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A drought is a period of drier-than-normal conditions. A drought can last for days, months or years. Drought often has large impacts on the ecosystems and agriculture of affected regions, and causes harm to the local economy. Annual dry seasons in the tropics significantly increase the chances of a drought developing and subsequent wildfires. Periods of heat can significantly worsen drought conditions by hastening evaporation of water vapour, drying out forests and other vegetation and increasing fuel for wildfires.
Evapotranspiration (ET) is the combined processes which move water from the Earth's surface into the atmosphere. It covers both water evaporation and transpiration. Evapotranspiration is an important part of the local water cycle and climate, and measurement of it plays a key role in agricultural irrigation and water resource management.
The Palmer drought index, sometimes called the Palmer drought severity index (PDSI), is a regional drought index commonly used for monitoring drought events and studying areal extent and severity of drought episodes. The index uses precipitation and temperature data to study moisture supply and demand using a simple water balance model. It was developed by meteorologist Wayne Palmer, who first published his method in the 1965 paper Meteorological Drought for the Office of Climatology of the U.S. Weather Bureau.
El Niño–Southern Oscillation (ENSO) is an irregular periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. The warming phase of the sea temperature is known as El Niño and the cooling phase as La Niña. The Southern Oscillation is the accompanying atmospheric component, coupled with the sea temperature change: El Niño is accompanied by high air surface pressure in the tropical western Pacific and La Niña with low air surface pressure there. The two periods last several months each and typically occur every few years with varying intensity per period.
Ecohydrology is an interdisciplinary scientific field studying the interactions between water and ecological systems. It is considered a sub discipline of hydrology, with an ecological focus. These interactions may take place within water bodies, such as rivers and lakes, or on land, in forests, deserts, and other terrestrial ecosystems. Areas of research in ecohydrology include transpiration and plant water use, adaption of organisms to their water environment, influence of vegetation and benthic plants on stream flow and function, and feedbacks between ecological processes, the soil carbon sponge and the hydrological cycle.
An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. The American Meteorological Society defined it in meteorology and climatology, as "the degree to which a climate lacks effective, life-promoting moisture". Aridity is different from drought because aridity is permanent whereas drought is temporary. A number of aridity indices have been proposed ; these indicators serve to identify, locate or delimit regions that suffer from a deficit of available water, a condition that can severely affect the effective use of the land for such activities as agriculture or stock-farming.
Baseflow is the portion of the streamflow that is sustained between precipitation events, fed to streams by delayed pathways. It should not be confused with groundwater flow. Fair weather flow is also called base flow.
The Keetch–Byram drought index, created by John Keetch and George Byram in 1968 for the United States Department of Agriculture's Forest Service, is a measure of drought conditions. It is commonly used for the purpose of predicting the likelihood and severity of wildfire. It is calculated based on rainfall, air temperature, and other meteorological factors.
The United States' contiguous western and especially southwestern region has experienced widespread drought since about year 2000. Below normal precipitation leads to drought, and is caused by an above average persistence of high pressure over the affected area. Changes in the track of extratropical cyclones, which can occur during climate cycles such as the El Niño-Southern Oscillation, or ENSO, as well as the North Atlantic Oscillation, Pacific Decadal Oscillation, and Atlantic multidecadal oscillation, modulate which areas are more prone to drought. Increased drought frequency and severity is also expected to be one of the effects of global warming.
An endorheic lake is a collection of water within an endorheic basin, or sink, with no evident outlet. Endorheic lakes are generally saline as a result of being unable to get rid of solutes left in the lake by evaporation. These lakes can be used as indicators of anthropogenic change, such as irrigation or climate change, in the areas surrounding them. Lakes with subsurface drainage are considered cryptorheic.
Prolonged, large-area droughts are among Canada's costliest natural disasters having major impacts on a wide range of sectors including agriculture, forestry, industry, municipalities, recreation, human health, society and ecosystems. They frequently stress water availability by depleting soil moisture, reducing stream flows, lowering lake and reservoir levels, and diminishing groundwater supplies. This ultimately affects several economic activities including for example, decreased agricultural production, less hydro-electric power generation, and increased freshwater transportation costs. Droughts also create major environmental hazards such as reduced water quality, wetland loss, soil erosion and degradation, and ecological habitat destruction.
A water year is a term commonly used in hydrology to describe a time period of 12 months for which precipitation totals are measured. Its beginning differs from the calendar year because part of the precipitation that falls in late autumn and winter accumulates as snow and does not drain until the following spring or summer's snowmelt. The goal is to ensure that as much as possible of the surface runoff during the water year is attributable to the precipitation during the same water year.
A vegetation index (VI) is a spectral imaging transformation of two or more image bands designed to enhance the contribution of vegetation properties and allow reliable spatial and temporal inter-comparisons of terrestrial photosynthetic activity and canopy structural variations.
