The different types of tropical storms

A storm at sea can be spectacular – seen from a safe distance. As the wind passes over the water’s surface it creates waves. But if the force of the wind is strong, powerful waves are generated, gathering momentum until a barrier in their path causes then to break will full force.

Not all winds are of equal height. This is partly because the wind seldom blows at a constant speed. When the wind dies down, wave length is maintained but wave height decreases gradually. Where there is no barriers in their path, waves crests may carry over vast distances. When waves created in different places come together, they produce a confused sea state. Boats may be completely overwhelmed by a storm at sea – getting swamped, smashed, or both, by the huge quantity of water falling on them.

The full force of a wave is not realized until it reaches the shore. As it sweeps in towards land, contact with the sea-bed slows down the lower part, but the wind keeps the top moving on. The wave becomes steeper, begins to overhang, and finally crashes down. On steep shores, waves do not have time to slow down. Suddenly, their way is barred and they smash against the rocks with tremendous force – 100 tonnes per square metre is not unusual.

Spinning destruction

Winds exceeding Force 12 (over 117km/h) can devastate anything that lies in their path. They are known as hurricanes in the Atlantic, typhoons in the North Pacific and cyclones in the Indian Ocean and around Australia. These great storms start when scattered cloud clusters of tropical thunderstorms are gathered together into a whirling spiral by the Earth’s rotation. At the centre of the spiral is a column lo low pressure – the eye.

Because of the low pressure, air is sucked into the spiral with great force, resulting in violent winds. These set up huge waves at sea, which have devastating effects. Hurricanes may persist for up to ten days, and although the path they will follow can be predicted to some extent, unexpected twists and turns are common.

A water spout is another example of the sea being whipped up. This is rather like a liquid tornado. Warm air rising from the sea creates a central column of low pressure which draws up a swirling rising wall of water. When a low pressure system – depression – passes quickly across the sea, the water level suddenly drops, then rises. A great swell is created, knows as a storm surge, which can flood huge areas as it hits land.

Tsunamis

Just as terrifying as rough seas, are tsunamis, caused by earthquakes and volcanic eruptions in the ocean. Small earthquakes occur along the ocean ridges, where the Earth’s crust in thin and hot. The largest ones are along the lines of collision of the plates.

The quake lifts the ocean floor, which buckles and collapses, and the shock tremors suddenly move the whole mass of water above, right from the ocean floor to the surface. As the tremors radiant outwards, the tsunami sweeps across the ocean at a terrifying speed of up to 720 km/h. At first, tsunamis are very small and may not be noticed in the open sea. However, as they come to shallower water, they are slowed down by the drag of the sea-bed and the waves build into a vast wall of water with an awesome power for destruction. They hit the coastline with a tremendous force. Boats are thrown high up on the shore, land is filled with sea water and houses destroyed.

Source :Helium.com

Blue whales can eat half a million calories in a single mouthful

The blue whale is the largest animal that has ever lived. Ironically, it sustains its massive bulk by eating some of the smallest creatures in the ocean – krill. A foraging whale lunges into a swarm of these shrimp-like animals, accelerating to high speed with its mouth open at a right angle. Pushed back by the rush of water, its mouth expands and its tongue (itself the size of an elephant) inverts to create more room.

The whale engulfs up to 110 tonnes of water and any krill within is filtered out and swallowed.

There’s every reason to think that filtering out small prey is an incredibly efficient way of feeding. The largest fish, both living (the whale shark and basking shark) and extinct (Leedsichthys), are all filter-feeders.

 And the biggest of the whales – the blue and fin – both use this technique. But no one has ever put the reputed efficiency of filter-feeding to the test, by calculating how much energy a blue whale spends on its lunges and how much it gets in return. Jeremy Goldbogen at the University of British Columbia is the first.

Goldbogen tagged 265 blue whales off the coast of California and Mexico, attaching recording devices to their backs when they surface. The data-loggers recorded the whales’ position, their acceleration, and the noise and pressure of the surrounding water. The noise was important – by measuring the sound of water rushing past the animal, Goldbergen could work out how fast it was travelling.

In total, he managed to record over 650 feeding lunges. On each one, the whale accelerates to a top speed of 8 miles per hour in less than a minute. If that seems low, bear in mind that this is an animal that weighs 180 tonnes; for comparison, Michael Phelps swam the 100m butterfly at a measly 4.4mph. Every attempt costs a huge amount of energy, around 770 to 1900 calories. Worse still, the water that rushes into the whale’s mouth produces so much drag that it grinds to a virtual halt. To lunge again, the whale needs to build up speed from a standstill, and it will do so around three or four times on a single ten-minute dive.

Nonetheless, when Goldbogen plugged the data from his recorders into a simulation of a feeding whale, he found that the lunge is staggeringly efficient. Despite the massive outlay in energy, the whale easily recoups anywhere from 6 to 240 times that amount, depending on how big it is and how tightly packed its krill targets are.
If a big whale attacks a particularly dense swarm, it can swallow up to 500 kilograms of krill, eating 457,000 calories in a single monster mouthful and getting back almost 200 times the amount it burned in the attempt. A smaller whale lunging at a sparse collection of krill would only get around 8,000 calories, but that’s still 8 times more than what it burned. Even when Goldbogen accounted for the energy needed to dive in search of prey, the whales still regained 3 to 90 times as much energy as they spent.

For comparison, sea otters get around 4 calories for every one they burn, and Weddell seals get around 10. If blue whales happen across a particularly thick glut of prey, their feeding efficiency is about ten times greater than for any other sea-going mammal.

All of these record-breaking numbers are probably a pale shadow of the true efficiency of a hunting whale, because he was being fairly conservative about the krill in his simulations. Photographs of krill suggest that these animals can gather in swarms a hundred (or even a thousand) times greater than those that Goldbogen used. If a whale swam into one of these swarms with mouth agape, it might even recover 1000 times more energy than it spent.

An efficient lifestyle is a big boon to the blue whale. Every year, it migrates from rich feeding areas close to the pole to relatively poorer mating areas towards the equator. If it’s to survive, it needs to feed as effectively as it can during the summer to build up a thick layer of blubbery reserves to fuel it through the harsh food-starved winter.

Reference: Journal of Experimental Biology