有趣天文現象：粒粒「乳狀雲」(Mammatus Clouds)
你有看過這樣可愛的粒粒「乳狀雲」(Mammatus Clouds)嗎？通常雲也是一團團的，但有時大點的雨水或冰在雲中累積，便會產生這個形狀的雲了！這情況不常見，有時會在暴風帶旁邊出現，有關詳情請參考Wikipedia。
Explanation: Normal cloud bottoms are flat. This is because moist warm air that rises and cools will condense into water droplets at a specific temperature, which usually corresponds to a very specific height. As water droplets grow, an opaque cloud forms. Under some conditions, however, cloud pockets can develop that contain large droplets of water or ice that fall into clear air as they evaporate. Such pockets may occur in turbulent air near a thunderstorm. Resulting mammatus clouds can appear especially dramatic if sunlit from the side. These mammatus clouds were photographed over Regina, Saskatchewan, Canada during the past summer.
Information from: APOD
Image Credit & Licence: Craig Lindsay, Wikipedia
