There are weekly updates from Drought Monitor from the University of Nebraska in Lincoln and I will be commenting on this topic regularly; I thought would be good idea to summarize in short on what a drought can be.
Droughts are natural and erratically occurring events that can happen anywhere around the world. It happens when there is a large-scale disruption with the global circulation of the atmosphere. Droughts are from the result of a shortage of precipitation over variable time periods and areal extents. The effects from lack of rainfall on the day-to-day use for needs of human and nature can create a natural disaster or hazard. Therefore, many disciples examine the causes and effects from droughts, like: geography, environmental science and studies, ecology, hydrology, meteorology, climatology, dendroclimatology, pedology, geology, and agriculture or horticulture.
Droughts can be classified into four types:
1) Meteorological—it is the variable time periods and areal extents where there is a shortage of precipitation
2) Agricultural—it is related to having soil moisture deficits and other parameters that negatively impacting the well-being of the vegetation and it is characteristically associated from the effects from a meteorological drought
3) Hydrological—it is the quicker reduction surface or subsurface water supplies and it is associated with a meteorological drought and additionally it can be intensified by a greater withdrawal from wells, rivers and lakes for human-use.
4) Socioeconomic—it is impacts on societal needs from the shortage of usable water for day-to-day activities for food, health and business needs and it happens from the convergence of the other three droughts.
There are three parameters that gauge a drought: intensity, duration, and area. Intensity is the degree from the deficit of precipitation. Duration is the length of time that it occurs. The area is the specified region that has been affected.