The future of cloud classification is bright and sunny...and packed with stratus and cirrus, not to mention cirrocumulus floccus and cumulus tuba. The World Meteorological Organization (WMO) has embarked on a whole new version of its international cloud atlas
, used by weather observers worldwide to ensure that clouds are described in a uniform fashion. The atlas was first published in 1939 based on work extending back to the 1800s. The most recent edition can be downloaded as a PDF
, but the next version will be web-based. This opens the door for entirely new ways of presenting and documenting the world’s seemingly endless variety of clouds.
Another cool feature this time: you’ve got a chance to pitch in. The WMO launched a website in October
that allows anyone to submit their photos--and videos--for consideration in the upcoming atlas. Your odds of getting imagery accepted will be highest if you go for the more obscure, harder-to-document cloud types and if you can provide details on the geographic and meteorological context of your image (see below).Figure 1.
Spectacular mamma (mammatus) clouds that formed on the back side of a severe thunderstorm that moved through the Austin, TX, area in April 2015. Although mammatus are often observed in association with tornadic supercells, they do not produce tornadoes themselves. Image credit: wunderphotographer txazgal
.An atlas for the 21st century
“Manual on the Observations of Clouds and Other Meteors” has been used for more than 80 years as the definitive reference book and guide for weather observers around the globe. (As one might guess from “meteorology,” the technical term “meteors” refers to pretty much anything found in the atmosphere.) The original 1939 atlas was split into two volumes in 1956, with Volume 1 focusing on detailed descriptions and Volume 2 on photos and brief captions. Volume 1 was updated in 1975 and Volume 2 in 1986, before the widespread availability of high-resolution digital cameras. Almost 100 of the 248 images in Volume 2 are in black and white only, so there is plenty of room to make the atlas more colorful.
Today, it’s a cinch to find web pages full of stunning cloud images and easy-to-read descriptions. However, “the classifications used in many descriptions are not accurate,” according to Steve Cohn (National Center for Atmospheric Research), who is serving as chair of the WMO committee that’s updating the cloud atlas. “There’s also a lot of really good cloud information on the web, but if you want to be sure, the International Cloud Atlas is the definitive and trusted source.”
The WMO is striving for both accuracy and accessibility in the new atlas. It’s expected to go online by 2017, when the agency's World Meteorological Day (March 23] will be centered on the theme "Understanding Clouds." Before then, said Cohn, “we’ve got an awful lot of work to do choosing photos, writing captions, and modernizing the writing style of the manual.”Figure 2.
The WMO’s Task Team on the International Cloud Atlas, pictured here, is part of the agency’s Commission for Instruments and Methods of Observations (CIMO
). Left to right: Kwong Hung Tam (Hong Kong, China), Colleen Rae (South Africa), Elaine Thurig-Jenzer (Switzerland), Mike Bruhn (Australia, Vice-Chair), Marinés Campos (Argentina), Jim Trice (UK), George Anderson (UK), Steve Cohn (USA, Chair), and Ernest Lovell (Barbados).
The new web-based format will allow for major improvements to the atlas. For example:
--Time-lapse video can illustrate the evolution of cloud types
--There will be room to show how a cloud type can vary by season and/or latitude
--Radar images, thermodynamic profiles, and other tools can enhance the explanation of how various clouds form
--A revamped, user-friendly flow chart will help observers identify clouds Figure 3.
A prototype version of the updated flow chart designed to help weather observers place clouds into the 10 cloud genera (top-level categories) recognized by the WMO’s International Cloud Atlas. Along with these genera, there are 14 species (second-level categories) that describe the shape and internal structure of clouds, as well as 9 varieties (third-level categories), which deal with the transparency and arrangement of cloud elements. The WMO committee working on the atlas update has proposed adding a 15th species: volutus (Latin for “rolled”), also known as roll clouds or morning glory clouds. The atlas also recognizes several types of supplementary features and accessory clouds. Image credit: WMO.What’s new and what’s needed from you
Working with an expert in the Latin language, the WMO committee has already come up with a few “preliminary official” names for some cloud features long recognized by weather enthusiasts. Below are a few examples of cloud features with their newly proposed Latinesque names, accompanied by images I’ve pulled from our vast WunderPhoto collection. We encourage these and other wunderphotographers to submit their work to WMO!
