The ERA5 global reanalysis

Changes in Atmospheric Constituents and in Radiative Forcing

This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

Anthropogenic and Natural Radiative Forcing

The JRA-55 Reanalysis: General Specifications and Basic Characteristics

The fourth version of the Community Climate System Model (CCSM4) was recently completed and released to the climate community. This paper describes developments to all CCSM components, and documents fully coupled preindustrial control runs compared to the previous version, CCSM3. Using the standard atmosphere and land resolution of 1° results in the sea surface temperature biases in the major upwelling regions being comparable to the 1.4°-resolution CCSM3. Two changes to the deep convection scheme in the atmosphere component result in CCSM4 producing El Nino–Southern Oscillation variability with a much more realistic frequency distribution than in CCSM3, although the amplitude is too large compared to observations. These changes also improve the Madden–Julian oscillation and the frequency distribution of tropical precipitation. A new overflow parameterization in the ocean component leads to an improved simulation of the Gulf Stream path and the North Atlantic Ocean meridional overturning circulati...

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The Community Climate System Model Version 4

One of the important open questions in solar irradiance studies is whether long-term variability (i.e., on timescales of years and beyond) can be reconstructed by means of models that describe short-term variability (i.e., days) using solar proxies as inputs. Preminger & Walton showed that the relationship between spectral solar irradiance and proxies of magnetic-flux emergence, such as the daily sunspot area, can be described in the framework of linear system theory by means of the impulse response. We significantly refine that empirical model by removing spurious solar-rotational effects and by including an additional term that captures long-term variations. Our results show that long-term variability cannot be reconstructed from the short-term response of the spectral irradiance, which questions the extension of solar proxy models to these timescales. In addition, we find that the solar response is nonlinear in a way that cannot be corrected simply by applying a rescaling to a sunspot area.

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Response of Solar Irradiance to Sunspot-area Variations

The Sun provides nearly all the energy powering the Earth climate system, far exceeding all other energy sources combined. The incident net radiant energy, the “total solar irradiance,” varies on timescales from minutes to centuries and can cause commensurate changes in Earth’s climate and can affect global and regional temperatures in different ways. Typical solar variations are 0.1% on timescales from days to the 11-year solar cycle and are well measured by precision space-based radiometric instruments. Variations on longer timescales rely on solar models providing historical reconstructions. These estimate similar magnitude changes over centuries, albeit with uncertainties that increase with historical time. Because of the importance of tracking solar irradiance variability to better understand solar influences on climate, space-borne measurements have been continual since 1978 via a series of temporally overlapping instruments. Improved accuracies and stabilities in the most modern instruments are approaching the needed climate-driven measurement requirements for detection of potential long-term solar trends.

Earth’s Incoming Energy: The Total Solar Irradiance

The Total Irradiance Monitor (TIM), to be launched in 2002 on the NASA Earth Observing System (EOS) SOlar Radiation and Climate Experiment (SORCE), will stare at the Sun for five years, and measure the absolute total solar irradiance (TSI). The TIM is an active cavity radiometer with a relative standard uncertainty 100 ppm and a fractional stability of ? 10 ppm/year. The estimated uncertainties are “type B” determined from the parametric uncertainties in a model of the instrument; and the dominant uncertainty will be in the effective aperture area. To obtain such low uncertainty, we: 1. Use metallic NiP as the cavity (diffuse) black. 2. Retrieve the irradiance in the frequency domain. 3. Use phase sensitive detection. 4. Use four separate, duty-cycled cavities. 5. Measure the aperture transmission integral over area. 6. Use diamond thermal/electrical nodes. 7. Use 400 seconds for each completely independent data point for low noise. 8. Use a pulse-width-modulated “standard digital watt” as the onboard standard. 9. Take advantage of the 1 ppm noise level to discover systematic effects. 10. Measure IR shutter radiation from in-flight measurements of dark space. We compare with other TSI measurements on orbit, and as separate shuttle experiments.

Total Irradiance Monitor (TIM) for the EOS SORCE mission

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder (CPF) mission consists of a high accuracy reflected solar spectrometer that will take measurements from the International Space Station for one year starting in 2023. CPF will demonstrate that its novel on-orbit absolute calibration approaches are capable of achieving 0.3% (1-sigma) radiometric uncertainty. Additionally, using its two-axis pointing gimbal which enables nearly-concurrent measurements matching look angles with other orbiting sensors, CPF will demonstrate a novel inter-calibration approach by inter-calibrating CERES and VIIRS. CPF is currently in its Final Design and Fabrication Stage and recently passed its Critical Design Review.

Clarreo Pathfinder: Mission Overview and Current Status

This topical collection summarizes recent advances in observing and modeling irradiance variations of the Sun and Sun-like stars, emphasizing the links between surface magnetic fields and the resulting solar and stellar variability. In particular, the articles composing this collection summarize recent progress in i) solar-irradiance measurements; ii) modeling of solar- and stellar-irradiance variability; and iii) understanding of the effects of such variability on Earth's climate and exoplanet environments. This topical-collection overview article gives background and more details on these aspects of variability.

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Greg Kopp

Papers

Response of Solar Irradiance to Sunspot-area Variations

Earth’s Incoming Energy: The Total Solar Irradiance

Total Irradiance Monitor (TIM) for the EOS SORCE mission

Clarreo Pathfinder: Mission Overview and Current Status

Irradiance Variations of the Sun and Sun-Like Stars -- Overview of Topical Collection