ETH

Assessing radiative fluxes in the climate system from surface and space

Libera Science team meeting Nov 16, 2020

Martin WildETH Zurich, Switzerland

wild@ethz.ch

With support from Doris Folini, Maria Hakuba, Matthias Schwarz, Chuck Long, Su

Yang, Richard Allen, Norman Loeb, Seiji Kato

ETH

Units Wm-2

Surface fluxes considering information from surface station observations

Earth Radiation Budget

Updated from IPCC AR5 / Wild et al. 2013, 2015 Climate Dynamics

TOA fluxes from CERES satellite observations

ETH

Shortwave radiation budgets in CMIP6 GCMsReflected shortwave radiation TOA

Downward shortwave radiation surface

Model range: 13 Wm-2

Variance: 2.7 Wm-2

Mean CMIP6: 101 Wm-2

CERES EBAF: 100 Wm -2

Model range: 21 Wm-2

Variance: 4.5 Wm-2

Mean CMIP6: 187 Wm-2

Wild et al 2015: 185 Wm-2

global means of 38 CMIP6 models

global means of 38 CMIP6 models

Wild 2020 Climate Dynamics

CERES-EBAF

ETH

Longwave radiation budgets in CMIP6 GCMsOutgoing longwave radiation TOA

Downward longwave radiation surface

Model range: 16 Wm-2

Variance: 2.8 Wm-2

Mean CMIP6: 238 Wm-2

CERES EBAF: 239 Wm -2

Model range: 20 Wm-2

Variance: 5.2 Wm-2

Mean CMIP6: 344 Wm-2

Wild et al 2015: 342 Wm-2

global means of 38 CMIP6 models

global means of 38 CMIP6 models

Wild 2020 Climate Dynamics

CERES-EBAF

ETH

• Worldwide measurements of historic energy fluxes at the surface (2500 sites)

• Recordsa at many sites since 1950s, some back to 1930s • Monthly mean values

• WCRP initiative, starting in 1992• Highest measurement quality at selected sites worldwide

(currently 51 anchor sites) • Minute values

Wild et al. 2017, ESSD

Loeb et al, 2018 J. Climate

TOA / Surface radiation observations

www.bsrn.awi.de

www.geba.ethz.ch

• monthly and climatological observed TOA all-sky, clear-sky (spatially complete), and cloud radiative effect (CRE) fluxes

• 1° x 1°spatial resolution • Edition 4.1

CERES EBAF

Ohmura et al. 1998 BAMSDriemel et al. 2018 ESSD

www.bsrn.awi.de

ETH

Atmospheric SW Absorption over EuropeCombination of collocated TOA SW Absorption from CERES EBAF and surface SW absorption from GEBA/MODIS at 137 GEBA sites in Europe

Fractional Atmospheric SW Absorption: 23 % (robust through seasons and latitudes)

Hakuba et al. JGR 2014Hakuba, M. Z., D. Folini, G. Schaepman-Strub, and M. Wild (2014), Solar absorption over Europe from collocated surface and satellite observations, J. Geophys. Res. Atmos., 119, 3420–3437

(% of TOA isolation)

CERES EBAF

GEBA/MODIS

TOA

Atmosphere

Surface

ETH

Estimating clear-sky climatologies at BSRN sites

SW clear sky detection algorithmLong and Ackerman (2002) JGRTakes into account magnitude and temporal variability of diffuse and total downward solar radiation

LW clear sky detection algorithmLong and Turner (2008) JGRMakes use of clear episodes detected by theSW algorithm and takes into account variabilityof downward longwave radiation, measured ambient air temperature and effective sky brightness temperature.

Clear sky BSRN data processed at ETH Zurichby Maria Hakuba in collaboration with Chuck Long

High resolution BSRN records (minute data) used to establish clear sky estimates

__ observed__ GCMs

BSRN site Payerne Switzerland

Wild et al. 2019

ETH

Earth Radiation Budget without clouds

Wild M, Hakuba M, Folini D, Ott P, Schär C, Kato S, Long C, 2019: Climate Dynamics 52, 4787-4812

Global mean surface clear sky fluxes BSRN observations + climate models

ETH

Clear sky TOA fluxes from CERES EBAF

Earth Radiation Budget without clouds

adjusted for GCM-type clear sky

Wild M, Hakuba M, Folini D, Ott P, Schär C, Kato S, Long C, 2019: Climate Dynamics 52, 4787-4812

Global mean surface clear sky fluxes BSRN observations + climate models

ETH

Clear sky TOA fluxes from CERES EBAF

73 Wm-2

Combining SW clear sky TOA and surface absorption to obtain atmospheric clear sky SW absorption of 73 Wm-2

Earth Radiation Budget without clouds

adjusted for GCM-type clear sky

Wild M, Hakuba M, Folini D, Ott P, Schär C, Kato S, Long C, 2019: Climate Dynamics 52, 4787-4812

cf. CERES EBAF Ed473 Wm-2 (Kato et al. 2018)

ETH

Clear sky atmospheric SW absorption in CMIP6

Ø Clear-sky atmospheric SW absorption in CMIP6 multimodel mean in perfect agreement with reference estimates

