PrecipitationPrecipitation Precipitation?Precipitation?What is precipitation?What is precipitation? What are the forms of precipitation?What are the forms of precipitation? What are the forms of precipitation?What are the forms of precipitation? What are the forms of precipitation?What are the forms of precipitation? Forms of PrecipitationForms of Precipitation1. 1. RainRain

- liquid deposits falling from the atmosphere- liquid deposits falling from the atmosphere to the surfaceto the surface - with a diameter > 0.5 mm - with a diameter > 0.5 mm- < 0.5 mm dri!!le - < 0.5 mm dri!!le- ma". si!e a#out 5 - $ mm - ma". si!e a#out 5 - $ mm%too large to remain suspended& %too large to remain suspended&- #e'ond this si!e( inter-molecular cohesi)e - #e'ond this si!e( inter-molecular cohesi)eforces #ecome to wea* to #e held in theforces #ecome to wea* to #e held in the mass of water together as a single drop mass of water together as a single drop

Forms of PrecipitationForms of Precipitation+. +. Freezing rainFreezing rain- when falling liquid water droplets reaches a surface - when falling liquid water droplets reaches a surfacewith a temperature #elow free!ing pointwith a temperature #elow free!ing point - so( the rain droplets quic*l' turn into ice - so( the rain droplets quic*l' turn into ice - another , condition where the rain de)elops( the - another , condition where the rain de)elops( thetemperature of rain de)elops must #e a#o)etemperature of rain de)elops must #e a#o)e free!ing free!inge.g. within a temperaturee.g. within a temperature in)ersion in)ersion

Forms of PrecipitationForms of Precipitation-. -. SleetSleet . . ice pelletsice pellets - transparent . translucent spheres of fro!en water - transparent . translucent spheres of fro!en water- with a diameter > 5 mm - with a diameter > 5 mm- de)elop first as raindrops in relati)el' warm- de)elop first as raindrops in relati)el' warm atmosphere %/emp > free!ing&(atmosphere %/emp > free!ing&( - then raindrops descend into a colder la'er of the - then raindrops descend into a colder la'er of theatmosphere %/emp 5 mm- hailstones concentric shells of ice with alternating- hailstones concentric shells of ice with alternating white cloud' appearance 2 those that arewhite cloud' appearance 2 those that are clear clear- cloud' white contain partiall' melted- cloud' white contain partiall' melted snowfla*es that free!e on to the snowfla*es that free!e on to the to the surface of the growing to the surface of the growing hailstone hailstone- clear shell de)elops when liquid water - clear shell de)elops when liquid water free!es onto the hailstone free!es onto the hailstone

Forms of PrecipitationForms of Precipitation5.5. Hail Hail- 3trong uprising currents in thunderstorm clouds- 3trong uprising currents in thunderstorm clouds pro)ide the mechanism for forming hail pro)ide the mechanism for forming hail- the updrafts mo)e hailstone em#r'os %e.g. large - the updrafts mo)e hailstone em#r'os %e.g. largefro!en raindrops& upward through the storm cloud fro!en raindrops& upward through the storm cloud- where the' encounter la'ers of ice cr'stals( snow 2 - where the' encounter la'ers of ice cr'stals( snow 2supercooled rain supercooled rain- each encounter causes the hailstone to grow larger - each encounter causes the hailstone to grow larger- hailstones can grow )er' large in si!e with- hailstones can grow )er' large in si!e with repeated updrafts repeated updrafts- until #eing too hea)' to #' supported #' updrafts( it - until #eing too hea)' to #' supported #' updrafts( it#egins falling under gra)it' #egins falling under gra)it'- on descending( it can lose great mass due to melting - on descending( it can lose great mass due to melting

Forms of PrecipitationForms of Precipitation5.5. Hail Hail

4 t'pical hailstone growth path through a thunderstorm cloud. 4 t'pical hailstone growth path through a thunderstorm cloud.5ailstones add most of their mass during updrafts. 5ailstones add most of their mass during updrafts.

6ecessar' conditions? 6ecessar' conditions? When clouds form in the atmosphere( the' When clouds form in the atmosphere( the' are non-precipitating in 778 of cases.are non-precipitating in 778 of cases. 6ecessar' conditions? 6ecessar' conditions? 1. cooling of air %e.g. con)ectional . orographic .1. cooling of air %e.g. con)ectional . orographic .

c'clonic %frontal& uplifting&c'clonic %frontal& uplifting&+. condensation and cloud formation+. condensation and cloud formation-. an accumulation of moisture-. an accumulation of moisture1. the growth of cloud droplets 1. the growth of cloud droplets

- - the the most criticalmost critical stage99stage99Water dropletsWater droplets and and ice crystalsice crystals of clouds need of clouds need to #e to #e transformed into transformed into heavier particlesheavier particles if the' if the' are to fall out of clouds as precipitation.are to fall out of clouds as precipitation. Wh'?Wh'? 6ecessar' conditions? 6ecessar' conditions? Water dropletsWater droplets and and ice crystalsice crystals of clouds need of clouds need to #e to #e transformed into transformed into heavier particlesheavier particles if the' if the' are to fall out of clouds as precipitation.are to fall out of clouds as precipitation. Wh'?Wh'?4s we *now( water droplets 2 ice cr'stals 4s we *now( water droplets 2 ice cr'stals can can onl' fallonl' fall to the :arth;s surface if the' grow to a to the :arth;s surface if the' grow to a sufficientl' large si!esufficientl' large si!e that that can can overcome overcome updraftsupdrafts 6ecessar' conditions? 6ecessar' conditions? Raindrop sizeRaindrop size

dri!!lea#out 0.+ mmdri!!lea#out 0.+ mm

light rain a#out 0.5 mm light rain a#out 0.5 mm

small rain a#out 1.0 mmsmall rain a#out 1.0 mm

raina#out 5.0 mmraina#out 5.0 mm

rainstorm up to a#out $.0 mmrainstorm up to a#out $.0 mm5ow a#out the 5ow a#out the condensed si!econdensed si!e generated fromgenerated from

condensationcondensation? % +00 ?m ?m %si!e of dri!!le onl'& %si!e of dri!!le onl'&%where 1 mm @ 1000%where 1 mm @ 1000 ?m?m& &