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Francesca Barnaba and Gian Paolo Gobbi

1. Introduction Atmospheric aerosols are both efficient scatterers of solar radiation and efficient cloud condensation nuclei. Overall, the combination of these effects translates into a negative radiative forcing, that is, a cooling that contrasts greenhouse gas warming (e.g., Penner et al. 2001 ). Despite such a climatic impact, these particles still represent a major unknown in the atmospheric system. This is mainly due to their high spatial and temporal variability and to their complex

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Wolfgang Junkermann

either enhanced or decreased in different altitudes of the planetary boundary layer ( Jacobson 1998 ), while at ground level reductions of more than 50% can be expected under high-pollution episodes. Model calculations were presented by Madronich (1987) , van Weele and Dynkerke (1993), de Arrellano et al. (1994) , Ruggaber et al. (1994) , Wendisch et al. (1996) , Wendisch and Keil (1999) , Dickerson et al. (1997) , Jacobson (1998) , and Früh et al. (2000) , either focusing on aerosol effects

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Daniel H. DeSlover, William L. Smith, Paivi K. Piironen, and Edwin W. Eloranta

1. Introduction The climatic importance of atmospheric anthropogenic gases such as carbon dioxide and methane, in addition to the state of the ozone layer, is currently a major scientific and political issue ( Schneider 1990 ; Chappelaz et al. 1993 ; Genthon et al. 1987 ). Cirrus clouds play a climatic role similar to that of the “greenhouse gases.” Studies have shown that both natural ( Prabhakara et al. 1993 ) and anthropogenic ( Smith et al. 1998 ) cirrus can produce a greenhouse warming

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Renske M. A. Timmermans, Martijn Schaap, Peter Builtjes, Hendrik Elbern, Richard Siddans, Stephen Tjemkes, and Robert Vautard

1. Introduction Aerosols play an important role in the earth’s radiation budget and the climate system through their interaction with clouds and solar radiation ( Kiehl and Briegleb 1993 ). Also, health studies have shown that short- and long-term exposure to aerosols has a negative effect on human health and can lead to premature death ( Brunekreef and Holgate 2002 ). To protect against the negative health effects, the European Union (EU) and the United States (US) have set limit values for

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L. Kristensen, J. Mann, S. P. Oncley, and J. C. Wyngaard

the sonic at 3 m, one at a horizontal distance of 0.25 m the other at 0.50 m. The latter was later moved to 0.75 m. Most of these sensors and the data acquisition system are part of the NCAR ASTER (Atmosphere–Surface Turbulent Exchange Research) facility ( Businger et al. 1990 ). b. RIMI measurements The RIMI site, approximately 1 km from Risø National Laboratory, was designed to study exchange of anthropogenic nitrogen compounds in rural Denmark. It is situated on a grass field in gently rolling

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Agnieszka Białek, Vincenzo Vellucci, Bernard Gentil, David Antoine, Javier Gorroño, Nigel Fox, and Craig Underwood

Satlantic-derived calibration coefficients, combined with the NPL laboratory-calibration uncertainty values (previously evaluated including all effects that are associated with the calibration process, such as the lamp current, aging, and uniformity effects as well as alignment, instrument reading stability, and reflectance panel uniformity), form the radiometric calibration uncertainty used in this work. These derived uncertainty values are presented in Table 1 per spectral channel for irradiance and

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Amin R. Nehrir, Kevin S. Repasky, and John L. Carlsten

reemitted downward infrared radiation. However, in the cold dry polar regions, the effects of a small increase in water vapor–CO 2 caused by equatorial convective circulations are much greater ( Trenberth et al. 2007 ). Water vapor is also the dominant positive feedback mechanism in our climate system and a major reason why temperature is so sensitive to changes in CO 2 . Unlike external forcings such as CO 2 , which can be added to the atmosphere, the level of water vapor in the atmosphere is a

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Yanzhou Wei, Sarah T. Gille, Matthew R. Mazloff, Veronica Tamsitt, Sebastiaan Swart, Dake Chen, and Louise Newman

), which take into account the effects of both Q net and EmP. (e),(f) As in (a) and (b), but for the difference between B net and Q net . All these figures are generated based on the JRA data. For some applications, the critical dynamical questions focus on processes that change water density, and therefore buoyancy flux ( B net ) is more important than heat flux; B net is the sum of air–sea heat flux and freshwater (EmP) heat-equivalent flux ( Cerovečki et al. 2011 ; Snow et al. 2016

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Hirofumi Sugawara and Junsei Kondo

temperature data. The physical processes by which the metadata-recorded factors influence temperature data have not been fully clarified. Therefore, the magnitude of temperature shifts caused by changes in site conditions remains unknown. Even if the metadata revealed suspicious changes that may influence temperature measurements, it is not always possible to precisely evaluate their effects on the temperature data ( Menne et al. 2010 ). Similarly, if any anomalies were found in temperature time series

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Yasmine Calisesi, René Stübi, Niklaus Kämpfer, and Pierre Viatte

decreasing atmospheric pressure is too low. Microwave results have been used to evaluate the amplitude of the column ozone deficit induced by this bias. The influence of the constant VMR profile extrapolation used to evaluate residual ozone from the soundings has also been investigated. The impact of both effects on total ozone was found to be very small. The average deficit induced by the BM measurement bias above 20 hPa represents, indeed, at most 3% of total ozone. Similarly, 20% residual ozone

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