Why do Stable Boundary Layer Simulations over Land Sometimes “Crash”?

Research output: Chapter in Book/Report/Conference proceedingConference paperAcademic

Abstract

Over the past decades, numerical weather prediction (NWP) and climate models around the world have been utilizing several ad-hoc approaches (e.g., long-tail stability correction functions, friction velocity limiters) to avoid three interrelated modeling issues -- decoupling of boundary layer from underlying land-surface, run-away cooling, and crashing -- in the context of stably stratified flows. In order to explain these NWP and climate modeling issues, a few researchers performed idealized single column and large-eddy simulations. They documented that these idealized simulations crashed (without much warning) when substantial amounts of downward (negative) sensible heat flux are prescribed as lower surface boundary conditions. Since these crashing simulations were usually accompanied by substantial temperature drop, these simulations were identified as runaway cooling events. In this presentation, we demonstrate that the previously reported crashing events in idealized simulations are not related to the runaway cooling problem experienced by the atmospheric models. The crashing and runaway cooling events in these models occur when surface fluxes become negligibly small (very stable condition). In contrast, the root of the crashing problem in the idealized simulations can be traced back to the prescription of un-physically large downward (negative) sensible heat flux.
Original languageEnglish
Title of host publication20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA)
Place of PublicationBoston
PublisherAmerican Meteorological Society
Pages6A.1
Publication statusPublished - 2012
Event20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction - Boston, United States
Duration: 9 Jul 201213 Jul 2012

Conference

Conference20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction
CountryUnited States
CityBoston
Period9/07/1213/07/12

Fingerprint

boundary layer
cooling
simulation
sensible heat flux
climate modeling
weather
stratified flow
large eddy simulation
surface flux
prediction
land surface
boundary condition
friction
land
modeling
temperature

Cite this

Basu, S., & Holtslag, A. A. M. (2012). Why do Stable Boundary Layer Simulations over Land Sometimes “Crash”? In 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA) (pp. 6A.1). Boston: American Meteorological Society.
Basu, S. ; Holtslag, A.A.M. / Why do Stable Boundary Layer Simulations over Land Sometimes “Crash”?. 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). Boston : American Meteorological Society, 2012. pp. 6A.1
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abstract = "Over the past decades, numerical weather prediction (NWP) and climate models around the world have been utilizing several ad-hoc approaches (e.g., long-tail stability correction functions, friction velocity limiters) to avoid three interrelated modeling issues -- decoupling of boundary layer from underlying land-surface, run-away cooling, and crashing -- in the context of stably stratified flows. In order to explain these NWP and climate modeling issues, a few researchers performed idealized single column and large-eddy simulations. They documented that these idealized simulations crashed (without much warning) when substantial amounts of downward (negative) sensible heat flux are prescribed as lower surface boundary conditions. Since these crashing simulations were usually accompanied by substantial temperature drop, these simulations were identified as runaway cooling events. In this presentation, we demonstrate that the previously reported crashing events in idealized simulations are not related to the runaway cooling problem experienced by the atmospheric models. The crashing and runaway cooling events in these models occur when surface fluxes become negligibly small (very stable condition). In contrast, the root of the crashing problem in the idealized simulations can be traced back to the prescription of un-physically large downward (negative) sensible heat flux.",
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Basu, S & Holtslag, AAM 2012, Why do Stable Boundary Layer Simulations over Land Sometimes “Crash”? in 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). American Meteorological Society, Boston, pp. 6A.1, 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, Boston, United States, 9/07/12.

Why do Stable Boundary Layer Simulations over Land Sometimes “Crash”? / Basu, S.; Holtslag, A.A.M.

20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). Boston : American Meteorological Society, 2012. p. 6A.1.

Research output: Chapter in Book/Report/Conference proceedingConference paperAcademic

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T1 - Why do Stable Boundary Layer Simulations over Land Sometimes “Crash”?

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PY - 2012

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N2 - Over the past decades, numerical weather prediction (NWP) and climate models around the world have been utilizing several ad-hoc approaches (e.g., long-tail stability correction functions, friction velocity limiters) to avoid three interrelated modeling issues -- decoupling of boundary layer from underlying land-surface, run-away cooling, and crashing -- in the context of stably stratified flows. In order to explain these NWP and climate modeling issues, a few researchers performed idealized single column and large-eddy simulations. They documented that these idealized simulations crashed (without much warning) when substantial amounts of downward (negative) sensible heat flux are prescribed as lower surface boundary conditions. Since these crashing simulations were usually accompanied by substantial temperature drop, these simulations were identified as runaway cooling events. In this presentation, we demonstrate that the previously reported crashing events in idealized simulations are not related to the runaway cooling problem experienced by the atmospheric models. The crashing and runaway cooling events in these models occur when surface fluxes become negligibly small (very stable condition). In contrast, the root of the crashing problem in the idealized simulations can be traced back to the prescription of un-physically large downward (negative) sensible heat flux.

AB - Over the past decades, numerical weather prediction (NWP) and climate models around the world have been utilizing several ad-hoc approaches (e.g., long-tail stability correction functions, friction velocity limiters) to avoid three interrelated modeling issues -- decoupling of boundary layer from underlying land-surface, run-away cooling, and crashing -- in the context of stably stratified flows. In order to explain these NWP and climate modeling issues, a few researchers performed idealized single column and large-eddy simulations. They documented that these idealized simulations crashed (without much warning) when substantial amounts of downward (negative) sensible heat flux are prescribed as lower surface boundary conditions. Since these crashing simulations were usually accompanied by substantial temperature drop, these simulations were identified as runaway cooling events. In this presentation, we demonstrate that the previously reported crashing events in idealized simulations are not related to the runaway cooling problem experienced by the atmospheric models. The crashing and runaway cooling events in these models occur when surface fluxes become negligibly small (very stable condition). In contrast, the root of the crashing problem in the idealized simulations can be traced back to the prescription of un-physically large downward (negative) sensible heat flux.

M3 - Conference paper

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Basu S, Holtslag AAM. Why do Stable Boundary Layer Simulations over Land Sometimes “Crash”? In 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). Boston: American Meteorological Society. 2012. p. 6A.1