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Storms 1: Meteorology Basics

Severe Weather

  • storms account for 75% of natural disasters deaths and damages in the US

  • 1980-2010: 134 weather-related disasters caused > $1 billion in damages each

    • total damages = >$880 billion

Weather

  • weather: conditions in the atmosphere at a given time and place

    • temperature

    • moisture

    • wind

    • pressure

  • occurs in troposphere

    • first 5-9 miles

Heat

  • energy that powers storms

  • heat energy from the sun is turned into sensible heat and latent heat

Sensible Heat

  • heat we can sense or feel (or measure)

  • when we measure temperature, we are measuring sensible heat

  • on an atomic level, this is really particles moving around

Latent Heat

  • “hidden” heat energy

  • energy absorbed during a state change like melting (ice to water)

  • can be released as sensible heat if the state change is reversed (ex: condensing, freezing)

  • if liquid water becomes gaseous: heat is taken from the surroundings

  • if gaseous water becomes liquid: heat is transferred to the surroundings

  • therefore, humid air (with lots of gaseous water) can be energy source for storms

Absolute Humidity

  • absolute humidity: amount of water vapor in air

  • absolute humidity = mass of water/ mass of air

  • grams of moisture per m^3

  • total amount of water vapor in air varies with temperature

    • more water in warmer air

    • less water in cooler air

  • so, the absolute measure is not very useful

Relative Humidity

  • relative humidity: percentage of the maximum water vapor that could be in the air at a given temperature

  • relative humidity = current absolute humidity/highest possible absolute humidity

  • 100% relative humidity = air is completely saturated with water vapor; rain is possible

  • highest possible absolute humidity changes with temperature

Storms 1: Meteorology Basics

Severe Weather

  • storms account for 75% of natural disasters deaths and damages in the US

  • 1980-2010: 134 weather-related disasters caused > $1 billion in damages each

    • total damages = >$880 billion

Weather

  • weather: conditions in the atmosphere at a given time and place

    • temperature

    • moisture

    • wind

    • pressure

  • occurs in troposphere

    • first 5-9 miles

Heat

  • energy that powers storms

  • heat energy from the sun is turned into sensible heat and latent heat

Sensible Heat

  • heat we can sense or feel (or measure)

  • when we measure temperature, we are measuring sensible heat

  • on an atomic level, this is really particles moving around

Latent Heat

  • “hidden” heat energy

  • energy absorbed during a state change like melting (ice to water)

  • can be released as sensible heat if the state change is reversed (ex: condensing, freezing)

  • if liquid water becomes gaseous: heat is taken from the surroundings

  • if gaseous water becomes liquid: heat is transferred to the surroundings

  • therefore, humid air (with lots of gaseous water) can be energy source for storms

Absolute Humidity

  • absolute humidity: amount of water vapor in air

  • absolute humidity = mass of water/ mass of air

  • grams of moisture per m^3

  • total amount of water vapor in air varies with temperature

    • more water in warmer air

    • less water in cooler air

  • so, the absolute measure is not very useful

Relative Humidity

  • relative humidity: percentage of the maximum water vapor that could be in the air at a given temperature

  • relative humidity = current absolute humidity/highest possible absolute humidity

  • 100% relative humidity = air is completely saturated with water vapor; rain is possible

  • highest possible absolute humidity changes with temperature