1 / 23

Isolating the Impact of Height Dependence on Cumulus Entrainment

Isolating the Impact of Height Dependence on Cumulus Entrainment. Walter Hannah May 25 th , 2011. EAPSI. 8 week visit (10 weeks or Japan) Myong -In Lee at Ulsan National Institute of Science and Technology in South Korea. Relaxed Arakawa-Schubert. Problems.

erasto
Download Presentation

Isolating the Impact of Height Dependence on Cumulus Entrainment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Isolating the Impact of Height Dependence onCumulus Entrainment Walter Hannah May 25th, 2011

  2. EAPSI • 8 week visit (10 weeks or Japan) • Myong-In Lee at Ulsan National Institute of Science and Technology in South Korea

  3. Relaxed Arakawa-Schubert

  4. Problems • Most cumulus schemes based on the “entraining plume” are not sensitive enough to the environmental conditions • Precipitation occurs too often • Precipitation occurs too early • Tropical wave and MJO variability is unrealistic • These problems are typically addressed with arbitrary trigger conditions • Environmental Humidity (Wang and Schlesinger, 1999) • Entrainment (Tokioka et al, 1988) • Large scale vertical velocity (Kain and Fritsch, 1992) • Cloud base height (Lee et al, 2008) • Precipitation evaporation (Sud and Walker, 1993) • Convective inhibition (Kain and Fritsch, 1992)

  5. Chikira and Sugiyama (2010) • Closure based on kinetic energy instead of mass flux • Entrainment rate is assumed to be inversely related to vertical velocity • Improved performance is credited to having large entrainment at low levels Gregory (2001) Neggers et al. (2002) Pan and Randall (1998)

  6. Height Dependent Entrainment • RAS constant entrainment • RAS linear entrainment

  7. The Normalized Mass Flux

  8. Chikira’s Test Case • Input profile calculated from TOGA-COARE • Precipitation rate > 20 mm/day

  9. SCM Results: GATE

  10. SCM Results: TOGA-COARE

  11. Diurnal Cycle Application • Lee et al. (2007) showed that only certain trigger mechanisms can significantlyeffect the diurnal timing of precipitation • Height of starting level • Defined as level of maximum MSE within 300 hPa from the surface • Convective inhibition • The LFC is constrained to be within 150 hPa from the starting level for convection to activate • Can modifying the cloud base entrainment have the same effect? Lee et al. (2007)

  12. Diurnal Cycle Application Lee et al. (2007)

  13. Is Height Dependence Realistic? • Romps (2010) presented a method for a direct measure of entrainment rate in LES models • Entrainment and detrainment are sources and sinks of cloud air

  14. Romps (2010) • Entrainment rate was found not to vary significantly with height • Entrainment did not scale with vertical velocity or buoyancy

  15. Romps (2010) Cloud air defined by moisture only Cloud air defined by moisture and vertical velocity

  16. Questions? Suggestions?

More Related