Introduction to Meteorology

• The earth is surrounded by a large envelope of gases known as the atmosphere.
• The conditions of the atmosphere and its changes influence all physical, chemical and biological activities on earth.
• Meteorology is the science of weather and includes the study of atmospheric phenomena in modern usage.
• Meteorology is defined as the science that deals with the study of the atmosphere.

Divisions of Meteorology

• Marine meteorology relates to the sea and ocean.
• Aeronomy investigates the chemical and physical properties of the atmosphere and the changes that occur as a result of external and internal forces.
• Bio-meteorology studies the interactions between living organisms and their atmospheric environment, called biometeorology.

Weather

• Weather refers to short period variation in the atmosphere at a given place.
• Weather at any place is defined as the momentary condition of the atmosphere.
• The variables that determine the condition of the atmosphere include temperature, pressure, humidity, rainfall, and wind.
• Temperature is the most basic and fundamental weather element.
• Changes in temperature cause changes in the other weather elements.

Troposphere

• In the troposphere, temperature decreases with altitude from the surface upwards.

Stratosphere

• Above the troposphere is an isothermal layer followed by a region of inversion extending up to nearly 50km called the stratosphere.

Thermosphere

• Temperatures rise rapidly above the mesopause, reaching nearly 1000°C by about 300km in the thermosphere.

Mesosphere

• Above the stratosphere is the mesosphere that extends from roughly 50 to 80km.
• The temperature in the mesosphere decreases with altitude, lowering to about -95°C at the mesopause around 80km.

Exosphere

• The lighter gases, hydrogen and helium, slowly become free of the earth's gravitational field and escape to space by about 600km in the exosphere.
• The exosphere gradually merges into interplanetary space.

Gases

• The atmosphere consists mainly of nitrogen and oxygen.
• The proportion of gases in the atmosphere by volume is 78% nitrogen, 21% oxygen, and 1% other gases.
• The remaining 1% is made up of small amounts of argon, carbon dioxide, neon, helium, krypton, xenon, hydrogen, and traces of ozone, methane, sulphur dioxide, and nitrogen oxides.

Water Vapor

• Water vapor is present in varying proportions in the atmosphere.
• The moisture content varies depending on latitude, temperature, wind, and atmospheric systems.
• Water vapor decreases as altitude increases.

Aerosols

• Atmospheric aerosols are a suspension of fine solid and liquid particles in the atmosphere.
• Aerosols range from dust and smoke to mists, smogs, and haze.
• Aerosols can result from volcanic eruptions or dust storms as well as from human activities and pollution.