Operational definitions attempt to identify the onset. Agricultural drought is a difficult concept to define as it involves not only the range of water deficiency but its shortage in. Well, these are the typical earth conditions that define drought in layman terms. Agricultural drought links the various characteristics of meteorological drought to agricultural impacts, focusing on precipitation shortages. Drought has traditionally been categorized as one of four types. The terms drought event definition and drought index are frequently being confused. In particular, we need to define a new type of droughtecological droughtthat integrates the ecological, climatic, hydrological, socioeconomic, and cultural dimensions of drought. Drought definition is a period of dryness especially when prolonged. It is defined by comparing the current precipitation or dryness to the average or normal precipitation or dryness.
Meteorological drought is principally defined by the deficiency of precipitation from expected or normal amount over an extended period of time. Background drought is an insidious natural hazard that results from lower levels of precipitations than what is considered normal. Instead, scientists measure it as a deviation from average rainfall. Zolotokrylin encyclopedia of life support systems eolss precipitation over the land mostly outside arid areas. A drought means a long period of dry weather during which the lack of rain results in a severe shortage of water. The south african weather service defines a drought as a period of 12 moths when.
These include definitions applicable to quantify temporal and spatial variations in meteorological droughts in terms of lack of precipitation, as well as hydrological. The dyk is a suite of notes that attempt to explain or clarify complex climate phenomena, climate monitoring products and methodologies, and climate system insights. Contrasting climate variability and meteorological drought with perceived drought and climate change in northern ethiopia elisabeth mezehausken department of geography, university of bergen, breiviken 40, 5045 bergensandviken, norway abstract. The study of meteorology dates back millennia, though significant progress in meteorology did not occur until the 18th century. Sep 28, 2018 hydrological drought is often linked with meteorological droughts. As mentioned, drought is difficult to define precisely, but operational definitions often help define the onset, severity, and end of droughts ashok et al. A completely adequate definition of drought is difficult to. Drought is one of the natural disasters that can be reverted by nature itself. The degree of risk is a function of exposure, vulnerability, and response. Sociopolitical impacts of meteorological droughts and. The state of drought is shown to be predicated on the existence of climatological norms for a multitude of processspecific terms.
Drought can be considered as a strictly meteorological phenomenon. A general working definition of meteorological drought is a reduction in rainfall supply compared with. The definition of drought should apply to broad aspects of the. Meteorological definitions of drought are the most prevalent.
It is a normal, recurrent feature of climate that occurs in virtually. It relates drought severity to the accumulated weighted differences between precipitation and evapotranspiration et. The impracticality of a universal drought definition. It is a normal, recurrent feature of climate that occurs in virtually all climate zones. Meteorological drought occurs when there is a prolonged time with less than average precipitation. Definitions of meteorological drought must be considered as specific to a region since the atmospheric conditions that result in deficiencies of precipitation. Drought impacts are a key indicator of vulnerability. Meteorological drought is a prerequisite for the other three droughts. Meteorologists define drought as a prolonged duration without rain. Many indices and indicators are available to assist in the quantitative assessment of drought severity. Drought united nations office for disaster risk reduction.
A drought in terms of meteorology takes into account deficiencies in measured precipitation. Identifying and explaining the effects of drought in rural. Meteorologists define drought on the basis of the degree of dryness and the duration of the dry period. These definitions of drought bring us to the main types of droughts, which include. Meteorological drought refers to a deficit in precipitation over some period of time while. Evaluation of meteorological, hydrological and groundwater. Dec 23, 2003 the impacts of future drought occurrences will be determined not only by the frequency and intensity of meteorological drought, but also by the number of people at risk and their degree of risk.
Socioeconomic drought socioeconomic drought is based on the impact of drought conditions meteorological, agricultural, or hydrological drought on supply and. Drought conditions and management strategies in zimbabwe s. Agricultural drought is based on the impacts to agriculture by factors such as rainfall deficits, soil water deficits, reduced ground water, or reservoir levels needed for irrigation. Agricultural, meteorological, hydrological and socioeconomic types of water droughts are there. The last deals with drought in terms of supply and demand, tracking the effects of water shortfall as it ripples through socioeconomic systems.
Drought is a protracted period of deficient precipitation resulting in extensive damage to crops, and a consequential loss of yield. Meteorological drought is usually defined on the basis of the degree of dryness in comparison to some normal or average amount and the duration of the dry period. There are different ways to define hydrological drought. A drought index is often a single number characterising the general drought behaviour at a measurement site, whereas a drought event definition is applied to select drought events in a time series including the beginning and end of the droughts. Meteorological drought usually precedes the other kinds of drought. Extreme drought in ethiopia stretches drought management. To this end, we define the term ecological drought as an episodic deficit in water availability that drives ecosystems beyond thresholds of vulnerability.
