Dynamics 3 Flashcards
(Tropical Weather)
What are tropical cyclones?
What is required for cyclones to happen?
- circulating storms of 500km to 2000km diameter (winds >15m/s)
- have the warming air and the lowest pressure in the center
- lasts for a few days
- rotates anti-clockwise in the North / clockwise in the South
- There must be warm water (tropics)
- Coriolis effect must be strong (no cyclones at the equator)
(Tropical Weather)
What is the Madden-Julien Oscillation (MSO)?
- 30 to 60 day oscillations in the tropical atmosphere
- superclusters of cloud/rain moving eastward from the East-African coast to Southeast Asia and then to the Pacific ocean
- high rainfalls for a few months, followed by a dry spell for a few months
(Tropical Weather)
What are equatorial waves?
Rossby Waves
- waves that move from east to west along the equator
- lasts for 3 to 10 days
Kelvin Waves
- waves that move from west to east along the equator
- last for 3 to 10 days
(Tropical Weather)
What are cold surge events?
- occurs during the North-East winter monsoon season
- bursts of cool dense air from Asian continent penetrate into the South China Sea
- lasts for a few days
(Tropical Weather)
What is a Borneo Vortex?
- occurs off the northwestern coast of Borneo
- spins anti-clockwise (in the North)
- bring a lot of rain to the region
(Tropical Weather)
What are squalls?
What is the Sumatra squall?
- squalls are convective storms
- size ranges from 10 to 100km in size
- lasts for a few hours to a day
Sumatra squall
- converges over Sumatra and Malacca
- in the early hours of the morning, moves eastwards towards Singapore and Malaysia and then into the South China Sea
- occurs during the South-West summer monsoon season
(Ocean Circulation)
What causes wind-driven currents?
What are the different wind-driven currents?
- trade winds cause ocean currents by surface wind drag
- they force warm easterly equatorial currents
Western boundary currents (warm currents, flow poleward):
- Gulf Stream
- Kuroshio
Eastern boundary currents (cold currents, close circulation):
- California
- Canary
(Ocean Circulation)
What causes the Thermohaline Conveyor Belt?
- warm water flows through Asia (indonesian throughflow), accumulates salt, and sinks at Greenland (North Atlantic Ocean)
- one cycle takes 1000 years
- flows at ~ 1 mm/s
(Ocean Weather)
What are eddies and how do they occur?
- circular current of water
- formed by surface winds on weather timescales
- caused by bathymetry (sea-floor topography) and instabilities in the currents
(Ocean Weather)
How are ocean waves formed?
How are tsunamis formed?
- waves are formed by friction with winds
- tsunamis are formed by underwater earthquakes or landslides
