用英语介绍干旱和干旱带来的灾害

用英语介绍干旱和干旱带来的灾害
用英语介绍干旱和干旱带来的灾害

用英语介绍干旱和干旱带来的灾害
Drought cause
Generally,rainfall is related to the amount of water vapor in the atmosphere,combined with the upward forcing of the air mass containing that water vapor.If either of these are reduced,the result is a drought.This can be triggered by an above average prevalence of high pressure systems,winds carrying continental,rather than oceanic air masses (ie.reduced water content),and ridges of high pressure areas form with behaviors which prevent or restrict the developing of thunderstorm activity or rainfall over one certain region.Oceanic and atmospheric weather cycles such as the El Niño-Southern Oscillation (ENSO) make drought a regular recurring feature of the Americas along the Pacific coast and Australia.Guns,Germs,and Steel author Jared Diamond sees the stark impact of the multi-year ENSO cycles on Australian weather patterns as a key reason that Australian aborigines remained a hunter-gatherer society rather than adopting agriculture.[30]
Human activity can directly trigger exacerbating factors such as overfarming,excessive irrigation[31],Deforestation,and erosion adversely impact the ability of the land to capture and hold water.[32] While these tend to be relatively isolated in their scope,activities resulting in global climate change are expected to trigger droughts with a substantial impact on agriculture[33] throughout the world,and especially in developing nations.[34][35][36] Overall,global warming will result in increased world rainfall.[37] Along with drought in some areas,flooding and erosion will increase in others.Paradoxically,some proposed solutions to global warming that focus on more active techniques,solar radiation management through the use of a space sunshade for one,may also carry with them increased chances of drought.[38]
Types of drought
Ship stranded by the retreat of the Aral Sea.As a drought persists,the conditions surrounding it gradually worsen and its impact on the local population gradually increases.People tend to define droughts in three main ways:[45]
Meteorological drought is brought about when there is a prolonged period with less than average precipitation.Meteorological drought usually precedes the other kinds of drought.
Agricultural droughts are droughts that affect crop production or the ecology of the range.This condition can also arise independently from any change in precipitation levels when soil conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops.However,in a traditional drought,it is caused by an extended period of below average precipitation.
Hydrological drought is brought about when the water reserves available in sources such as aquifers,lakes and reservoirs fall below the statistical average.Hydrological drought tends to show up more slowly because it involves stored water that is used but not replenished.Like an agricultural drought,this can be triggered by more than just a loss of rainfall.For instance,Kazakhstan was recently awarded a large amount of money by the World Bank to restore water that had been diverted to other nations from the Aral Sea under Soviet rule.[46] Similar circumstances also place their largest lake,Balkhash,at risk of completely drying out.[47]
The world is not only hungry,it is also thirsty.This may sound strange,since nearly seventy percent of the earth's surface is covered with water.But about ninety percent of this is sea water.Man and most of the animals can only drink and use the remaining percent of water--fresh water.
The need for water is increasing day by day.Only steps are taken to deal with this problem immediately can we avoid a severe world-wide water shortage later on.One of the first steps is to develop ways to reuse it.
Experiments have already keen carried out in this field.The used witer has been pumped to a water-purifying plant.There,it can be separated from waste matter and treated with chemicals so that it can be used again,just as if it were fresh water from a spring.