HYDERABAD: Every monsoon, the heaven and earth meet. The air is balmy, perfumed with petrichor. The sky is a mysterious piece of art as the clouds transfigure light and make us see everything anew.
These days, the Sun often disappears among fleecy, silken, grey and white clouds. Scientists say that these clouds can make the sky look brighter as they float around and reform constantly. Cloud droplets and aerosol particles -- which are essentially tiny bits of dirt and water in the air that cause haziness -- scatter light in three dimensions, even into cloud shadows.
“They transfigure light in the most beautiful ways, particularly during sunset in the monsoon,” Rajani, a member of the International Cloud Appreciation Society, says. Rajani, the weatherman who also keeps Hyderabadis updated with the city’s forecast on Twitter based on cloud movement, attributes the vivid colouration of the sky to the Altocumulus clouds.
“When the Sun casts its rays cast upon these clouds, they produce a diverse range of colours in the VIBGYOR wavelength. The most common colours being carmine, orange, ochroid, mauve, violet and sometimes even green. Green is unnatural unless there is a rainbow. But it can be seen and is caused because of the diffraction of the Sun’s rays,” he says.
During the day, most of what we see is visible due to sunlight. The sunlight, when transfigured through the clouds, can produce innumerable shades of daylight or a swathe of grey when the sky is overcast. “The Stratocumulus cloud formation causes dull grey skies. These are the days when people anticipate rain. The sky is usually grey, torn with a few patches of blue. We many not find different shades, but the entire ambiance turns gloomy,” explains Rajani.
Majority of the cloud formations can be witnessed during the monsoon and learning about some basic formations can help one predict the weather, just like Rajani does.
Know your clouds
Cumulus clouds, a.k.a. fair weather clouds
These clouds are the most common during the late summer and monsoon. Their tops are rounded, puffy and a brilliant white when sunlit, while the lower portions are flat and grey. They indicate instability in the atmosphere, meaning future rain.
Stratus clouds
These are featureless, sometimes foggy and greyish. They resemble fog that hugs the horizon (instead of the ground). A stratus cloud can form from ‘stratocumulus’, indicating a continuation of prolonged cloudy weather with drizzle.
Stratocumulus
These are low, puffy and greyish or whitish clouds that occur in patches with blue sky visible between them. These appear during sunset and produce ‘crepuscular rays’, a sunbeam effect and have a silver lining.
Altocumulus
These are formless, scattered and foggy clouds which make for colourful sunsets and sunrises. They signal thunderstorms later in the day or night.
Nimbostratus
Nimbostratus clouds cover the sky in a dark grey layer. These clouds usually cause continuous rain without lightning or thunder.
Cirrus
Cirrus clouds are thin, white, wispy strands of clouds that streak across the sky. They are formed of tiny ice crystals rather than water droplets. Cirrus typically occur in fair weather.
Cirrostratus
These transparent clouds, which cover nearly the entire sky, were responsible for the halo around the sun last week.
Cumulonimbus
These have bulging upper portions which make them look like a giant cauliflower.