The Atlantic Multidecadal Oscillation ( AMO ), also known as Atlantic Multidecadal Variability ( AMV ), is the theorized variability of the sea surface temperature (SST) of the North Atlantic Ocean on the timescale of several decades.
85-443: While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude , and whether it has a typical timescale and can be classified as an oscillation. There is also discussion on the attribution of sea surface temperature change to natural or anthropogenic causes, especially in tropical Atlantic areas important for hurricane development. The Atlantic multidecadal oscillation
170-457: A continued cooling shift beginning 2014, and the authors note, "..unlike the last cold period in the Atlantic, the spatial pattern of sea surface temperature anomalies in the Atlantic is not uniformly cool, but instead has anomalously cold temperatures in the subpolar gyre , warm temperatures in the subtropics and cool anomalies over the tropics . The tripole pattern of anomalies has increased
255-446: A decrease below the minimum leading to direct danger for amphibian life), increased pollution of surface water , the drying out of wetlands , more and larger wildfires , higher deflation intensity, loss of biodiversity , worse health of trees and the appearance of pests and dendroid diseases. Drought-induced mortality of trees lacks in most climate models in their representation of forests as land carbon sink . Economic losses as
340-491: A diverse climate, ranging from hot, dry regions to cooler, wetter highland regions. The region has considerable variability in seasonal rainfall and a very complex topography. In the northern parts of the region within the Nile basin (Ethiopia, Sudan), the rainfall is characterized by an unimodal cycle with a wet season from July to September. The rest of the region has a bimodal annual cycle, featuring long rains from March to May and
425-434: A factor which increases the gap between developed and developing countries . Effects vary according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food-sources. Areas with populations that depend on water sources as a major food-source are more vulnerable to famine. Further examples of social and health consequences include: Wind erosion
510-498: A high level of reflected sunlight and above average prevalence of high pressure systems , winds carrying continental, rather than oceanic air masses, and ridges of high pressure areas aloft can prevent or restrict the developing of thunderstorm activity or rainfall over one certain region. Once a region is within drought, feedback mechanisms such as local arid air, hot conditions which can promote warm core ridging, and minimal evapotranspiration can worsen drought conditions. Within
595-434: A longer duration. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Droughts occur mainly in areas where normal levels of rainfall are, in themselves, low. If these factors do not support precipitation volumes sufficiently to reach the surface over a sufficient time, the result is a drought. Drought can be triggered by
680-465: A multi-agency partnership, drought is generally defined as "a deficiency of precipitation over an extended period of time (usually a season or more), resulting in a water shortage". The National Weather Service office of the NOAA defines drought as "a deficiency of moisture that results in adverse impacts on people, animals, or vegetation over a sizeable area". Drought is a complex phenomenon − relating to
765-749: A quasi-periodicity of about 70 years, with a few distinct warmer phases between ca. 1930–1965 and after 1995, and cool between 1900–1930 and 1965–1995 has been identified. In models, AMO-like variability is associated with small changes in the North Atlantic branch of the Thermohaline Circulation . However, historical oceanic observations are not sufficient to associate the derived AMO index to present-day circulation anomalies. Models and observations indicate that changes in atmospheric circulation, which induce changes in clouds, atmospheric dust and surface heat flux, are largely responsible for
850-606: A result of droughts include lower agricultural, forests, game and fishing output, higher food-production costs, lower energy-production levels in hydro plants, losses caused by depleted water tourism and transport revenue, problems with water supply for the energy sector and for technological processes in metallurgy, mining, the chemical, paper, wood, foodstuff industries etc., disruption of water supplies for municipal economies. Further examples of common environmental and economic consequences of drought include: Droughts can cause land degradation and loss of soil moisture, resulting in
935-549: A result. This means even regions where overall rainfall is expected to remain relatively stable will experience these impacts. These regions include central and northern Europe. Without climate change mitigation, around one third of land areas are likely to experience moderate or more severe drought by 2100. Due to global warming droughts are more frequent and intense than in the past. Human activity can directly trigger exacerbating factors such as over-farming, excessive irrigation , deforestation , and erosion adversely impact
