• DROUGHT •
A drought is defined as "a period of abnormally dry weather sufficiently prolonged for the lack of water to cause serious hydrologic imbalance in the affected area." And it can be easily said that a drought is a period of unusually persistent dry weather that persists long enough to cause serious problems such as crop damage or water supply shortages or even long thirsts for animals (including humans).
A Drought is not purely physical phenomenon, but rather interplay between natural water availability and human demands for water supply.
Droughts are generally of three kinds-
•Agricultural drought refers to a situation where the amount of moisture in the soil no longer meets the needs of a particular crop.
•Hydrological drought is brought about when the water reserves available in sources such as aquifers, lakes, and other reservoirs falls below normal.
•Meteorological drought occurs when there is a prolonged period with less than average precipitation.
However, some departments mention another classification of drought-
Socioeconomic drought refers to a situation when physical water shortages begin to affect people.
The local climate of a region as well as atmospheric water vapor constitutes the main causes of a drought.
Most definitions of a drought refer to abnormal dryness and shortage of precipitation i.e. less rain and snow and other materials falling from the sky. Droughts can also be associated with higher than normal surface- air temperatures. For example the drought of 1986 in the south-eastern United States had associated surface-air temperatures so much higher than normal that year that Georgia, North Carolina, and South Carolina had their warmest July in the whole of the 20th century.
Atmospheric water vapor is another major cause of drought. Droughts commonly are referred to as "dry" in the sense that not only does less precipitation takes place, but also the air is drier than usual.
Relative humidity is the most common used measure of atmospheric water vapor. Relative humidity depends on two factors-the absolute quantity of water vapor in the air (absolute humidity) and the air temperature. Thus, the decrease in relative humidity during droughts extends through all levels of the atmosphere that contain substantial water vapor.
A drought is associated with persistent or persistently recurring atmospheric circulation patterns. A true example of which are the, summer droughts in the southeastern United States, which are generally are associated with the frequent recurrence of high-pressure circulations. Daily circulation patterns associated with a drought are not notably different from daily circulation patterns that occur during no drought periods.
Also, Large-scale vertical movement of air is a major factor in the occurrence of precipitation and thus plays a vital role in the occurrence of a drought.
Meteorologists play a vital role in warning before a drought as they determine the onset and the end of a drought by carefully monitoring meteorological and hydrological variables such as precipitation patterns, soil moisture, and stream flow. To do this, meteorologists make use of various indices that show deficits in precipitation over periods of time.
Droughts have serious and unmerciful impacts on the particular area of the Earth as well as the animals living in that area. Shortage of rainfall over an area for a large period of time can get farmers and the common citizens on their knees- as a result of which no one from the insects to the elite are spared. In deserts, weeks without rain are not uncommon but when the weeks turn into fortnights and then into months, the lives of the camels as well as the people in the areas are threatened.
The incident in the 1950's, when the Great Plains suffered a severe water shortage when several years went by with rainfall well below normal can not be forgotten by anyone. Crop yields failed and the water supply fell and the area suffered a he loss of all lives, wildlife, and cattle as well as economic prosperity.
And of course, one of the biggest results of a drought is this- “The Earth still is blue, but of water there’s no clue”