A numerical model of the cloudy marine boundary layer
A numerical model of the cloudy marine boundary layer
A numerical model of the cloudy marine boundary layer is developed to investigate the role of entrainment instability on the time-dependent evolution of the boundary layer. The model is one-dimensional but includes the presence of a variety of cloud types from stratus to active cumulus. In general, previous boundary layer models have been limited to boundary layers capped by convectively stable inversions where the equivalent potential temperature increases from the bottom to the top of the inversion layer. This study extends the convectively stable model to include boundary layers capped by convectively unstable inversions where the equivalent potential temperature decreases substantially from the bottom to the top of the inversion. In this case the inversion is very active and the entrainment rate is scaled on the active instability at the interface, in contrast to the mean turbulent motion within the boundary layer. Sensitivity studies are carried out to investigate the behaviour of the model in the simulation of the downstream modification of the boundary layer over the ocean. Particular attention is given to the relative importance of the initial conditions on the development of the model atmosphere. Convergence of moisture in the boundary layer due to excess evaporation over entrainment of dry air from aloft. This is explored further when the external mechanisms which force the onset of convective instability are investigated. In the tropical atmosphere air originating in cool coastal regions requires the advection of dryer, cooler air in the free atmosphere and - a large evaporation rate to induce convective instability and the transition from stratus to cumulus clouds. Finally, the model is used to simulate the observed boundary layer structure from the JASIN experiment. Cool, dry air is modified by prolonged passage over increasingly warmer ocean which leads to the development of a convectively unstable cloud layer.
University of Southampton
Rogers, David Peter
492f2216-b10c-4d71-a13f-f0122d4938cf
1983
Rogers, David Peter
492f2216-b10c-4d71-a13f-f0122d4938cf
Rogers, David Peter
(1983)
A numerical model of the cloudy marine boundary layer.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
A numerical model of the cloudy marine boundary layer is developed to investigate the role of entrainment instability on the time-dependent evolution of the boundary layer. The model is one-dimensional but includes the presence of a variety of cloud types from stratus to active cumulus. In general, previous boundary layer models have been limited to boundary layers capped by convectively stable inversions where the equivalent potential temperature increases from the bottom to the top of the inversion layer. This study extends the convectively stable model to include boundary layers capped by convectively unstable inversions where the equivalent potential temperature decreases substantially from the bottom to the top of the inversion. In this case the inversion is very active and the entrainment rate is scaled on the active instability at the interface, in contrast to the mean turbulent motion within the boundary layer. Sensitivity studies are carried out to investigate the behaviour of the model in the simulation of the downstream modification of the boundary layer over the ocean. Particular attention is given to the relative importance of the initial conditions on the development of the model atmosphere. Convergence of moisture in the boundary layer due to excess evaporation over entrainment of dry air from aloft. This is explored further when the external mechanisms which force the onset of convective instability are investigated. In the tropical atmosphere air originating in cool coastal regions requires the advection of dryer, cooler air in the free atmosphere and - a large evaporation rate to induce convective instability and the transition from stratus to cumulus clouds. Finally, the model is used to simulate the observed boundary layer structure from the JASIN experiment. Cool, dry air is modified by prolonged passage over increasingly warmer ocean which leads to the development of a convectively unstable cloud layer.
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Published date: 1983
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Local EPrints ID: 460117
URI: http://eprints.soton.ac.uk/id/eprint/460117
PURE UUID: 5f8df42f-a039-4d25-a946-92cc8db71a48
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Date deposited: 04 Jul 2022 17:55
Last modified: 23 Jul 2022 00:58
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Author:
David Peter Rogers
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