This question asks to identify a specific type of precipitation based on two characteristics: the size of its water droplets and its intensity.

Drizzle Characteristics

Let's examine the characteristics given:

• Water droplet size: Under 0.5 mm
• Intensity: Less than 1 mm per hour

We need to find which term among the options fits these criteria.

Comparing Precipitation Types

Here's a brief look at the different types of precipitation listed and their typical characteristics:

Identifying the Precipitation

Based on the standard definitions in meteorology:

• Rain consists of liquid water droplets that are typically 0.5 mm or larger in diameter.
• Drizzle consists of liquid water droplets that are smaller, specifically under 0.5 mm in diameter. Drizzle usually falls from low stratus clouds and has a low intensity.
• Snow is precipitation in the form of ice crystals.
• Sleet is precipitation in the form of ice pellets, which form when raindrops freeze before hitting the ground.

The criteria given in the question are water droplet size under 0.5 mm and intensity less than 1 mm per hour. This description precisely matches the definition of Drizzle.

Therefore, when water droplets are under 0.5 mm and the intensity is less than 1 mm per hour, it is called Drizzle.