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Perturbations of stratocumulus steady-state solutions

Perturbations of stratocumulus steady-state solutions. Stephan de Roode, Jasper Sival Sara Dal Gesso. Radiative cooling. z i. z b. Equilibrium Solutions ( Stevens 2006 ):. Liquid water path:. Five u nknowns. Changes in atmospheric state  Sea surface temperature q 0,SST

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Perturbations of stratocumulus steady-state solutions

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  1. Perturbations of stratocumulus steady-state solutions Stephan de Roode, Jasper Sival Sara Dal Gesso

  2. Radiative cooling zi zb Equilibrium Solutions (Stevens 2006): Liquid water path:

  3. Five unknowns Changes in atmospheric state  Sea surface temperature q0,SST  Horizontal wind velocity U  Free atmospheric moisture qFA  Free atmospheric temperature qFA  Large-scale divergence D Property of the model  Entrainment rate we Seven free parameters (some of which change in a perturbed CGILS run)

  4. Solving the inversion height (as a function of free parameters only)  Same can be done for qL,ML, etc., (long equations)

  5. Total change in LWP

  6. Total change in LWP ifonly the SST is changed  Negative feedback

  7. Total change in LWP if the SST and qt,FA are changed (with the same amount as qt,0)  Now a positive feedback

  8. Change in LWP for a change in the large-scale divergence  More ls-div, thinner clouds (lower cloud tops)

  9. Change in LWP for a change in the horizontal wind velocity  More wind, thicker clouds (BL becomes moister)

  10. Change in LWP for a change in the entrainment efficiency A  More entrainment, thicker clouds

  11. Effect of free parameters on the sign of the cloud feedback higher SST , lower LWP larger Div , lower LWP higher U , higher LWP qFA , both lower and higher LWP, depends on magnitude of change higher wENT , higher LWP (* for the base state discussed here) Entrainment rate is the only quantity that is determined by the model's parameterizations Conclusions

  12. Equilibrium inversion height as a function of the LTS.Mixed layer model results for a case with a weak large-scale cooling (net effect of radiation and horizontal advection) inversion height -> more stable (warmer free atmosphere) ->

  13. Equilibrium inversion height as a function of the LTS.Mixed layer model results starting with a dry convective boundary layer Cloudy boundary layer free atmosphere humidity -> Stable boundary layer large stability causes went<wsubs Clear convective boundary layer more stable (warmer free atmosphere) ->

  14. CGILS: Perturb equilibrium states and investigate what happens with the LWP

  15. Mixed Layer Model total specific humidity qT liquid water potential temperature qL entrainment flux entrainment flux zi zb zb Radiative cooling surface flux surface flux

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