Drought is the consequence of anticipated natural precipitation reduction over an extended period of time, usually a season or more in length. Extreme drought in ethiopia stretches drought management systems. Drought is different than aridity, which is a permanent feature of climate in regions where low precipitation is the norm, as in a desert wilhite, 1992. This kind of drought takes places when dry weather patterns outweigh other climatic conditions. From 20062010, on average 15 % of the eu territory and 17 % of the eu population have been affected by meteorological droughts each year. The severity and frequency of meteorological and hydrological droughts have increased in parts of europe, in particular in southwestern and central europe. A drought can last for months or years, or may be declared after as few as 15 days. Meteorological drought in pakistan, 19802010 for calculating this average, usually a thirty year time period is selected, since.
Each years measurements are then compared to what is determined as a normal amount of precipitation and drought is determined from there. Meteorological drought is defined as the deficiency of precipitation from expected or normal levels over an extended period of time i. Drought has been a recurrent feature of the european climate. A drought or drouth is an event of prolonged shortages in the water supply, whether atmospheric belowaverage precipitation, surface water or ground water. Center for agricultural meteorology and climatology, institute of agriculture and natural resources, university of nebraska, lincoln, nebraska 685830728, usa 2. Meteorological drought definition criterion in different parts of the world glossary of meteorology 1959 defines drought as a period of abnormally.
Types, causes and effects of droughts earth eclipse. Drought characteristics and its response to the global climate variability in the yangtze river basin, china article. Drought indices used to define departures from normal conditions include 1 meteorological drought indices that identify periods with belownormal precipitation and abovenormal temperatures dai. No single operational definition of drought works in all circumstances, and this is a big part of why policy makers. In this lesson youll learn what a drought is, how serious they can be, how droughts are categorized and how one area is dealing with an epic drought.
Meteorological drought american meteorological society. Drought can be defined in terms of precipitation and temperatures, that is, meteorological and hydrological drought. The distribution of water on the earths surface is not even. Drought is a creeping phenomenon with no universal definitiondefinitions are region and application impact specific. This electronic version of the second edition of the glossary of meteorology is a living document and meant to be periodically updated as terms in our field evolve. Crop farmers describe drought as the absence of moisture, which inhibits crop growth. Apr, 2020 the dyk is a suite of notes that attempt to explain or clarify complex climate phenomena, climate monitoring products and methodologies, and climate system insights. But because dry conditions develop for different reasons, there is more than one definition of drought. Meteorological drought is based on the degree of dryness or rainfall deficit and the length of the dry period hydrological drought is based on the impact of rainfall deficits on the water supply such as stream flow, reservoir and lake levels, and ground water table decline agricultural drought refers to the impacts on agriculture by factors such as rainfall deficits, soil water. Jan 03, 2018 in particular, we need to define a new type of droughtecological droughtthat integrates the ecological, climatic, hydrological, socioeconomic, and cultural dimensions of drought. Drought is often defined as a temporary situation when the water demand of a.
Many of these impacts are associated with hydrological drought drought in rivers, lakes, and groundwater. A definition such as this one could be used in an operational assessment of drought severity and impacts by tracking meteorological variables, soil moisture, and crop conditions during the growing season, continually reevaluating the potential impact of these conditions on final yield. Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. Meteorological drought and is insufficient to meet the demands of human activities and the environment impacts. Meteorological drought usually precedes other kinds of drought and is said to occur when the seasonal rainfall received over an area is. Droughts pdf download types of droughts and factors. It is, therefore, crucial to understand the development and recovery of hydrological drought. How ecologists define drought, and why we should do better ingrid j. Agricultural drought links various characteris tics of meteorological or hydrological drought to agricultural impacts, focusing on precipita tion shortages, soil.
Figure 1 presents meteorological drought definition criterion in different parts of the world and presents the concept that droughts are a result of deficient rainfall. We support this definition with a novel, integrated framework for fig. Article about what drought is, its types, causes and effects. Drought is a deficiency in precipitation over an extended period.
Approximately 80% of zimbabweans depend on this agriculture which is mostly rain fed for their livelihoods madzwamuse. Moreover, the results revealed that the study area has become drier over the last three decades. The frequency and severity of hydrological drought is often defined on a watershed or river basin scale. Meteorological and climatological drought is defined in terms of the magnitude of a precipitation shortfall and the duration of this shortfall event. Agricultural drought occurs due to the lack of moisture in the soil and affects crops. Sociopolitical impacts of meteorological droughts and their. Contrasting climate variability and meteorological drought. Conceptual definitions may also be important in establishing drought policy.
Droughts are notoriously difficult to define and there is an extensive literature on their definition. By intensity, droughts are moderate, severe, or extreme. It can also be defined based on the impacts of the reduced precipitation on the economy and social aspects of the lives of people, that is agricultural and socioeconomic drought fao, 2004. Meteorological drought this type of drought all about the weather and occurs when there is a prolonged period of below average precipitation, which creates a natural shortage of. Most people think of a drought as a period of unusually dry weather that persists long enough to cause problems such as crop damage and water supply shortages. Agricultural drought this type of drought occurs when there isnt enough moisture to support average crop production on farms or average grass. Some arid areas of africa suffered from sustained reduction of rainfall over several decades of the late twentieth century, and recurring droughts. Extensive literature is available on droughts with respect to definition, methods of analysis and management procedures. For example, australian drought policy incorporates an understanding of normal climate variability into its definition of drought.
