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So, what happens next?

So, what happens next?. Kate Thayer-Calder CMMAP Grad Student Clqm July 23, 2008. What Happened Before?. Undergraduate degree in Computer Science Spent 3 years working as a software developer on pharmaceutical robotic systems

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So, what happens next?

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  1. So, what happens next? Kate Thayer-Calder CMMAP Grad Student Clqm July 23, 2008

  2. What Happened Before? • Undergraduate degree in Computer Science • Spent 3 years working as a software developer on pharmaceutical robotic systems • Joined the group knowing basically nothing other than “I like clouds!”

  3. What Happened Next? • The MJO is an important and poorly understood phenomenon • Many GCMs are unable to simulate the MJO • We have two versions of the same model - one produces an MJO and one does not • GOALS: understand more about the models and more about the MJO

  4. Basics of the MJO • 30 to 70 day Oscillation, aka the intraseasonal oscillation • Starts in the Indian Ocean and slowly travels eastward (at 4-6 m/s or 9-13 mi/hr) • Spans 10º-20º of latitude and 50º-100º of longitude • Zonal wavenumbers 1-4 • Generally equatorially trapped, but can move northward or southward in certain cases. • More commonly appears in boreal winter Lin et al. 2006

  5. Basics of the MJO

  6. Current MJO Status You Are Here • EOF analysis used at BMRC to determine the current phase of the MJO • Forecasts done using a statistical model instead of traditional model MJO

  7. Lin et al. 2006 The Problem • The MJO is well observed, but not necessarily well understood • Many models have difficulty simulating the MJO • Only 2 of 14 IPCC AR4 models came close to having realistic MJO variability • Study suggests that the convective parameterizations in the models are the source of the differences • It is difficult to accurately simulate the MJO if we do not understand it!

  8. CAM Deep Convection Zhang and McFarlane (1995) • Triggered by instability, clouds persist until CAPE is mostly depleted • All detrainment occurs at cloud top, which must be above minimum of saturated MSE • All downdrafts exit below cloud base, and all clouds in the ensemble have the same base * * * * *

  9. SP-CAM Clouds and Convection • A 2-D Cloud Resolving Model is embedded in each GCM gridcell. • Clouds are explicitly simulated, allowing for many types, heights, and sizes of clouds. • Nudging from the LS values keeps the CRMs from drifting. • Results are returned to the LS as sub-grid scale tendencies due to clouds and radiation. • Currently, momentum is not fedback to the LS, and only the LS surface parameterizations are used.

  10. Moistening Through Many Levels 82% 96% 84% 80% 96% 60% >70%

  11. Discharge-Recharge Oscillation From Bladé and Hartman 1993 Figure from Benedict and Randall 2007 • Proposes MJO is an intrinsic oscillatory state of the tropics • During suppressed convection regimes, shallow clouds moisten and destabilize the area • Extra-tropical stochastic forcing sets off large-scale convection • Huge convective systems travel through the tropics restabilizing the area and suppressing convection after their passage.

  12. Discharge-Recharge Oscillation

  13. Moistening Through Many Levels • CRM in the SP-CAM does a better job of increasing relative humidity through the column, and loading the lowest levels with vapor • Heaviest rain occurs in a column with very high relative humidity, downdrafts are not as effective here • The CAM is much dryer through all layers 75% 65%

  14. Cycle of the MJO TPW (kg/m2) Rainrate (mm/hr) Rainrate (mm/hr) Rainrate (mm/hr) • Basic shape of SP-CAM, TC and ERA-40 are all very similar, well correlated precipitation and moistening keeps the cycle running • Disconnect between precipitation and increasing moisture breaks the Discharge-Recharge Oscillation in the CAM

  15. What’s Happening Now? • Defended my thesis last spring • Accepted into the Phd program • Taught a class on global climate change to undergraduates at Colorado College • Working on the paper from my thesis • Have to take the Prelims

  16. What Happens Next? • I have to decide exactly what I’m going to propose for my Phd dissertation • Will probably continue working with tropical dynamics • Will continue working with models, would like to add in some new observational toys • Would like to add an aspect of studying climate change to my research as well • Hope to continue to like clouds

  17. Questions?

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