Meteorological Science in the 9th Century AD

The work of Ibn Doraid Al-Azdi is an example of experimental observations of aerial phenomenon. He flourished in the late 9th Century AD. From him we find scientific descriptions of weather forecasting, clouds and the types of rainfall and effect on soil and ground water resources.

An example of Islamic science that records experimental observations of aerial phenomena is the work of Ibn Doraid Al-Azdi.

Born in Basra, 837 CE/223AH, died in Baghdad 933CE/321 AH he flourished in the late 9^th – early 10th century AD. He completed many works but his main work is the book “Description of Rain and Clouds”. The first of two editions was by the English Orientalist William Right (1830–1889), the second by Ezidden Al-Tanokhi (Damascus 1963).

The 27 chapters of this work describe observed aerial events and for the first time a scientific description of rain and clouds. The book deals with weather forecasting, a description of clouds, their motion, accumulation, thickening and change of form and the types of rainfall and their effect on soil and ground water resources.

The work makes specific descriptions and observations using a variety of Arabic idioms, which precisely fit a diversity of phenomena.

It describes cloud topography on pg. 111. It also observes clouds as they lie upon each other (pp. 18 – 21) such as Al-Rabab (clouds that connect with others), and their form with regard to the earth surface and topographic relief. It also describes their shades and colours (pp. 6, 7, 24, 25).

For example, Al-Hamma’a and Al-Hawwa’a (black clouds turning into red). It refers to Al-Karha’a (lightening appearing on the peak of clouds, like an ulcer in form) and to Al-Hawla’a (gorged with water). The clouds’ elevation and spread is also described especially as they  the skies at sunset. The work divides lightening, (pp. 4-6, 14, 15, 22, 24) according to the intensity of its light: Al-hafo the weakest form, Al-wamed, which `resembles a little smile and Al-wallaf, which strikes twice. There is description of heavy rain and thunder on pp. 6, 14, 18, 27 the diverse intensity of the sound associated with heavy rain such as Al-hanen, al-zamjara, that roars, Al-edrab with loud sound and Al-jaljala, the loudest of all.

By examining the motion and spread of clouds, as well as the intensity of lightening, it is possible to forecast the amount of rain and its progression in intensity from low to high. The work analyses the range of sizes of raindrops giving a name for each such as: Dath, Baghsh, Tash, Katkat, Deam, Wabel (pp. 14 –8).

The intensity of rainfall is categorised as: Ghaith Thare (heavy downpours), Tabk More’a (rainfall that wets the ground with a fertilising impact), Al-motha’anjer (flowing streams filling the ground) (pp. 26, 27).

The rain emergence from the clouds is divided into Al-inbejas (exploding) and Al-inbe’ak (heavy downpour) (pp. 9 – 13).

Cloud formation and motion are described with simplifying references to motions of animals and people. For example, Habo Al-mo’atanek refers to creeping like a camel ascending on sand, hence signalling the plentiful amount of water in them. As the clouds expand and spread, the text uses expressions likened to changing human forms, such as: its chest was puffed up and its waist was broadened (pp. 28 – 38).

The severity of the impact of rainfall on the ground is divided into that which:
– wets the soil and gatherable by the hand.
– penetrates rocks (thus more substantial).
– leaves the sand wet.
– forms large swamps.
– causes streams to form on the mountains (pp. 28 – 38).

This note has outlined some general meteorological phenomena described by Ibn Doraid Al-Azdi in late 9th Century.

Cem Nizamoglu