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#17327717801991020-663: A significant role in drought. ENSO comprises two patterns of temperature anomalies in the central Pacific Ocean , known as La Niña and El Niño . La Niña events are generally associated with drier and hotter conditions and further exacerbation of drought in California and the Southwestern United States , and to some extent the U.S. Southeast . Meteorological scientists have observed that La Niñas have become more frequent over time. Conversely, during El Niño events, drier and hotter weather occurs in parts of
1105-570: A single dataset can be limiting, as it may not capture the full spectrum of drought characteristics and impacts. Careful monitoring of moisture levels can also help predict increased risk for wildfires. Mechanisms of producing precipitation include convective , stratiform , and orographic rainfall. Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation over
1190-568: A transient loudness attack, decay, sustain, and release. With waveforms containing many overtones, complex transient timbres can be achieved by assigning each overtone to its own distinct transient amplitude envelope. Unfortunately, this has the effect of modulating the loudness of the sound as well. It makes more sense to separate loudness and harmonic quality to be parameters controlled independently of each other. To do so, harmonic amplitude envelopes are frame-by-frame normalized to become amplitude proportion envelopes, where at each time frame all
1275-666: A water supply crisis across much of the country. As a result, many desalination plants were built for the first time ( see list ). By far the largest part of Australia is desert or semi-arid lands commonly known as the outback . A 2005 study by Australian and American researchers investigated the desertification of the interior, and suggested that one explanation was related to human settlers who arrived about 50,000 years ago. Regular burning by these settlers could have prevented monsoons from reaching interior Australia. In June 2008 it became known that an expert panel had warned of long term, maybe irreversible, severe ecological damage for
1360-496: A widespread blanket deposit that covers areas of hundreds of square kilometers and tens of meters thick. Loess often stands in either steep or vertical faces. Loess tends to develop into highly rich soils. Under appropriate climatic conditions, areas with loess are among the most agriculturally productive in the world. Loess deposits are geologically unstable by nature, and will erode very readily. Therefore, windbreaks (such as big trees and bushes) are often planted by farmers to reduce
1445-718: Is a recurring feature of the climate in most parts of the world, becoming more extreme and less predictable due to climate change , which dendrochronological studies date back to 1900. There are three kinds of drought effects, environmental, economic and social. Environmental effects include the drying of wetlands , more and larger wildfires, loss of biodiversity . Economic impacts of drought result due to negative disruptions to agriculture and livestock farming (causing food insecurity ), forestry, public water supplies , maritime navigation (due to e.g.: lower water levels), electric power supply (by affecting hydropower systems) and impacts on human health. Social and health costs include
1530-426: Is a similar concept to water scarcity . The different categories of droughts have different causes but similar effects: Several indices have been defined to quantify and monitor drought at different spatial and temporal scales. A key property of drought indices is their spatial comparability, and they must be statistically robust. Drought indices include: High-resolution drought information helps to better assess
1615-524: Is also connected with shifts in hurricane activity, rainfall patterns and intensity, and changes in fish populations. Evidence for a multidecadal climate oscillation centered in the North Atlantic began to emerge in 1980s work by Folland and colleagues, seen in Fig. 2.d.A. That oscillation was the sole focus of Schlesinger and Ramankutty in 1994, but the actual term Atlantic Multidecadal Oscillation (AMO)
1700-453: Is also negatively effected by drought stress, the reduction in crop yield results from a decrease in photosynthetic rate, changes in leaf development, and altered allocation of resources all due to drought stress. Crop plants exposed to drought stress suffer from reductions in leaf water potential and transpiration rate. Water-use efficiency increases in crops such as wheat while decreasing in others, such as potatoes. Plants need water for
