Everyday Weather Notes

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This is a page of notes written by GoNerdHerd and used at their 2010 Michigan regional Meteorology event. The topic of the event was Everyday Weather.

  • High Clouds
    • Cirrocumulus – Above 20,000 feet. Sometimes releases precipitation, but may be virga. Appears as small patched clouds in rows.
    • Cirrus – Above 23,000 feet. Not a cloud that releases precipitation. Appears as thin, wisp-like strands.
    • Cirrostratus – Above 20,000 feet. Not a cloud that releases precipitation, but may appear before rain that happens in the next 12 to 24 hours, since these clouds may signal the beginning of a warm front.
  • Middle Clouds
    • Altostratus – 8,000 to 20,000 feet. Rain showers are possible in thickened clouds. If rain becomes persistent, clarification becomes nimbostratus. Appears as sheet or layer, you can usually see the sun through it.
    • Altocumulus – 8,000 to 20,000 feet. Not a precipitation cloud, but often signals an oncoming thunderstorm soon or later in the day if it appears in summer. Appears as large, dark patched clouds. Often seen before a cold front.
  • Low Clouds
    • Cumulus – Base below 6,500 feet. Can be a a precipitation cloud, but may be virga. Has a puffy appearance.
    • Stratocumulus – Usually below 8,000 feet. Appears lumpy, darker than most clouds, and in layers. Is a precipitation cloud but never intense. May indicate an oncoming storm.
    • Nimbostratus – Below 8,000 feet. Appears dark, widespread, formless layer. Is a precipitation cloud but may be virga.
    • Stratus – Below 6,000 feet. Appears in horizontal layers. It is a precipitation cloud, but usually minor precipitation.
  • Vertical Clouds
    • Cumulonimbus – 6,000 to 60,000 feet. Very tall and large. Is a precipitation cloud and often is intense, but may be virga. May develop into a supercell, which is a severe thunderstorm with special features.
    • Cumulus (See Low Clouds)
    • Pyrocumulus – Dense, associated with fire or volcanic activity. Appears as a gray or brown color because of the volcanic activity, and the cloud is puffy. The cloud can trigger a thunderstorm and/or lightning.
  • El Nino:
    • - Rise in surface pressure over the Indian Ocean, Indonesia and Australia.
    • - Fall in air pressure over Tahiti and east/central Pacific Ocean.
    • - Warm water spreads from the west Pacific and the Indian Ocean to the east Pacific. It takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific.
    • - Warm air rises near Peru, causing rain in the north deserts.
    • - Trade winds in the South Pacific weaken or head east
    • - Reduces hurricane activity.
    • - Occurred in 1997-1998.
    • - Causes more snowfall.
  • Nephology – the study of clouds and cloud formation.
  • Cloud cover – the amount of sky obscured by clouds in a particular location
  • Cloud seeding – the attempt to change or convert the type of precipitation falling from a cloud
  • Weather lore – the folklore related to the prediction of the weather
  • Albedo – a measure of a fraction of reflected incident sunlight
  • Virga – the precipitation falling from a cloud that evaporates before it hits the ground
  • Sundogs – a phenomenon that creates the illusion of a “mock sun” or a bright ring or halo, on either side of the sun. They can be seen in any season in any place.
  • Rainbows – a meteorological phenomenon that causes a spectrum of light to appear in the sky when the sun shines onto droplets of moisture in earth's atmosphere, taking the form of a multicolored arc.
  • Aurora – Sometimes called the “northern lights”, aurora is a natural light display in the sky; the result of the emissions of photons in the earth's upper atmosphere.
  • Crepuscular rays -these are rays of sunlight that appear to radiate from a single point in the sky. These are really just columns of sunlit air separated by darker cloud-shadowed regions.
  • Green flash – Optical phenomenon occurring before sunrise or after sunset, when a green spot is visible in the sky for a second or two. They are caused by a refraction of light in the atmosphere, light moves slower in the thinner air, and sunlight rays curve slightly, creating an illusion of a green flash.
  • Jet stream – Fast flowing, narrow air currents found in the atmosphere of planets
  • Chinook winds – Foehn winds in the interior west of North America
  • Coriolis effect – The apparent deflection of objects visually.
  • Alberta clippers – A fast moving, low pressure area affecting Canada and the Upper Midwest between December and February.
  • You can lose control of your car in six inches of water.

You should leave your vehicle if you are in a flash flood. Lightning occurs in ALL thunderstorms. Hail results in $1 billion in damages per year.

