"WIND: A GIFT or A WRATH"

PART-5

While they were having dinner Rajiv’s cell phone rang. It was Sarthak’s father calling. He picked up the phone. After ending the call he said, “Sarthak it was your dad. He said that he and your mother are going somewhere for some urgent work. It will take around half an hour. So I should not drop you back they will themselves pick you up from here.”

“Ok Uncle.” Sarthak said.

“That means you are here for another half an hour. Yiippeee!” Vayu said enthusiastically.

“Quickly let us finish our dinner then we will think how to utilize this half an hour.”

After finishing their meal they both went to the hall and decided to watch cartoon movie coming on TV. While they were watching Vayu’s dad came with two 2 ltrs empty coke bottle in his hands and kept them on the table in front of them.

Eager vayu said, “Dad what are you doing?”

“Just wait Vayu you will get to know everything but first bring one bowl full of water. And Sarthak will you please switch off the TV.”

“Sure Uncle.”

Meanwhile Vayu brought the bowl of water and gave it to his dad. Rajiv then poured the water into one the bottle and closed it. The water half filled the bottle.

“Dad, why have you drilled holes on both the caps?”

“Wait Vayu.”

Rajiv then placed the empty bottle on the table and the half filled bottle on top of the empty bottle such that both the caps touch each other. He then taped both the caps together.

“Kids now you are going to see a magic.”

“Magic… Wow!!” Both said.

Rajiv then held the upper bottle and gave a small swirling motion to the bottle. The kids saw that the small swirling motion started rotating the water inside the bottle forming a cyclone like structure. The hole drilled in both the caps caused the water to drip down to the empty bottle.

Both Vayu and Sarthak were astonished to see this. “What was this Dad?” Vayu asked

“This was a small experiment to tell you the shape of a cyclone.”

Before Sarthak could drift back to the memory of his cousin, Rajiv continued, “Sarthak, Vayu told me that when in the morning you told him about the tragic incidence of your cousin’s death in Hudhud you both in a way blamed God for not stopping these natural calamities from occurring. But kids this is not the case. Although these are natural calamities and no human can do anything to stop them our God is also innocent. He can never see his own creation dying like this.”

“Then why such calamities occur, Uncle?” Angry Sarthak asked.

“They occur because of certain changes in the environment.”

“What kind of changes Dad?”

“Yes, I am going to tell that only. And now when you both are aware of the concept of wind and you also know what Coriolis force, air masses and fronts is, I am sure you will be able to understand whatever I am going to tell you within next 15 minutes. But first you have to promise that none of you will interrupt me in between. Especially you, Vayu.”

“Fine Dad. Now tell us.”

Rajiv then powered his laptop and showed them the map of India with Indian Ocean surrounding it. “As you can see our Indian coastline is surrounded by Indian Ocean with Bay of Bengal on Eastern side and Arabian Sea on Western side this is naturally prone to cyclones like Hudhud or Tsunamis. These calamities are called with different names in different regions like in Indian Ocean they are called Cyclones, in Atlantic they are called Hurricanes, Typhoons in Western Pacific and South China Sea and Willy-willies in the Western Australia. But the uniform name is Tropical Cyclones. These types of cyclones are very destructive in nature and are formed only over the seas and on reaching the land they dissipate.”

Rajiv then showed them the picture of Eastern coastline and Bay of Bengal and further continued, “Now kids before we see how a cyclone is formed we should know certain conditions that are necessary to form a cyclone. Cyclones get their energies only from warm seas hence the temperature of the large Sea surface should be above 27 degrees also it should be a weak, low pressure area. Another necessary condition is the presence of Coriolis Force and also there should be small variations in the vertical wind speed. Now as we know the rules let me show you how cyclones form.”

Rajiv then switched on a video he had created and said, “Let us suppose this is Indian Ocean and the temperature of the surface is continuously rising. The temperature is now 27 degree centigrade. Now as we know the damp warm air above sea surface will rise and will meet the cold air present in the atmosphere. Also we already know about Cold Front. Can any of you tell me what was Cold Front?” He paused the video.

“Oh! Yes Uncle how can I forget that. Vayu beat me in that round. In Cold Front the Cold Air Mass beats the Warm Air Mass causing the warm air to move up in the atmosphere forming a Co… co…lumbus clouds.” Sarthak said.

“Ha ha ha! Not Columbus Sarthak it was cumulonimbus clouds. Doesn’t matter, I am impressed that you remember. Now kids, remember I also told you that the Cold Fronts lead to the formation of tornadoes, cyclones, etc.”

“Yes yes.” Both said.

“When the cumulonimbus clouds are formed by Cold Front they cause heavy rains. Now let us continue our video.” Rajiv said and continued, “This condensation process or change of water vapor to water droplets in the form of rain produces Latent Heat which further warms the atmosphere and make it more buoyant. Due to this the air rises more rapidly forming more thunder or cumulonimbus clouds.”

Rajiv then showed them how the clouds were formed.

“But Dad how can these be so devastating that they can destroy entire city?”

“Vayu I am coming to that. It’s just the beginning kid.” Rajiv said and continued the video.

“Now we know what Coriolis force is and what effect it has on the wind. Right kids?”

“Yes Uncle. We know that.” Sarthak said.

“Now as the trade winds arrives the Earth’s surface they curve and change their path due to Earth’s Rotation causing Coriolis Effect. Due to this winds coming from South curve to their right that is towards East and winds coming from North curves to their right that is towards West forming a pattern of spinning tropical storm, as you can see in this video. As the storm grows larger more moist warm air is drawn towards the surface. This in turn produces more water vapor that forms clouds which in turn forms more water droplets and thus producing more Latent Heat. This Latent Heat continuously gives Energy to the storm helping the storm to increase its speed of rotation. This is how a tropical storm is formed. See this video.”

