Earth Science Module 7

Weather

Daily or hourly conditions- temperature, pressure, humidity, etc.

Climate

Average state of atmosphere over a region or interval of time- daily highs, prevalent winds, average rainfall

Atmospheric Composition

78% nitrogen, 21% oxygen, 1% argon, carbon dioxide, etc.

Conventional view of origin of atmosphere

Various gasses escape earth’s interior, volcanoes add gas, gasses added from comets and meteors, oxygen added after photosynthesis

Biblical view of origin of atmosphere

Created on day 2 of creation as God made the expanse in the middle of the waters (“waters above” at the edge of space; God made space on this day)

Air pressure

Measured by the height or a column of mercury in a tube. As air pressure changes, the height or the mercury will rise and fall

High pressure

Relatively nice and cloudless days

Low pressure

Stormy and cloudy weather

“Standard” pressure

1013.25 mb

Troposphere

Located between the surface and 18 km, temperature decreases with height, most surface weather is confined to this layer

Stratosphere

Located between 18 and 50 km, temperature increases with altitude due to absorption of UV

Mesosphere

Located between 50 and 90 km, temperature decreases with altitude

Thermosphere

Extends from 90 km to the edge of space, location of auroras (northern lights)

Temperature

Measure of the potential and kinetic energy of atoms and molecules (thermometer)

Heat

How much thermal energy is in something

Sensible heating

Energy flow that results in a temperature change

Latent heating

Energy flow that results in a phase change and no temperature change (melting ice, boiling water and turning it into water vapor)

Conduction

Transfer of energy due to collisions between adjacent molecules

Convection

Transfer of energy due to rising motion of less dense warm fluids (tea in a kettle)

Radiation

Transfer of energy de to electromagnetic wavers (heat rising from the kettle)

Daily cycle

Heating during the day increases temperature, which reaches a maximum at about 4pm

Latitude effect

Higher latitudes are colder because sunlight comes in at a lower angle and travels through more atmosphere before reaching the surface

Oceans

Tend to moderate temperatures (temperatures is more “even”)

Higher elevations

Experience colder temperatures

Areas with prevailing winds from the ocean

Have more moderate temperatures than those with prevailing winds from the continent

Vernal equinox

First day of spring, usually occurs on March 20th, sun directly over the equator, daylight and nightime are 12 hours

Summer solstice

First day of summer, usually occurs on June 21st, sun directly over Tropic of Cancer

Autumnal equinox

First day of fall, usually occurs on September 22nd, equal hours of daylight and night time

Winter solstice

First day of winter, usually occurs on December 21st, sun directly over Tropic of Capricorn

Albedo

The percentage of solar radiation reflected or scattered by a surface

Orographic barriers

Mountains, plateaus, can block air movement and create rain shadow deserts

Ocean currents

One of the most important factors in determining climate

Jet stream

Pattern that weather and storms tend to follow

Aristotle

Measuring climate based on temperature

Koppen

Climate based on vegetation types (A, B, C, D, E), strongly linked to temperature and precipitation patterns

Adiabatic lapse rate

The rate at which rising air cools assuming no energy transfer occurs with the surroundings. Dry air cools at a rate of 10°C/km and moist air cools at 6°C/km.

Adiabatic process

A process where there is no heat transfer into or out of a system.

Advection

Horizontal motion of air flow. This motion is driven by pressure differences and is in contrast to convection, which is vertical air flow due to density differences.

Aggregation

A precipitation growth process where individual ice crystals and snowflakes cling to each other.

Altocumulus

Middle level clouds that form globular patches. They are larger and thicker than cirrocumulus, but thinner and smaller than stratocumulus. These cloud occur and altitudes between 2400 and 6100 m.

Altostratus

Middle level clouds that form a uniform layer. These clouds are not thick enough to completely obscure the sun; however, transmitted sunlight is not bright enough to cast shadows These clouds occur at altitudes between 2400 and 6100 m.

Blizzard

Severe weather characterized by high winds and reduced visibility due to falling or blowing snow.

Breeze

A wind ranging between 7 and 50 kph. These winds are named for the location of their source, such as sea or land breeze.

Cirrostratus

High level clouds that form a thin layer and are composed of ice crystals. These clouds are semi-transparent allowing for strong sunlight transmission. Halo phenomena are associated with this type of cloud. These clouds occur at altitudes between 6000 and 12,000 m.

Cirrus

High level clouds that form fibrous whips sometimes called mare’s tails. These clouds are composed of ice crystals and occur at altitudes between 6000 and 12,000 m.

Cloud condensation nuclei (CCN)

Aerosol particles in the atmosphere that provide a surface upon which a water droplet or ice crystal can initiate growth.

Coalescence

A precipitation growth process where water droplets collide with each other resulting in one larger droplet.

Condensation

A phase change by which vapor becomes a liquid. During this process the vapor loses energy to the surroundings. This process is the opposite of evaporation. In the atmosphere this process results in the formation of dew.

Convergence

A measure of how much substance is approaching a location. In the atmosphere this corresponds to more air entering a region than leaving it horizontally. This is the opposite of divergence.

Coriolis effect

An apparent force due to the rotation of the earth. In the Northern Hemisphere any moving object veers to the right relative to the surface.

Cumulonimbus

A thick cloud with extensive vertical development. This cloud is associated with heavy rain or snow and lightning.

Cumulus

A low level globular cloud with a flat base and rounded top.

Deposition

A phase change by which vapor becomes a solid. During this process the vapor loses energy to the surroundings. In the atmosphere the process results in the formation of frost.

