Types Of Precipitation

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Precipitation is the release of water from the sky to the ground. It is an important part of the water cycle. We know that the atmosphere contains water vapor. When this water vapor falls back on the earth in the form of liquid or frozen forms of water like rain, sleet, and snow, it is known as precipitation. Precipitation occurs when the air becomes saturated with water vapor and can no longer maintain the water vapor level in gaseous form. The temperature between the cloud bottom and the ground determines the type of precipitation.

HOW DOES WATER REACH THE SKY?

  1. Evaporation – Under typical atmospheric conditions, water vapor is continuously generated by the evaporation of liquid water from oceans, rivers, lakes, and ponds. Precipitation is always fresh water even if water originates from the ocean as sea salts do not evaporate with water!
  2. Transpiration – The process by which plants release water from their aerial parts like leaves in the form of water vapor is known as transpiration. It is one of the major contributors to water vapor in the atmosphere.
  3. Sublimation – Sublimation is a process by which solids like ice are directly converted into a gaseous state like water vapor. Hence, snow and ice in cold regions and high altitudes also contribute to the water vapor in the atmosphere by the process of sublimation.

 

Types of Precipitation

Liquid forms of precipitation include rain, drizzle, and dew. Frozen forms of precipitation include snow, ice crystals, ice pellets, hail, and graupel. When they freeze on contact within a subfreezing air mass, it is termed as freezing rains.

1.  RAINS 

When water vapor in the atmosphere rises and cools, it changes into tiny droplets of water that form clouds. When the water droplets come closer, they become large and heavy that falls down under the influence of gravity as liquid water. This results in rains. Rains are an important component of the water cycle that replenishes most of the freshwater on Earth. Heavy rainfall may cause floods, landslides, and damage to agriculture and infrastructure.

2. DRIZZLE 

Drizzle is light liquid precipitation consisting of water drops smaller than those of rain. They are small and light and appear to float while being carried by air currents. They are associated with clouds, which are close to the ground and form what looks like a blanket in the sky.

3. SNOW

It is precipitation in the form of solid, frozen water. It originates in clouds when temperatures are below the freezing point of water. The water vapor in the atmosphere condenses directly into ice without going through the liquid stage.

Once an ice crystal is formed in the cloud, it absorbs and freezes additional water vapor from the surrounding air, growing into a snowflake, which then falls to earth as snow. Snowflakes develop different patterns depending upon the temperature and humidity of air. Hailstones are hard, but snowflakes are soft. When snow falls in the form of a ball instead of soft flakes, it is called graupel.

4. HAIL 

Hail or hailstones are formed when drops of water freeze together in the cold upper regions of thunderstorm clouds. When a frozen droplet begins to fall from a cloud during a storm but is pushed back up into the cloud by a strong updraft of wind, it hits other liquid water droplets and freezes them adding another layer to it. Eventually, the hailstone becomes too heavy and falls down on the Earth. Hailstorms have the potentials to destroy plants, trees, crops, animals, and human life upon impact.

 

5. SLEET 

Sleet or ice pellets are seen during winter. For sleet to form there must be layer of air near the ground whose temperature is below freezing. Sleet starts as snowflakes, and then melts to form water droplets while passing through warmer air in the sky. But when they pass through the cold air near the ground, it re-freezes into small ice pellets. These ice pellets are small translucent balls composed of frozen raindrops and refrozen melted snowflakes. They are smaller than hail and bounce when they hit the ground.

6. ICE CRYSTALS 

Also known as diamond dust, it is a ground-level cloud similar to fog, composed of tiny ice crystals. It is most commonly observed in very cold places like Antarctica and the Arctic and they fall as crystals of ice in the form of needles, columns, or plates. Diamond dust crystals have well-defined shapes-usually either hexagonal plates or columns which behave like prisms and create halos in the sky by reflecting and refracting sunlight.

7. SNOW GRAINS 

Snow grains are precipitation in the form of small, white, and opaque grains of ice. They are flat or elongated and do not break upon impact on the ground. They fall in some amounts and not in the form of showers.

8. FREEZING RAINS 

Freezing rain is formed when a very shallow layer of cold air at the surface causes the freshly melted raindrops to freeze on contact with exposed objects on the ground which has a temperature below freezing. They can cause major damages to trees, power lines, bridges and overpasses.

Check Point

  1. Water from the oceans and rivers reach the sky by a process called ___________.
  2. Liquid forms of precipitation include _________ and __________.
  3. ___________ are small translucent balls composed of frozen raindrops and refrozen melted snowflakes.
  4. __________ also known as Diamond dust, are usually seen in polar regions and their crystals can create halos in the sky by reflecting and refracting sunlight.
  5. Heavy rainfall may cause _______ and ________.

Answer Key

  1.  Water from the oceans and rivers reach the sky by a process called evaporation.
  2. Liquid forms of precipitation include rains and drizzles.
  3. Sleet or ice pellets are small translucent balls composed of frozen raindrops and refrozen melted snowflakes.
  4. Ice crystals also are known as Diamond dust, are usually seen in polar regions and their crystals can create halos in the sky by reflecting and refracting the sunlight.
  5. Heavy rainfall may cause floods and landslides.