The correct option is The temperature is lower than 0°C..
Explanation
Precipitation is the release of water from the atmosphere in liquid or solid forms. The specific form-whether rain, snow, sleet, or hail-is determined primarily by the temperature profile of the atmosphere through which the moisture falls.
Detailed Analysis:
- The temperature is lower than 0°C. is Correct: Snow consists of ice crystals that form in clouds where the temperature is lower than 0°C (freezing point). In this condition, water vapour condenses directly into solid ice crystals (a process called deposition) without passing through the liquid phase. These crystals aggregate to form fine flakes of snow.
- The temperature is exactly at 4°C. is Incorrect: At 4°C, water exists in its liquid state (and is at its maximum density). Precipitation occurring at this temperature would fall as rain.
- Raindrops pass through a warm layer of air. is Incorrect: When raindrops pass through a warm layer of air, they remain liquid. Conversely, if snowflakes pass through a warm layer, they melt and become rain. This process does not generate snow.
- Condensation occurs on hygroscopic nuclei at ground level. is Incorrect: Condensation on hygroscopic nuclei at ground level leads to the formation of fog or mist. While related to condensation, this is a suspension of droplets near the surface, not precipitation falling from clouds.
Key Takeaway: Snowfall requires atmospheric temperatures to be below the freezing point (0°C), allowing water vapour to convert directly into ice crystals (snowflakes) via sublimation or deposition.