“But Uncle when does this storm becomes a cyclone?” Sarthak asked eagerly.

“You kids are so eager to know everything. Give me a break kids. Atleast give me a second to breathe.” Rajiv said smilingly.

“Oh! Sorry Uncle but I was worried that my parents will come any time and then I have to go. I don’t want to miss this.”

“We still have 5 minutes Sarthak till your Parents arrive. It’s just the ending now.” Rajiv said and drank some water. He then continued, “So kids when the speed of this rotating tropical storm becomes more than 74 mph it officially falls under the Category 1 Cyclone. If its speed reaches above 96 mph it falls under Category 2 Cyclone. Hence, with increase in speed of rotation the category keeps on changing and with it the wrath of the cyclone also increases. The most dangerous of all is the Category 5 Cyclone with rotation speed more than 157 mph. This is the last category of the Cyclone and it could be very devastating. Now let me tell you what exactly happens inside the cyclone.”

Rajiv then changed the video and said, “We have seen before that the moist warm air rises to form thunder clouds. As the air cools above it becomes denser and falls down. This as you can see here forms an alternate pattern of warm air rising and cold air sinking. In other words this process forms alternating storm clouds with white slots in between. This produces spiraling rain bands that we see in the satellite pictures of cyclones taken from above. These spiraling storm clouds are known as Eye Walls and in the center is the Eye of the Cyclone. Eye Walls are the most destructive part of the cyclone and all the destruction caused is only because of this Eye Wall. On the other hand in the Eye of the cyclone the wind drops to give rise to an airy calm.”

“No wind in the Eye at all?” Shocked Vayu asked.

“Yes my son the Eye of the cyclone is quite calm. Now as the cyclones are formed from warm damp air when they reached the coasts they start sucking dry air hence, start losing their power. This is the reason why tropical cyclones are formed overseas and not over lands. I hope you have understood the concept kids. And now you both know how Hudhud was formed.”

“Perfectly Uncle. You know what initially when you were telling us about wind in the park I thought it as a Gift of God but know I think it is a Wrath because of the destruction it causes.”

“Ha ha! It completely depends on us how we want to look.”

“What do you mean dad? Are you saying that cyclones can be good as well?”

“Yes that is what I am saying Vayu.”

Confused kids looked towards each other thinking that Rajiv has gone mad.

“See kids every coin has two sides. Cyclones are actually very important even though they are deadly. Cyclones help in balance out the temperature across the Earth. They act as equalizers that take heat energy from the tropics and transform them into colder climates when the environment requires.”

“Really?? That’s even more surprising. I am more confused now whether to consider winds as a gift or as a wrath.” Sarthak said.

Suddenly loud horn of a car came. Sarthak’s parents had arrived on the right time. Sarthak stood up hugged Vayu and was ready to go when Rajiv said, “Don’t think too much Sarthak. Just remember whatever you have learned today that’s important.”

“Sure Uncle. Thank you for your today’s efforts. We have actually learned a lot that we will never forget.” Sarthak said and bid them goodbye.

“Bye Sarthak.” Rajiv said.

“Bye Sarthak. We will meet tomorrow in school.” Vayu said and went inside.

"WIND: A GIFT or A WRATH"

PART-4

Inside Vayu’s mother was watching TV. On seeing them she said, “Oh! Hello kids. You are back. Hello! Sarthak beta. How are you? I came to know about the loss of your cousin brother. I am really sorry beta.”

“Namastey Aunty. Yeah! It was very bad incidence happened in our family.” Sarthak said in a sad tone. By now kids were getting out of that tragic memory but Vayu’s mother brought them back. Vayu stared at her mother that why in the whole world she had to say this. Meanwhile his father also came inside and feeling the tense atmosphere he realized what would have happened. He looked towards his wife who was already feeling very sorry to bring the subject and said, “Darling you know what, Sarthak will be having dinner with us today and I have come to know that he likes Shahi Paneer very much. Would you please cook it for all of us?”

“Oh! That’s great. I was myself thinking to make paneer only. It will be very nice we all be having dinner together. Right Sarthak?” Vayu’s mother said trying to mend her mistake.

“Yes aunty.” Sarthak said in a meek voice.

“Come kids meanwhile the food is being cooked I’ll go and change and then we will play a small game. What do you say?” Vayu’s father said.

“Yeah! That will be great idea dad.”

Sarthak was still in thoughts.

“Ok then Vayu go and bring your G.I. Joes we recently bought.”

Surprised Vayu and Sarthak went to the room and brought the G.I. Joes.

“I don’t know what is Dad thinking of. Sometimes he does very weird things.” Vayu said to Sarthak.

Soon Rajiv came out of his room in night clothes and found that the kids were already on the table waiting for him.

“Ok kids let us begin the game. First of all tell me who wants to be from G.I. Joe gang and who wants to be from Cobra gang?”

“I will be from Cobra gang.” Vayu said instantly.

“Then Sarthak would be from G.I. Joe gang. Are you fine with it Sarthak?” Rajiv said.

“Yes Uncle.”

“Fine then Sarthak hold your best G.I. Joe ninja warrior that is Snake-Eyes who is master of many weapons and is also known as Wolverine of G.I. Joe. On the other hand Vayu will hold all time rival of Snake-Eyes that is Storm Shadow. Storm Shadow is the most powerful ninja among the Cobra pack.”

“Yooo Hoooo! I will kill you Snake-Eyes.”

