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University of Thessaly (UTH) 2010

Spatial drought estimation

Kanellou, Efrosyni of Christoforos / Κανέλλου, Ευφροσύνη Χριστοφόρου

Titre : Spatial drought estimation

Περιοχική εκτίμηση ξηρασίας

Auteur : Kanellou, Efrosyni of / , Ευφροσύνη Χριστοφόρου

Université de soutenance : University of Thessaly (UTH)

Grade : Doctor of Philosophy (PhD) 2010

Résumé
In the last decades the study and investigation of environmental hazards has particularly increased due to the frequent recurrence of their extreme forms. Drought, which is included into those risks, causes great concern in a large part of the world population and for that reason the plans of its management are increased at all levels. In early 1980’s, only 3 states in the U.S.A. (New York, South Dakota and Colorado) had drought plans. Today, most states have already developed plans or are in the process of developing a plan. One of the main reasons for developing such plans is the enormous cost (financial, social and environmental) associated with the impact of this phenomenon. Drought is a complex natural phenomenon. It is acknowledged that the major cause of drought is lower than average rainfall. The rainfall deficit will have different impacts depending on other factors, including meteorological conditions, ecosystem type, and social and economic circumstances. A universally accepted definition of drought does not exist. Currently, there are four major types of drought (Meteorological, Agricultural, Hydrological and Socioeconomic drought impacts), which are broadly defined and agreed upon in the scientific literature (WMO, 1975 ; Alley, 1984, 1985 ; Wilhite and Glantz, 1985 ; White, 1990). Drought is certainly the costliest of all natural disasters. From 1991 to 2000, drought was responsible for more than 280,000 deaths and has costed tens of millions of dollars in damages. The areas, which are occasionally suffered from drought worst dry-spell, are the Southern Europe, North America, Africa (Sub Sahara) and the South East and Central Asia. The implications of this phenomenon are numerous and significant influencing a wide range of activities in areas where it occurs. For example, drought has serious consequences in the vegetation, causing significant reduction in its density and condition, mainly during the spring, in the region of Caspian Sea, in the West of India and in the most of the regions of Mongolia and China. Since 1991, nearly 15 million people in Ethiopia and 60% of the area of Kenya were hit by severe drought. In Afghanistan and Pakistan, the lack of rainfall in addition with the increase of temperature caused a significant reduction of vegetation, even in the winter period. In the U.S.A., the occurrence of drought is responsible for 228 the reduction of crops production, pasture disappearance and the intense of fire in many areas (Source : ISDR-International Strategy for Disaster Reduction). For drought assessment several studies have been carried out, which mainly estimate the precipitation shortage and the water supply deficit (Keyantash and Dracup, 2002). These studies have focused on the development of drought indices for drought identification and quantification. There are several drought indices, based on ground measurements that measure how much precipitation for a given period of time has deviated from historically established norms. Although none of the major indices is inherently superior to the rest in all circumstances, some indices are better suited than others for certain uses. The traditional, conventional methods using surface data are normally readily available throughout the world (compared to other data types) and they are used to describe most of the basic drought characteristics (as magnitude, duration, frequency, severity), but they are unable to determine the spatial variability of drought, since they calculate drought only at a point level (weather station). With the development of remote sensing, spatial drought monitoring and assessment becomes possible. Remote sensing is an important tool for the detection of the spatial and temporal drought distribution at different scales. Satellite data can significantly contribute to monitor drought.

Mots Clés : Drought ; Satellite data ; Spatial estimation ; Remote sensing ; Geographical Information Systems (GIS) ; Reconnaissance drought index (RDI)

Présentation (National Archive of PhD)

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Page publiée le 20 janvier 2017, mise à jour le 4 janvier 2022