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
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