Ahrens Extreme Weather and Climate
Q’s 1, 2, 4, 10, 13, 16, 19, 20
1. What is the primary difference between a cloud droplet and a raindrop?
A typical cloud droplet is 100 times smaller than a raindrop. Clouds are composed of many small droplets.
2. Describe how the process of collision and coalescence produces precipitation.
To produce the many collisions necessary to form a raindrop, some cloud droplets must be larger than others. Larger drops may form on large condensation nuclei, such as salt particles, or through random collisions of droplets. The amount of time a droplet spends in a cloud, the larger it will be. In warm clouds (above freezing at all ...view middle of the document...
This difference in vapor pressure causes water vapor molecules to move (diffuse) from the droplet toward the ice crystal. The removal of vapor molecules reduces the vapor pressure above the droplet. Since the droplet is now out of equilibrium with its surroundings, it evaporates to replenish the diminished supply of water vapor above it. This process provides a continuous source of moisture for the ice crystal, which absorbs the water vapor and grows rapidly. The ice crystal then grows even larger by colliding with supercooled liquid droplets, at which point the liquid droplets stick to the ice crystal. This is called accretion. The icy matter that forms is called graupel, which falls, splinters and forms ice crystals that act as seeds. These crystals then form snowflakes, which are an aggregate of crystals, which may melt before it reaches the ground.
10. Why is it never too cold to snow?
no matter how cold the air becomes, it always contains some water vapor that could produce snow. In fact, tiny ice crystals have been observed falling at temperatures as low as 53F. We air with “no snow” because the coldest winter weather occurs on clear, calm nights—conditions that normally prevail with strong high pressure areas that have few if any clouds.
13. What is the difference between freezing rain and sleet?...