Fog vs mist differences and definitions

Introduction

Fog and mist both are forms of condensation created by water droplets. There is a very minute difference between fog vs mist. The prime difference between fog and mist are altitudinal as well as density. Fog is formed around less than 1000 meters whereas mist is formed at more than 1000 meters. Fog is thick and mass of tiny water droplets while mists are less thick with tiny water droplets. Mist is thinner than fog. 

Both affect by reducing visibility to less than 1 km and above 1 km. According to density, fog lasts longer than mist. Fog is formed at the surface level and the composition of small droplets of water is responsible for appearing fog where the mist is formed as a layer of cloud due to volcanic activities and changes in the level of temperature and humidity in the atmosphere. So here we discuss the key differences between fog vs mist (1) & (3)

What is fog?

On long winter nights, the surface becomes very cold by radiating heat. When the air layer adjacent to the surface cools and reaches the dew point, the water vapor present in the air combine with the dust floating in the air. The air with dust then condenses and floats in an area close to the surface, called fog. 

 Fog is a cloud that touches the ground. Generally, Fog appears at the lower surface of water bodies like rivers, lakes, or oceans. Basically, it is formed when both dew point and air temperature go less than 2.5°C.

Another important point for forming fog is when gas liquefies into small water droplets and subsequently evaporates in the air. Water droplets evaporate from water bodies like the ocean or some other wetlands during the heating daytime. Over the water bodies, cool air moves over hot water and lifts air over mountains.

There are various interesting reasons behind the formation of fog due to water condensing on dust and other particles like smoke from houses and industries. It is called ‘ground cloud’ because it forms at the lower strata of the atmosphere. In industrial areas and developing countries like England and America, there is a smoky fog that is called smog. Because in those territories dense smokes are released from industry and many other things (3).

Different types of fog

1. Radiation fog

This fog forms when solar energy radiates from the earth and the temperature meets up with the dew point. The best condition to form radiation fog is after rain. This makes it easier for the air to become saturated and form fog.

2. Precipitation fog

This fog occurs when rain is falling through the cold air. The saturation of air and the rise of dew point causes the formation of precipitation fog.

3. Advection fog

Advection fog happens at the surface contact with horizontal winds. It is formed when warm air and moist air blow from the south and if there is snow or cool moisture on the ground touches the warm surface and becomes cool then the dew point rises with high humidity and forms fog.

4. Steam fog

This fog forms at the summer’s end when water temperature does not cool compared to the air temperature and cold air moves over a warmer lake and forms fog.

5. Freezing fog

Freezing fog occurs when the temperature falls down to 32°F air below. This fog produces drizzle and the tiny droplets become frozen by contact with an object.

6. Ice fog

This type of fog occurs at -10°C is too cold for the air to contain supercooled water droplets and forms small tiny ice crystals. Ice fog is basically seen in the polar and arctic regions.

7. Valley fog

Valley fog is generally formed in the valley when the soil’s condition is moist from previous rainfall. This fog is deep and dense.

8. Upslope fog

 Upslope fog forms adiabatically (the process relating to a condition where heat does not enter or leave). moist winds blow towards the mountain and therefore air-cooled to the dew point. This type of fog forms on the top of the mountains (3).

Characteristics of fog

There are various characteristics of fog as mentioned below.

1. Fog basically occurs due to pollution.

2. Dense fog commonly occurs in polluted or populated areas.

3. It is nothing but the suspension of water droplets or ice crystals in the atmosphere.

4. Fog is a mixture of dust and other particles in the atmosphere basically emerging from industrial and housing areas.

5. They are called ground clouds because they occur in the lower strata of the atmosphere.

6. When fog intermingles with smoke it forms smog.

7. Fog is basically formed when both dew point and air temperature go less than 2.5°C.

8. It is formed due to radiation of the earth caused by radiation fog.

9. Fog decreases its visibility to less than 1 km.

10. It occurs when the surface is colder than the air (3).

Formation of fog

Fog is a form of condensation that occurs at the lower surface of the earth. It is thick and denser than the mist which reduces the visibility during daytime and it vanishes the sunlight also. At first, water evaporates from various water bodies like rivers, oceans, lakes,s and many others. After evaporation, tiny water molecules reached the atmosphere and condensed subsequently in the presence of cold droplets formed by dust and tiny water particles. Then the dust floating in the air condenses and floats adjacent to the surface. In this way, fog is formed. 

