Droughts are always devastating as it completely changes the climatic and geographic conditions of a region and alters the natural vegetation, physiography, plant and animal life, and human lives completely. The gradual decrease of soil moisture results in soil erosion, soil fertility loss, destruction of natural vegetation, and damages the hydrological cycle. It is extremely rare and difficult for a long-time drought-prone area to come back to life again. So, the impact of drought lasts almost forever until and unless some extraordinary physical changes intervene in that area. On the other hand, seasonal droughts i.e., droughts that are caused because of lack of rainfall for one season (monsoon) only, affect the weather, soil, and natural vegetation of an area in that year only and if the area receives adequate rainfall in the next monsoon, it again rejuvenates back to life. 

Classification of Drought

For a better understanding of the exact situation and cause of drought, droughts can be broadly classified into three main categories. They are as follows;

• Based on the source of water availability

1. Meteorological Drought- Drought which is caused by lack of rain in a region is known as meteorological drought. According to the percentage of rainfall scarcity, they are further divided into three levels.

• Severe Drought- Occurs when rainfall is more than 50% lesser than the normal amount. 
• Moderate Drought- When rainfall is 26-50% less than normal.
• Slight Drought- When rainfall is 11 to 25 percent lesser than the normal rainfall in a region. 

1. Hydrological Drought- Refers to the situation of extremely low rainfall resulting in the drying up of streams, rivers, lakes, ponds in a particular drought-prone region.
2. Agricultural Drought- Due to lack of rain and loss of soil moisture, agricultural yield is damaged and farming practices become very difficult. This is known as agricultural drought.

• Based on the time of occurrence

1. Seasonal Drought- Referred to areas experiencing droughts due to large-scale seasonal circulations, these kinds of droughts occur in well-defined dry climates and wet climates too. This can be mainly seen in areas having monsoon types of climate.
2. Permanent Drought- Areas that have experienced drought over a long time have turned those areas into deserts and completely changed the natural vegetation of the place and replaced it with cactus, Xerophytes, thorny shrubs, etc. 
3. Contingent Drought- Many places may experience drought due to irregularity and variation in the amount of rainfall they receive in a particular season. The same areas may experience a lot of rain in the future. Agriculture takes a serious hit due to these droughts. 

•  Drought based on a medium

1. Soil Drought- Result of soil moisture depletion due to droughts. 
2. Atmospheric Drought- Drought is experienced due to certain atmospheric conditions like low humidity, low rainfall, etc. 

Four Stroke Cycle Engines

An internal combustion engine, the four-stroke cycle engine is used to complete one full operating cycle, the process of four definite piston strokes which are intake, compression, power, and finally, exhaust. This four-stroke cycle engine is a very common form of small engine and these are mostly powered by gasoline or diesel fuel. The four-stroke cycle engines are widely accepted as they are reliable, efficient, and emit very few unburned emissions. These engines are used widely in public transport vehicles. The intake and exhaust of the Integrated Circuit (IC) engine are the first and last stages of the Four-Stroke Cycle Engine respectively. In the intake stroke, the air/fuel mixture is drawn in the engine through the intake valve. In the exhaust stroke, the exhaust gases are thrown out of the cylinder and the cycle is completed and the intake stroke is once again ready to perform. 

Major parts of a Four-Stroke Cycle Engine 

1. Cylinder
2. Cylinder head
3. Piston
4. Piston Rings
5. Crank
6. Crankcase
7. Connecting Rod
8. Crankshaft
9. Water Jackets or Cooling Fins
10. Cam and Camshaft
11. Inlet Valve
12. Intake Manifold
13. Exhaust Valve
14. Spark Plug
15. Fuel Injector
16. Carburetor
17. Flywheel

     

    Conclusion

    Droughts are common in India, and it is difficult to control them. However, efforts can be made to reduce the rate of deforestation, and careless cutting down of trees, proper agricultural techniques to maximize yields and retain soil moisture as much as possible and protect the loss of water and wastage of water in streams, lakes, ponds, rivers, etc. 

    Climate change is also a major reason for droughts in many places, and atmospheric droughts can be mitigated in a slow but definite process which is to reduce the rate of pollution and reduce the atmospheric heat generation which alters the weather and climate of a region if experienced over a long period., for these reasons, the modern Four-Stroke Cycle Engine must be used to minimize air pollution.