1785-495: Is an increase in hurricane activity connected to a greenhouse gas induced global warming, it is currently obscured by the 60 year quasi-periodic cycle." With full consideration of meteorological science, the number of tropical storms that can mature into severe hurricanes is much greater during warm phases of the AMO than during cool phases, at least twice as many; the AMO is reflected in the frequency of severe Atlantic hurricanes. Based on
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#17327717801991870-398: Is dependent on waveform . If the wave shape being measured is greatly different from a sine wave, the relationship between RMS and average value changes. True RMS-responding meters were used in radio frequency measurements, where instruments measured the heating effect in a resistor to measure a current. The advent of microprocessor -controlled meters capable of calculating RMS by sampling
1955-477: Is insufficient rainfall to support vegetation. Drought is one of the most complex and major natural hazards , and it has devastating impacts on the environment, economy, water resources, agriculture, and society worldwide. One can divide the impacts of droughts and water shortages into three groups: environmental, economic and social (including health). Environmental effects of droughts include: lower surface and subterranean water-levels, lower flow-levels (with
2040-494: Is much more severe in arid areas and during times of drought. For example, in the Great Plains , it is estimated that soil loss due to wind erosion can be as much as 6100 times greater in drought years than in wet years. Loess is a homogeneous, typically nonstratified, porous, friable , slightly coherent, often calcareous, fine-grained, silty , pale yellow or buff, windblown ( Aeolian ) sediment . It generally occurs as
2125-446: Is not sinusoidal , peak amplitude is often used. If the reference is zero, this is the maximum absolute value of the signal; if the reference is a mean value ( DC component ), the peak amplitude is the maximum absolute value of the difference from that reference. Semi-amplitude means half of the peak-to-peak amplitude. The majority of scientific literature employs the term amplitude or peak amplitude to mean semi-amplitude. It
2210-451: Is proportional to the square of the RMS amplitude (and not, in general, to the square of the peak amplitude). For alternating current electric power , the universal practice is to specify RMS values of a sinusoidal waveform. One property of root mean square voltages and currents is that they produce the same heating effect as a direct current in a given resistance. The peak-to-peak value
2295-439: Is related to amplitude and intensity and is one of the most salient qualities of a sound, although in general sounds it can be recognized independently of amplitude . The square of the amplitude is proportional to the intensity of the wave. For electromagnetic radiation , the amplitude of a photon corresponds to the changes in the electric field of the wave. However, radio signals may be carried by electromagnetic radiation;
2380-410: Is related to low runoff, streamflow, and reservoir and groundwater storage. An agricultural or ecological drought is causing plant stress from a combination of evaporation and low soil moisture . Some organizations add another category: socioeconomic drought occurs when the demand for an economic good exceeds supply as a result of a weather-related shortfall in water supply. The socioeconomic drought
2465-481: Is represented by a scalar. Other sounds can have percussive amplitude envelopes featuring an abrupt onset followed by an immediate exponential decay. Percussive amplitude envelopes are characteristic of various impact sounds: two wine glasses clinking together, hitting a drum, slamming a door, etc. where the amplitude is transient and must be represented as either a continuous function or a discrete vector. Percussive amplitude envelopes model many common sounds that have
2550-493: Is the heterogeneous distribution of hydrologic extremes in space and time. For instance, El Niño can cause droughts in one part of the region and floods in the other. This is also a common situation within a country, e.g., in Ethiopia. The recent years with consecutive droughts followed by floods are a testament to the need to better forecast these kinds of events and their impacts. Approximately 2.4 billion people live in
2635-446: Is the most widely used measure of orbital wobble in astronomy and the measurement of small radial velocity semi-amplitudes of nearby stars is important in the search for exoplanets (see Doppler spectroscopy ). In general, the use of peak amplitude is simple and unambiguous only for symmetric periodic waves, like a sine wave, a square wave, or a triangle wave. For an asymmetric wave (periodic pulses in one direction, for example),
Atlantic multidecadal oscillation - Misplaced Pages Continue
