The Book of Clouds by John A. Day

Reviewed by Duane Dunkerson

The subjects of this book are the bane of astronomy. They are only ice crystals or water droplets. They have marvelous shapes and lovely forms. They are beautiful and terrifying. Dynamic swirls, fluffs. A show. A science. Never the same. They sport coming attractions. They are the clouds.

They are part of the water cycle. If you, on a cloudy day, are above a stream on a humid day as waves of moisture waft aloft after a very recent rain; then you are in the water cycle.

Mr. Day has grouped the clouds by shape and named them by shape and for the weather conditions they signify or foster. Many large magnificent photos of these always transient phenomena are in this book. The photos show them to be so thin at times, like ghosts.

Yet these ghosts are of water and water is a dominant part of Earth's area and unique in being capable of being solid, liquid, and gas. The boiling and melting points aren't normal. We are mostly water. And water floats, oddly less dense as a solid.

Clouds are water held in the air, supported in air. Differing amounts of water vapor in warm vs cold air is critical to cloud formation. Droplets remain above Earth, smaller than rain drops. Each of these droplets requires a seed to grow from such as an aerosol or dust or soil or minerals.

By the millions the droplets form into clouds. Mr. Day notes that they can be cumulus in classification with domes and towers. They can be seen as puffs or in cauliflower shape. He mentions how high is the base and how high is the top. He tells us of their air mass stability, buoyancy, moisture content, temperature, frontal lift, and precipitation type. He carries over these characteristics to stratus cloud - those clouds lying on the Earth, ground fog of mists, shrouds, and obscuration. Next are the mixing of cumulus and stratus in transitional forms. There are heaps and layers or rows. Ripples happen Agitated convection is frequent. Mackerel skies and buttermilk skies are found in this grouping. Then there are the precipitating clouds that can be heavy showers, light showers, or drizzle and then snow too. Also you sometimes expect hail or the dreaded tornado.

Mr. Day includes photos of rainbows, halos, sun dogs, the pastels of irisation, and coronas. More photos show rays of sunlight and the green flash. Unusual clouds are also photogenically represented with, for example billows, lenticulars of colorful beauty and wondrous form, and cap clouds over mountain peaks. Noctilucents are found shining at night at very high, very dry, altitudes of 250,000 to 300,000 feet and are rarely seen. Sea smoke is shown that give rise to tendrils of fog when very cold air drifts across warm water. The funnel cloud, not always destructive but usually associated with tornados, is pictured. Other oddities are the mammatus clouds like tennis balls hanging on the underside of other clouds and Kelvin-Helmholtz clouds, products of wind shear at the boundary of warm vs cold air are depicted. There were no photographs and no names in classification for the clouds until 1802.

In 1802 a pharmacist interested in meteorology, Luke Howard, presented his ideas for the classification of clouds to the Askesian Society in London. Before, this, people had put clouds in paintings, books, and poems as angelic or animalistic in shape or as an accepted part of the unexplained sky.

Before and since 1802, no matter what they are called, the usual astronomer did not or does not welcome the nighttime clouds. They were and are usually cursed at by the telescopist since nothing or less than the best can be seen through the intervening clouds. Adaptive optics can equal telescopes placed in orbit but the applied technology to remove the atmospheric annoyances of a cloudy night does not yet exist.

One can sometimes observe along with the clouds, giving them their due if the clouds move along and permit at least intermittent use of the telescope. If the Moon provides enough illumination, you can observe the Moon and enjoy the ephemeral clouds. Usually you can see the clouds in sunlight but nighttime illumination offers appreciation of their forms and function along with, perhaps, some indulgence in astronomy.

Should you not be a lunar observer or are unfortunate in having night like day due to commercial, industrial, military, or security lights in your area, then such clouds as can be seen at night represent for you inadequate compensation for a hobby not to be allowed.

For lunar observers, they can, if they so desire, use this book to learn what clouds obscured the view from time to time. They could also learn why the clouds were there, why they assumed the shapes they did, and why they may have more such visitors in the sky the next night. They could also learn that earlier daytime clouds could have forecast conditions for their nighttime observing session.

In 1922, Lewis Richardson's book, Weather Prediction by Numerical Process, was demonstrating how to grid the weather data and enter into predictions but Mr. Richardson didn't have the 64,000 people he would have needed to do the computations for him. Now computers can do it. Even so, highly accurate longer term forecasts are not generally possible even if supercomputers are used.

Mr. Day offers do-it-yourself forecasting done with a barometer and knowledge of cloud types. So then, for your locale, you can know when rain will occur in 12 hours, or if it will be cloudy in 24 hours. So too you can be aware of an approaching cold front or a warm front, and know if it should be fair or if you should soon seek shelter.

Mr. Day also offers tips on photographing clouds. Nearly all of his photos are of daytime formations. Moon and clouds as a compound subject would be of interest and if you are at the scope waiting for cloud passage, then snap a few photos. Don't complain about it, photograph it.