This article was downloaded by: 10.3.98.104 On: 30 Sep 2021 Access details: subscription number Publisher: CRC Press Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: 5 Howick Place, London SW1P 1WG, UK Handbook of Drought and Water Scarcity Principles of Drought and Water Scarcity Saeid Eslamian, Faezeh Eslamian Meteorological Drought Indices: Definitions Publication details https://www.routledgehandbooks.com/doi/10.1201/9781315404219-3 Nicolas R. Dalezios, Zoltan Dunkel, Saeid Eslamian Published online on: 12 Jul 2017 How to cite :- Nicolas R. Dalezios, Zoltan Dunkel, Saeid Eslamian. 12 Jul 2017, Meteorological Drought Indices: Definitions from: Handbook of Drought and Water Scarcity, Principles of Drought and Water Scarcity CRC Press Accessed on: 30 Sep 2021 https://www.routledgehandbooks.com/doi/10.1201/9781315404219-3 PLEASE SCROLL DOWN FOR DOCUMENT Full terms and conditions of use: https://www.routledgehandbooks.com/legal-notices/terms This Document PDF may be used for research, teaching and private study purposes. Any substantial or systematic reproductions, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The publisher shall not be liable for an loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. 3 Meteorological Drought Indices: Definitions Nicolas R. Dalezios 3.1 Introduction .......................................................................................27 University of Thessaly 3.2 Drought Concepts ..............................................................................29 and Drought Definitions and Types • Drought Quantification and Agricultural University Monitoring • Drought Features and Characteristics of Athens 3.3 Meteorological Drought and Indices ..............................................33 Zoltan Dunkel Meteorological Drought • Classification fo Meteorological Drought Hungarian Meteorological Indices • Description of Selected Meteorological Drought Indices Society 3.4 Discussions .........................................................................................39 Saeid Eslamian 3.5 Summary and Conclusions ..............................................................40 Isfahan University Authors ...........................................................................................................40 of Technology References ....................................................................................................... 41 Abstract Drought is part of nature’s climate variability recurring diachronically at a regional scale. Drought is considered as one of the major natural hazards having significant impact on several sectors of the economy, society, and environment. Drought is basically caused by the lack of precipitation events in a region over a period of time and can be regarded as an extreme climatic event. The early stages of accumulated precipitation deficiencies are referred to as meteorologi- cal drought being a region-specific natural event, since the atmospheric conditions that result in deficiencies of precipitation are highly variable from region to region. This chapter covers meteo- rological drought and its quantification through several drought indices. An attempt is under- taken to understand meteorological drought and explore several features through drought indices. There are many drought indicators and indices being used around the world. Indeed, the most commonly used drought indices are presented. Moreover, monitoring and assessment of meteo- rological droughts is also considered, along with significant drought impacts. The Standardized Precipitation Index is recommended by the World Meteorological Organization to be used uni- versally, but it may not be accepted as the only and absolute index. Based on specific regional and climatic conditions, the use of other indices should also be taken into consideration. 3.1 Introduction Drought is part of nature’s climate variability. Indeed, drought is considered as a natural regional phenomenon with a temporal periodicity. Essentially, droughts originate from a deficiency or lack of precipitation in a region over an extended period of time. This is why droughts are also referred to as “nonevents” and can be considered as extreme climatic events associated with water resources deficit. Moreover, drought is considered as one of the major natural hazards having significant impact on sev- eral sectors of the economy, society, and environment [35,37]. There are several unique characteristics, 27 Downloaded By: 10.3.98.104 At: 20:03 30 Sep 2021; For: 9781315404219, chapter3, 10.1201/9781315404219-3 28 Handbook of Drought and Water Scarcity which differentiate droughts from other environmental hazards, namely, its slow onset often charac- terized as a creeping phenomenon; its nonstructural impacts, which can be regional or local lasting for a long time or a very short time; and the absence of a universal definition leading to inaction 52[ ]. Moreover, the impacts of droughts may be severe and are neither immediate nor easily measured. All these may accumulate difficulties in drought assessment and response, which consequently may result in slow progress on drought preparedness plans and mitigation actions. There is a need to establish the context in which the drought phenomenon and its associated impacts are being described leading to a better definition. More than 150 published definitions of drought have been identified[ 46]. If drought is considered as a phenomenon, it is certainly an atmospheric phenome- non. However, when considering drought as a hazard, there is a tendency to define and classify droughts into different types. Definitions of drought help in identifying the duration and severity of drought and are useful in recognizing and planning for it. Four operational definitions are commonly used, namely, meteorological or climatological, agricultural or agrometeorological, hydrological, and socioeconomic drought [24]. With the exception of meteorological drought, the other types of drought, such as agricul- tural and hydrological, emphasize on the human or social aspects of drought in terms of the interaction between the natural characteristics of meteorological drought and human activities that depend on precipitation. As their names imply, these diverse drought types impact different sectors, but in most instances, the impacts related to each sector overlap both temporally and spatially. As already mentioned, all droughts begin with a deficiency of precipitation in a region over a period of time. These early stages of accumulated departure of precipitation from normal or expected are usually considered as meteorological drought [36]. A continuation of these dry conditions over a longer period of time, sometimes in association with above-normal temperatures, high winds, and low relative humidity, quickly results in impacts on agricultural and hydrological sectors (Figure 3.1). Meteorological droughts are characterized by a change in the local meteorological conditions, such as the prevalence of a high- pressure ridge. The geomorphological and climatological characteristics of a region play an important role in meteorological drought, since they may imply different precipitation regimes. Meteorological droughts can develop quickly, but they can also end just as quickly, if the precipitation deficits are Natural climate variability Precipitation deficiency High temp., high winds, low l (amount, intensity, timing) relative humidity, greater ca gi sunshine, less cloud cover Reduced infiltration, runoff, orolo drought deep percolation, and Increased evaporation te and transpiration groundwater recharge Me Soil water deficiency ural Plant water stress, reduced ricult drought biomass and yield Ag Time (duration) Time l Reduced streamflow, inflow to ca reservoirs, lakes, and ponds; gi reduced wetlands, wildlife habitat drought Hydrolo Economic impacts Social impactsEnvironmental impacts FIGURE 3.1 Drought types and temporal sequential procedure. (From Dalezios, N.R. et al., Nat. Hazards Earth Syst. Sci., 14, 2435, 2014.) Downloaded By: 10.3.98.104 At: 20:03 30 Sep 2021; For: 9781315404219, chapter3, 10.1201/9781315404219-3 Meteorological Drought Indices 29 relatively small. However, these types of drought may also develop into a multiseasonal event leading to one of the other types of drought. This chapter covers the subject of meteorological drought indices. A comprehensive presentation of drought concepts, definitions, and types is attempted. This is followed by a description of meteo- rological drought, along with its features and characteristics. Then, quantification of meteorological drought is presented through the use of indices. Drought monitoring and assessment is also consid- ered. Moreover, the improvement of drought prediction and early warning methods, as well as dis- semination of warnings, requires a continuous effort. Indeed, the impacts of drought are often slow to appear. A description of indicative meteorological drought indices is presented. The adoption of the Standardized Precipitation Index (SPI) and recommendation to be applied universally and the need for the development of a global