The atmosphere is a layer of gasses and tiny particles. • The study of the atmosphere is called meteorology. • Studies weather and climate.
Weather is the general condition of the atmosphere and includes temperature, air movements, and moisture content. • The general weather conditions over many years is climate.
Composition of the Atmosphere • The atmosphere is a mixture of chemical elements and compounds. • The most abundant are carbon dioxide and water vapor. • Water vapor is added to the air by evaporation that comes from the oceans.
Moist air contains as much as 4% water vapor. • Dry air has less than 1%, • Ozone is important because it protects the earth’s inhabitants by absorbing UV rays. • Ozone has 3 oxygen atoms per molecule.
Oxygen in the Atmosphere • Animals bacteria and plants remove oxygen from the air as part of their life processes. • Living things, burning, and weathering would quickly use up most atmospheric oxygen if it were not for various processes that add oxygen to air. • Land and ocean plants produce large quantities of oxygen in daylight.
Oxygen is released as a product of photosynthesis. • The amount of oxygen produced each year equals that consumed by all processes. • The amount of oxygen in the air is in a state of balance and has not changed significantly over hundreds or thousands of years.
Nitrogen in the Atmosphere • The amount of nitrogen in the atmosphere is maintained through the nitrogen cycle. • Nitrogen moves from air to the soil, to plants and animals, and back again to the air. • Nitrogen is removed by nitrogen-fixing bacteria.
The bacteria change the nitrogen in the air to a compound in the soil that is vital to the growth of all plants. • Animals get nitrogen by eating plants and then return it to the soil via wastes.
Atmospheric Pressure • Due to the pull of gravity, 99% of the total mass of atmospheric gasses found within 32 km of the earth's surface. • There is less air at higher altitude. • The ratio of the force of the air to the area of the surface on which it presses is called atmospheric pressure.
There is less pressure at higher altitudes because there is less air. • The popping of the ears when driving through mountains or on a plane is due to the decreased air pressure on the outside of the eardrum. • When pressure equalizes the popping stops.
Mercurial Barometer • An instrument that measures atmospheric pressure is called a barometer. • In a mercurial barometer pressure presses on the liquid mercury. • The height varies with atmospheric pressure. • Standard atmopheric pressure = 760 mm of mercury or 1 atmosphere.
The average atmospheric pressure at sea level is 1 atmosphere. • Official weather maps measures air pressure in millibars (mb). • One millibar is equal to abouat .001 of standard atmospheric pressure.
Aneroid Barometer • The most common barometer used today is called an aneroid barometer and does not contain mercury. • Aneroid means without liquid. • When the atmospheric pressure increases the sides of the barometer bend inward.
An aneroid barometer can also measure altitude above sea level. • When it used for this purpose it is called an altimeter.
Special instruments are needed to record the temp. • Have recorded temps of more than 2000 C. • The lower region, 80 km – 550 km, is called the ionosphere. • The layers of ions in this layer can reflect radio waves back to earth.