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

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

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

4. Honolulu Mean Precipitation 4

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

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

7. Precipitation Types 7

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? 8

9. 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? 9

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

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

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

13. Precipitation Types 13

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

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

16. Table 7-3, p. 176 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.

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

18. Fig. 4, p. 179 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

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

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

21. Snow in Hawaii !! 21 Mauna Kea

22. Precipitation Types 22

23. Fig. 7-19, p. 180 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

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

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

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

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

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

29. Precipitation Types 29

30. Fig. 4, p. 179 30 Snow Grains and Snow Pellets Snow GrainsSnow Pellets Diameter< 1 mm< 5 mm Showernoyes Brittleness/bouncynoyes OriginStratus cloudCumulus congestus Opaqueyes

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

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

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

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

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

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

38. 38 Radar Transmitted energy backscatter

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

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

41. THE END 41

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

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

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

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

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

47. Fig. 7-32, p. 189 47

48. Fig. 7-32, p. 189 48