Published Tuesday, Mar 9, 2004 in the San Jose Mercury News

Names of cloud families traced to English chemist

By Jan Null

When many people look at clouds they say things like, ``Look at those puffy white clouds over the hills,'' or ``Here come the usual night and morning low clouds.'' The more astute readers of this column may know that the puffy clouds are cumulus and the usual low clouds around the Bay Area are stratus clouds. But who named the clouds?

Most of the credit goes to an English chemist and pharmacist named Luke Howard who devised a classification system in 1802 that is still in use. Howard presented a paper to the Askesian Society titled ``On the Modification of Clouds'' which described three basic categories or families of clouds. He used Latin root words to describe them, following the 18th-century methodology of Carl von Linne, who gave us the Latin-based classification systems for plants and animals.

Howard describes clouds with conical shapes increasing upward from a flat base as ``cumulus'' from the Latin term for ``heap.'' A bit more colorfully, he also described them as ``wool bag clouds.'' Our ``stratus'' clouds derive from the Latin term for ``layer or sheet'' and their appearance is indeed one of a flat horizontal sheet. Howard's third family of clouds was ``cirrus'' which he took from the Latin word of ``curl of hair,'' and these are the thin, wispy ice-crystal clouds high in the atmosphere. To the three families he added the ``nimbus'' category, from the term for ``rain.''

He also reasoned that clouds could combine their form and change shape to become amalgamations like ``cumulostratus,'' ``cirro-stratus'' and ``cirrocumulus.''

Despite huge strides in meteorology over the past two centuries, Howard's system remains the foundation for cloud naming.

Want more information about the clouds? Read ``The Invention of Clouds'' by Richard Hamblyn or John Day's ``The Book of Clouds.'' On the Web, an excellent resource is www.cloudman .com/.

Q I heard a weathercaster from a Midwest TV station say that ``meteorological winter'' was ending. What is meteorological winter and how does it differ from the usual meaning of winter? Sal Murillo - Gilroy

A ``Meteorological winter'' is defined as the three coldest months of the year: December, January and February. Using whole months makes it easier from a statistical point of view to keep track of weather data.

Q My sister-in-law, who lives in Newport Beach, says that storms pick up moisture from the ocean and deposit it on land. My question is, if this is true, what happens to the salt picked up from the ocean? Tom Brown - San Jose

A Yes, storms that move over water do pick up additional moisture. This is especially true over the relatively warmer waters off the Southern California coast. The moisture that gets pulled into storm systems is water vapor that has evaporated from the ocean. When water evaporates it leaves behind the heavier salt in the ocean.

Q I had always heard that there was nitrogen in snow, that it was good for the farmer's crops. In fact, sometimes they would plow under the first snowfall, calling it ``poor man's fertilizer.'' My daughter is a meteorologist and said that I am telling old wives' tales, and that there is only water and particulate matter in snow. Who is right? - Diana Hulbert
Morrice, Mich.

A You are both right! It's not just the first snowfall that has nitrogen. Any snow (and rain) brings at least trace amounts of nitrogen compounds that are suspended in the air. The water content, of course, would also be beneficial.

The suspended nitrogen acts just like the nitrogen fertilizer that you buy at local garden store. It is estimated that 2 to 12 pounds of nitrogen are deposited per acre. The amount of nitrogen compounds in the air has increased due to industrialization and the burning of fossil fuels.

Jan Null, founder of Golden Gate Weather Services, is a retired lead forecaster with the National Weather Service. Send questions to him c/o WeatherCorner, San Jose Mercury News, 750 Ridder Park Drive, San Jose, Calif. 95190. You also can telephone questions at (510) 657-2246, fax them to (510) 315-3015 or e-mail, or fill out a form online at Please indicate in your e-mail what city you live in.