Earth gases {atmosphere, Earth} are five miles thick at poles and ten miles thick at equator. Carbon dioxide and water absorb infrared radiation. Ground absorbs infrared, because it has water and wet dirt. Atmosphere layers are troposphere, tropopause, stratosphere, mesosphere, D layer, E layer, ionosphere, F layer, G layer, exosphere, and magnetosphere.
Warm air can flow and warm cold air {advection radiation}.
Jet airplanes leave water-drop or ice-drop white lines {contrail}|.
sky {firmament}|.
If sunlight from behind observer hits air water droplets, droplets act like prisms and spread sunlight into color spectrum {rainbow}|.
sky {welkin}.
Water vapor can condense on sea salt, dust, smoke particles, volcanic ash, or nitrous oxide, to make drops one millionth raindrop size {cloud}|. Nitrous oxide forms by lightning. Tiny drops coalesce. When big enough, they drop. Fine raindrops come from low clouds, and big raindrops come from high or thick clouds. Clouds are white if water density is small and are dark if water density is great. Cloud shapes depend on fronts that make them.
Cloud-cover lower side has altitude {ceiling}|. Above ceiling is limited visibility.
Light and dark clouds {mackerel sky, cloud}| indicate rain.
Upper-atmosphere dust and clouds reflect 30% of solar energy {reflectance, atmosphere}. Ozone, dust, and clouds absorb 20%. Ground absorbs 50%.
Dry ice and silver iodide crystals {seeding}| in clouds can cause rain or reduce fog.
Cold fronts can make dark-cloud lines {squall line}|, from which can come tornados or waterspouts.
Warm front first makes cirrus clouds, then cirrostratus clouds, then gray clouds {altostratus cloud}, and then nimbostratus clouds.
Warm front first makes cirrus clouds, then wispy clouds {cirrostratus cloud}, then altostratus clouds, and then nimbostratus clouds.
Clouds {cirrus cloud}| can be white, feathery, and 4 to 8 miles high.
Cold front first makes high and thick clouds {cumulonimbus cloud} and later makes dark, low clouds and small strong storms.
Clouds {cumulus cloud}| can be billowy, deep, fluffy, white, and one mile high.
Warm front first makes cirrus clouds, then cirrostratus clouds, then altostratus clouds, and then low, thick, dark clouds {nimbostratus cloud} with broad light rain.
Clouds {nimbus cloud}| can be gray or dark.
Clouds {stratus cloud}| can be flat, scattered, low or high, and white or gray.
Mirages {fata morgana}| can be high in sky, unrelated to surface conditions.
Brilliant green or blue light {green flash}| can flash at sunset, by prism effect. Prism effects cause Sun to appear flattened and/or irregular on horizon.
Atmosphere refraction bends light rays, so light seems to come from ground {mirage}|, instead of from sky. Temperature differences, with hotter air closer to ground, cause mirages.
Still warm-air layer can lie under cool air {air inversion}|.
Humid air can cool to temperature {dew point} at which water condenses.
Water can condense on ground {dew}|, instead of in air, when ground is cooler than air, often after midnight on still autumn nights.
In air inversion, ground can lose heat by radiation at night and condense water {fog}| from warm air. Warm air cooled by rain can condense water and make fog.
Dew {frost}| can freeze.
Frost {hoarfrost}| can form on artificial surfaces.
Air layer {troposphere} next to surface has 3/4 of all air and has all clouds, dust, wind, and storms. Surface pressure is 15 lb/in^2. Average surface temperature is 63 F. At troposphere top, temperature is -60 F to -100 F. Troposphere is 78% nitrogen, 21% oxygen, 2% average water vapor, 0.9% argon, and 0.03% carbon dioxide. On hot humid days, water vapor can be 3% or 4%.
Above troposphere is a boundary layer {tropopause}.
Above tropopause, a 10-to-15-mile-thick layer {stratosphere}| has temperature -60 F to -100 F. Lower part is sulfate layer. Higher part is ozone layer. Ozone absorbs ultraviolet rays from Sun.
Above stratosphere, a 25-to-35-mile-thick layer {mesosphere} has temperature 50 F.
