Using routine meteorological data to derive sky conditions

International audienceSky condition is a matter of interest for public and weather predictors as part of weather analyses. In this study, we apply a method that uses total solar radiation and other meteorological data recorded by an automatic station for deriving an estimation of the sky condition. The impetus of this work is the intention of the Catalan Meteorological Service (SMC) to provide the public with real-time information about the sky condition. The methodology for deriving sky conditions from meteorological records is based on a supervised classification technique called maximum likelihood method. In this technique we first need to define features which are derived from measured variables. Second, we must decide which sky conditions are intended to be distinguished. Some analyses have led us to use four sky conditions: (a) cloudless or almost cloudless sky, (b) scattered clouds, (c) mostly cloudy ? high clouds, (d) overcast ? low clouds. An additional case, which may be treated separately, corresponds to precipitation (rain or snow). The main features for estimating sky conditions are, as expected, solar radiation and its temporal variability. The accuracy of this method of guessing sky conditions compared with human observations is around 70% when applied to four sites in Catalonia (NE Iberian Peninsula). The agreement increases if we take into account the uncertainty both in the automatic classifier and in visual observations

Assessing large-scale weekly cycles in meteorological variables: a review

Several studies have claimed to have found significant weekly cycles of meteorological variables appearing over large domains, which can hardly be related to urban effects exclusively. Nevertheless, there is still an ongoing scientific debate whether these large-scale weekly cycles exist or not, and some other studies fail to reproduce them with statistical significance. In addition to the lack of the positive proof for the existence of these cycles, their possible physical explanations have been controversially discussed during the last years. In this work we review the main results about this topic published during the recent two decades, including a summary of the existence or non-existence of significant weekly weather cycles across different regions of the world, mainly over the US, Europe and Asia. In addition, some shortcomings of common statistical methods for analyzing weekly cycles are listed. Finally, a brief summary of supposed causes of the weekly cycles, focusing on the aerosol-cloud-radiation interactions and their impact on meteorological variables as a result of the weekly cycles of anthropogenic activities, and possible directions for future research, is presented

Downward shortwave radiation trends in Europe since the 20th century: what we know from direct measurements and sunshine duration records?

Póster presentado en: AGU Fall Meeting celebrado en San Francisco del 15 al 19 de diciembre de 2014.This work was supported by the Ministry of Economy and Competitiveness of the Government of Spain through the projects NUCLIERSOL (CGL2010-18546) and HIDROCAES (CGL2011-27574-CO2-02). The first author was supported by the “Secretaria per a Universitats i Recerca del Departament d’Economia i Coneixement, de la Generalitat de Catalunya i del programa Cofund de les Accions Marie Curie del 7è Programa marc d’R+D de la Unión Europea” (2011 BP-B 00078) and the postdoctoral fellowship JCI-2012-12508. ASR received a grant from the FPU program (FPU AP2010-0917) of the Spanish Ministry of Education

Neuronal glycogen synthesis contributes to physiological aging

Glycogen is a branched polymer of glucose and the carbohydrate energy store for animal cells. In the brain, it is essentially found in glial cells, although it is also present in minute amounts in neurons. In humans, loss-of-function mutations in laforin and malin, proteins involved in suppressing glycogen synthesis, induce the presence of high numbers of insoluble polyglucosan bodies in neuronal cells. Known as Lafora bodies (LBs), these deposits result in the aggressive neurodegeneration seen in Lafora's disease. Polysaccharide-based aggregates, called corpora amylacea (CA), are also present in the neurons of aged human brains. Despite the similarity of CA to LBs, the mechanisms and functional consequences of CA formation are yet unknown. Here, we show that wild-type laboratory mice also accumulate glycogen-based aggregates in the brain as they age. These structures are immunopositive for an array of metabolic and stress-response proteins, some of which were previously shown to aggregate in correlation with age in the human brain and are also present in LBs. Remarkably, these structures and their associated protein aggregates are not present in the aged mouse brain upon genetic ablation of glycogen synthase. Similar genetic intervention in Drosophila prevents the accumulation of glycogen clusters in the neuronal processes of aged flies. Most interestingly, targeted reduction of Drosophila glycogen synthase in neurons improves neurological function with age and extends lifespan. These results demonstrate that neuronal glycogen accumulation contributes to physiological aging and may therefore constitute a key factor regulating age-related neurological decline in humans

