiance in the visible range.
This paper presents the results of the analysis of the spectral, global, and direct solar irradiance measurements in the visible range (400–700 nm) that were made in the framework of the first Iberian UV–visible (VIS) instruments intercomparison. The instruments used in this spectral range were four spectroradiometers: three Licor 1800s equipped with different receiver optics and one Optronic 754. For the direct solar irradiance measurements the spectroradiometers were equipped with collimators with different fields of view. Parallel studies have been carried out with the data given by the spectroradiometers with their original calibration file and with the same data that is corrected, foll…
Aerosol Lidar Intercomparison in the Framework of SPALINET—The Spanish Lidar Network: Methodology and Results
Abstract—A group of eight Spanish lidars was formed in order to extend the European Aerosol Research Lidar Network–Advanced Sustainable Observation System (EARLINET-ASOS)project. This study presents intercomparisons at the hardware and software levels. Results of the system intercomparisons are based on range-square-corrected signals in cases where the lidars viewed the same atmospheres. Comparisons were also made for aeros backscatter coefficients at 1064 nm (2 systems) and 532 nm (all systems), and for extinction coefficients at 532 nm (2 systems). In total, three field campaigns were carried out between 2006 and 2007. Comparisons were limited to the highest layer found before the free tr…
Aerosol radiative forcing efficiency in the UV region over southeastern Mediterranean: VELETA2002 campaign
Atmospheric aerosol effects on spectral global UV irradiance were evaluated during the VELETA2002 field campaign between 8 and 19 July 2002 in southeast Spain. In the first stage, seven UV spectroradiometer and six CIMEL Sun photometer measurements were carried out simultaneously, allowing them to be calibrated and intercompared. The mean ratio obtained for the global irradiance between the spectroradiometers, with regards to a reference instrument, ranges from 0.98 up to 1.04 with standard deviations that oscillate between ±0.01 and ±0.17. In particular, the two spectroradiometers used to obtain the aerosol forcing efficiencies have a ratio of 1.000 ± 0.001. The aerosol optical depth (AOD)…
Determination of sea surface temperature using combined TOVS and AVHRR data. Application to the Canary Islands area, Spain
Abstract The determination of sea surface temperature from satellite is performed by means of multi-channel algorithms with channels 4 and 5 of AVHRRNOAA or using radiative transfer models and radiosounding profiles of air temperature and humidity. In this work, an alternative to the current algorithms has been established. A new method combining the information supplied by sensors of TOVS and AVHRR systems onboard NOAA satellites is proposed. It is based on the split-window technique, the coefficients A and B being determined as a function of the water vapour content, which is calculated using the TOVS sensors. The T4 and T5 temperatures are supplied by the AVHRR system. Then, combining bo…
UV Index Experimental Values During the Years 2000 and 2001 from the Spanish Broadband UV-B Radiometric Network¶
An analysis is made of experimental ultraviolet erythemal solar radiation data measured during the years 2000 and 2001 by the Spanish UV-B radiation evaluation and prediction network. This network consists of 16 Robertson-Berger type pyranometers for evaluating solar erythemal radiation and five Brewer spectroradiometers for evaluating the stratospheric ozone. On the basis of these data the Ultraviolet Index (UVI) was evaluated for the measuring stations that are located either in coastal regions or in the more densely populated regions inland on the Iberian Peninsula. It has been checked that in most cases the maximum irradiance values corresponded to solar noon, although there were except…
Altitude effect in UV radiation during the Evaluation of the Effects of Elevation and Aerosols on the Ultraviolet Radiation 2002 (VELETA-2002) field campaign
[1] The Evaluation of the Effects of Elevation and Aerosols on the Ultraviolet Radiation 2002 (VELETA-2002) field campaign was designed to study the influence of aerosols and altitude on solar UV irradiance. The altitude effect (AE) was evaluated for UV irradiance under cloudless conditions by taking spectral and broadband measurements in SE Spain in the summer of 2002 at three nearby sites located at different heights (680 m, 2200 m, and 3398 m). A spectral radiative transfer model (Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART)) was also applied, mainly to evaluate the tropospheric ozone impact on AE. Results are related to the optical properties and air mass origin of the a…
Comparison of AERONET and SKYRAD4.2 inversion products retrieved from a Cimel CE318 sunphotometer
SKYNET is an international research network of ground based sky – sunphotometers for the observation and monitoring of columnar aerosol properties. The algorithm developed by SKYNET is called SKYRAD.pack, and it is used on Prede instruments only. In this study, we have modified the SKYRAD.pack software in order to adapt it to Cimel sunphotometers. A one month database of Cimel data obtained at Burjassot (Valencia, Spain) has been processed with this program and the obtained inversion products have been compared with AERONET retrievals. In general, the differences found were consistent with the individual error assessments for both algorithms. Although the aerosol optical depth com…