2720-438: Is used, for example, when choosing rectifiers for power supplies, or when estimating the maximum voltage that insulation must withstand. Some common voltmeters are calibrated for RMS amplitude, but respond to the average value of a rectified waveform. Many digital voltmeters and all moving coil meters are in this category. The RMS calibration is only correct for a sine wave input since the ratio between peak, average and RMS values
2805-1084: The Amazon River Basin, Colombia , and Central America . Winters during the El Niño are warmer and drier than average conditions in the Northwest, northern Midwest, and northern Mideast United States, so those regions experience reduced snowfalls. Conditions are also drier than normal from December to February in south-central Africa, mainly in Zambia , Zimbabwe , Mozambique , and Botswana . Direct effects of El Niño resulting in drier conditions occur in parts of Southeast Asia and Northern Australia , increasing bush fires , worsening haze , and decreasing air quality dramatically. Drier-than-normal conditions are also in general observed in Queensland , inland Victoria , inland New South Wales , and eastern Tasmania from June to August. As warm water spreads from
2890-527: The Amazon basin , Australia , the Sahel region and India . For example, in 2005, parts of the Amazon basin experienced the worst drought in 100 years. Australia could experience more severe droughts and they could become more frequent in the future, a government-commissioned report said on July 6, 2008. The long Australian Millennial drought broke in 2010. The 2020–2022 Horn of Africa drought has surpassed
2975-605: The North Atlantic tropical cyclone activity. Paleoclimatologic studies have confirmed this pattern—increased rainfall in AMO warmphase, decreased in cold phase—for the Sahel over the past 3,000 years. A 2008 study correlated the Atlantic Multidecadal Mode (AMM), with HURDAT data (1851–2007), and noted a positive linear trend for minor hurricanes (category 1 and 2), but removed when the authors adjusted their model for undercounted storms, and stated "If there
3060-508: The drainage basin of the Himalayan rivers. India , China , Pakistan , Bangladesh , Nepal and Myanmar could experience floods followed by droughts in coming decades. More than 150 districts in India are drought vulnerable, mostly concentrated in the state of Rajasthan, Gujarat, Madhya Pradesh and its adjoining Chhattisgarh, Uttar Pradesh, northern Karnataka and adjoining Maharashtra of
3145-437: 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, with subsequent increased wildfire risks. Heat waves can significantly worsen drought conditions by increasing evapotranspiration . This dries out forests and other vegetation, and increases the amount of fuel for wildfires. Drought
3230-506: The square root of the mean over time of the square of the vertical distance of the graph from the rest state; i.e. the RMS of the AC waveform (with no DC component ). For complicated waveforms, especially non-repeating signals like noise, the RMS amplitude is usually used because it is both unambiguous and has physical significance. For example, the average power transmitted by an acoustic or electromagnetic wave or by an electrical signal
3315-511: The AMO being an oscillation or cycle. There was also a lack of oscillatory behaviour in models on time scales longer than El Niño Southern Oscillation; the AMV is indistinguishable from red noise , a typical null hypothesis to test whether there are oscillations in a model. Referring to the 2021 study, Michael Mann, the originator of the term AMO, put it more succinctly in a blog post on the matter: "my colleagues and I have provided what we consider to be
3400-511: The AMO is in its warm phase, these droughts tend to be more frequent or prolonged. Two of the most severe droughts of the 20th century occurred during the positive AMO between 1925 and 1965: The Dust Bowl of the 1930s and the 1950s drought. Florida and the Pacific Northwest tend to be the opposite—warm AMO, more rainfall. Climate models suggest that a warm phase of the AMO strengthens the summer rainfall over India and Sahel and
3485-506: The AMO." In 2014 Mann, Steinman and Miller showed that warming (and therefore any effects on hurricanes) were not caused by the AMO, writing: "certain procedures used in past studies to estimate internal variability, and in particular, an internal multidecadal oscillation termed the "Atlantic Multidecadal Oscillation" or "AMO", fail to isolate the true internal variability when it is a priori known. Such procedures yield an AMO signal with an inflated amplitude and biased phase, attributing some of
Atlantic multidecadal oscillation - Misplaced Pages Continue
3570-650: The Alps and glaciers' mass variability. Rainfall patterns are affected in North Eastern Brazilian and African Sahel. It is also associated with changes in the frequency of North American droughts and is reflected in the frequency of severe Atlantic hurricane activity. Recent research suggests that the AMO is related to the past occurrence of major droughts in the US Midwest and the Southwest. When
