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Droughts
\"The weather anchor announces that your area is experiencing a drought. Where do droughts happen? How do we know that we are in a drought? Why is rainfall important? Do droughts just affect people? Can scientists keep track of rainfall? Read and find out\"--Amazon.com.
Book
Climate Change and Drought: a Perspective on Drought Indices
Droughts occur naturally, but climate change has generally accelerated the hydrological processes to make them set in quicker and become more intense, with many consequences, not the least of which is increased wildfire risk. There are different types of drought being studied, such as meteorological, agricultural, hydrological, and socioeconomic droughts; however, a lack of unanimous definition complicates drought study. Drought indices are used as proxies to track and quantify droughts; therefore, accurate formulation of robust drought indices is important to investigate drought characteristics under the warming climate. Because different drought indices show different degrees of sensitivity to the same level of continental warming, robustness of drought indices against change in temperature and other variables should be prioritized. A formulation of drought indices without considering the factors that govern the background state may lead to drought artifacts under a warming climate. Consideration of downscaling techniques, availability of climate data, estimation of potential evapotranspiration (PET), baseline period, non-stationary climate information, and anthropogenic forcing can be additional challenges for a reliable drought assessment under climate change. As one formulation of PET based on temperatures can lead to overestimation of future drying, estimation of PET based on the energy budget framework can be a better approach compared to only temperature-based equations. Although the performance of drought indicators can be improved by incorporating reliable soil moisture estimates, a challenge arises due to limited reliable observed data for verification. Moreover, the uncertainties associated with meteorological forcings in hydrological models can lead to unreliable soil moisture estimates under climate change scenarios.
Journal Article
Sunshine and drought
Learn all about sunshine, what it is, why it is important, and how it affects our world.
Book
Drought Spatial Extent and Dependence Increase During Drought Propagation From the Atmosphere to the Hydrosphere
As droughts propagate both in time and space, their impacts increase because of changes in drought properties. Because temporal and spatial drought propagation are mostly studied separately, it is yet unknown how drought spatial extent and connectedness change as droughts propagate though the hydrological cycle from precipitation to streamflow and groundwater. Here, we use a large‐sample dataset of 70 catchments in Central Europe to study the propagation of local and spatial drought characteristics. We show that drought propagation leads to longer, later, and fewer droughts with larger spatial extents. 75% of the precipitation droughts propagate to P‐ET, among these 20% propagate further to streamflow and 10% to groundwater. Of the streamflow droughts, 40% propagate to groundwater. Drought extent and dependence increase during drought propagation along the drought propagation pathway from precipitation to streamflow thanks to synchronizing effects of the land‐surface but decreases again for groundwater because of sub‐surface heterogeneity. Plain Language Summary As rainfall deficits develop into discharge and groundwater deficits, the impacts of droughts increase. While we know that drought impacts and properties change during drought development, it is yet unknown how the spatial characteristics of droughts change over the duration of an event. Here, we use a large dataset of 70 watersheds in Central Europe to study the development of drought characteristics over the duration of a drought event. We show that drought development leads to longer, later, fewer, and larger droughts. 20% of the rainfall droughts develop into discharge droughts, and 10% into groundwater droughts. Of the discharge droughts, 40% develop into groundwater droughts. Drought extent increases during drought development from rainfall to discharge thanks to effects at the land‐surface but decreases again for groundwater because of sub‐surface variations. Key Points Drought propagation affects local and regional drought characteristics and leads to longer, later, fewer, and larger droughts Only 20% of the precipitation deficits propagate to streamflow, while 40% of the streamflow deficits propagate to groundwater Spatial drought connectedness increases from precipitation to streamflow but decreases again for groundwater
Journal Article
Droughts : be aware and prepare
\"Describes how droughts form, their effects, and how people can prepare for them\"--Provided by publisher.
Book
A comprehensive assessment of remote sensing and traditional based drought monitoring indices at global and regional scale
This study reports a comprehensive review on drought indices used in monitoring meteorological, agricultural, hydrological, and socio-economic drought. Drought indices have been introduced as an important approach to quantitative and qualitative calculations of drought's severity and impact. There were 111 drought indices reviewed in this study, which fall into two categories: traditional (location-specific/model) and remote sensing (RS). Out of 111 indices, 44 belong to the traditional indices and 67 belong to the RS section. This study shows that meteorological drought monitoring has the highest number (22) of traditional indices, about 20% overall, while the lowest (7) agricultural drought monitoring is 6.3%. The specialty is that when considering remote sensing-based drought indices, 90% are used for agricultural drought monitoring and 10% for hydrological and meteorological drought monitoring. However, the study found that advances in satellite technology have accelerated the design of new drought indices and that replacing traditional location-specific data with satellite observation makes it easier to calculate more spatial distribution and resolution.
Journal Article
Evaluating the spatiotemporal patterns of drought characteristics in a semi‐arid region of Limpopo Province, South Africa
Drought is a complex phenomenon resulting from below-average rainfall and is characterized by frequency, duration, and severity, occurring at a regional scale with dire consequences, especially in semiarid environments. This study used the Reconnaissance Drought Index (RDI) to assess drought severity in two district municipalities in Limpopo Province. Rainfall and air temperature data from 12 stations covering 1970–2020 were obtained from the Agricultural Research Council. The calculation of RDI relies on the monthly accumulation ratio of total rainfall to potential evapotranspiration (PET). For this study, PET was estimated using the Hargreaves and Samani temperature-based approach. The RDI results showed a high spatial–temporal variation in drought characteristics over the study area. All stations experienced extreme drought conditions in different years, with the maximum drought severity (-3.40) occurring from 2002–2003 in the western parts of the study area, indicating extreme drought. Furthermore, the results revealed continuous drought conditions over various periods, including severe droughts between 1995 and 1998 and between 2014 and 2016, with the severity varying between mild and moderate drought conditions. The results reveal notable but nonuniform drought patterns as the climate evolves, with potential implications for water availability and livelihoods. The study's findings underscore the significance of adopting multidimensional approaches to drought assessment that encompass meteorological and hydrological factors to inform strategies for adaptive water management and policy formulation in the face of a changing climate.
Journal Article