Q1.
Consider two hypothetical Earth-sized planets that have an atmosphere. Assume that one planet is entirely covered by oceans and the other is entirely by land. Knowing that the Sun heats the equator more than the poles, how would the wind patterns on these planets compare with the wind systems we observe on Earth, with its combination of land and sea?
Answer
Both planets would still have the great equator-to-pole circulation, because that is caused by latitude and by the Earth's rotation. What they would lose is everything that depends on land and sea lying side by side — sea breezes, land breezes, and above all the monsoon.
| All-ocean planet | All-land planet | The real Earth | |
|---|---|---|---|
| Pressure belts and planetary winds | Present — smooth, unbroken belts right round the planet | Present — but far more violent, because land heats and cools fast | Present, but broken up by continents |
| Daily and seasonal temperature swing | Very small — water has a huge heat capacity and stores heat | Very large — land has a small heat capacity, so it heats and cools quickly | Intermediate; coasts mild, interiors extreme |
| Land and sea breezes | None — no coast exists | None — no sea exists | Present all along the coasts |
| Monsoon | None | None | Present — driven by the land heating faster than the sea in summer |
| Water cycle and rainfall | Abundant evaporation and rain everywhere | Almost no evaporation source — a desert planet, dry and dusty | Uneven; wet coasts, dry interiors |
| Ocean currents | Strong, uninterrupted — no continents to block or redirect them | None at all | Bent into gyres by rotation and blocked by continents |
The reasoning:
- What survives on both planets. Unequal heating between equator and poles still creates the equatorial low and the sub-tropical highs, and the planet's rotation still deflects the winds — to the right in the Northern Hemisphere and to the left in the Southern. So planetary winds exist on both.
- What disappears. The chapter says local winds and the land–sea breeze arise from "uneven heating of land and water". Remove one of the two and the mechanism has nothing to work with. India's southwest monsoon is a giant seasonal sea breeze — so an all-ocean or an all-land planet has no monsoon at all.
- Why the all-land planet is stormier. Land has a much smaller heat capacity than water. It heats fiercely by day and cools sharply at night, so pressure differences build faster and winds are stronger and gustier — with dust storms rather than rain storms, since there is little water to evaporate.
- Why the all-ocean planet is calmer but wetter. Water resists temperature change, so pressure gradients build slowly and the winds are steadier. But evaporation is everywhere, so cloud and rainfall are abundant and the currents run unbroken around the globe.
Sample conclusion to write: "Latitude and rotation set up the planetary wind belts on any rotating, heated planet. The contrast between land and sea sets up the regional and local winds. Earth has both, which is why its wind systems are the most varied of the three."