Above mesosphere is an ionized boundary layer {D layer}.
Above D layer is a dust belt {noctilucent cloud}, with high thin clouds visible at night.
Above dust belt is an ionized boundary layer {E layer} {Heaviside layer}.
Above E layer, a 300-to-550-mile thick layer {ionosphere} has temperature 2000 F. It contains mostly oxygen ionized by x-rays and ultraviolet rays. It reflects short-wave radio waves.
In ionosphere is an ionized layer {F layer}.
Above ionosphere is an ionized boundary layer {G layer}.
Above G layer {exosphere} contains mostly helium for 900 miles and then mostly hydrogen for 4000 miles and has magnetosphere.
Electric discharges {lightning}| can go between clouds or between clouds and ground. Strength can be 10^8 volts. Lightning strikes 44,000 times a day and makes 200 forest fires a day. Lightning can be streaks or sheets. Rare lightning form is hot ionized gas {ball lightning}. Lightning makes nitrous oxide, which fertilizes soil.
process
As warm air rushes up and raindrops fall, they rub each other and separate charges, making voltage. If charge path is between cloud and ground or another cloud, first a thin current streak {leader, lightning} flows, followed by main discharge at more than 1000 amperes for 10^-2 seconds.
Metal conductors {lightning rod}| can conduct lightning current into ground, to dissipate it.
Lightning heats air suddenly and expands it rapidly, making noise {thunder}| as shock waves. People can hear thunder up to 15 kilometers away.
Lightning can make radio waves {whistler}| that strike magnetosphere and come back along magnetic-force lines. High frequencies come back first, followed by low frequencies.
Lightning {blue jet} can flash between upper clouds and ionosphere, 44 to 50 miles away, in tree-like structure.
Far-away lightning reflections {heat lightning} can be on horizon clouds on hot summer evenings. Thunder is too far away to hear.
Lightning can cause mushroom-shaped flashes {red sprite} in ionosphere.
Water returns to ground from clouds as rain, sleet, hail, or snow {precipitation, weather}|. Pressure changes and wind surges cause storms in tropics. Above tropics, fronts cause precipitation.
Yearly rainfall {rain}| averages 30 inches per year. Sea precipitation averages 44 inches per year. Land precipitation averages 26 inches per year. 25% goes into rivers, and 75% is on land.
When frozen raindrops pass through thunderstorm, they {hail}| pick up snow and ice.
When raindrops pass through very cold air, they {sleet}| can freeze.
If clouds are 0 C, snowflakes {snow, precipitation} form. Snowflakes have thin surface unfrozen-water film, which makes them stick to other snowflakes in special ways. That is why snowflakes are always hexagons. Snow can fall only above latitude 30 degrees. One foot of snow equals one inch of rain.
water-saturation percentage {aridity}|.
Air water decreases with humidity and increases with temperature and wind speed {evaporation}|. Latitudes from 10 to 40 degrees have more evaporation than precipitation, and lose heat. Other latitudes have more precipitation than evaporation, and gain heat. Oceans have more evaporation than precipitation. Land has more precipitation than evaporation.
Air can hold variable water amounts {humidity}|. Water in air is 0% to 4%.
measurement
Humidity can be water mass in air mass {specific humidity}. It can be water mass in air volume {absolute humidity}. It can be water vapor mass compared to maximum amount possible at that temperature and pressure, expressed in percent {relative humidity}.
levels
Relative humidity is most comfortable at 50%. High humidity makes cold air feel colder and warm air feel warmer. High temperatures feel cooler if humidity is lower. Higher humidity makes temperature feel higher or lower, because water does not evaporate from skin as easily.
altitude
Humidity is highest at surface and decreases greatly with altitude.
latitude
Humidity is highest at equator and decreases toward poles.
time of day
Humidity increases at night as air cools. Humid air can cool to dew point.
air pressure
More water in air makes lower air pressure, because water molecules weigh less than average air molecule. Wet days have low air pressure. Dry days have high air pressure.
Human-hair-length change {hygrometer}| can measure humidity.
