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Precipitation Types

Precipitation Types. Global and Regional Mean Precipitation 1. Types of Precipitation: 2. Measurement:. FIT, Feb 15, 2012. Global Mean Precipitation. Satellite measurement of precipitation What happens in Hawaii?. Hawaii Mean Precipitation. Mean = 70 in Without land = 25 in.

florrie-morris
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Precipitation Types

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  1. Precipitation Types Global and Regional Mean Precipitation 1. Types of Precipitation: 2. Measurement: FIT, Feb 15, 2012

  2. Global Mean Precipitation Satellite measurement of precipitation What happens in Hawaii?

  3. Hawaii Mean Precipitation Mean = 70 in Without land = 25 in Precipitation measurement by Rain Gauge

  4. Honolulu Mean Precipitation

  5. Surface Analysis (Feb 11, 2012, 18 UTC)

  6. Hawaii (Feb 12, 2012, 0245 UTC) Radar measurement of rain

  7. Precipitation Types

  8. Precipitation Types • Drizzle: diameter < 0.5 mm • Rain: diameter >= 0.5 mm • Where are the raindrops larger, Miami or Seattle? • Raindrops almost always < 6 mm because • collision among raindrops • too large raindrops tend to break up • Start as rain, but may fall as drizzle. Does rain always reach the surface?

  9. Does rain always reach the surface? • Falling precipitation that evaporate before reaching surface --- Virga • Low humidity - - evaporation - - drops become smaller - - rate of fall decreases • Strong updraft • Sudden rain shower and cloudburst (Cumuliform) • Rain and no-rain in places next to each other (Cumulonimbus) • Continuous rain at small vertical currents (layered cloud or Nimbostratus) How does “Virga” look like and where does it happen?

  10. Virga (Rain not reaching the surface) Fig. 7-14, p. 174

  11. Shape of Raindrops Spherical < 2 mm ; Parachute > 2 mm (surface area / volume) is minimum for 2. Fig. 2, p. 175

  12. Intensity of Rainfall Table 7-2, p. 175

  13. Precipitation Types

  14. Snow c Falling ice-crystals and snowflakes (Fallstreaks) from cirrus clouds. Fig. 7-15, p. 176

  15. Common forms of ice crystal Fig. 7-16, p. 176 Why is dendrite most common? Dendrite Fig. 7-17, p. 178

  16. Why is dendrite most common? Growth = f(temperature, sat. vap. Pr. difference) Maximum growth rate is at -12 to -16 C, when saturation vapor pressure difference between water and ice is maximum. Table 7-3, p. 176

  17. Intensity of Snowfall Is visibility the best way to measure snowfall? Can wind lead to visibility problem? Table 7-4, p. 178

  18. Some more terms related to snowfall Flurries: light and intermittent from developing cumulus cloud Snow squall: brief but more intense than flurries, usually from cumuliform clouds Drifting snow: surface movement Blowing snow: in air movement Ground blizzard: after falling snow has ended Blanket of snow: snow covering the landscape Fig. 4, p. 179

  19. Snow as Sound Absorbant Fig. 4, p. 179

  20. Annual Average Snowfall over US Why is Hawaii not included? Fig. 7-18, p. 179

  21. Snow in Hawaii !! Mauna Kea

  22. Precipitation Types

  23. Sleet and Freezing Rain Partially melted snowflake or cold raindrop - - freezes Deep freezing layer - - Sleet <= 5 mm Shallow freezing layer - - freezing rain >=0.5 mm Fig. 7-19, p. 180

  24. Formation of Rime Supercooled droplets in contact with object at below freezing temperature - - white milky granular ice Fig. 7-20, p. 180

  25. Destruction due to Freezing Rain Syracuse, New York, January 1998 Fig. 7-21, p. 180

  26. Aircraft de-icing Fig. 5, p. 181

  27. Average number freezing rain/drizzle days Fig. 7-22, p. 181

  28. Vertical Temperature Profile and Precipitation Type Fig. 7-23, p. 182

  29. Precipitation Types

  30. Snow Grains and Snow Pellets Fig. 4, p. 179

  31. Formation of Graupel / Snow Pellets gr Ice particle + cloud droplets -- rimed ice crystal -- graupel (dift shape than rime) -- snow pellet During summer: graupel - - large raindrop Vigorously convective cloud: graupel - - hailstones Fig. 7-24, p. 182

  32. Formation of Hail/Hailstone Fig. 7-27, p. 183

  33. Hail and Hailstone Dia = 17.8 cm (7 in) ; Circumference = 47.6 cm (18.7 in); weight > 1.75 lb Fig. 7-25, p. 182 Fig. 7-26, p. 183

  34. Summary of Precipitation Types Table 7-5, p. 185

  35. Measurement of Precipitation In-situ measurement: Rain gauge; accurate but spotty. Remote measurement: Radar, Satellite; not so accurate but large coverage. Combination of the above.

  36. Components of the standard rain gauge Area of collector = 10 x area of measuring tube Fig. 7-29, p. 184

  37. Tipping bucket rain gauge Fig. 7-30, p. 185

  38. Transmitted energy backscatter Radar

  39. Reflectivity Precipitation Oklahama, April 24, 1999 Fig. 7-31a, p. 187

  40. Precipitation due to Fay (2008) Precipitation Reflectivity Fig. 7-31a, p. 187

  41. THE END

  42. Fig. 7-23a, p. 182

  43. Fig. 7-23b, p. 182

  44. Fig. 7-23c, p. 182

  45. Fig. 7-23d, p. 182

  46. Fig. 7-28a, p. 184 Fig. 7-28b, p. 184

  47. Fig. 7-32, p. 189

  48. Fig. 7-32, p. 189

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