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Toward All-sky Optimal Fingerprinting

Toward All-sky Optimal Fingerprinting. Yi Huang Stephen Leroy James Anderson John Dykema CLARREO Langley, Feb. 24, 2009. Outline. Likely changes of the Outgoing Longwave Radiation (OLR) spectrum Simulation based on one GFDL GCM + MODTRAN 4 Recent evolution

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Toward All-sky Optimal Fingerprinting

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  1. Toward All-sky Optimal Fingerprinting Yi Huang Stephen Leroy James Anderson John Dykema CLARREO Langley, Feb. 24, 2009

  2. Outline • Likely changes of the Outgoing Longwave Radiation (OLR) spectrum • Simulation based on one GFDL GCM + MODTRAN 4 • Recent evolution • Pre-industry to present-day difference • Attribution of the OLR change • GCM simulations submitted to CFMIP (monthly means) + MODTRAN 4 • Fingerprints (spectral change due to different physical causes) • Linearity

  3. 1980-2004 evolution of atmosphere and surface conditions T_sfc T_atm H2O OLR Cld OLR_c Blue lines and color contours: Evolution of the variables in the GFDL CM2 Allforc experiment. Red dotted lines and black dots: change (relative to 1980) larger than 3 times the standard deviation in Nat.

  4. Clear-sky Increase in outgoing radiation decrease in outgoing radiation CO2 Window CH4 H2O vib.-rot. CO2 [K] H2O rot. All-sky O3 1980-2004 evolution of OLR spectrum Global ocean annual mean radiance changes relative to 1980; Black dots: larger than 3 times the standard deviation in Nat.

  5. Linear trends Clear-sky H2O rot. Window H2O vib.-rot. CO2 O3 CH4 CO2 All-sky Red dashed line: trend estimated from linear regression; Green shaded areas: a measure of the uncertainty [Weatherhead et al. 1998].

  6. Tropics H2O rot Window H2O vib-rot. O3 CO2 CO2 CH4 Global Mean Extra-tropics 140-year end-to-end difference • Notations: • Red: climate change signature from the “Allforc” run; <2000-2004> minus <1861-1865> • Blue: variability among 3 ensemble members (3xSTD)‏ • Green: natural variability measured with the “Nat” run (3xSTD) • Results: • window regions – surface warming; • CO2 bands – stratospheric cooling partly offset by the raised emitting level (similar in O3 and CH4 bands); • H2O bands – atmospheric warming is compensated by water vapor feedbacks in tropics, but dominates in extra-tropics – optimal detection!

  7. Outline • Likely changes of the Outgoing Longwave Radiation (OLR) spectrum • Simulation based on one GFDL GCM + MODTRAN 4 • Recent evolution • Pre-industry to present-day difference • Attribution of the OLR change • GCM simulations submitted to CFMIP (monthly means) + MODTRAN 4 • Example: CCCMA • Fingerprints (spectral change due to different physical causes) • Linearity

  8. Random Overlapping Clouds: Ttot=Tcld*A+Tclr*(1-A), where A is cloud fraction Top: all-sky, clear-sky and cloud forcing of 960 cm-1 brightness temperature [K] (CCCMA, Jan, year 40) Bottom: corresponding spectra

  9. All-sky Clear-sky TOA Radiation change Xi: meteorological variable (e.g. atmospheric temperature, water vapor concentration, or cloud properties.) Forcing + Feedbacks Changes in OLR broadband flux (δOLR [W m-2]) and spectrum (δR [W m-2 sr-1 cm]) in 2xCO2 experiment. Note: x-axis in the spectral plot: wavenumber [cm-1]; spectra (δR) are color-coded to correspond to OLR change (δOLR).

  10. CO2 Surf. Temp. Atmos. Temp Water vapor Linear Regression Cloud Optimal detection 1. Identification of the fingerprints (spectral changes due to different physical causes) 2. Attribution – optimized by using linear regression.

  11. Table 1. The spectral radiance simulations performed on output of the CCCMA climate model for CFMIP.

  12. All-sky Clear-sky Changes in OLR broadband flux (δOLR [W m-2]), spectrum (δR [W m-2 sr-1 cm]) and normalized spectrum δRN due to CO2 forcing.

  13. All-sky Clear-sky Changes in OLR broadband flux (δOLR [W m-2]), spectrum (δR [W m-2 sr-1 cm]) and normalized spectrum δRN due to surface temperature response.

  14. All-sky Clear-sky Changes in OLR broadband flux (δOLR [W m-2]), spectrum (δR [W m-2 sr-1 cm]) and normalized spectrum δRN due to tropospheric temperature response.

  15. All-sky Clear-sky Changes in OLR broadband flux (δOLR [W m-2]), spectrum (δR [W m-2 sr-1 cm]) and normalized spectrum δRN due to tropospheric water vapor response.

  16. Changes in OLR broadband flux (δOLR [W m-2]), spectrum (δR [W m-2 sr-1 cm]) and normalized spectrum δRN due to lower, middle and upper tropospheric clouds. Lower-cloud Middle-cloud High-cloud

  17. All-sky Clear-sky Changes in OLR broadband flux (δOLR [W m-2]), spectrum (δR [W m-2 sr-1 cm]) and normalized spectrum δRN due to stratospheric temperature response.

  18. All-sky Clear-sky Changes in OLR broadband flux (δOLR [W m-2]), spectrum (δR [W m-2 sr-1 cm]) and normalized spectrum δRN due to stratospheric water vapor response.

  19. All-sky Clear-sky Global mean spectral fingerprints of CO2 forcing and various associated feedbacks, and the sum of them (“Sigma”) compared to the overall change (“all”) directly simulated.

  20. END

  21. 1. Correlation (blue) and p-value (red) between δRN due to tropospheric temperature and climatologic mean 850 hPa specific humidity; 2. Scatter plots at five selected frequencies.

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