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RISS 인기검색어
- 검색키워드
- 저자 : Ermolli, I. (검색결과 5 건)
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Recent variability of the solar spectral irradiance and its impact on climate modelling
Ermolli, I.,Matthes, K.,Dudok de Wit, T.,Krivova, N. A.,Tourpali, K.,Weber, M.,Unruh, Y. C.,Gray, L.,Langematz, U.,Pilewskie, P.,Rozanov, E.,Schmutz, W.,Shapiro, A.,Solanki, S. K.,Woods, T. N. Copernicus GmbH 2013 Atmospheric chemistry and physics Vol.13 No.8
<P>Abstract. The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate. We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temperature and ozone distributions in the stratosphere, and indirectly, through dynamical feedbacks. We investigate these direct and indirect effects using several state-of-the art CCM simulations forced with measured and modelled SSI changes. A unique asset of this study is the use of a common comprehensive approach for an issue that is usually addressed separately by different communities. We show that the SORCE measurements are difficult to reconcile with earlier observations and with SSI models. Of the five SSI models discussed here, specifically NRLSSI (Naval Research Laboratory Solar Spectral Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar Radiation Physical Modelling), and OAR (Osservatorio Astronomico di Roma), only one shows a behaviour of the UV and visible irradiance qualitatively resembling that of the recent SORCE measurements. However, the integral of the SSI computed with this model over the entire spectral range does not reproduce the measured cyclical changes of the total solar irradiance, which is an essential requisite for realistic evaluations of solar effects on the Earth's climate in CCMs. We show that within the range provided by the recent SSI observations and semi-empirical models discussed here, the NRLSSI model and SORCE observations represent the lower and upper limits in the magnitude of the SSI solar cycle variation. The results of the CCM simulations, forced with the SSI solar cycle variations estimated from the NRLSSI model and from SORCE measurements, show that the direct solar response in the stratosphere is larger for the SORCE than for the NRLSSI data. Correspondingly, larger UV forcing also leads to a larger surface response. Finally, we discuss the reliability of the available data and we propose additional coordinated work, first to build composite SSI data sets out of scattered observations and to refine current SSI models, and second, to run coordinated CCM experiments. </P>
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Chatzistergos, Theodosios,Ermolli, Ilaria,Solanki, Sami K.,Krivova, Natalie A. Springer-Verlag 2018 Astronomy and astrophysics Vol.609 No.-
<P><I>Context. </I>Historical Ca II K spectroheliograms (SHG) are unique in representing long-term variations of the solar chromospheric magnetic field. They usually suffer from numerous problems and lack photometric calibration. Thus accurate processing of these data is required to get meaningful results from their analysis.</P><P><I>Aims. </I>In this paper we aim at developing an automatic processing and photometric calibration method that provides precise and consistent results when applied to historical SHG. </P><P><I>Methods. </I>The proposed method is based on the assumption that the centre-to-limb variation of the intensity in quiet Sun regions does not vary with time. We tested the accuracy of the proposed method on various sets of synthetic images that mimic problems encountered in historical observations. We also tested our approach on a large sample of images randomly extracted from seven different SHG archives.</P><P><I>Results. </I>The tests carried out on the synthetic data show that the maximum relative errors of the method are generally <6.5%, while the average error is <1%, even if rather poor quality observations are considered. In the absence of strong artefacts the method returns images that differ from the ideal ones by <2% in any pixel. The method gives consistent values for both plage and network areas. We also show that our method returns consistent results for images from different SHG archives. </P><P><I>Conclusions. </I>Our tests show that the proposed method is more accurate than other methods presented in the literature. Our method can also be applied to process images from photographic archives of solar observations at other wavelengths than Ca II K. </P>
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Phase Changing Materials in Buildings
Braganca, Luis,Ermolli, Sergio Russo,Koukkari, Heli Sustainable Building Research Center 2011 International journal of sustainable building tech Vol.2 No.1
New technologies are needed in structures and services in order to reduce the great energy consumption of buildings. A major share of the energy demand is used for controlling the indoor climate. The requirements are only growing due to tightening regulation and increasing comfort expectations of the users. The wide use of air conditioning systems illustrates this trend. Phase Changing Materials (PCM) open an alternative potential to return a part of cooling needs based upon melting and solidifying properties of some special components within a room temperature range. Thanks to this phenomenon, some degrees of additional control can be achieved. Experimental results from laboratory tests and monitoring results in two rooms of two actual buildings presented in this paper show that gypsum plaster finishings with a thin layer of 5 mm of PCM are favourable to achieve 2 to $5^{\circ}C$ reduction in the temperature swing in rooms.
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