“You will never succeed in your evil plans Storm Shadow.”

Both the kids were very excited on getting the best of the packs.

“Calm down kids the game is yet to begun.” Rajiv said.

“You must be thinking why we are playing this game. Am I right?”

“Yes dad. Why?” Vayu said.

“Vayu I am going to explain you the concept of Air Masses.”

“Air Masses? What is that Uncle?” Sarthak said.

“When the air remains over an ocean surface or over plains for sufficiently longer time it acquires the characteristics of that surface. This air with distinctive characteristics in terms of temperature and humidity is known as an Air Mass.”

Vayu and Sarthak started looking toward each other feeling bit confused.

“Wait kids, you both will get to know everything.” Rajiv said and further continued “As we know Vayu’s Storm Shadow is very dark and evil, we can say he is Cold hearted and on the other hand Sarthak’s Snake-Eyes is bright and helpful, we can say he is Warm-hearted. Similarly we have two Air Masses one is Cold Air Mass and the other is Warm Air Mass. Now let us mark an area or arena in which the fight will take place. In actual it is a land area surrounded by water and other lands from all sides. Now these Cold and Warm air masses can be further divided depending upon whether they are flowing over land or sea. Air Mass formed over land is called Continental Air Mass and Air Mass formed over sea or ocean is known as Maritime Air Mass.

Now, if they are coming from Polar Regions these air masses can be called as Maritime Polar air mass or Continental Polar air mass. On the other hand if they come from other bodies of land they are known as Maritime Tropical or Continental Tropical. Also Air coming from Polar Regions is very cold and air coming from Tropical Regions is warm. There is one more Air Mass that is formed over Arctic Region known as Arctic Air Mass. This is also a cold air mass.”

Vayu’s father took a brief pause and let the kids grasp. He then continued, “Ok kids let us begin the fight. Vayu’s Storm Shadow is Cold hearted we can call it Cold Air Mass. As we know that cold air sinks so the signature move of Storm Shadow is that it goes down on its opponent. On the other hand Sarthak’s Snake-Eyes is Warm hearted we can call it Warm Air mass. Now, as we know warm air rises so the signature move of Snake-Eyes is to come and rise over its opponent. C’mon kids let us begin the fight. 1…2….3 and Fight.”

“Here I come, Snake-Eyes. You are going to be history.” Vayu said excitingly.

“Not so soon Storm Shadow.” Sarthak said and plunges with equal force.

“Now as you both collide with each other you will be forming a front. Similarly when two air masses collide they form Fronts.”

Both of them started fighting with each other. The battle was very fierce. No one was ready to lose. Both Vayu and Sarthak were giving tough competition to each other.

“See none of you is ready to lose, this stage of the battle can be called stationery as no one is moving ahead. Similarly when Warm and Cold Air masses push each other but neither wins it is called as STATIONARY FRONT. This front causes several days of overcast weather and it drizzle.”

  

Sarthak’s Snake-Eyes then came from up which Vayu saw and kicked with his Storm Shadow to throw Snake-Eyes off balance and up in the air.

“Very good, Vayu that was a nice move.” Rajiv said.

Vayu started jumping in excitement as if he had already won. And Sarthak was feeling bad.

“Calm down Vayu the battle is not yet over. Now as you have beaten Snake-Eyes similarly cold air mass beats Warm air mass to form a COLD FRONT. Because of this Cold Front cumulonimbus clouds are formed in atmosphere which give birth to thunderstorms, hails, tornadoes or cyclones. We will be coming on to it after some time. Let us continue the fight.”

This time Sarthak came slowly with his Snake-Eyes from the top and sneaked over Vayu’s Storm Shadow and attacked Storm Shadow move thus winning the round.

“I must say that was a strong counter attack Sarthak.”

 “Thank you Uncle.” Sarthak said smilingly.

“Kids in actual Warm Air also sneak up the Cold Air in similar way covering whole of the Cold Air Mass and thus forms a WARM FRONT. Since warm air is slow hence, the Warm Front forms stratus cloud due to which there is drizzling for few days.”

“Come everyone dinner is ready. You can continue after wards.” Vayu’s mother shouted from the kitchen.

“Wait honey we are coming in 5 minutes. Let us finish the game kids. One last round. But we will make this round a bit difficult for our hero Snake-Eyes. We will be playing a 2-on-1 Handicap Match. What say kids?” Rajiv said.

“That will be fun Dad. Now I will definitely beat Snake-Eyes.”

“No ways Vayu. Snake-Eyes will win.” Sarthak said.

“That’s the spirit guys. Ok here take Cobra Commander with you Vayu. He is also cold in nature like Storm Shadow depicting another Cold Air Mass. Now, you are 2, Storm Shadow and Cobra Commander against Sarthak’s Snake-Eyes. Let us start.”

Vayu started with Cobra Commander and attacked Sarthak’s Snake-Eyes but Snake-Eyes being stronger then Cobra Commander it sneaked from up and took Cobra Commander in his signature move. Seeing his Commander losing Vayu brought his Storm Shadow inside the arena. He seemed to be really angry so he punched both of them up in the air thus winning the battle.

“Yoooo Hoooo! I won. I won.” Vayu said and started dancing.

Sarthak felt embarrassed that he lost.

“Yes yes Vayu you won. Now stop boasting.” Rajiv said. He then further continued, “Now in terms of fronts this is known as OCCLUDED FRONT in which two cold air masses beat one warm air mass as done by Vayu. Together these three masses form a scattered type of weather conditions. Sometimes its cloudy and sometime it rains but nothing too severe. These are all 4 types of fronts. Come now let’s have dinner otherwise Vayu’s mom will shout again.”

