“Rain, rain go away… little Johnny wants to play” is the stupidest rhyme we teach kids in India. Here, we WELCOME rain; we PRAY for rain. There are songs in every language asking rains to come on time. When the rains arrive, we rejoice by going out and playing in the rain!The monsoons have officially arrived on the southwestern Indian coast – Kerala – on 30 May 2010. Here is what the India Meteorological Department had predicted for this year’s southwest monsoons. (All links open in a new tab or page. Sometimes servers experience problems and may be slow If this happens, try again later).
As it happens, the monsoons arrived a day earlier!
The monsoons are seasonal winds. They bring a lot of rain to much of India – hence they are called the wet monsoons. They come from the southwest – so, they are called southwest monsoons. They advance from the equator to the Tropic of Cancer – so, they are called advancing monsoons.
The other monsoons that come from the northeast don’t bring much rain. They go from the Tropic of Cancer towards the equator. Yes, these are retreating, “dry”, northeast monsoons.
The monsoons are extremely complex atmospheric systems. They bring life to millions of people in the Indian subcontinent. Without them, our lives, cultures, history, economy, art, poetry, literature, diet, geography, agriculture … everything would be vastly different from what it is today.
How do the southwest monsoons occur? Here is a very simple description.
By June in India, the sun’s rays fall increasingly directly (vertically) on our latitudes. This is because Earth’s position in relation to the sun tilts the northern latitudes to face the sun more and more.
On 21 June, the sun is directly over the Tropic of Cancer (23-1/2 degrees North). This latitude passes very close to Gandhinagar, Bhopal, Ranchi, Agartala, and Aizawl.
As the sun’s position shifts from the equator (zero degrees latitude) to 23-1/2 degrees N, the areas directly under the sun get hotter and hotter. Land areas heat up more quickly than the water areas.
Watch this interactive animation of Earth’s revolution around the sun and you will understand how the relative positions of Sun and Earth change. This results in different seasons at different latitudes during different times of the year. Thus, latitude is considered one of the important “controls” of climate. (A climatic control influences the climate of a place.
The land transfers its heat to the air above it. The heated air rises. This means the atmospheric pressure over the land decreases.
This low pressure circles the globe like a belt; a wavy belt. This is called the Inter-Tropical Convergence Zone (ITCZ). As the relative positions of Earth and Sun change during the year, the position of the ITCZ also changes. Approximately where is the ITCZ as you read this? Check this animation and find out. While you are checking it out, see how the atmospheric pressure varies.
The heating is also happening over the water areas (Indian Ocean, Arabian Sea, and Bay of Bengal). But there are two important differences. The water heats more slowly and a lot of water vapor is formed. This water vapor is like any other gas. Because of its heat, it rises.
Apply your knowledge of physics here. Air moves from higher pressure to lower pressure. The air from over the seas (higher pressure), rushes in towards the lower pressure areas (over land). They rush towards the ITCZ because the pressure is lower along that belt. This pressure difference is vital! It determines the movement of the winds.
As they race towards central India, they run into a huge high wall! The western Ghats! Oh, no! What are they to do now? They can’t go back – there is more and more wind rushing in and pushing them. They can’t go forward, the Ghats are in the way. The only way they can go? Up!
When they rise up, these winds start cooling down! Because of this the water vapor condenses into drops. Liquid water is heavier than water vapor (gas). They billions and billions of water drops fall down to Earth – this is ‘torrential rain’! Therefore, altitude is considered another climatic control.
Check out the latest cloud cover over India here in this beautiful satellite image.
Until these rains come, the lands have experienced several months of dry heat. The crops need water to grow. In the forests, animals need the water to not just to drink but also to stay cool. The plants in the forests need water to grow. Without these plants, the animals will have no food or shelter. It is the season for many animals to reproduce.
For millennia, people living in India have depended on these rains for producing enough food. The rains are not just for producing food, but they bring new life to India every year. They are our life!
Indian culture is closely tied to these rains. From classical music to folk music and film music, from traditional scriptures to folk and popular poetry, in every art form, in every region, … we find the people of India hoping and praying for rain. There are many romantic songs and poems about the wet monsoons, there are seasonal food items that we enjoy, children’s rhymes in Indian languages celebrate it, and all life in India welcomes the rains for the many benefits it brings. There are also many dangers, so people also try to make themselves safe.
But the rains are vital for us!
At least once in your life-time, you must experience the arrival of the southwest monsoon standing on the shore of the Arabian Sea. It is simply awesome!
Then, you can understand why so many Indian poets wrote such beautiful poetry about the monsoons, and why the southwest monsoons are so important in our lives.
Here are some things you can do:
- This year, pay attention to the arrival of the monsoons wherever you live in India. Write down the date. If possible, the time. Observe how the whole environment changes just before it rains, during the rains, and after the rains. Notice how you, yourself, feel.
- I have named a few climatic controls in this blog. Which ones have I not mentioned?
- Did you go out and get drenched in the monsoon rains this year yet?
- If yes, How would you like to express your feelings about this year’s southwest monsoon? Photographs? Art? Poetry? Short prose (10 – 15 sentences)? Or some other way ….?
- If you did not go and get drenched in this year’s monsoon, why not? (This answer could help you understand many interesting cultural and geographical things.)
Send your responses by entering the information in the “Send us a comment / Get involved!” box below or send it by email to geo@tiigs.org before 24 June 2010.
When you send your responses be sure to include these details:
- Your full name
- Your correct email address
- Name of your school
- Your school’s location (city, state)
- Your geography teacher’s name (be sure to begin with Mr. Or Ms.)
Selections from your responses will be published in a GeoVidyaa blog posting on 28 June 2010
For teachers: Whatever subject you teach, including the southwest monsoons in your subject makes your subject more interesting, relevant, and applicable. If you want to organize a workshop at your school for you and your colleagues, contact TIIGS using the “get involved” box below or by email.