Download Tropical Cyclones

Tropical Cyclones
AICE MARINE SCIENCE AS
LEVEL
2015-2016
Normal Wind Pattern
El Nino (southern oscillation)
 sequence of events occurring in
southern Pacific Ocean
 Normal conditions



cold nutrient-rich water flows North along west
coast of S. America.
Upwelling of nutrients due to winds from the
South
plankton-rich water
High productivity
large numbers of:
Anchovies
Sardines
 Supports:
substantial fisheries industry
various sea bird species

Normal vs. El Nino
El Nino Conditions
 Every ~7-10 years
 Winds stop blowing from East or SE
 Warm equatorial water is blown by abnormal
winds from the West.
 Pressure gradients in East and West Pacific are
reversed
Reverse in wind direction and equatorial currents
 Large area of warm water forms = cold-water
species death
 Upwelling stops
 Nutrient supply to surface is reduced = lack of
nutrients = primary production rapidly decreases
 Affects higher trophic levels
 Collapse of commercial fish stocks

El Nino Example
 Major event in 1982-83
 Surface temps decreased by 5⁰C
 Heavy rain in normally dry
eastern Pacific
 Cause not known: possibly
global warming?
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Monsoons
 Asia = largest continent
 Climate swing: hot/wet to cold/dry
 Monsoon (rainy season) -
seasonal shift in wind of the Indian
Ocean
 Land absorbs heat faster than sea, so
it heats up faster

In winter, sea is warmed but not land
Warm air over sea rises and is less dense
 Draws in cooler northeasterly air from land
 India: occurs during post-monsoon season:
October - December

Monsoon
 Summer (May-August) = land
quickly heats and there is big
temp. difference between
Central Asia and Indian Ocean


Land air warms, is less dense, rises
Saturated air (water vapor) from
southwest over Indian Ocean
Thunderstorms
 Very heavy rain (80% of India’s
annual)

 September, land mass cools,
monsoon weakens & replaced
with a dry, northeast postmonsoon
Tropical Cyclone
 Large mass of warm, humid, rotating air
 Thunderstorms, strong winds, & rain centered
around a Low Pressure
 AKA: Tropical depressions, Tropical storms,
Hurricanes, & Typhoons
HOW TROPICAL CYCLONES FORM
Conditions Needed
 Warm water, @ least 26.5OC (79.7OF)
 Low Pressure
 Evaporationtropical air rises & expandscools until
unable retain the moistureprecipitation
 When water vapor rises, it condenses & releases large
amounts of heat energy, increasing evaporation & driving
the development of the cyclone
Rotation & Movement
 Northern Hemisphere:
Counterclockwise rotation
 Southern Hemisphere:
Clockwise rotation
 Due to the Coriolis Effect &
the way the winds are
deflected as they approach
the Low pressure
 Usually tropical cyclones
develop near the equator &
move westward & towards the
poles (determined by
prevailing winds)
Eye of Hurricane Wilma
What hemisphere?
Impact on Coastal Communities
 High wind
 Heavy rain
 Tornadoes
 Lightning
 Storm surge
Typhoon Sanba
Hurricane Sandy
Water spouts!
Hurricane Sandy
More from Sandy
Hurricane Irene Bahamas
Hurricane Ike, Galveston, TX
Hurricane Ike, Galveston TX
Hurricane Ike, Galveston TX