To this end, we define the term ecological drought as an episodic deficit in water availability that drives ecosystems beyond thresholds of vulnerability, impacts ecosystem services, and triggers feedbacks in natural andor human systems. Drought can be analyzed from multiple disciplinary perspectives, leading to several definitions of drought types of drought which include meteorological, hydrological, agricultural, and socioeconomic drought dracup et al. Droughts can be classified as meteorological, hydrologic, agricultural, and socioeconomic. Unisdr drought can be defined according to meteorological, agricultural, hydrological, and socioeconomic criteria. They use the previous 30 years of rainfall to create the. Drought is a complex natural hazard that impacts ecosystems and society in many. Drought conditions and management strategies in zimbabwe. Meteorological drought meteorological sometimes referred to as climatological droughts are simply defined as a shortfall of precipitation, over a period of time. The 19th century saw modest progress in the field after weather observation networks. Pdf definitions and effects of droughts researchgate. Depending on seasons, droughts are classified as spring, summer, or autumn.
A meteorological drought in terms of lack of precipitation is the primary cause of a drought. Many of these impacts are associated with hydrological drought drought. Analysis of future changes in meteorological drought. Usually, drought is talked about in one of two perspectives meteorological and hydrological. Dictionary defines drought as a long period with no rain, especially during a planting season. Drought is a complex natural hazard that impacts ecosystems and society in many ways.
Drought is usually based on longterm precipitation departures from normal, but there is no consensus regarding the threshold of the deficit or the minimum duration of the lack of precipitation that make a dry spell an official drought. The influence of human intervention through water management is shown to be intrinsic to the definition of drought in the universal sense and can only be eliminated in the case of purely meteorological drought. It is greatly determined by the overall absence of moisture in the atmosphere, for instance, lack of precipitation coupled with other weather conditions like high temperatures and dry winds. Definitions of meteorological drought must be considered as region specific since the atmospheric conditions that result in deficiencies of precipitation are highly variable from region to region. A wellknown index to describe meteorological droughts is the standard. Defining ecological drought for the twentyfirst century. Since drought differs so much from place to place, there is no absolute figure that defines a drought. Agriculture in zimbabwe contributes to 19% of the countrys gdp.
This type of drought is focused on the physical characteristics of drought, i. It usually first leads to an agricultural drought due to lack of soil water. To that end, ams has established a chief editor for the glossary who is responsible for updatingrevising existing terms and adding new terms. The rationale of this paper is to investigate peoples perception of climate variability, cli. Drought is a normal part of virtually all climatic regions, including areas with high and low average rainfall. It is due to the below normal rainfall and water shortage due to that.
Meteorological drought is caused by the lack of rains and dry weather is the main factor for this type of natural calamity. Mar 31, 2020 the definition of drought varies from place to place. Meteorological droughtthis type of drought all about the weather and occurs when there is a prolonged period of below average precipitation, which creates a natural shortage of available water. How ecologists define drought, and why we should do better. Drought indices spi different time scales reflect the impact of drought on the availability of the different water resources mckee et al. This is es sentially the definition given by the american. Droughts pdf download types of droughts and factors the term drought in simple words is the absence of water for a long period of time, at a place where it is considered abnormal as compared to its usual conditions. Drought can simply be defined as extended periods of precipitation shortage, normally for a season or more resulting in water deficiency for some human activities or environmental sustainability. Meteorological drought occurs when there is a lack of precipitation over a large.
Drought can be defined according to meteorological, hydrological, and agricultural criteria. A common criticism of meteorological criteria to define drought centers on the basis for the calculation of normal glantz and katz 1977. Review of literature will always help one to have information and. Extreme drought in ethiopia stretches drought management systems ci m at e cera funded by background ethiopia is one of the most populous countries in subsaharan africa and one of the fastestgrowing economies. Drought is therefore defined here as a prolonged and abnormal moisture deficiency.
Supplement to work package 2 hydrometeorological drought. When this phenomenon extends over a season or a longer period of time, precipitation is insufficient to meet the demands of human activities and the environment. In general, the results showed that the study area suffered from the meteorological drought more than the other two types of droughts. The amount of the shortfall and the duration are specific to location or region. Meteorological drought is defined usually on the basis of the degree of dryness in comparison to some normal or average amount and the duration of the dry period. For example, only six days without rain is a drought in bali. Agricultural droughts affect crop production or the ecology of the range. What is drought, its types, causes and effects natural. Hydrologists define drought as an extended period of less precipitation and stream flow. To this end, we define the term ecological drought as an episodic deficit in water availability that drives ecosystems beyond thresholds of. The impact of drought on subsaharan african economies.343 91 1088 712 1513 856 1093 482 1263 1408 1062 1132 1593 1387 1637 1015 97 724 482 113 168 586 822 981 1481 581 474 349 1008 466 1462