All of them went to the dining table where the food was already laid down. Vayu was still teasing Sarthak for his loss.

“Don’t worry Vayu next time I will win. You will see.” Sarthak said jokingly. With this all of them started their dinner. 

"WIND: A GIFT or A WRATH"

PART-3

“As we know that Earth is not still, but it rotates on its axis and that too from West to East, hence, causing an impact on the Global Wind Currents. What happens actually is that hot air rises from the Equator and flows towards the North and South Poles but at around 30 degree latitudes near the tropics the hot air losses some steam and begins to cool. Due to this the cool air now sink back to Earth surface and in turn returns to the Equator forming a small loop or convection cell. This cell is called Hadley Cell because the person who found this was George Hadley. Similarly around the Polar Regions, both in North and South, the sinking cold air which had started moving towards the Equator gains some heat at around 60 degree latitude or sub-polar latitude. Due to this it starts rising up in the atmosphere and in turn returns back to the Poles forming another convection cell. This cell is known as Polar Cell and I suppose the reasons are obvious. Isn’t it amazing kids? Wait let me show you a picture.” Harshit shared a picture showing Hadley Cell and Polar Cell.

“Sir truly it’s amazing. It’s hard to believe. But what happens in the middle of Hadley Cell and Polar Cell?” Sarthak asked in amusement.

“Oh yes. Kids, the Hadley Cell and Polar Cell create yet another convection cell in between. It is a moderate temperature cell which follows the similar pattern as the other two cells. This cell is called Ferrel Cell named after William Ferrel who actually found it.”

“This is completely amazing. Thank you sir for sharing this information with us.” Vayu said. Rajiv was also feeling happy by the fact that his friends have actually spared time to teach all this.

“Wait, there is some more. Let me tell you some more amazing things. The rising up of the warm air takes place all along the Equator and not just at one point. This had caused some problems in the earlier times for the sailors. Since the hot air all along the Equator rises up and flows towards the 30 degree latitudes this made equatorial region devoid of any horizontal wind, making it difficult for the early sailors to carry their sails. Hence, this region got his name as DOLDRUMS. Doldrums are a state of inactivity or stagnation. Similarly at around 30 degree latitudes both in Northern and Southern Hemisphere, sailors find it difficult to travel because the air there sinks down making the area devoid of horizontal wind. In earlier days Spanish sailors used to transport horses to their colonies in the West Indies or America. But due to no horizontal wind around these latitudes their voyage prolonged severely. This resulted in the shortage of water supply for keeping their horses alive. Hence, they started throwing the dead or the dying horses down into the ocean. This incidence gave the name HORSE LATITUDE to this region. In similar way region around 60 degrees latitude also do not receive horizontal winds. No special name is given to them. It is just known as Sub-Polar Latitudes. Apart from these regions the rest of the Earth receives at least some sort of horizontal wind. So kids these are the Global Wind currents. Moreover the Earth’s weather moves with these currents. Interesting right?” Harshit said.

“Very interesting sir.” Both said in unison and looked towards each other in amusement. No one had taught this to them before. In school they only get to know what was printed in book.

“I am amazed Harshit you know so much.” David said jokingly. “But you forgot to explain one thing.”

“What? Really? What is that Mr. Intelligent?”

“About how do Coriolis force acts on the winds.”

“Oh! Yes. But I have left only 5 more minutes than I have to go.” Harshit said feeling sad.

“Doesn’t matter dude. I will explain it. It will take just 5 minutes.”

“Oh! Really? Let us see.”

“So kids it may seem that the winds flow from north to south and from south to north as shown in the earlier pictures but this is not the case as the Earth is not still. It is rotating along its axis. This is where Coriolis force comes into action. Due to the rotation of the Earth the Coriolis force causes the wind to deflect from its path. As told by Rajiv earlier in the Northern Hemisphere the Coriolis force causes the wind to turn to their right and in the Southern hemisphere it causes the wind to turn to their left. Hence, in the northern hemisphere, between 30 degree latitude and the equator coriolis force causes the wind to flow from North-East to South-West direction. Since these winds were very helpful for European Sailors to travel to new America hence, these winds got their name as Trade Winds because of the boost they provided for trade between Europe and America. And flowing in the northern hemisphere they were called as North Easterly Trade Winds because they start from North East Direction. Similarly in Southern Hemisphere they were known as South Easterly Trade Winds because they start from South East Direction and moves to North West Direction.

Now moving up between 30 degree and 60 degree latitude as we know that wind here flows from Horse Latitude to Sub-Polar latitude, these winds also deflect from their path towards Right side in Northern Hemisphere and towards Left side in Southern Hemisphere. But since the Coriolis force is greater in these regions it seems as if winds are coming from West directions and flowing to East direction. Hence, these winds are called Prevailing Westerlies. These are the winds which cover entire US and Canada. Hence, did you see why I said that we ourselves receive winds?”
“Oh! Yes Uncle now we understood.” Sarthak and Vayu said.

“Good. Now moving further up and coming to the Polar Regions. As we know here in these regions the wind flows from Poles towards the 60 degree latitude or Sub-Polar Latitude. These winds are also deflected by the Great Coriolis force. Since these winds flow from East to West hence, these are known as Polar Easterlies. I guess now you know why these are called as Polar Easterlies.”  

“Yes, because they are present at Polar Regions.” Sarthak said.

“Yes Sarthak. With this we finish the concept of Global Winds. Like Winds Oceans also form various currents and cells but that we will tell some other time. Your Harshit sir might be getting late. See Harshit I finished it in 5 minutes.” David said teasingly.