3655-518: The Horn of Africa during the period 2020–2023 leading to the third longest and most widespread drought on record with dire implications for food security (see Horn of Africa drought (2020–present) ). Conversely, other parts experienced extreme floods, e.g., the 2020 East Africa floods in Ethiopia, Rwanda, Kenya, Burundi, and Uganda, and the 2022 floods in South Sudan. A key feature in the region
3740-478: The ability of the land to capture and hold water. In arid climates, the main source of erosion is wind. Erosion can be the result of material movement by the wind. The wind can cause small particles to be lifted and therefore moved to another region (deflation). Suspended particles within the wind may impact on solid objects causing erosion by abrasion (ecological succession). Wind erosion generally occurs in areas with little or no vegetation, often in areas where there
3825-526: The absence of water − which is difficult to monitor and define. By the early 1980s, over 150 definitions of "drought" had already been published. The range of definitions reflects differences in regions, needs, and disciplinary approaches. There are three major categories of drought based on where in the water cycle the moisture deficit occurs: meteorological drought, hydrological drought, and agricultural or ecological drought. A meteorological drought occurs due to lack of precipitation . A hydrological drought
3910-434: The amplitude is a displacement . The amplitude of sound waves and audio signals (which relates to the volume) conventionally refers to the amplitude of the air pressure in the wave, but sometimes the amplitude of the displacement (movements of the air or the diaphragm of a speaker ) is described. The logarithm of the amplitude squared is usually quoted in dB , so a null amplitude corresponds to − ∞ dB. Loudness
3995-418: The amplitude of frequency - and phase -modulated waveform envelopes . In this simple wave equation The units of the amplitude depend on the type of wave, but are always in the same units as the oscillating variable. A more general representation of the wave equation is more complex, but the role of amplitude remains analogous to this simple case. For waves on a string , or in a medium such as water ,
4080-433: The analysis. However, if the global warming signal is significantly non-linear in time (i.e. not just a smooth linear increase), variations in the forced signal will leak into the AMO definition. Consequently, correlations with the AMO index may mask effects of global warming , as per Mann, Steinman and Miller, which also provides a more detailed history of the science development. Several methods have been proposed to remove
4165-448: The destruction of cropland productivity. This can result in diminished crop growth or yield productions and carrying capacity for livestock . Drought in combination with high levels of grazing pressure can function as the tipping point for an ecosystem, causing woody encroachment . Water stress affects plant development and quality in a variety of ways: firstly drought can cause poor germination and impaired seedling development. At
4250-417: The differences between the variable's extreme values . In older texts, the phase of a periodic function is sometimes called the amplitude. For symmetric periodic waves, like sine waves or triangle waves , peak amplitude and semi amplitude are the same. In audio system measurements , telecommunications and others where the measurand is a signal that swings above and below a reference value but
4335-458: The end of the twentieth century is externally forced. Frajka-Williams et al. 2017 pointed out that recent changes in cooling of the subpolar gyre , warm temperatures in the subtropics and cool anomalies over the tropics, increased the spatial distribution of meridional gradient in sea surface temperatures, which is not captured by the AMO Index. Based on the about 150-year instrumental record
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#17327717801994420-497: The forced and internally generated variability using signal to noise maximizing EOF analysis. Van Oldenborgh et al. derived an AMO index as the SST averaged over the extra-tropical North Atlantic (to remove the influence of ENSO that is greater at tropical latitude) minus the regression on global mean temperature. Guan and Nigam removed the non stationary global trend and Pacific natural variability before applying an EOF analysis to
4505-558: The global trend and El Niño-Southern Oscillation (ENSO) influence over the North Atlantic SST . Trenberth and Shea, assuming that the effect of global forcing over the North Atlantic is similar to the global ocean, subtracted the global (60°N-60°S) mean SST from the North Atlantic SST to derive a revised AMO index. Ting et al. however argue that the forced SST pattern is not globally uniform; they separated
