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 * Cloud fraction profiles * Total, high, middle, and low clouds * Liquid water path and precipitable water vapor * Surface radiative fluxes * TOA radiative fluxes * Soundings * NWP analysis data * Surface sensible and latent heat fluxes * Surface precipitation * Surface temperature, relative humidity, and horizontal winds

6. Methods Composite Weighted Composite Regression

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

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

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

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

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

12. Composite vs. Weighted Composite mm/hr

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

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

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

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

17. Comparison: Regression vs. weighted composite Regression Coefficient Weighted composite t = whole time series t lag = [-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 Weighted [%] Regression [%/(mm/hr)] Non-weighted [%]

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

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

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

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

25. Summer vs. Winter Precipitation

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

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

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

29. Summer vs. Winter Surface Pressure

30. Summer vs. Winter Relative Humidity

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

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

33. Summer vs. Winter LWP

34. Summer vs. Winter Cloud Fraction

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

36. Summer vs. Winter Cloud Top Height

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

38. 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