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Chevallier F.,CEA Saclay Nuclear Research Center | Ciais P.,CEA Saclay Nuclear Research Center | Conway T.J.,National Oceanic and Atmospheric Administration | Aalto T.,Finnish Meteorological Institute | And 28 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

This paper documents a global Bayesian variational inversion of CO 2 surface fluxes during the period 1988-2008. Weekly fluxes are estimated on a 3.75 × 2.5 (longitude-latitude) grid throughout the 21 years. The assimilated observations include 128 station records from three large data sets of surface CO2 mixing ratio measurements. A Monte Carlo approach rigorously quantifies the theoretical uncertainty of the inverted fluxes at various space and time scales, which is particularly important for proper interpretation of the inverted fluxes. Fluxes are evaluated indirectly against two independent CO2 vertical profile data sets constructed from aircraft measurements in the boundary layer and in the free troposphere. The skill of the inversion is evaluated by the improvement brought over a simple benchmark flux estimation based on the observed atmospheric growth rate. Our error analysis indicates that the carbon budget from the inversion should be more accurate than the a priori carbon budget by 20% to 60% for terrestrial fluxes aggregated at the scale of subcontinental regions in the Northern Hemisphere and over a year, but the inversion cannot clearly distinguish between the regional carbon budgets within a continent. On the basis of the independent observations, the inversion is seen to improve the fluxes compared to the benchmark: the atmospheric simulation of CO2 with the Bayesian inversion method is better by about 1 ppm than the benchmark in the free troposphere, despite possible systematic transport errors. The inversion achieves this improvement by changing the regional fluxes over land at the seasonal and at the interannual time scales. Copyright © 2010 by the American Geophysical Union. Source

Chevallier F.,CEA Saclay Nuclear Research Center | Deutscher N.M.,University of Bremen | Deutscher N.M.,University of Wollongong | Conway T.J.,National Oceanic and Atmospheric Administration | And 29 more authors.
Geophysical Research Letters | Year: 2011

We present the first estimate of the global distribution of CO 2 surface fluxes from 14 stations of the Total Carbon Column Observing Network (TCCON). The evaluation of this inversion is based on 1) comparison with the fluxes from a classical inversion of surface air-sample-measurements, and 2) comparison of CO 2 mixing ratios calculated from the inverted fluxes with independent aircraft measurements made during the two years analyzed here, 2009 and 2010. The former test shows similar seasonal cycles in the northern hemisphere and consistent regional carbon budgets between inversions from the two datasets, even though the TCCON inversion appears to be less precise than the classical inversion. The latter test confirms that the TCCON inversion has improved the quality (i.e., reduced the uncertainty) of the surface fluxes compared to the assumed or prior fluxes. The consistency between the surface-air-sample-based and the TCCON-based inversions despite remaining flaws in transport models opens the possibility of increased accuracy and robustness of flux inversions based on the combination of both data sources and confirms the usefulness of space-borne monitoring of the CO 2 column. Copyright 2011 by the American Geophysical Union. Source

Guirado C.,University of Valladolid | Guirado C.,Meteorological State Agency of Spain | Ramos R.,Meteorological State Agency of Spain | de Frutos A.,University of Valladolid | And 9 more authors.
Optica Pura y Aplicada | Year: 2012

During the last years a new optical calibration facility has been developed and deployed at the Izaña Observatory for the calibration and characterization of the radiation measuring instruments within research activities. These activities require a traceable Quality Assurance & Quality Control system. This new facility allows the absolute, spectral and cosine response calibration. At present there are six set-ups running at the laboratory for radiance calibration, angular response determination, spectral response characterization, slit function determination and absolute irradiance calibration (vertical and horizontal set-ups). Each method and procedure has required the development of the corresponding protocol. These systems, as well as some examples of instrument calibrations, are presented in this work. © Sociedad Española de Óptica. Source

Garcia R.D.,Meteorological State Agency of Spain | Garcia R.D.,University of Valladolid | Cachorro V.E.,University of Valladolid | Cuevas E.,Meteorological State Agency of Spain | And 4 more authors.
Optica Pura y Aplicada | Year: 2012

In this work we have compared UV spectral global irradiance measurements performed with the spectroradiometer Bentham DMT 300 (UIIMP, University of Innsbruck, Institute of Medical Physics Austria, ATI) and the simulations obtained with two radiative transfer models: UVA-GOA and LibRadtran. The measurements were performed on 1st June 2005, during the QASUME (Quality Assurance of Solar Ultraviolet Spectral Irradiance Measurements) intercomparison campaign at the Izaña (Tenerife) observatory. The results of UVA-GOA model shows differences with experimental data between 50% and 70% for wavelengths lower than 320 nm, which decrease to 10% around 320 nm. For the LibRadtran model the differences range from 20% at 280 nm to 3%-5% at 320 nm. These differences, which are in the range of ozone absorption, are due to the simplified approach used in UVA-GOA to treat the absorption-transmittance. For the range between 320 nm and 400 nm, the differences are lower than 6% (i.e. within the experimental error) for the comparison between both models and the measurements. © Sociedad Española de Óptica. Source

Mendez-Ramos J.,University of La Laguna | Acosta-Mora P.,University of La Laguna | Ruiz-Morales J.C.,University of La Laguna | Sierra M.,Meteorological State Agency of Spain | And 5 more authors.
Optical Materials | Year: 2015

Rare-earth doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fluoride glasses have been successfully synthesized showing outstanding UV-VIS up-conversion luminescence of Er3+ and Tm3+, sensitized by Yb3+ ions, under near-infrared excitation at 980 nm. The ratio between blue, green and red up-conversion emission bands can be adjusted by varying the pump power density of the incident infrared radiation, resulting in a controlled tuneability of the overall emitting colour from greenish to yellowish. Additionally, the observed high energy UV intense up-conversion emissions are suitable to enhance photocatalytic activity of main water-splitting semiconductor electrodes (such as TiO2) used in sustainable production of hydrogen. Photocatalysis and photolysis degradation of methylene blue in water under sun-like irradiation using benchmark photocatalyst (TiO2 Degussa P25) have been boosted by 20% and by a factor of 2.5 respectively, due to the enhancement of UV radiation that reaches the TiO2 particles by the addition of ZBLAN powder into a slurry-type photo-reactor. Hence, up-conversion ZBLAN phosphors contribute to demonstrate the possibility of transforming the incoming infrared radiation into the UV region needed to bridge the gap of photocatalytic semiconductors. © 2014 Elsevier B.V. All rights reserved. Source

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