Drought is directly related to the changes of plant system distribution, temperature balance distribution, atmospheric circulation state and chemical element distribution caused by human activities; including geographical location and altitude, distance from major river systems, slip and drift of the earth's crustal plate, astronomical tide and flood, local vegetation coverage level and so on, distribution and severity of the lack of precipitation are closely related to the reserve, demand and use of water at that time. Population growth, agricultural demand for water and changes in land use will directly affect water reserve conditions and the hydrological response of catchment areas. Increased pressure on water demand also makes resistance to drought more fragile.
The degree of drought damage is related not only to the intensity but also to the scope of drought. Serious droughts tend to be droughts with larger ranges and longer duration. The large-scale drought in China depends largely on the location and intensity of the subtropical high in the western Pacific Ocean and the stable development of the westerly circulation situation.
For example, the national drought that occurred in 1972 was mainly due to the fact that the subtropical high active location was more easterly and less intense than usual. Widespread drought is also associated with planetary activity outside the Earth. For example, the 11-year cycle of sunspot activity is obviously related to the severe droughts and floods on the earth.In recent years, meteorologists have found that EI Nino is also closely related to large-scale drought and flood in China.It can be seen that the conditions for large-scale drought are mainly caused by the abnormal changes of atmospheric circulation and sea temperature.
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