Two ultraviolet radiation datasets that cover China

Ultraviolet (UV) radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization's measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes

Retrieving cloud characteristics from ground-based daytime color all-sky images

A discussion is presented of daytime sky imaging and techniques that may be applied to the analysis of full-color sky images to infer cloud macrophysical properties. Descriptions of two different types of sky-imaging systems developed by the authors are presented, one of which has been developed into a commercially available instrument. Retrievals of fractional sky cover from automated processing methods are compared to human retrievals, both from direct observations and visual analyses of sky images. Although some uncertainty exists in fractional sky cover retrievals from sky images, this uncertainty is no greater than that attached to human observations for the commercially available sky-imager retrievals. Thus, the application of automatic digital image processing techniques on sky images is a useful method to complement, or even replace, traditional human observations of sky cover and, potentially, cloud type. Additionally, the possibilities for inferring other clou

Using routine meteorological data to derive sky conditions

Sky condition is a matter of interest for public and weather predictors as part of weather analyses. In this study, we apply a method that uses total solar radiation and other meteorological data recorded by an automatic station for deriving an estimation of the sky condition. The impetus of this work is the intention of the Catalan Meteorological Service (SMC) to provide the public with real-time information about the sky condition. The methodology for deriving sky conditions from meteorological records is based on a supervised classification technique called maximum likelihood method. In this technique we first need to define features which are derived from measured variables. Second, we must decide which sky conditions are intended to be distinguished. Some analyses have led us to use four sky conditions: (a) cloudless or almost cloudless sky, (b) scattered clouds, (c) mostly cloudy – high clouds, (d) overcast – low clouds. An additional case, which may be treated separately, corresponds to precipitation (rain or snow). The main features for estimating sky conditions are, as expected, solar radiation and its temporal variability. The accuracy of this method of guessing sky conditions compared with human observations is around 70% when applied to four sites in Catalonia (NE Iberian Peninsula). The agreement increases if we take into account the uncertainty both in the automatic classifier and in visual observations.Key words. Meteorological and atmospheric dynamics (instruments and techniques; radiative processes) – Atmospheric composition and structure (cloud physics and chemistry

Using digital image processing to characterize the Campbell-Stokes sunshine recorder and to derive high-temporal resolution direct solar irradiance

The Campbell–Stokes sunshine recorder (CSSR) has been one of the most commonly used instruments for measuring sunshine duration (SD) through the burn length of a given CSSR card. Many authors have used SD to obtain information about cloudiness and solar radiation (by using Ångström–Prescott type formulas), but the burn width has not been used systematically. In principle, the burn width increases for increasing direct beam irradiance. The aim of this research is to show the relationship between burn width and direct solar irradiance (DSI) and to prove whether this relationship depends on the type of CSSR and burning card. A method of analysis based on image processing of digital scanned images of burned cards is used. With this method, the temporal evolution of the burn width with 1 min resolution can be obtained. From this, SD is easily calculated and compared with the traditional (i.e., visual) determination. The method tends to slightly overestimate SD, but the thresholds that are used in the image processing could be adjusted to obtain an improved estimation. Regarding the burn width, experimental results show that there is a high correlation between two different models of CSSRs, as well as a strong relationship between burn widths and DSI at a high-temporal resolution. Thus, for example, hourly DSI may be estimated from the burn width with higher accuracy than based on burn length (for one of the CSSR, relative root mean squared error is 24 and 30%, respectively; mean bias error is −0.6 and −30.0 W m−2, respectively). The method offers a practical way to exploit long-term sets of CSSR cards to create long time series of DSI. Since DSI is affected by atmospheric aerosol content, CSSR records may also become a proxy measurement for turbidity and atmospheric aerosol loading. © Author(s) 2015.This research was supported by the Spanish Ministry of Science and Innovation project NUCLIERSOL (CGL2010-18546). The first author enjoys a grant from the FPU program (FPU AP2010-0917) of the Spanish Ministry of Education. A. Sanchez-Lorenzo was supported by the “Secretaria per a Universitats i Recerca del Departament d’Economia i Coneixement, de la Generalitat de Catalunya i del programa Cofund de les Accions Marie Curie del 7è Programa marc d’RCD de la Unió Europea” (2011 BP-B 00078) and the postdoctoral fellowship JCI-2012-12508. The Negretti & Zambra Campbell–Stokes recorder was provided by the Pyrenean Institute of Ecology (CSIC).Peer Reviewe

