1. PRECIPITATION Def: H 2 O (solid or liquid) falling from an atmosphere at 100% RH (saturation)

2. Forms of precipitation Rain Rain Freezing Rain Freezing Rain Snow Snow Sleet Sleet Hail Hail

3. Forms of precipitation Rain Rain – Coalescence- drops collides with smaller drops, and grow

4. Forms of precipitation Drizzle Drizzle – Liquid drops that are less than 0.5mm in diameter. Usually results from precipitation from Low Level Clouds (stratus clouds).

5. FORMS OF PRECIPITATION Freezing Rain Freezing Rain –Liquid freezes when it strikes a surface near the ground. –Results from liquid being “super- cooled”. –VIDEO VIDEO

9. FORMS OF PRECIPITATION Snow Snow

10. FORMS OF PRECIPITATION Snow Snow –Flakes increase with more humidity –Would colder or warmer air cause bigger flakes?

11. FORMS OF PRECIPITATION Sleet Sleet –When rain falls through a layer of freezing air –Ice pellets Ground Below 0°C Above 0°C

12. FORMS OF PRECIPITATION Sleet

13. sleet

14. FORMS OF PRECIPITATION Hail Hail –Cumulonimbus clouds –Start as rain –Updrafts LIFT rain…freezes –Every updrafts adds a layer of ice –VIDEO VIDEO

18. Hailstone size MeasurementUpdraft Speed in.cm.mphm/s bb< 1/4< 0.64< 24< 11 pea1/40.642411 marble1/21.33516 dime7/101.83817 penny3/41.94018 nickel7/82.24621 quarter12.54922 half dollar1 1/43.25424 walnut1 1/23.86027 golf ball1 3/44.46429 hen egg25.16931 tennis ball2 1/26.47734 baseball2 3/47.08136 tea cup37.68438 grapefruit410.19844 softball4 1/211.410346

22. Coalescence the process by which two or more droplets or particles merge during contact to form a single daughter droplet (or bubble). the process by which two or more droplets or particles merge during contact to form a single daughter droplet (or bubble).

23. SUPERCOOLING the process of chilling a liquid below its freezing, without it becoming a solid or a gas. the process of chilling a liquid below its freezing, without it becoming a solid or a gas. VIDEO VIDEO VIDEO

24. Cloud Seeding Man-made technique Man-made technique Freezing nuclei (silver iodide) are added to supercooled clouds Freezing nuclei (silver iodide) are added to supercooled clouds Provides surface for drops to form on Provides surface for drops to form on Ex: Beijing Olympics 2008 Ex: Beijing Olympics 2008

25. The Beijing Weather Modification Office spent a lot of time researching how to prevent rain in the city on Aug. 8, 2008, during the opening ceremonies of the 2008 Summer Olympics. The government even guaranteed clear skies for the event. Their plan: to do it by tracking cloud formations and causing rain in the days leading up to the ceremonies. The Beijing Weather Modification Office spent a lot of time researching how to prevent rain in the city on Aug. 8, 2008, during the opening ceremonies of the 2008 Summer Olympics. The government even guaranteed clear skies for the event. Their plan: to do it by tracking cloud formations and causing rain in the days leading up to the ceremonies.Olympics