Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme
Abstract Several studies have pointed out the dependence of low‐cloud feedbacks on the strength of the lower‐tropospheric convective mixing. By analyzing a series of single‐column model experiments run by a climate model using two different convective parametrizations, this study elucidates the phys...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
American Geophysical Union (AGU)
2016-12-01
|
| Series: | Journal of Advances in Modeling Earth Systems |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/2016MS000740 |
| _version_ | 1818320299017371648 |
|---|---|
| author | Jessica Vial Sandrine Bony Jean‐Louis Dufresne Romain Roehrig |
| author_facet | Jessica Vial Sandrine Bony Jean‐Louis Dufresne Romain Roehrig |
| author_sort | Jessica Vial |
| collection | DOAJ |
| description | Abstract Several studies have pointed out the dependence of low‐cloud feedbacks on the strength of the lower‐tropospheric convective mixing. By analyzing a series of single‐column model experiments run by a climate model using two different convective parametrizations, this study elucidates the physical mechanisms through which marine boundary‐layer clouds depend on this mixing in the present‐day climate and under surface warming. An increased lower‐tropospheric convective mixing leads to a reduction of low‐cloud fraction. However, the rate of decrease strongly depends on how the surface latent heat flux couples to the convective mixing and to boundary‐layer cloud radiative effects: (i) on the one hand, the latent heat flux is enhanced by the lower‐tropospheric drying induced by the convective mixing, which damps the reduction of the low‐cloud fraction, (ii) on the other hand, the latent heat flux is reduced as the lower troposphere stabilizes under the effect of reduced low‐cloud radiative cooling, which enhances the reduction of the low‐cloud fraction. The relative importance of these two different processes depends on the closure of the convective parameterization. The convective scheme that favors the coupling between latent heat flux and low‐cloud radiative cooling exhibits a stronger sensitivity of low‐clouds to convective mixing in the present‐day climate, and a stronger low‐cloud feedback in response to surface warming. In this model, the low‐cloud feedback is stronger when the present‐day convective mixing is weaker and when present‐day clouds are shallower and more radiatively active. The implications of these insights for constraining the strength of low‐cloud feedbacks observationally is discussed. |
| first_indexed | 2024-12-13T10:22:48Z |
| format | Article |
| id | doaj.art-66583b70c39a4c79befbb9b2336a5e28 |
| institution | Directory Open Access Journal |
| issn | 1942-2466 |
| language | English |
| last_indexed | 2024-12-13T10:22:48Z |
| publishDate | 2016-12-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj.art-66583b70c39a4c79befbb9b2336a5e282022-12-21T23:51:08ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662016-12-01841892191110.1002/2016MS000740Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection schemeJessica Vial0Sandrine Bony1Jean‐Louis Dufresne2Romain Roehrig3Laboratoire de Météorologie DynamiqueUniversité Pierre et Marie Curie (UPMC)Paris FranceLaboratoire de Météorologie DynamiqueUniversité Pierre et Marie Curie (UPMC)Paris FranceLaboratoire de Météorologie DynamiqueUniversité Pierre et Marie Curie (UPMC)Paris FranceCentre National de Recherches Météorologiques ‐ UMR 3583 Météo France/CNRSToulouse FranceAbstract Several studies have pointed out the dependence of low‐cloud feedbacks on the strength of the lower‐tropospheric convective mixing. By analyzing a series of single‐column model experiments run by a climate model using two different convective parametrizations, this study elucidates the physical mechanisms through which marine boundary‐layer clouds depend on this mixing in the present‐day climate and under surface warming. An increased lower‐tropospheric convective mixing leads to a reduction of low‐cloud fraction. However, the rate of decrease strongly depends on how the surface latent heat flux couples to the convective mixing and to boundary‐layer cloud radiative effects: (i) on the one hand, the latent heat flux is enhanced by the lower‐tropospheric drying induced by the convective mixing, which damps the reduction of the low‐cloud fraction, (ii) on the other hand, the latent heat flux is reduced as the lower troposphere stabilizes under the effect of reduced low‐cloud radiative cooling, which enhances the reduction of the low‐cloud fraction. The relative importance of these two different processes depends on the closure of the convective parameterization. The convective scheme that favors the coupling between latent heat flux and low‐cloud radiative cooling exhibits a stronger sensitivity of low‐clouds to convective mixing in the present‐day climate, and a stronger low‐cloud feedback in response to surface warming. In this model, the low‐cloud feedback is stronger when the present‐day convective mixing is weaker and when present‐day clouds are shallower and more radiatively active. The implications of these insights for constraining the strength of low‐cloud feedbacks observationally is discussed.https://doi.org/10.1002/2016MS000740convective mixinglow cloud feedbacklatent heat fluxconvective parameterization |
| spellingShingle | Jessica Vial Sandrine Bony Jean‐Louis Dufresne Romain Roehrig Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme Journal of Advances in Modeling Earth Systems convective mixing low cloud feedback latent heat flux convective parameterization |
| title | Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme |
| title_full | Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme |
| title_fullStr | Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme |
| title_full_unstemmed | Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme |
| title_short | Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme |
| title_sort | coupling between lower tropospheric convective mixing and low level clouds physical mechanisms and dependence on convection scheme |
| topic | convective mixing low cloud feedback latent heat flux convective parameterization |
| url | https://doi.org/10.1002/2016MS000740 |
| work_keys_str_mv | AT jessicavial couplingbetweenlowertroposphericconvectivemixingandlowlevelcloudsphysicalmechanismsanddependenceonconvectionscheme AT sandrinebony couplingbetweenlowertroposphericconvectivemixingandlowlevelcloudsphysicalmechanismsanddependenceonconvectionscheme AT jeanlouisdufresne couplingbetweenlowertroposphericconvectivemixingandlowlevelcloudsphysicalmechanismsanddependenceonconvectionscheme AT romainroehrig couplingbetweenlowertroposphericconvectivemixingandlowlevelcloudsphysicalmechanismsanddependenceonconvectionscheme |