The WMO International Cloud Atlas

Cloud Bible of the International Weather Community

altocumulus sky sunset
An altocumulus sky. John B. Meuller Photography/Getty Images

The International Cloud Atlas (ICA) is a collection of cloud photographs, definitions, and descriptions that serves as a key to the over 100 cloud types and over 30 precipitation types that form across our skies worldwide. Of the cloud atlases in existence, the ICA is considered to be the "cloud bible" -- the internationally accepted authoritative resource used for identifying, classifying, and naming clouds anywhere in the world.

Weather Observation Tool or Coveted Coffee Table Book?

Besides being a valuable handbook and at-a-glance training guide for meteorologists and others whose professions are tied to weather (such as aviators, agriculturists, and mariners), the ICA has  become a bit of a collector's item. Weather enthusiasts are obsessed with its beautifully illustrated color plates.

Cloud Atlas vs. Cloud Chart

Most weather enthusiasts are familiar with cloud charts, but not as much so with the ICA. The difference being that cloud charts show the 10 genera (basic classifications) which describe where in the sky clouds form and their general appearance:

  • High Clouds: Cirrus, Cirrocumulus, Cirrostratus;
  • Middle Clouds: Altocumulus, Altostratus, Nimbostratus;
  • Low Clouds: Stratocumulus, Stratus, Cumulus;
  • Cumulonimbus.

In addition, cloud charts include the 14 species (secondary classifications) which describe shape and structure.

(More: How clouds are named and classified)

Much like a road atlas of maps, a cloud atlas is a collection of cloud images types . Whereas cloud charts only include 30-some basic and secondary cloud types, atlases include all 100+ possible cloud classification combinations.  

A Revised Edition Coming in 2016

First published in 1896 by the International Meteorological Organization, the World Meteorological Organization (WMO) currently oversees publication of the ICA.

The atlas is currently in it's third edition (released in 1975) with it's 4th edition planned for release sometime in 2016. Not only will the 2016 roll out be the first revision in over four decades, it will include new cloud type additions and a web-based version of the atlas -- it's first ever! (Currently, the ICA is available online in electronic pdf format only.)

The WMO Wants Your Cloud Photos!

As part of the 2016 Cloud Atlas revision, the WMO is asking the weather community to submit their best high-resolution color images of all types of clouds and precipitation. A special task team will then review and select the best photographs with the intent of including them as reference images in the 2016 edition of the Cloud Atlas!

For more information, and to submit your photos, visit the WMO ICA photo submission site.

How to Access the ICA

An online pdf version of the latest edition (1987) of the International Cloud Atlas, Volume I: Manual on the Observation of Clouds and Other Meteors, can be accessed here. Volume II of the ICA can be viewed here.

To purchase a 200-page hard copy version, visit the WMO bookstore.