perturbations of stratocumulus steady state solutions
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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

Perturbations of stratocumulus steady-state solutions

Stephan de Roode, Jasper Sival

Sara Dal Gesso

slide2
Radiative cooling

zi

zb

Equilibrium Solutions (Stevens 2006):

Liquid water path:

seven free parameters some of which change in a perturbed cgils run
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)

slide4
Solving the inversion height

(as a function of free parameters only)

 Same can be done for qL,ML, etc., (long equations)

slide7
Total change in LWP if the SST and qt,FA are changed

(with the same amount as qt,0)

 Now a positive feedback

slide8
Change in LWP for a change in the large-scale divergence

 More ls-div, thinner clouds (lower cloud tops)

slide9
Change in LWP for a change in the horizontal wind velocity

 More wind, thicker clouds (BL becomes moister)

conclusions
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

slide12
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) ->

slide13

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

Clear convective

boundary layer

more stable (warmer free atmosphere) ->

slide15
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

ad