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Clouds, Cirrus, and the Climate

Clouds, Cirrus, and the Climate. “Who are these that fly as a cloud, And as the doves to their window?”. “Wer sind die, die heranfliegen wie Wolken, Wie Tauben zu irhem Schlag?” (Jesaja 60:8). OUTLINE. Cloud Effects Cloud Radiative Forcing General Feedbacks The Recondite Cirrus

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Clouds, Cirrus, and the Climate

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  1. Clouds, Cirrus, and the Climate “Who are these that fly as a cloud, And as the doves to their window?” “Wer sind die, die heranfliegen wie Wolken, Wie Tauben zu irhem Schlag?” (Jesaja 60:8)

  2. OUTLINE • Cloud Effects • Cloud Radiative Forcing • General Feedbacks • The Recondite Cirrus • Low- and Mid-level Clouds • Cirrus Clouds • Addressing a Problem • Four Difficulties • Current Efforts • Future Work

  3. (Hartmann, 1994) CLOUD RADIATIVE FORCING General Avenues of Effect Cloud Temperature Albedo Absorptivity/Emissivity Cloud Cover Cloud Layer Latitude

  4. CLOUD FEEDBACKS I Sensitivity of Surface Temperature to CO2 Then Net Radiative Flux at TOA But…

  5. CLOUD FEEDBACKS II Where ui’s are Cloud-Related Parameters Therefore: (Paltridge, 1980) UNCLE!

  6. CLOUD FEEDBACKS IIV • Consider Some Known Feedbacks: • Cloud Water Path--Albedo/Emissivity • Cloud Temperature--Emissivity • Cloud Temperature--Surface Albedo • Surface Albedo--Surface Temperature

  7. RADIATIVE FORCING DEPENDS UPON CLOUD TYPE Model-Run Experiments Vary One Parameter at a Time Low- and Mid-level Clouds Cirrus Clouds

  8. CLOUD MODEL RESULTS(Stephens and Webster, 1980) • Cirrus Result in Warmer Surface Temperature (Cloud-Free Temp = 280K) • Cooler Cloud Tops Result in Lower Net Flux out of Cloud Top than Net Flux into Cloud Bottom

  9. CLOUD MODEL RESULTS(Stephens and Webster, 1980) • Variation Of Surface Temperature WRT Cloud Cover (Linear?) • Opposite Effects for Low- and Mid-level Clouds than for Cirrus • Related to Height and Cloud-top Temperature

  10. CLOUD MODEL RESULTS(Stephens and Webster, 1980) • Albedo Stronger Function of Water Path than Emittance • Water Path Variations More Important For More Tenuous Clouds

  11. CLOUD MODEL RESULTS(Stephens and Webster, 1980) • Albedo Function of Both Cloud Water Path and Zenith Angle

  12. CLOUD MODEL RESULTS(Stephens and Webster, 1980) • Three Types of Clouds, Surface Temperature as Function of CWP and Latitude • Small CWP, Heating Due to Emissivity Overwhelming Albedo--Tenuous Cirrus Have Smaller CWP • Lower Clouds: Higher Temperature, Less Heating • High Latitude, Small Insolation, LW Effects Dominate SW Effects

  13. CONCLUSIONS ON CIRRUS Changes in Optical Properties More Important for Cirrus (Esp. Water Path and Particle Size) At Lower Latitudes, May Contribute to Either Heating or to Cooling Effects Seem Less Certain than those of Lower, Thicker Clouds

  14. SOME DIFFICULTIES • Poorly Understood Feedbacks • Feedbacks Not Really Implemented in Model--Other Things are not Equal • Cirrus Radiative Properties not Fully Understood • Clouds Must be Parameterized • Due to Model Resolution • Math Description of Sub-Cell Processes • Incomplete Understanding of Cirrus Microphysics

  15. WHERE TO NOW? CURRENT EFFORTS A Recent Parameterization (Stephens et al, 1990

  16. WHERE TO NOW? FUTURE WORK (Mace 2002) • ARM • MMCR,MPL,AERI • The A-Train • Not the Duke Ellington song(http://www.empire.k12.ca.us/capistrano/Mike/capmusic/modern/american%20composers/ellington/ellingto.htm) • Constellation(http://www.nasa.gov/images/content/119021main3_A-Train-CALIPSO.jpg)

  17. To Study the Subtle and the Sublime A Cloud withdrew from the Sky Superior Glory be But that Cloud and its Auxiliaries Are forever lost to me Had I but further scanned Had I secured the Glow In an Hermetic Memory It had availed me now Never to pass the Angel With a glance and Bow Till I am firm in Heaven Is my intention now. (Emily Dickenson)

  18. THANK YOU!I will be happy to hear any questions “As the clouds the clouds chase; And we go, And we drop like the fruits of the tree, Even we, Even so.” (George Meredith)

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