Unit 2.4: Weather and Climate Flashcards
What are air masses? Where do they acquire their characteristics from and how do they move?
Large regions with uniform temperature, humidity, and stability. Acquire characteristics from source regions and move from one region to the next by pressure gradient and winds.
How large are air masses?
They can be several 1000km wide.
What are source regions?
Places that are classified by latitudinal position and nature of underlying surfaces.
What are 6 important air masses? What are their characteristics?
- maritime equatorial (mE)
- maritime tropical (mT): warm, humid
- continental tropical (cT): hot, dry, subtropical high
- maritime polar (mP): cold, humid, polar high/subpolar low
- continental polar (cP): cold, dry
- continental arctic/Antarctica (cA/cAA): very cold, dry
What is a midlatitude cyclone? What are some of its characteristics?
Large cyclonic systems that occur in mid latitudes. They have a circular wind flow, low-pressure field, and interact with air and different properties. In the northern hemisphere they move from west to east with the westerlies.
What is a warm front?
Warm air that moves into a region that is dominated by cold air. The warm air will rise because it is less dense, the rising will result in the formation of horizontal clouds and light precipitation. They are rarely associated with extreme weather.
What is a cold front?
Usually comes after a warm front. It is when cold air moves into a region dominated by warm air. Cold air pushes the warm air up and causes considerable instability with vertical clouds and heavy rain.
What is the life cycle stages of mid latitude cyclones?
- Stationary front: when warm and cold air move parallel to one another.
- Stationary wave: undulation forms in the boundary between warm and cold air due to mountains, surface temperature contrasts, or Rossby waves in upper atmosphere. At this stage, cyclonic motions develop.
- Mid latitude cyclone stage: when warm air is forced north and cold air is forced south; this creates cold and warm fronts.
- Occluded front: cold front overtakes warm front.
- Dissipation stage: warm air is forced aloft resulting in a temperature inversion. Eventually air becomes stable.
Define thunderstorm.
Intense local storm associated with dense cumulonimbus clouds and strong updrafts of air. Produces lighting and thunder.
What are the stages of a thunderstorm?
- Cumulus stage: convective process in unstable atmosphere that creates cumulus clouds. Moist heated air rises, undergoes condensation and releases latent heat. Updrafts form pithing clouds.
- Mature stage: Updrafts continue, producing cumulonimbus clouds. Heavy rainfall begins from clouds base, produces downdrafts of cold air.
- Dissipating stage: storm weakens due to downdraft and evaporation.
What are features of a thunderstorm?
- Great atmospheric instability which develops vertical clouds.
- thunder and lightning occur, caused when up and down drafts create accumulation of positive and negative static charges.
- heavy rainfall and hail created by large instability in air.
Describe the difference between lightning and thunder.
- Lightning is the rapid distribution of electrons across a voltage gap. Results in development of current and sparks
- Thunder is when current heats the air and makes it expand which sends out the noise of thunder.
What is the 30/30 rule?
Wait 30 minutes to go outside if lightning is within 30 seconds/10km range.
How can you tell how far away lighting is?
After the flash, count the seconds until thunder occurs. Divide seconds by three and that is the distance in kms.
What is a tornado?
Small but intensive cyclonic vortex that forms in cold fronts. Air spirals at rapid speeds.
