Who would question the reliability of the weather as a source of conversation? Weather regulates our lives by means of arbitrary powers that effect our dispositions, govern our health and in many cases dictates the character and extent of our worldly goods. The day's meteorological dish causes the foghorns to sound their mournful warnings or paints glowing sunsets in the western skies. Meager or bountiful crops are dependent upon its whims. We spring joyously from bed by the subtle command of a sunny morning, or we are herded into the office of our physician due to a penalty imposed because of our refusal to recognize its powers over our well being. Every cloud is indicative of the weather's moods. Great mountains crumble before the tools which weather uses in the work of continental sculpture. The presence of great forests or treeless plains are dependant upon its varied factors. Lightning flashes; snow falls, fog stealthily hobbles our movements on the trails, the highways, in the air or on the sea--yes, Old Jupiter Pluvious is a fickle, though relentless taskmaster. No wonder we speak about the weather. Yet, in spite of the fact that it approaches us so closely most of us rarely consider the causes of these phemonena or attempt at an understanding of them. We merely blame the weather man if what the day brings forth displeases us!
What causes our weather? Basically, the controlling force is the sun. The effects of its energy upon the globe--upon the land, sea and air--as it revolves and tips to give us alternate night and day and the seasonal variations in orderly sequence accounts for the general character of the weather. As the sun's energy varies so changes the temperature--air currents move about, clouds are formed or dispersed, air pressure changes. These and other related factors influence the state of our weather. But how does the energy of the sun do all this? First, in order to obtain the maximum energy of the sun its rays must strike the earth directly; they must be concentrated, and to be so concentrated the sun must be directly overhead (see diagram). We have summer, and consequently longer and warmer days, because the earth as it circles the sun on its great journey of 290 million miles around this celestial body leans so that the northern hemisphere is subjected to the more direct rays of the sun at that period. Likewise, we have winter because the reverse is true.
When the sun's rays strikes the earth obliquely their energy is disseminated over a wider area and does not warm our section of the globe as do the more direct summer rays. The same reasoning applies in the variation of temperature during the day. As the sun rises over the eastern horizon its rays strikes the earth at an angle. As it rises higher in the heavens the rays become more concentrated until at mid day they strike with their greatest force--their energy being concentrated in a comparatively smaller area. Then, as Old Sol sinks into the west they rays gradually become less concentrated and intense, and it becomes cooler again.
But the character of our weather is the result of more complex things than the shape of the earth of or its revolving and tipping. The sun's energy re-acts differently upon the land, sea and air and these differences introduce complex factors that account for the weather's many moods. Cool breezes that sweep from the sea, warm dry winds that sap moisture from the earth over which they pass, storms that bring us snow and sleet, billowy clouds in the sky or warm pleasant days that coax our gardens into unseasonal bloom--all these things can be readily understood if one seeks the weather's secrets. We'll try to explain some of these things in later issues of Nature Notes. Watch for them! (C.F.B.)
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