How to submit your image:
--Go to the Image Submission website
--Download the “Read Me First” file (PDF
as a user
--When you’re ready to contribute, use the “Submit New Imagery” pull-down
The “Read Me First” file contains a great deal of helpful guidance, including a list of details required for each photo submitted (e.g., date and time of photo, latitude/longitude, direction the camera was pointing) and additional context that can improve the chance of an image being accepted (photo metadata, weather observations, etc.). There’s also a wish list of several dozen categories where WMO is in the greatest need of good imagery. Here are some categories that grabbed my eye:Cirrus virga rainbow
— virga has melted and a rainbow is visible in the water dropletsAltostratus duplicatus
— two or more superposed layers, at slightly different levels, sometimes partly mergedClouds from industry
— examples are clouds of smoke and steam in industrial areas, smoke clouds created for frost protection purposes, clouds of insecticide gas or powders in agricultural areas.Clouds from waterfalls
— spray saturates air and cloud forms, usually in the form of cumulus. Brilliant rainbows often present.
“We’re already getting many photos of the more common clouds, and this is exciting,” Cohn told me. “We’ll probably have to hunt for people to contribute great images of the more unusual ones.” The team has already picked an image to illustrate asperitas (also known as asperatus), one of the most recently identified cloud features. Australian photographer Gary McArthur was named in September as the winner of a competition sponsored by the Cloud Appreciation Society
in conjunction with the WMO. McArthur’s winning image was honored
in an event held at the Royal Geographic Society in London.
Although the WMO website lists no firm deadline, Cohn encourages photographers and videographers to submit their work by April 2016. A poster
created by Cohn and colleagues to publicize the new atlas was presented last week in New Orleans at the 96th Annual Meeting of the American Meteorological Society.Meteotsunami!
Now that our unusual midwinter burst of Northern Hemisphere hurricane activity has subsided, Jeff Masters and I will be posting later this week on some of the weather and climate highlights of 2015. In the meantime, here's a helpful explainer
from WU contributor Lee Grenci on the physics behind the meteotsunami
associated with powerful thunderstorms that struck the southwest Florida coast on Sunday morning. Marshall Shepherd (@DrShepherd2013
) also penned an excellent recap of the event
for Forbes, and WU contributor Larry Atkinson provides additional background and links
Bob Henson Below: Latin-derived names and descriptions for some of the cloud features and special clouds proposed to be added to the International Cloud Atlas
: all photos shown here are from wunderground members rather than the WMO. No official selections have yet been made in these categories.)Figure 4.
Cavum (Latin for cavity/hole/hollow) — a well-defined, generally circular (sometimes linear) hole formed in a thin layer of super-cooled cloud, which generally grows larger with time. Common names: fallstreak hole, hole-punch cloud, distrail, canal cloud. Image credit: wunderphotographer PSLTony
Murus (Latin for wall) — A localized, persistent, and often abrupt lowering of cloud from the base of a cumulonimbus and from which tuba (funnel clouds) and spouts (tornadoes) sometimes form. Common name: wall cloud. Image credit: wunderphotographer wxchaser97
. Figure 6.
Flammagenitus (Latin for fire + generated) — Cloud that develops as a consequence of convection initiated by heat from localized natural heat sources, such as forest fires and wild fires. Common name: pyrocumulus. Image credit: wunderphotographer FrancesJeanne
Homogenitus (Latin for manmade) — Cloud that forms as a direct consequence of human activity. Common names include contrails. Image credit: wunderphotographer GVIslander
Fluctus (Latin for wave/billow) — A relatively short-lived wave formation, usually on the top surface of the cloud, in the form of curls, or breaking waves. Common name: Kelvin-Helmholtz waves. Image credit: wunderphotographer Nordicmom