Belfort Instrument Blog

Author: Ray J. Walberg

A very common proverb that is somewhat true is, no one does anything about the weather though everyone discusses about it. In fact it is one of the most common topic that people speculate and talk about. Millions of people look over the internet to know about the local and global weather and also weather hazards. All are curious about whether umbrella is required today or whether this weekend’s big game is going to be spoiled by rain or not.

If you stay on the Earth, weather is bound to affect you in diverse ways. The kind of house you stay in, the type of clothes you were, even the type of leisure activities and games you enjoy - all are determined by the weather.

Weather influences the nature of the soil on which we live. Even plants and animals adapt to various living conditions due to weather variations. Depending on their surrounding weather, plants adapt to survive in extreme dry or wet conditions. The shapes of their branches also depend on the prevailing weather. Similarly, the animals also get acclimatized to endure the extremities of their natural habitat.

Even though we cannot ‘do’ much regarding the weather conditions, our meticulous study about the weather helps sharpen our ability to predict the approaching weather conditions. The ability to accurately foresee the oncoming adverse weather conditions help to reduce the loss to the farmers as they can modify their farming practices according to the predicted weather.

Weather conditions vary depending on the form of the atmosphere of the earth. A feature unique to the atmosphere that surrounds our world is that it contains water vapor, and a temperature that maintains this water in three different forms - solid, liquid and gas.

Technically, the day to day changes in the atmosphere conditions is referred to as the weather. Different aspects of weather like the windspeed, humidity, temperature, type and amount of precipitation etc. are measured to give us an idea of what kind of conditions we face on earth.

The sun causes these atmospheric variations and determines the condition of the atmosphere based on the location on the globe. The temperature rises up and falls down faster in land areas than oceans. The Polar Regions receive less intense radiation from the sun than the equatorial regions.

The atmosphere is a massive complex phenomenon that wants to maintain an equilibrium of its own, in the same way like every other complicated systems. The cooler regions around the poles of the earth suck in the warm air from the equatorial regions. The rotation of the earth and the friction with the land also determines the movement of air. This whole system is contained within a small area by the gravity of the earth.

Complex patterns of low and high air pressure are caused because of the combination of a variety of factors like the geography of an area, the uneven heating, balancing force of the earth to even out the irregularities, and the gravitational and rotational forces. Different weather conditions are produced as result of interaction between these low and high air pressures with the ground.

Author: Leroy K. Calstard
We know that if the atmosphere did not exist, the earth would go without weather. Imagine for a moment for argument’s sake that the earth has an atmosphere indeed, as it is today, though the sun is absent. Absence of sun would mean absence of weather and that is not only because a frozen solid form the atmosphere will take. Actually the interaction between heat of the sun and our atmosphere builds air masses, while circulation patterns appear due to that. Pressure differences motivate air movements and wind is the end result of the same.

As in case of other materials, the air in the earth’s atmosphere is built of molecules that move about incessantly. Greater is the air pressure where denser concentration of molecules is found. Since air molecules are governed by gravity, the greatest air pressure is found nearest the earth’s surface and with altitude that decreases. The atmospheric pressure at sea level is about 14 and a half pounds on each square inch about which are normally not much conscious.

If air pressure is measured in hectopascals or millibars, normal air pressure ranges from 980 to 1040 hectopascals while on local conditions that is very much dependent.

At different speeds these molecules incessantly move while the speeds depend on temperature, lower the temperature slower is the peed and for higher temperature faster is the speed. The molecules speed up as a mass of air is heated and that results in expansion of air. The density of the molecules decreases as expansion takes place and thereby the air mass becomes lighter. The air mass that has become lighter starts rising now. Convection is the term for the entire process.

All through the world convection is going on constantly in the atmosphere. However neither regular nor uniform is the process. It depends on many local factors whether convection will take place, and if it does at all, how much that will be.

As air rises it cools. Therefore in due course the rising warm air masses get cooled down and to the ground that its starts sinking back. With the rise of air, low pressure results. High pressure is the result where it is sinking. As equilibrium is the goal of atmosphere, air moves from high pressure areas to low pressure ones. Wind is this very movement of air. More the difference between the high pressure and low pressure zones, more forceful winds would be the result.

An elliptical orbit the earth or the third rock from the sun follows and to complete that the time it takes is one year. The time to complete one orbit marks stretch of the earth’s year. Since elliptical is the earth’s orbit, in certain parts of the year it really comes closer to the sun. However that does not cause seasons even though more solar heat the earth receives then.

The earth’s movement is not limited to its travel through space in its own orbit, but it spins also on its axis like a top. In every 24-hour one spin it completes. Alteration between day and night is caused by the earth’s rotation. Weather conditions differ between day and night as is reflected in high and low temperatures and the effect of that is felt on weather patterns too.

On its axis the planet earth is tilted about 23 degrees and that causes really the change of seasons. Due to tilting different parts of the earth come closer to the sun as around the sun the earth travels in its orbit. Therefore during certain parts of the year different parts of the earth receive different amounts of heat.

In December the Northern Hemisphere receives less light since the North Pole is tilted away from the sun then. Thus the days become shorter there while the temperatures go down.

But as the earth moves on its orbit, North Pole comes close to the sun due to earth’s tilt. Till June 21 it continues to come closer to the sun and then the summer reaches its maximum. On that very day the sun is just above the Tropic of Cancer. Around the sun the earth continues to move until December 21 when the winter reaches its peak and the cycle is complete.

Just opposite are the seasons in the Southern Hemisphere even though the same cycle it experiences. In December the Southern Hemisphere is the closest to the sun and therefore it is summertime there. Quite logically June21 is the date marked for winter peak in the Southern Hemisphere.

The middle and high latitudes only, i.e., above 23.5 degrees north and below 23.5 degrees south, enjoy four seasons precisely. Normally for the tropics only wet and dry seasons are the two seasonal variations.