What is cloud base and how else do we measure clouds

What is cloud base and how else do we measure clouds

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Cloud base is a well-known weather parameter for outdoors enthusiasts that do various wind sports and activities in the air: for example, paragliding. If you haven't tried this or other air sports yet but want to, this article is right for you.

Learn what the cloud base is, why you may need it, and how to use it for your outdoor activity.

What is cloud base?

A cloud is the tiny liquid particles of water vapor, frozen water crystals, and other particles suspended in the air. Clouds form in the sky because the air becomes saturated with moisture when it cools to the dew point, or when much water evaporates from the earth's surface and water vapor forms.

The cloud base or the base of the cloud is the height of the lowest visible part of the cloud. Therefore, the base is most often measured in the same way as, for example, the height of mountains — in meters above sea level, feet, or other units in your region. (Sometimes cloud base is also measured in hectopascal (hPa), as the pressure level corresponding to the altitude of the base of the cloud.) In other words, the cloud base parameter in your weather forecast answers the question of how high the clouds are from the earth, if you count to their base.

The base of the cloud is measured with an instrument called "ceilometer" or a type of atmospheric lidar, the working principle of which is based on the laser. This device reflects rays of laser from the base of the clouds and calculates the travel time to it.

Why do we need to know the base of the cloud? It is useful for anyone who practices various wind sports in the air, such as paragliding, parachuting, or, for example, air ballooning and different types of aviation. In all these sports good visibility is a not just an important, but a vital weather parameter. From there, knowing the base of the clouds is useful so you don't go above a certain height in the air and find yourself in the clouds and loose visibility.

Photo: Katerina-kerdi / Unsplash

How else do we measure clouds?

Clouds are measured not only by this weather parameter but by several others that are related to it. Here we will mention them briefly, and later we will talk more about each of them in separate articles (take this article as a bookmark):

  • Cloud top. Similar to the base of the clouds, this is the height at which the top of the visible part of the cloud is located. The difference between the two can be significant because certain types of clouds, for example, envil clouds, can be quite high: up to 15–18 km!
  • Cloud height. It is the distance between the base of the cloud and the top of the cloud. It is also often called cloud thickness of cloud depth. This and the previous parameter is also measured in meters above sea level or hPa.
  • Cloud ceiling. It is used in aviation for measurement of the height of the base of the lowest visible clouds. At the same time these clouds should cover more than half of the sky. So this parameter shouldn't be confused with cloud base.
  • Cloud cover. This parameter shows what total part of the sky is covered by clouds. Today, it is usually measured as a percentage. For example, if the sky is 100% covered by clouds, it is a cloudy day. If only 20% — the day is more clear than cloudy. So it is also called the percent of the cloud coverage of the sky.
  • Cloud reflectivity. This is the ability of the cloud to reflect sunlight and not let it go further to the ground. It is also called albedo. This parameter is related to the Ultraviolet Index, which is harmful to humans, when it is high.

Where to find cloud base in Windy.app?

You can find the cloud base parameter in Windy.app in a special weather profile for all wind sports in the air called the same — "Air". To do so:

1. Open your favorite or nearest spot from the Home screen or from the Wind and Precipitation Map. For example, the Monte Avena paragliding spot located in the Dolomites mountains in Veneto region in Italy. It is a fairly flat mountain that is easy to jump from. The height of this mountain is 1,450 m (4,770 ft) above sea level.


2. Select the Air profile using the icon to the right of the weather models.



3. Get a cloud base forecast for today as well as for the next 10 days. You can also change the forecast step from 1 to 3 hours.



In the forecast we see that the maximum cloud base will be 3,100 m (10,170 ft) on Thursday, May 20 at 11 am, the minimum cloud base will be 896 m (2,939 ft) on Tuesday, May 25 at 5 pm.



This means that at the minimum cloud base the clouds will cover the highest point of the mountain, so jumping on that day and at that time will be problematic.

You can calculate the average base of clouds for the spot by yourself. This is somewhere around 1500–2000 m (4,921–6,561 ft).

Learn more about clouds in the Windy.app Meteorological Textbook.


Text: Ivan Kuznetsov, an outdoor journalist, editor and writer from the Dolomites, Italy, and Karelia, Finland, with eight years of professional experience. Read his other articles.

Cover photo: Katerina-kerdi / Unsplash.

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