Signs {weather sign} that forecast fair weather are evening rainbow or deep-blue sky color, even between clouds. Signs that forecast rain are gray and lowering sunset, green or yellow-green sky at sunset, red sunrise with clouds lowering later, sun dog around Sun or Moon after fine weather, morning rainbow, or sky whiteness. Clouds that look like lenses indicate high winds. Light and dark clouds {mackerel sky, weather} indicate rain. Low dark clouds indicate stormy weather.
Prolonged air contact with surface gives air {air mass}| same temperature and humidity as surface. Air masses {tropical mass} over Sahara Desert are warm and dry. Tropical masses in tropics are warm and wet. Air masses {polar mass} over plains of Canada or Siberia are cold and dry. Cold air masses make high pressure. High-pressure air masses can stay offshore, blocking east-west wind flow.
Atmosphere pressure {air pressure}| depends on temperature, water content, friction, centrifugal force, and flow. Cooler air has higher pressure. Spinning air can have higher pressure. Air with less water has higher pressure. Air blocked by mountains has higher pressure. Air-pressure patterns vary by latitude. High-pressure swirling cells are more near poles and in subtropics. Low-pressure cells are more in temperate zones.
Difference, between average daily temperature and 20 C, times number of days in month {degree-day}, directly relates to fuel to use to keep warm.
Warm air mass makes low pressure {depression, atmosphere}|, because it is less dense than cold air.
Weather forecasting {meteorology}| depends on atmosphere, humidity, pressure, and wind photographs and measurements.
A halo {sun dog}| around Sun or Moon after fine weather forecasts rain.
Weather maps {weather map} {map, weather} can show isotherms and isobars.
Equal-pressure points {isobar} can be on weather maps.
Equal-temperature points {isotherm} can be on weather maps.
Temperature differences cause air movement {wind}|. Hot air rises, and cool air falls.
mountains
Wind goes up mountains by day, because top heats first, and goes down by night, because top cools first.
land and sea
During day, wind goes from sea to land, as land heats first and air rises from it. At night, wind goes from land to sea, because water's high heat capacity causes sea to stay warmer longer.
ocean
Jet streams and polar winds make oceans flow clockwise in Northern Hemisphere and counterclockwise in Southern Hemisphere, making west coasts dry near equator and wet near pole, and east coasts humid, with big storms.
Earth rotation
Warm air at equator rises and flows toward poles under tropopause. Cold air at poles stays near ground and moves toward equator. Earth rotation makes air at surface flow from east to west in Arctic and east to west in equatorial zone.
Equatorial hot air rises and flows north as cold air from north slides under it, while spinning Earth spins these masses clockwise in Northern Hemisphere and counterclockwise in Southern Hemisphere. Middle, temperate latitudes have no steady surface winds but usually two or three great swirls, with eddies.
Tropical-cyclone wind speed has score 0 to 12 {Beaufort scale}|, or 0 to 17, for 0 to 200 miles per hour.
High-pressure swirls {cell, air}| are more near poles and in subtropics. Low-pressure cells are more in temperate zones.
Earth rotation causes {Coriolis force} air-spin direction.
Tropical-cyclone centers {eye, storm}| are calm and several kilometers wide.
Cold-air mass and warm-air mass can contact {front, air}| when air masses start to move. Polar easterlies can meet southern westerlies {polar front}. At fronts, warm air rises and cools to make clouds and precipitation.
Cold air can replace warm air {cold front}|, or cold-air masses can move into regions. Cold fronts bring rolling dark clouds and lightning, moving fast and steep, as cold air tunnels under warm air, with hard rain. Cold fronts first make cumulonimbus clouds and later make dark low clouds and small strong storms. Cold fronts can make squall lines, from which can come tornados.
Warm air masses can move into regions {warm front}|. Warm fronts first bring high clouds, because warm air goes over cold-air top, and then low clouds, moving slow and long with steady rain. Warm fronts first make cirrus clouds, then cirrostratus clouds, then altostratus clouds, and then nimbostratus clouds, with broad light rain.
Objects can be downwind {leeward}|.
Objects can be upwind {windward}|.
