How large-scale subsidence affects stratocumulus transitions
Some climate modeling results suggest that the Hadley circulation might weaken in a future climate, causing a subsequent reduction in the large-scale subsidence velocity in the subtropics. In this study we analyze the cloud liquid water path (LWP) budget from large-eddy simulation (LES) results o...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/691/2016/acp-16-691-2016.pdf |
| Summary: | Some climate modeling results suggest that the Hadley circulation might
weaken in a future climate, causing a subsequent reduction in the large-scale
subsidence velocity in the subtropics. In this study we analyze the cloud
liquid water path (LWP) budget from large-eddy simulation (LES) results of
three idealized stratocumulus transition cases, each with a different
subsidence rate. As shown in previous studies a reduced subsidence is found
to lead to a deeper stratocumulus-topped boundary layer, an enhanced
cloud-top entrainment rate and a delay in the transition of stratocumulus
clouds into shallow cumulus clouds during its equatorwards advection by the
prevailing trade winds. The effect of a reduction of the subsidence rate can
be summarized as follows. The initial deepening of the stratocumulus layer is
partly counteracted by an enhanced absorption of solar radiation. After some
hours the deepening of the boundary layer is accelerated by an enhancement of
the entrainment rate. Because this is accompanied by a change in the
cloud-base turbulent fluxes of moisture and heat, the net change in the LWP
due to changes in the turbulent flux profiles is negligibly small. |
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| ISSN: | 1680-7316 1680-7324 |