As mentioned earlier, Alberuni asserts that water being the basic need for life, God created a reservoirs of it in the form of oceans. However, as the habitations of man and animals are often far away from these reservoirs and also as they need fresh water, God has 'designed the continuous motion of the Sun and the moon, and commanded them both… to evaporate it (the water), and to lift its vapour upwards"⁸⁹ As these water vapours mix with the air above, the air becomes moist and in the form of clouds the winds carry them to far off desolate and waterless lands.⁹⁰ These clouds, when they ascend the mountains, cause rainfall.⁹¹

Alberuni's knowledge of rainfall is limited to the orographic type and he is not aware of the other types, namely, convectional and cyclonic. As far as orographic rainfall is concerned, he observes that when clouds 'reach...