Drought and desertification.

Mind Map by , created about 4 years ago

Degree- Environmental Science and Outdoor Education at University of Stirling, Scotland 3rd Year (ENV U 6EH - Environmental Hazards.) Mind Map on Drought and desertification., created by meghansarah on 04/13/2015.

Created by meghansarah about 4 years ago
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Drought and desertification.
1 What
1.1 Aridity
1.2 drought
1.2.1 caused by unusual dry weather, which can be caused by shifts in global weather patterns and increased by human climate change. there is no guaranteed end point to a drought.
1.3 Desertification
2 Impacs
2.1 Aridity
2.1.1 Aggravate health conditions such a asthma.
2.1.2 difference between different zones and why something's can grow and others cannot
2.3 Drought
3 Desertification
4 Drought
4.1 Seen thought history
4.1.1 4,200 years aga, lasted for centuries was the world mega drought, caused by the cooling of the Atlantic and decreased rainfall by 30% and linked to the fall of civilisations. (Heffernan 2013)
4.1.2 Global drought info service states that there is a drought currently in the planes of the USA
4.2 several different types: Hefferman 2013
4.2.1 Meterlogical Occurs when a persisitant declines at the first stage of te hydrological cycle, which reduces the water which is stored in ice/snow it dosent rain as often
4.2.2 Soil moisture affected by the hydrological and meteorological drought Soil has dried out and the water table has dropped; potential high evapotraspiration
4.2.3 Hydrological drought caused by meteorological and affects soil moisture. when the water is not available or has depleted below a level. seen in the lake/lochs/resivoirs
5 Aridity
5.1 How dry a place
5.1.1 Depends on several factors Agroclimatic Zones The agro-climatic classification is nothing but an extension of the climate classification keeping in view the suitability to agriculture. The most widely used classifications being Koeppen’s and Thronghwaite’s. Generally, the climate types may be distinguished on the rainfall, temperature and as these two characteristics are influenced by altitude, the climate can also be classified on the basis of above three parameters. National commission on agriculture (1971) classified the country into 127 agro-climatic zones. The planning commission has adopted agricultural Zones on the various parameters for agricultural planning. The soil climatic zones can be classified on the basis of rainfall, temperature and prevalent soil types in the region. Evapotransperation Hobbins et al (2001) ststes that evapotraspiration is climate controlled and that with a dryer climate due to osmosis there is a biological drive of the balance of water density to be statbiled in an equilibrium. Humidity levels Levels of water in the air With high humidity can cause asthma attacks and aggravate other heath conditions
5.2 Formula to work out
5.2.1 An approach to the determination of recharge is to calculate actual (versus potential) evapotranspiration (accounting for processes such as soil-moisture storage and direct evaporation) and determine the amount of precipitation that passes through the root zone (and thus becomes recharge). The difficulty lies with determination of actual evapotranspiration without extensive field measurements. Due to shortcomings in other methods for estimating reference evapotranspiration, including the earlier Blaney-Criddle FAO method, the FAO developed an approach dubbed the FAO Penman-Monteith equation (Allen and others, 1998). The reference evapotranspiration calculated with this newer equation is then used with crop evapotranspiration coefficients to estimate crop-water requirements. The FAO Penman-Monteith equation for calculating reference evapotranspiration is:
5.2.2 penman-Monteith formula
5.2.3 used to work out the rate of evapotrasperation.
5.3 Hot/Cold!
5.3.1 Hot Sahel
5.3.2 Cold and Dry <0 c average tem for 6 months >6C for 3 months of summer