The Water Cycle And Water Insecurity Flashcards
What is a drought?
A period of below average precipitation in a given region resulting in prolonged shortages in water supply
What is water scarcity?
When the demand for clean fresh water exceeds the available supply
Why is drought called a creeping hazard?
As drought has a long period of onset so it is hard to tell if its just a dry period or drought
What are the four types of drought?
Socio-economic drought
Hydrological drought
Agricultural drought
Meteorological drought
What is Meteorological drought?
Occurs when actual rainfall in an area is significantly lower than then climatological mean of that area
What is agricultural drought?
Lack of sufficient moisture in the surface soil layers to support crop and forage growth
What are indicators of agricultural drought?
Precipitation (reduced)
Temperature (increased)
Soil moisture (reduced)
What is socioeconomic drought?
Demand for an economic good exceeds supply as a result of a weather related deficit in water supply
What is hydrological drought?
The effects of periods of precipitation (including snowfall) shortfalls on the surface or subsurface water supply (reservoir, lake levels)
What are the three atmospheric cells?
Hadley
Ferrel polar
What is an example of an extreme meteorological drought?
ENSO
El Niño southern oscillation
2003 European drought
What are the three phases of El Niño?
Neutral phase (normal)
El Niño (negative phase)
La Niña (positive phase)
What is neutral ENSO like?
Trade winds blow from S.Am to AUS (easterly trade winds)
Warm surface water advected to western side of basin
Evaporation higher at area of warm water pool (west/ AUS)
More warm wet air near AUS
Air rises, cools and condenses
Rainfall over AUS coastal regions
Atmospheric divergence over AUS
Cold dry air sinks over AUS and S.Am
Upwelling near S.Am
What is upwelling?
When the warm water sinks by Australia it becomes cold and dense it moves towards S.Am and then rises to replace moving warm water
What is the positive of Neutral phase for S.Am/
Upwelling makes nutrient rich water that is good for fishing
What are conditions like for El Niño?
Weakening of easterly trade winds (reversal- extreme)
Trade winds don’t reach AUS
Warmer water centred in centre of equatorial pacific
Evaporation is higher in this area (warm air rises, cools ,condenses)
Rainfall
Air sinks over AUS causing dry coastal conditions
Weaker upwelling
What are conditions like for La Niña?
Stronger then normal easterly trade winds
Warm water advected closer to the Australian coast
normal rain production processes
Rainfalls just more inland then neutral phase
Flooding in AUS
Atmospheric divergence
Cold dense air sinks over S.Am leading to dry/arid conditions
Good commercial fishing in S.Am
Very strong upwelling
How does ENSO affect the globe?
Heats up equatorial Atlantic
Increasing chance of storms as water might more readily reach 26.5*c needed for hurricanes
What were the impacts on Australian climate from El Niño? (2014-16)
Counteracted by warm temp in Indian Ocean causing above average rainfall
Spring 2015 Australias third driest spring
Fewer clouds and less tropical rain resulted in mot severe coral bleaching on record
Bushfire season started earlier
Less rainfall
Increased temperature
Increased frost risk
Later monsoon onset
Increased fire risk
What were the effects on the South American climate from El Niño? (2014-16)
September and December 2015 were generally dry
South east Brazil experienced extreme drought in 2015
Above average temperatures and decline in several rivers and reservoirs (Brazil)
Residents had to save water, cutoffs made
South region experienced a period of severe thunder storms causing flooding and homelessness
What are the impacts of La Niña on the Australian climate? (2020-22)
Last La Niña was from 2010-12 wettest 2 yrs on record
Widespread flooding
5 tropical cyclones were in the severe category
Above average rainfall
Colder days
More tropical cyclones
Earlier onset of wet season
What are the impacts of La Niña on the South American climate?
Positive impact on fishing industry (strong upwelling)
Drought affects coastal regions of Peru and Chile
December to February Brazil is wetter than usual
Higher then average rainfall in central Andes which causes catastrophic flooding
What happened in August 2003?
An anticyclone stationed above Western Europe prevented precipitation and led to record high temperatures over sustained periods