The signal of aerosol-induced changes in sunshine duration records: A review of the evidence

Aerosols play a significant yet complex and central role in the Earth's radiation budget, and knowledge of long-term changes in the atmospheric turbidity induced by aerosols is therefore fundamental for a better understanding of climate change. However, there is little available information on changes in aerosol concentration in the atmosphere, especially prior to the 1980s. The present paper reviews publications reporting the suitability of sunshine duration records with regard to detecting changes in atmospheric aerosols. Some of the studies reviewed propose methods for estimating aerosol-related magnitudes, such as turbidity, from sunshine deficit at approximately sunrise and sunset, when the impact of aerosols on the solar beam is more easily observed. In addition, there is abundant evidence that one cause of the decadal changes observed in sunshine duration records involves variations in atmospheric aerosol loading. Possible directions for future research are also suggested: in particular, detailed studies of the burn (not only its length but also its width) registered by means of Campbell-Stokes sunshine recorders may provide a way of creating time series of atmospheric aerosol loading metrics dating back to over 120-years from the present. Key Points Sunshine records suitability to detect atmospheric aerosol is reviewed Despite short comings of the data, aerosol effect on sunshine is evident Possible directions for future research are highlighted. © 2014. American Geophysical Union. All Rights Reserved.This research was supported by the Spanish Ministry of Science and Innovation project NUCLIERSOL (CGL2010-18546). The first author received a grant from the FPU program (FPU AP2010-0917) of the Spanish Ministry of Education. The second author was supported by a postdoctoral fellowship from the “Secretaria per a Universitats i Recerca del Departament d'Economia i Coneixement, de la Generalitat de Catalunya i del programa Cofund de les Accions Marie Curie del 7è Programa marc d'R + D de la Unió Europea” (2011 BP-B 00078). The fifth author was given a grant by the “Juan de la Cierva” program (JCI-2011-10263) of the Spanish Ministry of Science and Innovation.Peer Reviewe

Tendencias recientes observadas en la evaporación en España y su posible relación con las variaciones de la radiación solar en superficie (1985-2010)

[ES] Existe un creciente interés sobre las causas de las tendencias de la evaporación observadas en diferentes regiones del planeta. En este trabajo se analizan las tendencias recientes de la evaporación potencial en España durante el periodo 1985-2010 a partir de registros mensuales homogeneizados de evaporímetros de tanque (21 series que inician sus observaciones en los 1980) y Piché (71 series, muchas de más de 60 años). Los resultados muestran una ausencia de cambios significativos de la evaporación en tanque durante el período 1985-2010. La ausencia de tendencias no se explica por la variación de la radiación, que aumentó en ese período, y probablemente debe estar influenciada por otras variables meteorológicas como la velocidad media del viento. Por otra parte, las tendencias derivadas de las series de evaporímetros Piché muestran una mejor relación con las variaciones de la radiación solar, lo que resulta llamativo ya que dicho instrumento está protegido de la radiación por la garita meteorológica. Probablemente, el efecto de la radiación es indirecto, al modificar las temperaturas y el déficit de presión de vapor ambiental ; [EN] There is growing interest on the causes of evaporation trends observed in different regions of the planet. This paper analyses recent trends in potential evaporation in Spain over the 1985-2010 period from monthly homogenised records both for pan evaporation measurements (21 series that start in the 1980s) and for Piché atmometers (71 series, most of them with more than 60 years of data). Despite of increasing solar radiation during the period 1985-2010, results show no significant trends in pan evaporation over the period 1985-2010. Therefore, the absence of trends must probably be related to other meteorological variables such as average wind speed. Moreover, the trends derived from Piché atmometers series show a better relationship with variations in solar radiation, which is striking because the instrument is protected from radiation by the weather shelter. Probably, the radiation effect is indirect, through a modification of the environment temperature and vapour pressure deficit.Esta investigación ha sido financiada por el Ministerio Economía y Competitividad, a través de los proyectos NUCLIERSOL (CGL2010-18546) e HIDROCAES (CGL2011-27574-C02-02). El segundo autor está financiado por una beca postdoctoral Beatriu de Pinós de la Generalitat de Catalunya (2009 BP-A 00035). Igualmente, el trabajo se encuadra en los objetivos del Grup de Física Ambiental (2009 SGR 213). Los datos han sido proporcionados por la Agencia Estatal de Meteorología (AEMet).Peer Reviewe