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clouds and radiation

clouds and radiation . … recent hot topics Stefan Kinne. 348 ? CERES. 165 ? CERES. Question: how to balance the incoming extra 20W/m2 by CERES at the surface ?. overview. look at combined solar + IR netflux for CERES SRBAVG (the new ToA reference) SRB ISCCP

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clouds and radiation

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  1. clouds and radiation … recent hot topics Stefan Kinne

  2. 348 ? CERES 165? CERES Question: how to balance the incoming extra 20W/m2 by CERES at the surface ?

  3. overview • look at combined solar + IR netflux for • CERES SRBAVG (the new ToA reference) • SRB • ISCCP • IPCC-model median • CERES is about • 20W/m2 larger than IPCC modeling • 10W/m2 larger than SRB • 8W/m2 larger than ISCCP

  4. all-sky netflux at surface

  5. all-sky diff-netflux at surf

  6. diagnostics • diagnose … why ? • solar down fluxes • all-sky • CE (all-sky minus clear-sky) • IR down fluxes • all-sky • CE (all-sky minus clear-sky)

  7. all-sky dn-solar at surface

  8. all-sky diff-dn-solar at surf

  9. CE dn-solar at surface

  10. CE diff-dn-solar at surface

  11. all-sky dn-IR at surface

  12. all-sky diff-dn-IR at surf

  13. CE dn-IR at surface

  14. CE diff dn-IR at surface

  15. all sky cloud-free sky different definitions of the clear-sky flux • satellite clear-sky: only data from cloud-free areas • modeled clear-sky: (= cloud-free) data with cloud removed • … but in ‘cloudy columns’ there is more water vapor than in ‘clear-columns’ • model simulations underestimate the derived cloud radiative effect … as it includes the increased water vapor in cloudy regions

  16. expected are … overestimates to OLR (IR up at ToA) IR dn at surface IR divergence solar divergence underestimates to solar transmission solar reflection modeled cloud-effect biases on fluxes OLR error ~ 10W/m2 ! B.J.Sohn (2005) OLR error (B.J. Sohn, 2010) theoretical simulations

  17. IPCC-modeling minus CERES (obs) divergence cloud effect on up-flux cloud effect on dn-flux solar IR OLR effects are smaller due to compensating differences in cloud altitude

  18. ISCCP (model based)minus CERES (obs) divergence cloud effect on up-flux cloud effect on dn-flux solar IR lack of absorbing aerosol in tropics for ISCCP explains unexpected sA bias

  19. take-home messages • data products of the same name often do not mean the same (not identical by definition) • water vapor is expected often to be larger near clouds … thus clear-sky definitions in modeling • by differing from observations introduce biases • interestingly, expected differences often do not fully materialize due to other inconsistencies (e.g ancillary data of aerosol) • - careful assessments of data-products and assumptions are essential prior to conclusions

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