Understanding Earth’s Atmosphere, Weather, and Climate
Earth’s Atmosphere, Weather, and Climate
Troposphere
The troposphere is the lowest layer of the atmosphere, extending from the ground to an average height of 11 km. It contains approximately 80% of the atmosphere’s total mass of gases and 90% of its water vapor. This is where most meteorological phenomena occur, such as cloud formation, precipitation, and wind.
Other Atmospheric Layers
The other layers of the atmosphere include:
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
Unequal Distribution of Solar Energy
The unequal distribution of solar energy on Earth is due to two main factors:
- The terrestrial sphere (Earth’s spherical shape)
- The inclination of Earth’s axis of rotation
Earth’s Spherical Shape
If the Earth were flat, the sun’s rays would strike all locations at the same angle. However, because the Earth is a sphere:
- Solar radiation strikes different areas at different angles.
- The length of solar radiation’s path through the atmosphere varies.
Inclination of Earth’s Axis
The inclination of Earth’s axis has two primary consequences:
- Changes in the length of day and night
- Variations in the angle of incidence of sunlight
Thermal Lift
Thermal lift occurs when temperature decreases rapidly with increasing altitude.
Air Movement
Air has two basic types of movement:
- Vertical movement: Due to differences in density. Warm air is less dense and rises. As it rises into the higher, colder altitudes of the troposphere, it cools and descends.
- Horizontal movement: Air moves over the surface to fill the void left by rising hot air.
These two movements combine to form convection currents.
Isobars and Isotherms
Isobars are imaginary lines connecting points on Earth with the same atmospheric pressure, reduced to sea level, at a given time. The figures on isobars indicate atmospheric pressure in millibars.
Isotherms are curves connecting points on land with the same average air temperature over a given period. Sometimes, they represent areas with the same temperature at the instant of measurement.
Storms and Anticyclones
Storms originate in areas where warm air rises. If moisture is present, clouds form upon cooling.
Anticyclones bring stable and sunny weather.
Fronts
A front is the boundary between two air masses of different temperatures. When a front passes over a continent, it usually causes changes in the weather.
Effect of the Hydrosphere
The hydrosphere has a regulatory effect on climate due to water’s ability to store and transfer energy, and to absorb or release it depending on the temperature. This effect helps to:
- Maintain a stable greenhouse effect: Water vapor increases with evaporation, and atmospheric carbon dioxide decreases as it is consumed by phytoplankton.
- Redistribute the planet’s heat and dampen climatic variations.
Ocean currents play a role in the exchange of heat between the poles and the equator. Warm currents moderate the extreme conditions of polar coasts, while cold currents mitigate the heat of tropical regions.
Greenhouse Effect
Natural Greenhouse Effect
The natural greenhouse effect occurs due to the presence of CO2 and water vapor in the atmosphere. Without it, life as we know it could not exist on Earth.
Induced Greenhouse Effect
The induced greenhouse effect is caused by human activities that generate greenhouse gases, including:
- Burning of fossil fuels
- Intestinal fermentation
- Combustion of biomass
- Emissions of nitrogen oxide from nitrogen fertilizers
Effects of Increased Greenhouse Gases
Increased greenhouse gases can lead to:
- Decreased icy surface of the polar caps
- Increased frequency of meteorological phenomena
- Water shortages affecting approximately 3 billion people
- Loss of tropical forests