“Yeah! Yeah! Whatever. Ok Kids we hope you have learned something today that you can tell your other classmates moreover to your teacher also. Ha ha! Now I will take leave. It was nice meeting you all. Thank you Rajiv for putting me into this conference otherwise I would have missed it. Take care all of you.” Harshit said and logged out.

“This guy I tell you. He is always in hurry. Anyways children now I will also go. We will talk some other time.” David said.

“Thank you David for giving us your time.” Rajiv said.

“Thank you so much Sir. We learned a lot today.” Kids said

“Oh! No need to thank kids. And Rajiv now you have to tell them about other winds.”

“Yeah! Sure David. Bye. Take care. Give our love to family.”

“Sure brother. Bye.” With this David also logged out.

Sarthak and Vayu started discussing whatever they had learned.

“C’mon kids it’s getting late. We will go back. Sarthak you also come with us. I will drop you back after dinner. We will inform at your home. On the way I will tell you about Local and Seasonal Winds.”

“Yippeee! You will be having dinner with us. I will ask mom to cook your favourite dish.” Vayu said enthusiastically.

On the way back home Rajiv said, “Vayu remember last summer we went to Pondicherry. Can you tell Sarthak and me what change we noticed in the weather there?”

“Oh! Yes. I very well remember Dad. Sarthak you know what we found there, the days used to extremely hot but the nights were very cold.” Vayu said.

“Really? How come?” Sarthak asked in amusement.

“Sarthak this is because of Local Winds. These winds cover a small area and only flow during a particular period of day or year. Land Breeze and Sea Breeze are type of Local Winds.”

“But how are they formed Uncle?” Sarthak asked innocently.

“I am coming to that Sarthak. As we have learned the concept of convection today, the same applies here too. Only difference is that both land and sea absorb and transfer heat differently. As we know sun rays heat the land surface faster than the sea because in the case of sea the rays of the sun travels deep down under the sea and the heating starts from the sea bed but in case of land it only has to heat up the surface. So during Day time land heats up faster and becomes warmer than the sea. And according to the concept of convection the warm air on the land becomes lighter and rises up creating a low pressure area. On the other hand air is cool above the sea so it sinks down creating a high pressure area. As we know wind flows from high to low pressure hence, here also wind flows from Sea to Land. This is known as Sea Breeze because it flows from the sea.”

“What happens in the night Dad?” Vayu asked.

“During night reversal takes place. The sea becomes hot because of the heat it had absorbed the whole day and the land becomes cooler than sea. Hence, during the night the wind flows from Land to Sea. This is called Land Breeze.” Rajiv said and took the last turn to reach their home.

“There is yet another type of winds called Seasonal Winds. When these Sea and land breezes flow over a large regions and change directions with the seasons they cause Seasonal Winds. Our favourite monsoon season is caused because of the Seasonal Winds only.” Rajiv continued. By this time they had reached to their house.

“C’mon kids, you go inside. I will park the car and come.”

"WIND: A GIFT or A WRATH"

PART-2

Vayu’s father then switched on the laptop and inserted his 3G dongle into the port. Within few seconds he was online on the skype. After a minute or so Skype showed an incoming call from a person called David. Vayu’s father connected the call and said, “Hello David, how are you? Long time dude.”

“Hi Rajiv. I am perfectly fine. Oye Balle balle!” David said while raising both his hands in air doing traditional bhangra movement.

“Ha ha! What is this David? Are you learning Punjabi?”

“Ha ha ha! No no brother. It’s just that recently some Punjabi family has shifted in our neighborhood. Whenever we meet them they always say Balle Balle. Hence, I also said so. I must tell you Rajiv there are so many Punjabis shifting here from India. Canada is becoming mini Punjab. You also plan and come stay with us. It would be lovely.”

“Yeah! Sure David some day we will definitely come. Oh! I completely forgot. David this is my son Vayu and his friend Sarthak. Kids say hello to Uncle.”

“Uncle??? Rajiv do you think I am so old? I will not leave you. No need to call me Uncle, kids. Anyways how are you doing?”

“Hello sir. We are fine. It is nice to meet you.” Both Vayu and Sarthak said.

“Why are you both sounding dull? You should be more energetic. I will tell you a nice joke which will make you laugh.” David said.

“Wait David…. Do you remember Harshit, who had shifted to Australia last year?”

“The same lean guy with a moustache. How can I forget him? I have thrown ketchup on his shirt during our college days. Ha ha ha!”

“Yes yes that Harshit only. He is also calling me on Skype. Wait I will bring all three of us on conference.”

“Hello Harshit. How are you? What a pleasant surprise.” Vayu’s father said.

“Hey ya Rajiv. Hows ya? I am fine. Yeah! Dude, it has been a long time. Today I was a bit free so thought to call ya. What are ya doing?” Harshit said.

“Nothing much Harshit. Its good you called. You remember David who went to Canada, he is also on Skype. Wait I will add you in conference.”

Vayu’s father added him to the ongoing call.

“Hello Harshit bro how are you?” David said.

“I am fine dude. Hows ya? How’s the weather in Canada?”

 “It’s very cold here dude. Constantly snow is falling. You tell what about Australia?”

“Dude its very hot here. Send some cool air to Australia also. We are always sending wind to others but do not receive any.”

“Ha ha ha! Dude we ourself receive winds from countries like India. How can we send it to you?”

Both Vayu and Sarthak started laughing. They thought that David was kidding.

“You did not introduce me to these kids Rajiv.” Harshit asked.

“Oh! I am sorry. Harshit this is my son Vayu and he is his friend Sarthak.”

“Hello Kids. How are you and why did you laugh?”

