Monday, 20 June 2016: 2:30 PM
The Canyons (Sheraton Salt Lake City Hotel)
Usually the mean state of the stable boundary layer (SBL) can be divided in two major regimes. A regime with fully developed turbulence, where the surface is energetically connected to the air layers above, and a second dominated by the presence of light winds and weak, or almost totally suppressed, turbulence with the surface energetically decoupled from the air above. Commonly, the first regime is referred as connected and the former one as disconnected. Besides this, the transition from one regime to another is sharp and occurs unpredictably, and many times can be related to the global intermittency. The reproduction of this feature of the nighttime regime is a challenge for atmospheric models. Many simplified models are able to reproduce the transition, however, the reproduction of global intermittency is even more difficult, by these models. In this work we analyze the performance of single column models, using classical turbulence formulations, to reproduce the transition between the SBL regimes. The simulations provided by the different orders of closure are compared. In all cases, the results show that the models have a huge difficulty in reproducing the transition. Other problem that was observed is that, the models are not able to reproduce the decrease in the temperature gradient that occurs in the neutral limit. Finally, the probably causes of those deficiencies are pointed out as a task for future work.
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