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The nature of rain events in summer vs. winter at the SGP ARM Facility

The nature of rain events in summer vs. winter at the SGP ARM Facility. MPO 581 Class Project Emily Riley, Siwon Song, & Brian Mapes. Background. ARM – Atmospheric Radiation Measurements Several Sites (facilities) funded by DOE. Background. ARM – Atmospheric Radiation Measurements

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The nature of rain events in summer vs. winter at the SGP ARM Facility

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  1. The nature of rain events in summer vs. winter at the SGP ARM Facility MPO 581 Class Project Emily Riley, Siwon Song, & Brian Mapes

  2. Background • ARM – Atmospheric Radiation Measurements • Several Sites (facilities) funded by DOE

  3. Background • ARM – Atmospheric Radiation Measurements • SGP-Southern Great Plains

  4. Data • Climate Modeling Best Estimate (CMBE) Data • 1996 – 2009 • Data averaged over one hour time intervals

  5. Data • Climate Modeling Best Estimate (CMBE) Data • 1996 – 2009 • Data averaged over one hour time intervals • * Soundings • * NWP analysis data • * Surface sensible and latent heat • fluxes • * Surface precipitation • * Surface temperature, relative • humidity, and horizontal winds * Cloud fraction profiles * Total, high, middle, and low clouds * Liquid water path and precipitable water vapor * Surface radiative fluxes * TOA radiative fluxes

  6. Methods • Composite • Weighted Composite • Regression

  7. July 1996 – RH and Precipitation Relative Humidity (RH) at surface – ψ(t) [%] Days on July 1996 Precipitation Rate at surface – p(t) : Rain Event [mm/hr] Days on July 1996

  8. non-weighted composite method • non-weighted composite tlag = [-7*24, 7*24] hours N = total number of selected rain events

  9. non-weighted composite Relative Humidity (RH) at surface – ψ(t) [%] Days on July 1996 Precipitation Rate at surface – p(t) : Rain Event [mm/hr] -7 days -7 days -7 days -7 days -7 days -7 days +7 days +7 days +7 days +7 days +7 days +7 days

  10. Weighted composite method • weighted composite Non-weighting tlag = [-7*24, 7*24] hours N = total number of selected rain events

  11. Weighted composite Relative Humidity (RH) at surface – ψ(t) [%] Days on July 1996 Precipitation Rate at surface – p(t) : Rain Event [mm/hr] -7 days -7 days -7 days -7 days -7 days -7 days +7 days +7 days +7 days +7 days +7 days +7 days

  12. Composite vs. Weighted Composite mm/hr mm/hr

  13. Regression method • Regression Coefficient t = whole time series tlag= [-7*24, 7*24] hours

  14. Regression method: t = 0 hour Relative Humidity (RH) at surface – ψ(t) [%] Days on July 1996 Precipitation Rate at surface – p(t) [mm/hr]

  15. Regression method: t = -10 hour Relative Humidity (RH) at surface – ψ(t) [%] Days on July 1996 Precipitation Rate at surface – p(t) [mm/hr]

  16. Regression method: t = +10 hour Relative Humidity (RH) at surface – ψ(t) [%] Days on July 1996 Precipitation Rate at surface – p(t) [mm/hr]

  17. Comparison: Regression vs. weighted composite • Regression Coefficient • Weighted composite t = whole time series tlag = [-7*24, 7*24] hours N = total number of selected rain events

  18. Weighted Composite vs. Regression % RH on precipitation

  19. Weighted Composite vs. Regression % SAME, except for units RH on precipitation

  20. Relative Humidity Perturbation Non-weighted [%] Weighted [%] Regression [%/(mm/hr)]

  21. Time for some results…. • Oklahoma JJA vs. DJF precipitation

  22. Cumulative Fraction of Rain Events • DJF - ~45% time not raining • JJA - ~32% time not raining DJF JJA

  23. Cumulative Fraction of Rain Events ~20% rain events > 5 mm/hr • DJF - ~45% time not raining • JJA - ~32% time not raining DJF JJA 5

  24. Cumulative Fraction of Rain Events ~5% rain events > 5 mm/hr • DJF - ~45% time not raining • JJA - ~32% time not raining DJF JJA 5

  25. Summer vs. Winter Precipitation

  26. Summer vs. Winter Temperature Strong Diurnal Cycle Weak Diurnal Cycle

  27. Summer vs. Winter Temperature Strong Diurnal Cycle Afternoon Convection Frontal Precip Weak Diurnal Cycle

  28. Seasonal:Temperature perturbation [K] JJA: Summer DJF: Winter

  29. Summer vs. Winter Surface Pressure

  30. Seasonal:Relative Humidity perturbation [%] JJA: Summer DJF: Winter

  31. Seasonal:Relative Humidity perturbation [%] JJA: Summer DJF: Winter

  32. Summer vs. Winter LWP

  33. Seasonal:All Cloud Fraction perturbation [%] JJA: Summer DJF: Winter

  34. Summer vs. Winter Cloud Top Height

  35. Seasonal:Omega perturbation [Pa/s] JJA: Summer DJF: Winter

  36. Summary • Summer (JJA): • More rain events • Heavier, but shorter rain events • Stronger diurnal cycle • Higher cloud tops • Winter (DJF): • Tilted vertical structure for RH and Cloud Fraction • THOUGH, hourly time composites might reveal tilted structure in summer

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