“Hi Sir. We are fine. We laughed on the joke told by David sir about wind.” Both of them said.

“But kids, David is right they do receive winds. You don’t know this?” Harshit asked.

“No Uncle. Is it really true?” Vayu said and looked towards his father.

“Rajiv I am surprised to know that being a son of a great scientist they do not know the concept of Global Winds. Have you never told them?”

“No Harshit not till now.” Rajiv said.

“Ok. Doesn’t matter today we will explain them what are global winds and how are they distributed around the world. What say Harshit?” David said excitingly.

“Yeah dude sure why not.”

“It would be very nice friends.” Rajiv said.

“But let me first explain them about Coriolis force. It will take just 5 minutes. Stay on line. You both could also see and correct me where ever I am wrong.” Rajiv continued.

“Yeah! We will love to see your explanation. You always try to explain in different way.” Harshit said.

“Vayu go and bring football from the boot of our car. Meanwhile we will go to that merry-go-round.” Rajiv said pointing towards the Red and blue coloured Merry –go-round.

Vayu following his father’s order ran to the car to bring the ball. On the other hand Rajiv and Sarthak went to the Merry-Go-Round. Rajiv placed his laptop on a nearby bench with the camera facing the Merry-Go-Round so that both David and Harshit could also see. He then asked Sarthak to go and sit inside the Merry-Go-Round.

By now Vayu had also come carrying a football. He saw Sarthak sitting in Merry-Go-Round and asked his dad, “What is Sarthak doing there?”

“Wait Vayu you will get to know.” Rajiv said and took the ball from Vayu and gave it to Sarthak.

“Vayu go and stand a little far away. I will rotate this Merry –Go-Round.”

Vayu did as asked for. He moved few steps back from Marry-Go-Round.

“Now Sarthak I am going to rotate this Merry-Go-Round and when I say you have to throw this ball.”

“Ok Uncle.”

Rajiv rotated the Merry-Go-Round and when it came into motion, he told Sarthak to throw the ball. Sarthak threw the ball to the ground.

“Vayu what did you see? What path did the ball follow?”

“Dad the ball went in a straight line.”

“Nice. We will do this one more time.”

Rajiv did the same procedure again but this time he asked Sarthak, “Sarthak what did you see?”

“Uncle the ball took a curved path.” Sarthak said.

Vayu was surprised to hear his answer. He asked, “Dad how is it possible? I saw that ball fall in a straight line but Sarthak is saying he saw a curved path. Was I wrong?”

“No my child. You both are correct. What Sarthak saw was because of Coriolis force. Come let us join our Skype friends then I will explain you in detail.”

They returned to the bench and sat down, Rajiv keeping the laptop on his lap continued, “Children Coriolis force is a fictitious force i.e. a force which is actually an illusion. Moreover it only acts on a moving objects and only when you are taking measurements from rotating prospective. The same happen on earth. When on earth wind flows in certain direction the rotation of the earth on its axis causes the Coriolis effect on the wind and as a result wind deviates from the straight path and follows a curved path. Hence, when the rotation of the Earth causes the moving air and water to change directions it is known as Coriolis Effect. In the Northern Hemisphere of the Earth Coriolis force causes the winds to curve to their RIGHT and in the Southern Hemisphere it causes the winds to curve to their LEFT. I hope now you have got a basic idea of the Coriolis force.”

“Yes yes. We have.” Both the kids said.

“I must say that was a wonderful and the easiest explanation for coriolis force Rajiv.” David said.

“Thank you David for the appreciation.” Rajiv said smilingly.

“C’mon guys don’t forget the task. We have to explain them Global Winds not just Coriolis force. Let us do that. I have to go somewhere after half an hour.” Harshit said.

“Oh! Yes yes. David will you start or shall I?” Rajiv said.

 “I will start Rajiv.” David said excitingly. “Kids first of all you should know that there are 3 types of winds that we experience on Earth. One is Permanent or Global Winds that I and Harshit will explain and the other two are Seasonal and Local winds that Rajiv can explain you afterwards. Right Rajiv?”

“Aye aye Captain!” Rajiv said and all started laughing. Vayu and Sarthak were very excited as they were going to learn something new and interesting.

“Ok ok no jokes for next half an hour. Let us begin.” David said and shared a photo of Earth’s Globe on Skype so that all of them could see. “Ok kids, first tell me do you know how the hot air and cold air flows?”

“Yes Uncle. Dad had told us today only. Hot air being lighter rises up and cold air being heavier sinks down.” Vayu said.

“Very Good Vayu. And this concept is known as Convection. In simple terms Convection is the circular motion that happens when a warmer air or water which is less dense rises up and colder air or water which is denser sinks down consequently resulting in transfer of heat.” David explained.

“Ok now can you see this Globe picture I have shared here?”

“Yes Uncle.” Both said together.

“So can any of you tell me that in which part of the Earth receives maximum rays of the Sun and which part receives the minimum rays from the sun?”

“It’s easy Uncle. The equator will receive the maximum rays and the poles, both north and south, will receive minimum rays from the sun.” Sarthak said.

“Brilliant. I must say you both kids are very intelligent.”

“Thank you Uncle.” Both of them said blushingly.

“You are correct Sarthak. At the equator the sun rays directly hit making an angle almost equal to 90 degrees and at the poles the sun rays hit at a very small angle. That is the reason the Polar Regions are very cold and the equator is very warm.” David said.

Without waiting for anyone to say anything he continued, “I hope that you both know that our Earth rotates on its axis.”

“Yes Uncle we very well know that.” Both said in unison.

