In the beginning of a rain storm you might experience large, heavy raindrops. Explain why these occur first, and where they originated

Question

What will be an ideal response?

Answer 1

ANSWER: Large raindrops fall faster and reach the ground before smaller ones, which is why they typically occur at the beginning of a rain shower. These large drops originate in warm, convective cumulus clouds. Clouds that have above-freezing temperatures at all levels are called warm clouds. In such clouds, precipitation forms by the collision and coalescence process. For example, in tropical regions, where warm cumulus clouds build to great heights, convective updrafts of at least 1 m/sec (and some exceeding many tens of meters per second) occur. Suppose a cloud droplet of 100 µm is caught in an updraft whose velocity is 6.5 m/sec (about 15 mi/hr). As the droplet rises, it collides with and captures smaller drops in its path and grows until it reaches a size of about 1000 µm. At this point, the updraft in the cloud is just able to balance the pull of gravity on the drop. Here, the drop remains suspended until it grows just a little bigger. Once the fall velocity of the drop is greater than the updraft velocity in the cloud, the drop slowly descends. As the drop falls, larger cloud droplets are captured by the falling drop, which then grows larger. By the time this drop reaches the bottom of the cloud, it will be a large raindrop with a diameter of over 5000 µm (5 mm).