Nearly all the atmosphere is confined to a thin shell surrounding Earth. The atmosphere is a mixture of gases, including nitrogen and oxygen with small amounts of water vapor, carbon dioxide, and other trace gases. The atmosphere is stratified into layers, each having distinct properties. Nearly all weather occurs in the lowest layer of the atmosphere.
The majority of the lithosphere is covered by a relatively thin layer of water called the hydrosphere.
Water circulates through the atmosphere, lithosphere, and hydrosphere in what is known as the water cycle.
Weather describes the conditions of the atmosphere at a given location for a short period of time.
Climate is the characteristic weather that prevails from season to season and year to year.
The uneven heating of Earth's surface is the cause of weather.
Air masses form when air remains nearly stationary over a large section of Earth's surface and takes on the conditions of temperature and humidity from that location. Weather conditions at a location are determined primarily by temperature, humidity, and pressure of air masses over that location.
Most local weather condition changes are caused by movement of air masses.
The movement of air masses is determined by prevailing winds and upper air currents.
Fronts are boundaries between air masses. Precipitation is likely to occur at these boundaries.
High-pressure systems generally bring fair weather. Low-pressure systems usually bring cloudy, unstable conditions. The general movement of highs and lows is from west to east across the United States.
Hazardous weather conditions include thunderstorms, tornadoes, hurricanes, ice storms, and blizzards. Humans can prepare for and respond to these conditions if given sufficient warning.
Substances enter the atmosphere naturally and from human activity. Some of these substances include dust from volcanic eruptions and greenhouse gases such as carbon dioxide, methane, and water vapor. These substances can affect weather, climate, and living things.
Earth systems have internal and external sources of energy, both of which create heat.
The transfer of heat energy within the atmosphere, the hydrosphere, and Earth's interior results in the formation of regions of different densities. These density differences result in motion.
Weather patterns become evident when weather variables are observed, measured, and recorded. These variables include air temperature, air pressure, moisture (relative humidity and dewpoint), precipitation (rain, snow, hail, sleet, etc.), wind speed and direction, and cloud cover.
Weather variables are measured using instruments such as thermometers, barometers, psychrometers, precipitation gauges, anemometers, and wind vanes.
temperature and humidity affect air pressure and probability of precipitation
air pressure gradient controls wind velocity
Air temperature, dewpoint, cloud formation, and precipitation are affected by the expansion and contraction of air due to vertical atmospheric movement.
Weather variables can be represented in a variety of formats including radar and satellite images, weather maps (including station models, isobars, and fronts), atmospheric cross-sections, and computer models.
Atmospheric moisture, temperature and pressure distributions; jet streams, wind; air masses and frontal boundaries; and the movement of cyclonic systems and associated tornadoes, thunderstorms, and hurricanes occur in observable patterns. Loss of property, personal injury, and loss of life can be reduced by effective emergency preparedness.
Seasonal changes can be explained using concepts of density and heat energy. These changes include the shifting of global temperature zones, the shifting of planetary wind and ocean current patterns, the occurrence of monsoons, hurricanes, flooding, and severe weather.
the intensity caused by differences in atmospheric transparency and angle of incidence which vary with time of day, latitude, and season
characteristics of the materials absorbing the energy such as color, texture, transparency, state of matter, and specific heat
duration, which varies with seasons and latitude.
Heating of Earth's surface and atmosphere by the Sun drives convection within the atmosphere and oceans, producing winds and ocean currents.
natural events such as El Nino and volcanic eruptions
human influences including deforestation, urbanization, and the production of greenhouse gases such as carbon dioxide and methane.