“So let us assume for some time that the Earth is still. God has stopped Earth’s rotation for some repair work.” David said and started laughing. With him every one else also laughed.

“No jokes David.” Harshit said with a wink.

“Oh! Yes. Sorry sorry. Now as we know that the Sun rays hit directly at the equator hence, the air present there is very warm. And at the poles the air is very cold. According to the concept of Convection we just learned that the warm air from the Equator rises up in the atmosphere to some level from where it will start moving towards the poles, both north and south, and the cold air from the poles sinks down and moves towards the Equator to form a Convection Loop or a Convection Cell. This happens at all areas of the Earth.” David said and showed them a picture depicting the movement of air.

“But actually this is not the case.” Harshit said. “You take some rest David. I will explain further.”

“Sure Harshit. Go ahead.” 

"WIND: A GIFT or A WRATH"

PART-1

Intellectual Minds, a smart school famous for its teaching methodology is located at the heart of the city Chandigarh. Every parent living in and around Chandigarh wants to admit their child in this school. Since past 10 years school has built up very good rapport. Moreover the students who pass from this school excel in various fields. The school has a very strong alumni base. Getting admission in Intellectual Minds is not easy. Parents as well as the children have to clear a rigorous interview test before getting admission. The school always takes cream of the children. The school does not lay burden on the children. Study is more practical than theoretical. It has a large open playground with latest gaming slides and equipments.

The time was 12 noon and lunch break was going on. Most of the children were playing in the play ground. Many were having their lunch. Weather was cool and cloudy. It could rain anytime but none of the children wanted to stay inside. Hence, everyone was in the play ground to enjoy the cloudy weather. All of them were very happy and excited except one student who was sitting under a tree and crying. His name was Sarthak. He was the most active student of his class but today his activeness was reduced to negative. He wanted to cry but fearing that anyone could see him he controlled his tears.

Vayu, his best friend saw him and ran towards him. “What are you doing here Sarthak? I have been looking for you all around. C’mon let’s play a game of football.”

“Sorry Vayu not today. I am in no mood to play football.” Sarthak said with moist eyes.

“Hey buddy! What happened? You are the most active student among us and you are saying you don’t want to play. Why? Is everything all right? Why are your eyes moist?”

“Nothing much dude it’s just that something is bothering me.”

“Oh! C’mon Sarthak you can tell me what is bothering you. I won’t tell anyone.”

“Thank you Vayu. You are my true friend.” Sarthak said and drank some water from his water bottle.

“Have you heard about Hudhud that recently hit Vizag coastline and has caused huge destruction.”

“Hudhud?” Vayu asked thoughtfully.

“Oh! Yes I remember. My father had told me that it is a type of tropical cyclone which is very intense and dangerous and mostly occurs in sea. But why are you asking?”

“You know what one of my cousin brothers was posted to Vizag by his company. On the day Hudhud hit Vizag he was in there only. And… And he lost his life Vayu due to the cyclone.” Sarthak said and started crying. “He was very nice Vayu. He used to love me a lot. I am not able to believe that he is no more.”

Vayu was in shock on hearing this. He hugged Sarthak and said, “Please don’t cry Sarthak. Everything will be fine. I know my words cannot cover your loss friend but I don’t know what should be said under such situations.”

“Hmmmmmm…..”

 “One thing I fail to understand. Our geography teacher says that cyclones, tornadoes are natural calamities. If they really are natural calamities why couldn’t God stop them from occurring? My mom says that God loves everyone then why these calamities occur?”

“Yes Vayu, you are right. I also fail to understand this. These calamities cause so much destruction but how are they actually formed? Is it really a natural phenomenon or something else? We should have asked our Geography teacher.” Sarthak said wiping his tears.

Bell rang indicating the end of lunch break. Everyone started moving towards their classes.

“C’mon Sarthak cheer up. Let us go to our class otherwise teacher will scold us.” Vayu took Sarthak inside the classroom.

At 2 o’ clock final bell rang and everyone packed their bags to go home.

On reaching home, Vayu saw that his father was engaged in some science project for his lab. Without saying a word he went to his room. His father saw this but ignored. When after 10 mins Vayu didn’t come out he went to his room and knocked the door.

Vayu opened the door and let his father come in.

“Vayu are you all right? Is there something disturbing you? Anything happened in school?” His father asked.

“Yes dad there is something which is disturbing me.” Vayu narrated the whole conversation he had with Sarthak that afternoon.

“Oh! Ok ok. You should not burden yourself with such things kid. C’mon take some rest and in the evening we will go to the town park. Ask Sarthak also to come along.” His father said and left the room.

Vayu just nodded and lied down on his bed not happy with his father’s response. He had thought his father will be able to explain the reason behind cyclones or tornadoes to him.

In the evening all of them went to the town park. Vayu’s father brought his laptop along with him. Vayu and Sarthak found a bench and sat down. Vayu’s father asked them to go and play like other kids meanwhile he will do some work. But none of them moved. It seemed as if they were not interested in anything. Vayu’s father then kept his laptop on the bench and took out a white paper.

“C’mon kids we will play something.”

None of them moved initially.

“Vayu come here and take this white paper from me.”

Vayu stood up least interested in the activity, went to his father and took the white paper.

“Ok now I hope you know how to make a paper plane. Can you please make one for me?”

Not understanding what his father was trying to do Vayu made a paper plane and gave it to his father.

“Very good Vayu, you have made a very nice plane. Now Sarthak could you come here please?”

“Sure Uncle.” Sarthak said and went to him.

“Hold this plate and stand 5 ft. away from Vayu.”

Sarthak did the same.

“Now Vayu take this paper plane and try to hit that plate.”

