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C. W. Fairall, P. O. G. Persson, E. F. Bradley, R. E. Payne, and S. P. Anderson

1. Introduction Atmospheric radiative fluxes represent a critical component of atmospheric dynamics, climate, boundary layer physics, and air–surface interactions. Advances in radiative transfer models and continued improvements in the technology of atmospheric turbulent fluxes are placing increasing demands for improvements in radiative flux methods and instruments. For example, the recent Tropical Oceans Global Atmosphere (TOGA) Coupled Ocean–Atmosphere Response Experiment (COARE) set a goal

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Matthias Mauder, R. L. Desjardins, Zhiling Gao, and Ronald van Haarlem

shortwave flux density R s , and the area normal to the incident solar radiation A s ; L and S are the heat transfer terms for forced and natural convection. In accordance with AB98 , R s can be described as where θ is the sun’s elevation angle, and SW ↓ is the flux density of shortwave radiation normal to the surface. Here, a constant ratio r d of diffuse radiation to total downward radiation of 0.1 is assumed. The justification is that the largest radiative heating occurs under

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R. Paul Lawson, Knut Stamnes, Jakob Stamnes, Pat Zmarzly, Jeff Koskuliks, Chris Roden, Qixu Mo, Michael Carrithers, and Geoffrey L. Bland

: Recent variations of sea ice and air temperatures in high latitudes . Bull. Amer. Meteor. Soc. , 74 , 33 – 47 . Chen, Y. , Francis J. A. , and Miller J. R. , 2002 : Surface temperature of the Arctic: Comparison of TOVS satellite retrievals with surface observations . J. Climate , 15 , 3698 – 3708 . Curry, J. A. , and Ebert E. E. , 1992 : Annual cycle of radiative fluxes over the Arctic Ocean: Sensitivity to cloud optical properties . J. Climate , 5 , 1267 – 1280 . Emanuel, K. A

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Larry McMillin, Michael Uddstrom, and Alessandro Coletti

shortwave emissivity, the longwave flux on thesensor surface, the shortwave flux on the sensor surface, and the sensor temperature. Of these quantities, theheat-transfer coefficient is determined by properties of both the sensor and the atmosphere, the reflectivities aredetermined by the sensor, and the fluxes and air temperature are determined by the atmosphere. For a typicalradiosonde, the radiative properties of the sensor can be determined, the coefficient of heat transfer can beestimated, and

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Robin J. Hogan, Malcolm E. Brooks, Anthony J. Illingworth, David P. Donovan, Claire Tinel, Dominique Bouniol, and J. Pedro V. Poiares Baptista

when the lowest 400 m of the profile is excluded from the calculation of optical depth, the error is considerably less (around 0.2, or 5%) in blind test 1. The KNMI errors in blind test 2 are around twice as large, possibly due to difficulties with the boundary assumptions when multiple scattering degrades the lidar signal. The large IPSL errors in blind test 2 are due to uncorrected multiple scattering, discussed in section 4e . In section 5 the sensitivity of the radiative fluxes to these

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James K. Luers

determining the sensitivity of the radiosonde temperature error to environmental conditions is as follows. A complete derivation of the heat balance equation for the radiosonde thermistor is developed. Input to the heat balance equation includes the dimension and radiative properties of the therm istor, the conduction and convective heat transfer pa rameters and the radiative fluxes that irradiate the thermistor as a function of environmental parameters. The significant environmental parameters included

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Elizabeth C. Kent, Raoul J. Tiddy, and Peter K. Taylor

relating the radiative heatingerror to the incoming solar radiation and the relativewind speed. Both of these factors can be estimated fromthe parameters currently reported by the VOS. The solar radiation effects were found to increasemean estimates of sensible and latent heat fluxes overthe North Atlantic by up to 4 W m-2. The monthlymean total turbulent heat flux would be increased byabout 6 W m-2 during summer months. Although theseerrors are small they would result in a significant changein the

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Mario Blumthaler, Barbara Schallhart, Michael Schwarzmann, Richard McKenzie, Paul Johnston, Michael Kotkamp, and Hisako Shiona

aims of the study. 2. Materials and methods a. ATI spectral measurements The spectral measurements of ATI were carried out with a commercial Bentham DTM300 double monochromator spectroradiometer, which was modified by custom-made extensions in several ways to allow the measurement of global irradiance, actinic flux, direct irradiance, sky radiance, and polarization of sky radiance. The instrument is equipped with two sets of holographic gratings, 1200 and 2400 lines per millimeter, which can be

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Martial Haeffelin, Robert Kandel, and Claudia Stubenrauch

well as south of the Australia coast and south of Polynesia. Large positive values are found on continents east of the subtropical ocean highs, such as in Angola and Namibia in Africa, Peru and Chile in South America, and parts of Australia. The difference between the two hemispheres, which is particularly clear in Fig. 5b , is due to the much greater insolation of the summer hemisphere. The RSFs are greater not only because the incident solar flux is larger but also because radiatively induced

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David I. Berry, Elizabeth C. Kent, and Peter K. Taylor

in sign of the implied sensible heat flux and unrealistic direct heat gain by the ocean. In addition evaporative heat loss by the ocean will be underestimated as atmospheric conditions may appear to be stably stratified rather than near neutral or unstable. For calculation of surface fluxes to 10 W m −2 it is necessary to know the mean air temperature to better than ±0.2°C ( Taylor et al. 2000 ). The radiative heating biases in VOS air temperature can be much larger than this target accuracy

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