1 / 18

Boundary Layer of Shallow Convection and Deep Convection

Boundary Layer of Shallow Convection and Deep Convection. Review of last lecture. Definition of stratocumulus clouds Global distribution Importance for global warming Vertical structure and formation mechanism of STBL

Download Presentation

Boundary Layer of Shallow Convection and Deep Convection

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. Boundary Layer of Shallow Convection and Deep Convection

  2. Review of last lecture • Definition of stratocumulus clouds • Global distribution • Importance for global warming • Vertical structure and formation mechanism of STBL • Modeling of STBL: non-local forced by surface heating and cloud-top cooling

  3. Global distribution of shallow convection and deep convection Deep convection Shallow convection From Shumacher and Houze (2003)

  4. Hadley circulation and cloud types Tropics L H Deep convection Trade wind cumulus Stratocumulus

  5. Walker circulation and cloud types Deep convection Trade wind cumulus Stratocumulus

  6. Trade wind cumulus • Cloud top height generally below 4 km • Often associated with light rain • Sometimes topped by stratocumulus

  7. Deep convection • Cloud top height above 9 km • Generally associated with rain • Sometimes organized into mesoscale convective systems

  8. Vertical structure of deep convection: Four components Convective updrafts (controlled by lower troposphere moisture) High θe Mesoscale updrafts Low θe Mesoscale downdrafts High θe Convective downdrafts Zipser (1977), modified by Houze (1993)

  9. Differences in boundary layer structure Trade wind cumulus Deep convection Stratocumulus Stratocumulus has shallow well-defined BL Trade wind cumulus has deep well-defined BL Deep convection does not have well-defined BL

  10. Differences in boundary layer T and q Trade wind cumulus Deep convection

  11. Differences between shallow convection and deep convection: Change of boundary layer T Shallow/midtop convection: T decreases Deep convection: T decreases

  12. Differences between shallow convection and deep convection: Change of boundary layer q Shallow/midtop convection: q increases Deep convection: q decreases

  13. Differences between shallow convection and deep convection: Change of boundary layer moist static energy h Moist static energy h = Cp T + L q + g z Shallow/midtop convection: h keeps constant Deep convection: h decreases

  14. Convective wake of deep convection

  15. Self-suppression processes in deep convection Missing physics III, IV Convective updrafts (controlled by lower troposphere temperature and moisture) High θe Mesoscale updrafts Low θe Missing physics II Mesoscale downdrafts High θe Convective downdrafts Missing physics I Zipser (1977), modified by Houze (1993)

  16. Over-stabilized state: A state far awayfrom quasi-equilibrium Model atmosphere fluctuates around the quasi-equilibrium state (always drizzle) The observed atmosphere swings far away from the quasi-equilibrium state (switch between heavy shower and clear sky)

  17. Summary • Global distribution of shallow and deep convection • Vertical structure of trade wind cumulus (shallow convection) • Vertical structure of deep convection. Four components: convective updraft, convective downdraft, mesoscale updraft, mesoscale downdraft • Differences between shallow convection and deep convection: change of T, q and h in the boundary layer • Self-suppression processes in deep convection: Overly stabilized state after deep convection • Problems in current global climate models: lack of self-suppression processes

  18. Works cited http://apollo.lsc.vsc.edu/classes/met455/notes/section2/4.html http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/navmenu.php_tab_2_page_5.2.0.htm http://www.atmos.ucla.edu/~bstevens/Research/research.html

More Related