Precipitation Flashcards
What is the collision-coalescence process?
the process of producing precipitation by liquid particles (cloud droplets and raindrops) colliding and joining (coalescing)
What is coalescence?
merging of cloud droplets into a single larger drople
What is the process of coalescence within a cloud?
smaller droplets are pushed upward during the updraft within the cloud, colliding with larger droplets in their path.
What is supercooled water?
-Liquid water at temperatures below freezing
- below –40 degrees C (40 degrees F), only ice exists
Which molecule has better saturation than the other?
Since there is more water vapor pressure above the water droplet than above the ice; there is a greater water vapor pressure above the droplet. As saturation, the pressure exerted by the water molecules is greater over the water vapor droplet than the ice crystal.
What is an ice nuclei?
Particles that act as nuclei for the formation of ice crystals in the atmosphere.
Based off the Ice Crystal Process, what is supersaturated and what’s unsaturated?
air is supersaturated with respect to ice; air unsaturated with respect to supercooled water drop
What is the process of the Ice Crystal Process?
1) The greater number of water vapor molecules around the liquid droplet causes water molecules to diffuse from the liquid droplet toward the ice crystal.
(2) The ice crystal absorbs the water vapor and grows larger, while
(3) the water droplet grows smaller
What are the four ice crystal forms?
-Plate
-Column
-Dendrite (most common)
-Needle
What is the process of snow?
snow would continue below freezing as it gets closer to the surface
What is the process of Sleet?
snow begins in the below freezing zone, then to above freezing, and half-way before it hits the surface, it freezes turning into sleet.
What is the process of freezing rain?
snow begins in the below freezing zone, then to above freezing, and last minute before hitting the surface, it freezes turning into freezing rain
What is the process of rain?
snow begins in the below freezing zone, then turns into rain when the temperature is above freezing.
What is the set-up of a cumulonimbus cloud?
Bottom level– liquid water only
Mid-level– mixed ice and water
High-level– ice only
What is a Graupel Formation?
-ice crystals (at the surface) collide with the supercooled water droplets, producing a spherical accumulation of icy matter (rime) containing many tiny air spaces.
-white, opaque grains of ice
What is a Hail Formation?
updrafts (from ice crystals and graupel) to hailstone embryos (up and down the cloud) making it big enough to fall through the cloud
What are contrails?
-A cloudlike streamer frequently seen forming behind aircraft flying in clear, cold, humid air.
-contrails persist for a long time if the air is cool and moist compared to dry and warm
-adds water vapor to the sky
What are distrails?
-linear hole through cloud layer
What is a hole punch cloud?
-remains of a contrail cloud for is to become glaciated, then heat of the contrail punches through the cloud layer.
What are mountain waves and lee waves (lenticular clouds)?
- air hitting the mountain, forcing air to rise and form a cloud on top of the mountain.
What is a Pileus cloud?
-smooth cloud in the form of a cap
-moist winds are deflected up and over the top of a building cumulus congestus or cumulonimbus, air flowing over the top of the cloud condenses
What is a Lenticular cloud?
-clouds that form in wave crest usually have a lens shape, a cloud in the shape of a lens.
-represents a hovering spacecraft
What is a Mammatus cloud?
forms from sinking air; forms mainly underneath a cumulonimbus cloud; sinking air remains saturated and cooler than the air around it, the sinking air can extend below the cloud base, appearing as the rounded masses.
What is a fractostratus?
-pieces of cloud breaks off of a stratus cloud
What is a Virga?
-rain evaporating before hitting the surface
What is a castellanus cloud?
-forms when rising currents within the cloud extend into conditionally unstable air above the cloud
-vertical development and produce tower like extensions; resembles floating castles.
What is a billow cloud?
-looks like waves
-two fluids with different densities
-clouds with windshears (Kelvin-Helmholtz instability, change in wind speed and direction.
What are cloud streets?
Lines or rows of cumuliform clouds: winds uniform throughout a cloud layer
