Peter Yovu, age 15, of Staten Island, n.y., for his question:

What causes the region of doldrums?

The word doldrums means dullness. It was used by the mariners of old sailing ships to name the region of calm air near the equator. Our meteorologists, however, suspect that some features of the region are far from calm. For it is the breeding place of tropical hurricanes.

The system of prevailing winds circles the planet in we11 worn paths between the equator and the poles. One of the trickiest circles is the region of doldrums that shifts north and south of the equator with the seasons. The prevailing trade winds blow toward the equator from latitudes 30 degrees north and south. They come from the northeast and the southeast, and the zone of doldrums occurs where you would expect the two wind belts to meet in a head on collision.

This region at or near the equator is heated by a steady diet of daily sunshine from directly overhead. The strips of land and the vast stretches of ocean below heat the air above them. Currents of this light, warm air expand and stream upward. For days and often for week after weary week the surface weather is deadly calm.. No breath of wind ruff1es the sail of a ship.

Then a brood of gusty breezes may arise, puffing from this way and that. Along spell of deadly calm is just as likely to end with a pelting shower or an even more violent storm. These sudden heavy downpours in the doldrums produce a heavy annual rainfall.

Throughout the year the sun moves north and south between the tropics of capricorn and cancer and the zone of doldrums follows the sun. When the noon sun is directly overhead, currents of light, warm air ascend from the surface. This occurs in late June above the tropic of cancer, in late September above the tropic of Capricorn and above the equator in March and September. The calm doldrum belt that separates the converging trade winds varies in width and sways north and south with the seasons between the two Tropics.

Sometimes the trade winds invade the doldrums and meet in a clash of spiraling winds. Our hurricane season starts in the summer, when the southeast trades are likely to cross the equator and tangle with the northeast trades of the northern hemisphere. These conflicts, we suspect, may contribute to the birth of the raging hurricanes that later move on to batter their way northward.

The prevailing winds are twisted in opposite directions in the two hemispheres. This twisting is caused by the rotation of the round globe, and it does not occur at the equator. Here the converging trades do not form pockets of spiraling winds, and no hurricanes are born above the wide waist of the world. Our hurricanes are born when the belt of doldrums moves north of the equator. In the southern hemisphere the hurricane season starts when the doldrums belt migrates south of the equator.