The African humid period is a climate period in Africa during the late Pleistocene and Holocene geologic epochs, when northern Africa was wetter than today. The covering of much of the Sahara desert by grasses, trees and lakes was caused by changes in the Earth's axial tilt; changes in vegetation and dust in the Sahara which strengthened the African monsoon; and increased greenhouse gases. During the preceding Last Glacial Maximum, the Sahara contained extensive dune fields and was mostly uninhabited. It was much larger than today, and its lakes and rivers such as Lake Victoria and the White Nile were either dry or at low levels. The humid period began about 14,600–14,500 years ago at the end of Heinrich event 1, simultaneously to the Bølling–Allerød warming. Rivers and lakes such as Lake Chad formed or expanded, glaciers grew on Mount Kilimanjaro and the Sahara retreated. Two major dry fluctuations occurred; during the Younger Dryas and the short 8.2 kiloyear event. The African humid period ended 6,000–5,000 years ago during the Piora Oscillation cold period. While some evidence points to an end 5,500 years ago, in the Sahel, Arabia and East Africa, the end of the period appears to have taken place in several steps, such as the 4.2-kiloyear event.
BAITSSS is biophysical Evapotranspiration (ET) computer model that determines water use, primarily in agriculture landscape, using remote sensing-based information. It was developed and refined by Ramesh Dhungel and the water resources group at University of Idaho's Kimberly Research and Extension Center since 2010. It has been used in different areas in the United States including Southern Idaho, Northern California, northwest Kansas, Texas, and Arizona.
Climate change in the Middle East and North Africa (MENA) refers to changes in the climate of the MENA region and the subsequent response, adaption and mitigation strategies of countries in the region. In 2018, the MENA region emitted 3.2 billion tonnes of carbon dioxide and produced 8.7% of global greenhouse gas emissions (GHG) despite making up only 6% of the global population. These emissions are mostly from the energy sector, an integral component of many Middle Eastern and North African economies due to the extensive oil and natural gas reserves that are found within the region. The region of Middle East is one of the most vulnerable to climate change. The impacts include increase in drought conditions, aridity, heatwaves and sea level rise.
The effects of climate change on the water cycle are profound and have been described as an intensification or a strengthening of the water cycle. This effect has been observed since at least 1980. One example is the intensification of heavy precipitation events. This has important negative effects on the availability of freshwater resources, as well as other water reservoirs such as oceans, ice sheets, atmosphere and land surface. The water cycle is essential to life on Earth and plays a large role in the global climate and the ocean circulation. The warming of our planet is expected to cause changes in the water cycle for various reasons. For example, warmer atmosphere can contain more water vapor which has effects on evaporation and rainfall.
The Thornthwaite climate classification is a climate classification system created by American climatologist Charles Warren Thornthwaite in 1931 and modified in 1948.
A flash drought is a type of drought characterized by its rapid onset, intensification, and severity over a relatively short timescale, usually within a few days or weeks. This concept has evolved during the last decade as researchers have become more interested in understanding and mitigating its impacts. Flash droughts differ from other drought categories such as meteorological, hydrological, agricultural, ecological, and socioeconomic droughts, in that they develop and intensify more quickly, posing unique challenges for monitoring, prediction, and mitigation.
References
- ↑ Svoboda, Mark D.; Fuchs, Brian A. (2017-09-25), "Handbook of Drought Indicators and Indices*", Drought and Water Crises, Second edition. | Boca Raton : CRC Press, 2018. | 1st edition published in 2005.: CRC Press, pp. 155–208, doi:10.1201/b22009-11, ISBN 978-1-315-26555-1 , retrieved 2023-05-18
{{citation}}: CS1 maint: location (link) - ↑ Vicente-Serrano S.M.; Santiago Beguería; Juan I. López-Moreno (2010). "A Multiscalar Drought Index Sensitive to Global Warming: The Standardized Precipitation Evapotranspiration Index". Journal of Climate. 23 (7): 1696–1718. Bibcode:2010JCli...23.1696V. doi: 10.1175/2009JCLI2909.1 . S2CID 3826822.
- ↑ Stagge, J. H.; Tallaksen, L. M.; Xu, C. Y.; Van Lanen, H. A. (2014). "Standardized precipitation-evapotranspiration index (SPEI): Sensitivity to potential evapotranspiration model and parameters". Hydrology in a changing world. IAHS-AISH Proceedings and Reports. Vol. 363. pp. 367–373. ISBN 9781907161414.
- ↑ Tirivarombo, S.; Osupile, D.; Eliasson, P. (2018). "Drought monitoring and analysis: standardised precipitation evapotranspiration index (SPEI) and standardised precipitation index (SPI)". Physics and Chemistry of the Earth, Parts A/B/C. 106: 1–10. Bibcode:2018PCE...106....1T. doi:10.1016/j.pce.2018.07.001. S2CID 134507763.
- ↑ Hayes, Michael J. (2006-10-13), "Drought Indices", Van Nostrand's Scientific Encyclopedia, Hoboken, NJ, USA: John Wiley & Sons, Inc., doi:10.1002/0471743984.vse8593, ISBN 0471743984 , retrieved 2023-05-18