Ø 35 out of 38 models within 2 Wm-2 of reference estimates

40 models

global means of 38 CMIP6 models

Wild 2020 Climate Dynamics

Model range: 8 Wm-2

Variance: 1.8 Wm-2

Mean CMIP6: 73 Wm-2

Wild et al 2019 : 73 Wm -2Kato et al 2018 : 73 Wm -2

ETH

Atmospheric clearsky SW Absorption: Historic evolution

Climate model Generation Atmos. clear sky SW absorptionMultimodel global mean

Pre AMIP (late 1980s models) 63 Wm-2

AMIP II (1990s models) 67 Wm-2

CMIP3 (early 2000s) 69 Wm-2

CMIP5 (2010s) 70 Wm-2

CMIP6 (2020s) 73 Wm-2

Reference values 73 Wm-2 (Wild et al. 2019)73 Wm-2 (Kato et al. 2018)

Wild 2020 Climate Dynamics

Upward adjustment by 10 Wm-2 over model generations in line with recent reference estimates

ETH

All sky Clear sky

Wild et al 2015 Clim. Dyn.

Cloud radiative effects (CRE)

Wild et al 2019 Clim. Dyn.

Units Wm-2 SW CRE LW CRE Net CRE

TOA -47 28 -19Atmosphere 7 0 7Surface -54 28 - 26

Wild et al. 2019 Clim Dyn / Wild 2020 Clim Dyn

ETH

All sky Clear sky

Wild et al 2015 Clim. Dyn.

Cloud radiative effects (CRE)

Wild et al 2019 Clim. Dyn.

Units Wm-2 SW CRE LW CRE Net CRE

TOA CMIP6 -47 -48 28 24 -19 -24Atmosphere CMIP6 7 3 0 -1 7 2Surface CMIP6 -54 -51 28 26 - 26 -25

Wild et al. 2019 Clim Dyn / Wild 2020 Clim Dyn

ETH

Collocated SW changes at the surface and TOA

Downward Surface Solar Composite of 84 observation sites

ChinaCompositeof 84 sites

Schwarz et al. 2020 Nature Geoscience

1965-2015

ETH

Collocated SW changes at the surface and TOA

Absorbed TOACERES / DEEP-C

Downward Surface Solar Composite of 84 observation sites

ChinaCompositeof 84 sites

1985 - 2015

Schwarz et al. 2020 Nature Geoscience

1965-2015

ETH

Collocated SW changes at the surface and TOA

Surface AlbedoGLASS-AVHRR/MODIS

Downward Surface Solar Composite of 84 observation sites

ChinaCompositeof 84 sites

Absorbed TOACERES / DEEP-C

1985 - 2015

Schwarz et al. 2020 Nature Geoscience

1965-2015

ETH

Collocated SW changes at the surface and TOA

Absorbed SurfaceDownward solar x (1-albedo)

Surface AlbedoGLASS-AVHRR/MODIS

Downward Surface Solar Composite of 84 observation sites

ChinaCompositeof 84 sites

Absorbed TOACERES / DEEP-C

1985 - 2015

Schwarz et al. 2020 Nature Geoscience

1965-2015

ETH

Collocated SW changes at the surface and TOA

Absorbed TOACERES / DEEP-C

Absorbed AtmosResidual TOA - Surface

Absorbed SurfaceDownward solar x (1-albedo)

Surface AlbedoGLASS-AVHRR/MODIS

Downward Surface Solar Composite of 84 observation sites

ChinaCompositeof 84 sites

1985 - 2015

Schwarz et al. 2020 Nature Geoscience

1965-2015

ETH

Collocated SW changes at the surface and TOA

Absorbed TOACERES / DEEP-C

Absorbed AtmosResidual TOA - Surface

Absorbed SurfaceDownward solar x (1-albedo)

Surface AlbedoGLASS-AVHRR/MODIS

Downward Surface Solar Composite of 84 observation sites

ChinaCompositeof 84 sites

1985 - 2015

Schwarz et al. 2020 Nature Geoscience

1965-2015

ETH

Conclusions• Combination of space-born and surface-based radiation measurements

enables to assess the distribution and changes in radiative energy flowsin the climate system.

• Allows quantification of energy balance components both under all skiesand clear skies > estimation of cloud effects

• Estimates used for model validation: latest climate model generation(CMIP6) generally in good agreement with reference estimates in multimodel mean, but still large discrepancies between individual models

• Collocated surface and TOA records allow to track changes in thepartitioning of radiative energy in the climate system: eg. recent recoveryof surface solar radiation in China is due to a less absorbing atmosphere

• A long term commitment in monitoring radiative fluxes from both spaceand surface is essential to capture changes in the energy flows in theclimate system > WE COUNT ON LIBERA!

ETH

Conclusions• Combination of space-born and surface-based radiation measurements

enables to assess the distribution and changes in radiative energy flowsin the climate system, both under all sky and clear sky

• Estimates used for model validation: latest climate model generation(CMIP6) generally in good agreement with reference estimates in multimodel mean, but still large discrepancies between individual models

• Collocated surface and TOA records allow to track changes in thepartitioning of radiative energy in the climate system: e.g. recent recoveryof surface solar radiation in China is due to a less absorbing atmosphere

• A long term commitment in monitoring radiative fluxes from both spaceand surface is essential to capture changes in the energy flows in theclimate system > WE COUNT ON LIBERA!