# Drought: A Common Environmental Disaster
## 1 Introduction
Droughs are most common when typical weather patterns are disrupted, leading the water cycle to be disrupted. Storm tracks can be blocked for months or years due to changes in atmospheric circulation patterns [11]. This interruption can have a significant impact on the amount of precipitation that a region regularly receives [11]. Wind patterns can also have an impact on how moisture is absorbed in different areas. Scientists have discovered a relationship between drought and certain climate trends. El Nino is a weather phenomenon in which the temperature of the surface water in the Pacific Ocean along the central South American coast rises. Droughs in Indonesia, Australia and northeastern South America are linked to these warmer waters, which affect storm patterns. El Nino episodes, which occur every two to seven years, keep climate experts guessing. La Nina, on the other hand, occurs when the temperature of the surface water in the Pacific Ocean off the coast of the southern hemisphere drops. The cooler waters contribute to drier-than-normal weather in regions of North and South America, which affects storm patterns that can influence drought episodes [12; 13]. El Nino and La Nina both last around a year on average. La Nina has a more complicated impact on weather patterns than El Nino. The effects of La Nina have been linked to two of the most devastating droughs in US history: The Dust Bowl of the 1930s and the Midwest drought of 1988 [14]. The connection between drought and global warming in the current phase of climate change is still up for debate. Warmer global temperatures, according to a study published in 2013 Mahlstein [14], will result in more rainfall in some parts of the world and lower rainfall in others, resulting in more flooding and droughs around the planet [15; 16; 17]. Other experts disagree with the prediction of increasing droughs, believing that global warming will result in a wetter environment around the planet. From the foregoing, it becomes abundantly clear that drought requires close monitoring, to aid in the understanding of its evolution and impacts over time. Sudden warming and associated changes can affect global circulation patterns, and consistent adjustments in drought regimes are expected to influence not only the local climate but also the global climate [18]. It might be difficult to identify the beginnings of a drought. Unlike many natural disasters that have immediate and spectacular consequences, such as earthquakes, tornadoes and hurricanes, drought can develop gradually and subtly [2; 19]. The full impacts of long-term insufficient rainfall can take weeks, months or even years to manifest. It may also be difficult to predict the cessation of drought episodes [19; 20]. While a single rainfall can give relief from drought in the short term, it may take weeks or months for precipitation levels to recover to normal. The beginning and end of a drought are sometimes only discernible in retrospect. Therefore, as a result of these attributes, drought events are very difficult to predict [11] but associations and precursors have been identified the world over. Drought monitoring should be done frequently to recognise the severity of the drought, as well as its duration and spread, so that adequate preparation and mitigation of the possible negative effects on the environment, agriculture and economy may be implemented. Drought indices for quantitative drought severity estimation have been developed using meteorological and hydrological indicators, such as temperature, precipitation, soil moisture, and streamflow, as inputs in many scientific studies [21; 22]. Because droughs are dynamic, new indices have been established and current ones have been enhanced for varied locations and meteorological conditions. As a result, there are now over 150 drought indicators in use in drought research [23].