  • Derecho – A long-lived, violent thunderstorm associated with a fast-moving band of severe thunderstorms.
  • Doppler radar – Radar to produce data about objects at a distance. It does this by beaming a microwave signal towards a desired target and listening for its reflection, then analyzing how the original signal has been altered by the object that reflected it.
  • Isobar – A line of equal or constant pressure on a graph, plot, or map.
  • Air mass – A large volume of air defined by its temperature and water vapor content.
  • Weather front – A boundary separating two masses of air of different densities.
  • Cold front – The leading edge of an advancing mass of cold air. When it encounters a mass of less dense warm air, instability results, often triggering heavy rain.
  • Warm front – The leading edge of an advancing mass of warm air. When it meets a stationary cold air mass, the warm air rises and cools. Condensation may follow, forming clouds, and usually producing widespread precipitation.
  • Occluded front – An occluded front is formed when a cold front overtakes a warm front.
  • Stationary front – A non-moving or stalled boundary between two air masses, neither of which is strong enough to overtake the other.
  • Squall line – A line of severe thunderstorms that can form along or ahead of a cold front. It contains heavy precipitation, frequent lightning, hail, strong straight-line winds, and possibly tornadoes.
  • Albedo – How strongly an object reflects light from sources such as the sun.
  • Meteograms -a time cross-section that produces and uses data for a specific weather station on the ground
  • Radiosondes - a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver.

  • Exosphere

The outermost layer of Earth's atmosphere extends from the exobase upward. Here the particles are so far apart that they can travel hundreds of km without colliding with one another. Since the particles rarely collide, the atmosphere no longer behaves like a fluid. These free-moving particles follow ballistic trajectories and may migrate into and out of the magnetosphere or the solar wind. The exosphere is mainly composed of hydrogen and helium.

  • Thermosphere

Temperature increases with height in the thermosphere from the mesopause up to the thermopause, then is constant with height. The temperature of this layer can rise to 1,500 °C (2,730 °F), though the gas molecules are so far apart that temperature in the usual sense is not well defined. The International Space Station orbits in this layer, between 320 and 380 km (200 and 240 mi). The top of the thermosphere is the bottom of the exosphere, called the exobase. Its height varies with solar activity and ranges from about 350–800 km (220–500 mi; 1,100,000–2,600,000 ft).

  • Mesosphere

The mesosphere extends from the stratopause to 80–85 km (50–53 mi; 260,000–280,000 ft). It is the layer where most meteors burn up upon entering the atmosphere. Temperature decreases with height in the mesosphere. The , the temperature minimum that marks the top of the mesosphere, is the coldest place on Earth and has an average temperature around −100 °C (−148.0 °F; 173.1 K).

  • Stratosphere

The stratosphere extends from the tropopause to about 51 km (32 mi; 170,000 ft). Temperature increases with height, which restricts turbulence and mixing. The , which is the boundary between the stratosphere and mesosphere, typically is at 50 to 55 km (31 to 34 mi; 160,000 to 180,000 ft). The pressure here is 1/1000th sea level.

  • Troposphere

The troposphere begins at the surface and extends to between 7 km (23,000 ft) at the poles and 17 km (56,000 ft) at the equator, with some variation due to weather. The troposphere is mostly heated by transfer of energy from the surface, so on average the lowest part of the troposphere is warmest and temperature decreases with altitude. This promotes vertical mixing (hence the origin. The troposphere contains roughly 80%[ of the mass of the atmosphere. The tropopause is the boundary between the troposphere and stratosphere.

  • Stuve diagram – one of four thermodynamic diagrams commonly used in weather analysis and forecasting. Temperature and dew point are plotted on these.
  • Wind shear – a difference in wind velocity over a short distance. Severe thunderstorms require this, as do supercells and squall lines.
  • Energy budget - The Earth’s Energy Budget is determined by the amount of incoming energy and the amount of outgoing energy. Nearly all of Earth’s incoming energy (99.98%) is from solar radiation. About .013% comes from geothermal energy that is created by the radioactive decay of Earth’s core. About .002% of Earth’s incoming energy comes from the action of tides caused by the interaction of Earth with the Sun and Moon. Waste heat energy from fossil fuel consumption accounts for about .007% of Earth’s Energy Budget. The Earth has an average albedo of about 30% which means that ~30% of incoming solar radiation is radiated back into space before it reaches Earth's surface. After the 30% the atmosphere absorbs 19% and the earths surface absorbs 51%