Fog is displayed to us when the humidity level is so high in the atmosphere and a lot of water vapor is present simultaneously.

The presence of dust and some kinds of air pollutants is responsible for the formation of fog where water vapor condenses around these microscopic solid particles.

Depending upon humidity and temperature fog forms and vanishes quickly and this is called flash fog (2) & (3)

What is mist?

A mist is an accumulation of liquid water particles. It is a natural phenomenon. Mist is formed when tiny water droplets are suspended in the air and condense subsequently. It is the suspension of chemicals and combustible liquids in the air that threatens human health and safety.

Mist is a fine cloud formed by tiny water droplets and hygroscopic particles. This type of condensing is thinner and exists less long than fog. It is commonly seen in warm and moist weather. It hangs in the air. Mist restricts its visibility between 1 and 2 km (1).

Characteristics of mist

1. Mist is tiny droplets of water hanging in the air.

2. It is a fine cloud formed by tiny water droplets and hygroscopic particles.

3. They formed basically when tiny droplets of water condensed into the atmosphere.

4. Mists often form when warm air moves over the water of the ocean, rivers, and other water bodies suddenly meet with the cooler surface and vice versa.

5. It is less dense than fog. One can see more than 1 km.

6. Mist can form due to volcanic activity where hot water vapor is extracted along with gasses.

7. Mist reduces visibility like fog.

8. It disappears more quickly into the atmosphere.

9. Mist is responsible for refraction and scattering.

10. It is seen in cool places or in cold weather. Because when warm air moves over cold surfaces and is saturated with the cold air and ultimately forms mist (1) & (3).

Fog vs mist differences and similarities.

Fog vs mist: Differences

Fog

Mist

 

Fog is a thick cloud-like mass or layer of tiny water droplets near the surface of the earth.

 

Mist is a cloud of tiny water droplets suspended in the atmosphere

It decreases its visibility to less than 1 km

Mist decreases its visibility above 1 km

Fog is denser and thicker than mist.

Mist is less dense and thicker than fog

Fog exists longer than mist

Mist disappears more quickly than fog

On the other hand, fog is formed at ground level.

Mist is formed due to changes in thermal inversion, volcanic activity, etc.

 

Fog vs mist: Similarities

1. Both fog and mist are condensed water vapor clouds prepared by tiny water droplets from the surface of the earth in the atmosphere.

2. Fog and mist both are responsible for reducing visibility during their presence.

3. They both have an impact on human health.

4. Smoke and gaseous particles are present in both fog and mist.

5. Water droplets are responsible for forming both fog and mist (3).

Q&A

1. What is the difference between fog and mist?

Following is the difference between fog and mist

1. Thick and tiny water droplets near the surface of the earth is fog.

     Mist is a tiny water droplet suspended in the atmosphere.

2. The fog is visible at less than 1 km.

     Mist is visible above 1 km.

3. Fog is denser than mist.

     Mist is less dense.

4. It lasts longer than mist.

     Mist is visible more quickly than fog (3).

2. Is mist water or fog?

Mist is tiny water droplets hanging in the air. When tiny water droplets evaporate from the water bodies during warm conditions and condensed subsequently after reaching the atmosphere and touching cold gaseous molecules in the nighttime. Simultaneously falling temperature is caused to form a mist. Mist is the mixture of water and air and is called heterogeneous activity.

3. Does fog have mist?

It is a thick cloud formed at the lower surface of the earth or ground level. Mist forms tiny water droplets suspended in the air by water bodies, temperature inversion, volcanic activity, or changes in humidity. So there are not many differences between them except temperature and location. So it is considered that fog and mist are the same in various ways.

4. Which is more visible, fog or mist?

Well, fog is denser than mist. So fog reduces visibility more than mist. It impacts much greater the visibility of the eye compared to mist.

Reference

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