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

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