Winds go clockwise around high-pressure region near Azores. Winds {Arctic Oscillation} (AO) go counterclockwise around low-pressure region near Iceland. If low pressure is very low, north Europe, north Asia, and Alaska receive warm wind, and Greenland, east Canada, and south Europe receive cold wind.
Yugoslavia mountains make cold air {bora} that flows to Adriatic Sea.
Warm winds {brickfielder} can be in Australia.
Squalls {bull's eye squall} can be at Cape of Good Hope.
Strong winds {buran} can be in Russia.
Warm day winds {chinook}| can come down east Rocky Mountains, because that side receives no sunlight and is cool.
Warm air surrounded by cold air rises and spins counterclockwise {cyclone}| in Northern Hemisphere or clockwise in Southern Hemisphere. Earth rotation causes spin direction. Warm air can hold more water than cold air. As warm moist air rises, it cools and condenses water, causing precipitation.
anticyclone
If surrounded by warm air, cold air falls and spins clockwise {anticyclone} in Northern Hemisphere or counterclockwise in Southern Hemisphere. Cold air is drier, so as it rises, it causes clear skies.
density
In Northern Hemisphere, warm air goes north to cooler regions and rises, because it is less dense, and cool air goes south to warmer regions and falls, because it is more dense. Moving air masses can cause air to swirl counterclockwise or clockwise. Cyclone makes warmer, wetter air rise, causing low pressure and wet days. Anti-cyclones make colder, dryer air fall, causing high pressure and dry days.
West winds {datoo} can be in Gibraltar.
Just north or south of equator {doldrums}|, winds are weak.
Cool Greek winds {etesian} can blow in summer.
Warm day winds {foehm} can come down north Alps, because that side receives no sunlight and is cool.
strong Swedish wind {frisk vind}.
From 25 to 30 degrees south latitude or north latitude {horse latitudes}|, winds are small.
Temperate-zone high-altitude winds {jet stream}| flow east at lower latitudes and west at higher latitudes.
Japan has gentle breezes {matsukaze} in pines.
Rhone-River-valley glacier makes cold air {mistral}| that flows to Mediterranean Sea.
Winds go clockwise around high-pressure region near Azores. Winds {North Atlantic Oscillation} (NAO) go counterclockwise around low-pressure region near Iceland. If low pressure is very low, north Europe, north Asia, and Alaska receive warm wind, and Greenland, east Canada, and south Europe receive cold wind.
Hot dry summer winds {Santa Ana}| can be in California.
Sahara Desert heats wind {sirocco}|, which picks up water from Mediterranean Sea and rains on Italy.
Winds {solano} can be in Spain.
Equator east-to-west winds {trade wind}| are steady at low altitude.
Japan has strong winds {tsumuji}.
Winds {vento coado} can flow on Portuguese hills.
Humid winds {waimea} are in Hawaii.
Winds {williwaw} can blow in Alaska.
gentle warm wind {zephyr}|.
Hot dry winds {zonda} from Andes Mountains can blow across Argentina pampas.
Winds {gale}| can blow from 51 to 102 kilometers per hour.
Desert sandstorms have high humidity, low temperature, and 45-mph winds {haboob}, such as along Nile River.
In Caribbean Sea, cool air can surround warm moist air that rises faster, spinning into tropical cyclones {hurricane}| with winds up to 200 mph. About 48 hurricanes and typhoons happen a year, usually in late summer.
In Southeast Asia, warm land and cool sea causes summer storms {monsoon}|, but October to April is cool and dry.
In northeast USA, northeastern winds {northeaster}| can bring storms.
Sandy hot strong winds {simoom}| can be in Sahara and Arabian deserts.
Cool winds {squall}| can come suddenly and finish soon, typically with rain or snow.
Strong cold fronts can cause funnel-shaped clouds {tornado}| {whirlwind}, 300 to 600 feet diameter, with 200 mile per hour winds. Tornadoes move 25 miles per hour and travel up to 100 miles. Tornadoes are mostly in central USA and in Australia. 1500 tornadoes happen each year.
Pacific Ocean and Indian Ocean have tropical cyclones {typhoon}|. About 48 hurricanes and typhoons happen a year, usually in late summer.
Squall lines can make sea tornados {waterspout}|.
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Date Modified: 2022.0225