“What? It is so stupid to do this Dad. It is so easy.”

“If it’s easy then try it.” His father said.

Uninterested Vayu took the plane, aimed and threw it towards the plate. But to their surprise the plane didn’t even touched the plate rather it flew in different direction. Vayu looked towards Sarthak feeling embarrassed.

“What happen, Vayu? You said it was very easy. Ok, try it once again.” His father said with a smile.

Vayu again took the plane and aimed at the plate but this time he threw it with more force. Again the result was same. The plane flew away from the target. Both of the boys got confused and curious.

“Uncle what is happening? Why is Vayu not able to hit the plate even from a small distance?” Curious Sarthak asked.

“Because of Wind Sarthak. As you can see flowers are moving, leaves are moving and moreover our hairs are also moving. This is all because of a certain force present around us. And that is known as Wind. That is why when Vayu threw the plane the wind pushed it away because it is stronger than a paper plane.” Vayu’s father told them.

“Can you tell us more Dad?” Vayu requested his father. By now both the kids started showing interest.

“Yeah! Sure Vayu. Let us go to that pond.” Vayu’s father took them to the pond situated at the centre of the park.

“Now immerse your hand inside the pond completely and then bring it out. What did you notice?”

Vayu’s father asked Vayu.

“I felt as if something is pushing my hands down from top.” Surprised Vayu said.

“Correct. When you were trying to bring your hand out, water applied some pressure on your hand. Similarly like water air also presses our body with great force. But we never feel it because air presses our body from all sides and in turn our body exerts a counter pressure. This air pressure is present all around us. It changes with height and temperature. Ok now Sarthak you tell me have you ever seen anyone climbing a mountain or anyone diving deep in the sea?”

“Hmmm… Yes Uncle I have seen them on TV in Tom & Jerry cartoon where Tom wore a suit and jumped inside the water to catch Jerry.” Sarthak replied innocently.

“Ha ha ha! I didn’t know cartoons are so knowledgeable. That’s good. Do you know why Tom wore that suit?”

“No Uncle. Why?”

“Vayu can you tell us?”

“Nope.”

“Kids if Tom would have gone inside the sea without that suit he would have died.”

“Really? How?” Both of them asked in unison.

“Yes. This is because when one goes deep undersea the pressure increases tremendously that our body is unable to bear. In order to withstand that tremendous pressure that diving suit is very necessary. It also helps us to breath. Similarly a person climbing a mountain experiences a very low pressure. Hence, he also carries special equipments with him.”

“That means Dad on sea air pressure is high and on mountains it is low. Meaning air pressure decreases as we go up.” Vayu said.

“Brilliant Vayu. I am happy to know that you are so smart.” Vayu’s father said.

Vayu looked at Sarthak and smiled, feeling proud.

“Now let us consider two places in India. One is our place Chandigarh and the other let us take Simla in Himachal Pradesh. Can you tell me what the temperature in Chandigarh and Simla is? Which one is hotter?” Vayu’s father asked.

“Chandigarh is hot. Simla is cool.” Sarthak replied immediately.

“Very Good Sarthak. Now, in Chandigarh as the temperature is high the air gets heated up and hence rises up, creating a low pressure area. Whereas in Simla as the temperature is low the air gets cooled and heavy hence, it sinks down, creating a high pressure area. The air always moves from High pressure area to low pressure area. Hence, when there is snowfall in Simla we experience cold air here in Chandigarh as well.”

“But dad, why are you telling us about pressure? We had asked about wind not air pressure.” Vayu said getting curious.

“I know Vayu. I am coming to that only. So kids this movement of air from high pressure area to low pressure area is known as Wind. And it flows in all directions.”

Sarthak then started looking around in all directions. Something was disturbing him.

“What is it Sarthak? Do you want to ask something?” Vayu’s father said.

“One thing is bothering me Uncle. I looked around and saw that flowers are moving horizontally. Our hairs also move horizontally. The plane that Vayu threw also flew sideways. If wind flows in all the directions as you said then why don’t we experience it in vertical direction? Why didn’t the paper plane fly upwards?” Confused Sarthak asked.

“Ah! Very good observation Sarthak. It’s good you both are showing interest. But before answering the question I will tell you about some important forces which acts on air. One of them is Pressure Gradient Force and the other is Coriolis force. As I have told you earlier that the air pressure is different in different places. This difference in pressure produces a force. Hence, rate of change of pressure with distance is called Pressure Gradient. In turn this Pressure Gradient Force causes the air to move depicting the flow of wind. This force guides the wind to flow in various directions. Horizontal Pressure Gradients cause the wind to flow in horizontal direction and Vertical Pressure Gradient cause it to move in vertical direction. Now coming back to the question asked. When Pressure Gradient Force causes the wind to move up in vertical direction there is Gravitational Force, with which we are all aware of, that is caused by Earth’s Gravity, acts on the wind and tries to pull it down. This Gravitational Force is equal to the Vertical Pressure Gradient Force producing a Hydrostatic Balance or equilibrium. This is the reason we don’t experience wind in vertical direction. I hope you have got your answer Sarthak.”   

Sarthak gave a node in affirmative. With this Vayu’s father took out his mobile phone and started reading a text message he recently received. On reading the message he smiled and opened his laptop.

Vayu and Sarthak were discussing what they have learned today. After few minutes Vayu asked, “Dad what is Coriolis force? You didn’t tell about that.”

“I will explain about Coriolis effect after some time. Right now one of my friends from Canada has just sent me a message. He wants to talk to me on Skype. Let us talk to him. I will introduce you both to him. He is very nice. You will love him.”