Dew point depression

The difference between air temperature and the dew point temperature.

Dew point temperature

The temperature at which air becomes saturates with water vapor. Any reduction in temperature below this value results in the condensation of water vapor into water droplets of dew.

Divergence

A measure of how much substance is leaving a location. In the atmosphere this corresponds to more air leaving a region that entering it horizontally. This is the opposite of convergence.

Drizzle

A form of precipitation that consists of water droplets smaller than 0.50 mm in diameter. These droplets fall slowly and are uniform in size.

Environmental lapse rate

The measured rate of temperature change in the atmosphere relative to altitude.

Evaporation

A phase change by which liquid becomes a vapor. During this process the liquid surface loses energy and may result in cooling.

Flurry

A light snow shower lasting a short period of time.

Fog

Small water droplets suspended near Earth’s surface that reduce visibility below 1 km.

Freezing rain

A form of precipitation that consists of water droplets striking sub-zero surfaces. The precipitation instantly freezes resulting in a thickening coat of ice.

Friction

A force that resists motion and tends to bring objects to rest.

Frost wedging

When water freezes it expands. It underground, the expanding ice can lift objects like roads, sidewalks and buildings.

Geostrophic wind

A horizontal flow of air that is parallel to straight isobars. This type of wind occurs away from Earth’s surface where friction has little effect. Resulting from a balance between the pressure gradient force and Coriolis Effect, this wind influences how weather patterns move across the country.

Gradient wind

A horizontal flow of air that is parallel to curved isobars. This type of wind occurs in the proximity of low and high pressure systems.

Hail

A form of precipitation that consist of balls or lumps of ice that are 5 mm in diameter or larger.

Halo

An optical phenomenon due to refraction through ice crystals. This results in a ring of color surrounding the sun at an angle of 22°. In dimmer light the color separation is not evident giving only a bright band of light around the moon.

Haze

Small particles suspended in the air that reduce clarity due to scattered light. If the particles are small enough they appear yellow against a light background. A haze does not reduce visibility as much as fog does.

High pressure system, anticyclone

A synoptic scale pressure system that consists of isobars surrounding a region of high pressure. In the Northern Hemisphere air circulates in a clockwise direction around the central high.

Hygrometer

A device used to measure water vapor content in the atmosphere.

Iridescence

An optical phenomenon due to diffraction by water drops or ice crystals in the atmosphere. This occurs near the edges of thin clouds and results in pastel colors.

Isobar

A line representing locations that have the same pressure value.

Lifting condensation level

The level in the atmosphere where lifted air reaches a relative humidity of 100%. Water vapor begins to condense at this level forming the flat base of a cumulus cloud.

Inversion

A location in the atmosphere where air temperature increases with altitude. This represents a region of very stable air.

Low pressure system, cyclone

A synoptic scale pressure system that consists of closed isobars surrounding a region of low pressure. In the Northern Hemisphere air circulates in a counterclockwise direction around the central low.

Nimbostratus

A low level could from which precipitation is falling. These clouds form a layer and give the sky a dark appearance.

Orographic forcing

A process that lifts air vertically due to the presence of large geographic features.

Precipitation

All liquid and solid forms of water that originate in the atmosphere and fall to the surface.

Parcel of air

An imaginary mass of air that has uniform properties and does not exchange energy or mix with its surroundings.

Pressure gradient force

A force resulting from a difference in pressure between two locations. If the pressure changes rapidly over distance, the pressure gradient force is large.

Psychrometer

A device used to measure humidity. It uses both a dry and wet bulb thermometer to determine how close the air is to saturation.

Radar

An instrument that transmits and measures radio waves to determine the range and reflective properties of distant objects.

Radiosonde

An instrument package used to measure properties of the atmosphere away from the surface. Most often it is attached to a free-flight ballon and data is transmitted to a ground station using radio waves.

Rain

A form of precipitation that consists of water droplets 0.50 mm in diameter or larger. These droplets can have a variety of sizes and can reach diameters of 5.0 mm.

Rainbow

An optical phenomenon resulting in an arc of colored light die to interaction with a large number of water droplets.

Rain gauge

An instrument used for measuring rain amounts.

Refraction

A change in direction of a propagated wave as it moves from one medium to another.

Relative humidity

The ratio of water vapor present in a volume of air compared to the saturation value at the same temperature.

Ridge

An elongated area of high atmospheric pressure. This is present in upper-air charts when warm air extends further north than usual in the Northern Hemisphere.

Riming

The process by which super-cooled water freezes on contact with an object. This contributes to the growth of hail stones, as well as the buildup of ice on aircraft.

Saturation

The condition where water vapor is in equilibrium with a flat surface of pure liquid water.

Scud

Ragged low-level clouds occurring below the main cloud base.

Showers

Precipitation coming from convective clouds that starts and stops suddenly and varies by location.

Sleet

A form of precipitation that consists of frozen water droplets. They are translucent and bounce when they hit the ground.

Snow

A form of precipitation that consists of single ice crystals that are hexagonal in shape or aggregations of crystals.

Sounding

A vertical measurement of the atmosphere’s properties. This is done with a radiosonde and contains measurement of temperature, humidity, pressure, wind direction and speed.

Stratus

A low level cloud that forms a uniform gray layer.

Sublimination

A phase change by which solid becomes a vapor. During this process the solid surface looses energy and may result in cooling. This is the opposite of deposition.

Subsidence

A sinking of the land surface.