Introduction

When water vapor in the atmosphere condenses and falls to the ground under the influence of gravity in a liquid or solid state, it is called precipitation. Graupel occurs in the same process. It is formed when supercooled water droplets freeze onto a snow crystal. This type of precipitation is also called snow pellets or soft hail. Graupel is a coating of rime ice that overtakes a snowflake to form these small snowballs. It forms in convective storms. This type of precipitation looks like Dippin’ dots (1).

Meaning

The Germanic word ‘graupel’, means pearl barley. It was first seen in an 1889 weather report and has been included in metrology.

Definition

A type of precipitation that forms when water droplets become supercooled after touching the surface of the snow is called graupel.

Description

Graupel is a small and round mass of snow. It is formed when water droplets become supercooled after touching the surface of snowflakes. The circumference of snowflakes is approximately 0.08-0.2 inches. It has a milky white color and is small in size and shape.

According to the World Meteorological Organization, it is a tiny pellet of snow that breaks down after touching the surface. And is commonly seen in high-altitude climates and is more dense and granular than ordinary snow.

This type of precipitation mainly occurs in autumn and spring. It is also called corn snow or hominy snow. Graupel can cause some dangerous conditions like breaking power and telephone lines, damage to unstable structures, trouble with car driving, etc. This type of precipitation is fragile and breaks down when it touches the earth’s surface (1).

Facts about graupel

• Graupel is a winter storm. Mainly this type of precipitation is seen in inter countries.
• This type of precipitation is cloudy or white and not clear like sleet.
• It falls especially in springs at higher altitudes.
• The Meter code for graupel is GS.
• It is also called soft hail, or snow pellets.
• These types of precipitation are usually brittle and partially sized. They usually combine with ice crystals instead of snow.
• It is thicker than normal snow.
• Macroscopically, the graupel resembles a smaller size of polystyrene.
• The size is usually under 5 millimeters, but some graupel can be the size of a quarter (coin).
• It is mainly a form of wintry precipitation (1).

Process of graupel formation

Graupel is formed when supercooled water droplets become frozen after touching the cold surface, resulting in approximately 2 to 5 mm small pellets. Due to some atmospheric activity, ice crystals meet with super cool water droplets and transform into snowflakes. After touching the surface or hitting the surface, they usually break down and it is referred to as graupel. It is commonly seen in high-altitude climates and is more dense and granular than ordinary snow. The process of graupel formation is

Snow forms in the atmosphere → then those snow crystals fall through a layer of supercooled water droplets→ after that the droplets become frozen or rime and form into snowflakes→ then the snowflakes fall down onto the surface as graupel and are crushed. Unlike sleet, they are fragile in character (1).

Q&A

1. How rare is graupel?

It is not very common but does seasonally fall in the Midwestern region of the United States.

2. What is graupel snow?

Is a small particle of snow with a brittle crust of ice or soft hail. It mainly occurs in the winter season.

3. What is graupel in weather?

It is a form of solid precipitation. In the case of weather, a small coating of ice overtakes a snowflake. It is also known as snow pellets or soft hail.

4. What does graupel mean?

THIS WORD comes from the German word “Graupe” which means pearl barley.

Reference

• Savindra Singh. Climatology. Pravalika Publications, Allahabad. Chapter 9: Fogs, Clouds, and Precipitation. Page No: 174 to 201.