2. Background and Purpose of Study Definition of Desertification Mechanism of Desertification Summary Air Environment Engineering 2

3. 3  Average temp. of the earth goes up due to global warming gas like carbon.  The climate change become bigger.  Extremely high temperature or heavy rain.  Arid area expends.(Desertification)  Average temp. of the earth goes up due to global warming gas like carbon.  The climate change become bigger.  Extremely high temperature or heavy rain.  Arid area expends.(Desertification)

4. The phenomenon that arid land is changed into desert by various causes like climate change and human activity Air Environment Engineering 4

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6. Air Environment6

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8. Drought Desertification Albedo↑ Descending current Global Warming Air Environment Engineering 8

9. Increase the number of extremely hot and cold days Temperature rising accelerates hydrologic cycle, so a drought and a flood have become more frequently, extremely. Air Environment Engineering 9

10. Albedo - Overall average reflection coefficient of an object Air Environment Engineering 10 SurfaceAlbedo(%) Desert(sand)30~60 Crops(Green)5~25 Forest(Green)5~10 Grassy plain(Green)5~25 Farm land14~17 Soil(Dark)5~15 Soil(Bright)25~30 Desert emits energy as long wave radiation more than forest and crops, due to its high temperature and albedo. Temperature of air over desert goes down, and then descending current begin.

11. High pressure area is clear, because air is compressed as it drops. Low pressure area is cloud, because air swells as it ascends. Air Environment Engineering 11

12. Desert Surface( Albedo: 30~60%) Upper Air (Emitting radiation energy >Absorbing energy ) ① Solar radiation 100 ③ Temperature ④ Descending air current 70 60 ⑥ Extension of Desert ⑤ No rain, no cloud = clear ② Earth radiation Air Environment Engineering12

13. During descending air current, volume of air decrease, so temp. of air goes up due to adiabatic change. Owing to continued descending air current, desert isn’t rain, more and more it becomes arid and expands. Air Environment Engineering 13

14. Air Environment14