EQ2 Flashcards
(74 cards)
what are the meteorological causes of drought?
short term precipitation
longer trends
ENSO cycles
what is the UN’s general definition of drought?
an extended period-a season, year, or several years-of deficient rainfall relative to the statistical multi-year average for a region.
what is meteorological drought?
occurs when long term precipitation is much lower than normal. it is region specific since the atmospheric conditions that result in deficiencies of precipitation are highly variable between climate types.
what is agricultural drought?
occurs when there’s insufficient soil moisture to meet the needs of a particular crop at a particular time.
when does agricultural drought usually happen?
after a meteorological drought but before a hydrological drought
what is agricultural drought caused by?
precipitation shortages
differences between actual and potential evapotranspiration
soil water deficits
reduced groundwater and reservoir levels
what is hydrological drought?
occurs when there are deficiencies in surface and subsurface water supplies as measured in rivers, lakes, reservoirs, groundwater etc
what is socio-economic drought?
occurs when water demand for social and economic purposes exceed water availability.
what percent of the world experience some form of drought?
38
what are some examples of places with high drought?
LA, Myanmar, Somalia, Spain, UAE
what are the 3 kinds of atmospheric cell (from equator to pole)
Hadley
ferrel
polar
what is the ITCZ?
belt of low pressure which circles earth generally near the equator, where trade winds of the northern and southern hemispheres come together
what is a trade wind?
a wind blowing steadily towards the equator from the north-east in the northern hemisphere and south-east in the southern hemisphere.
where is the ITCZ in the northern hemisphere summer?
further north
what does the ITCZ cause when it arrives?
wet season
what does the ITCZ cause when it leaves?
dry season
what happens to the Sahel in drought years?
the ITCZ doesn’t move as far north as usual, due to an anticyclone in the north preventing the southwesterly winds from bringing the usual rain.
what happens in the pacific during an el nino year?
warm water moves to west coast of south America.
what happens to Australia during an el nino year?
sinking air causes dry conditions and drought
what happens to the west coast of south America in an el nino year?
warmer waters cause increased rainfall and floods
what happens in the pacific during a la nina year?
v strong trade winds move warm water westwards towards east coast of Australia.
what happens to the east coast of Australia during a la nina year?
increased heat causes air to rise rapidly forming thick clouds, heavy rain, and floods.
what happens to the west coast of south Australia during a la nina year?
there’s a strong swelling of deep cold water. unusually high pressure due to sinking air causes v high dry weather and drought.
what’s causing the aral sea to shrink?
cotton production