4590-479: The harmonic amplitudes will add to 100% (or 1). This way, the main loudness-controlling envelope can be cleanly controlled. In Sound Recognition, max amplitude normalization can be used to help align the key harmonic features of 2 alike sounds, allowing similar timbres to be recognized independent of loudness. Drought 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
4675-459: The health of people who are directly exposed to this phenomenon (excessive heat waves ). Droughts can also cause limitations of water supplies, increased water pollution levels, high food-costs, stress caused by failed harvests, water scarcity , etc. Reduced water quality can occur because lower water-flows reduce dilution of pollutants and increase contamination of remaining water sources. This explains why droughts and water scarcity operate as
4760-419: The horrific drought in 2010–2011 in both duration and severity. More than 150 districts in India are drought vulnerable, mostly concentrated in the state of Rajasthan, Gujarat, Madhya Pradesh and its adjoining Chhattisgarh, Uttar Pradesh, northern Karnataka and adjoining Maharashtra of the country. Throughout history, humans have usually viewed droughts as disasters due to the impact on food availability and
4845-444: The intensity of the radiation ( amplitude modulation ) or the frequency of the radiation ( frequency modulation ) is oscillated and then the individual oscillations are varied (modulated) to produce the signal. Amplitude envelope refers to the changes in the amplitude of a sound over time, and is an influential property as it affects perception of timbre. A flat tone has a steady state amplitude that remains constant during time, which
4930-507: The lack of water in the plants, bushfires are common. Since water vapor becomes more energetic with increasing temperature, more water vapor is required to increase relative humidity values to 100% at higher temperatures (or to get the temperature to fall to the dew point). Periods of warmth quicken the pace of fruit and vegetable production, increase evaporation and transpiration from plants, and worsen drought conditions. The El Niño–Southern Oscillation (ENSO) phenomenon can sometimes play
5015-414: The most definitive evidence yet that the AMO doesn't actually exist." Amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period ). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplitude (see below), which are all functions of the magnitude of
5100-415: The negative effect on the health of people directly exposed to this phenomenon (excessive heat waves), high food costs, stress caused by failed harvests, water scarcity , etc. Drought can also lead to increased air pollution due to increased dust concentrations and wildfires . Prolonged droughts have caused mass migrations and humanitarian crisis . Examples for regions with increased drought risks are
5185-515: The occurrence of droughts has increased as a result of the increase in temperature and atmospheric evaporative demand . In addition, increased climate variability has increased the frequency and severity of drought events. Moreover, the occurrence and impact of droughts are aggravated by anthropogenic activities such as land use change and water management and demand. The IPCC Sixth Assessment Report also pointed out that "Warming over land drives an increase in atmospheric evaporative demand and in
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#17327717801995270-410: The peak amplitude becomes ambiguous. This is because the value is different depending on whether the maximum positive signal is measured relative to the mean, the maximum negative signal is measured relative to the mean, or the maximum positive signal is measured relative to the maximum negative signal (the peak-to-peak amplitude ) and then divided by two (the semi-amplitude ). In electrical engineering,
5355-543: The rainforest towards a " tipping point " where it would irreversibly start to die. It concludes that the rainforest is on the brink of being turned into savanna or desert , with catastrophic consequences for the world's climate. According to the WWF , the combination of climate change and deforestation increases the drying effect of dead trees that fuels forest fires. The 1997–2009 Millennium Drought in Australia led to
5440-409: The recent NH mean temperature rise to the AMO. The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming." There are only about 130–150 years of data based on instrument data, which are too few samples for conventional statistical approaches. With the aid of multi-century proxy reconstruction, a longer period of 424 years
5525-543: The reduction in plant growth and yields. Another factor influencing reduced plant growth and yields include the allocation of resources; following drought stress plants will allocate more resources to roots to aid in water uptake increasing root growth and reducing the growth of other plant parts while decreasing yields. The most negative impacts of drought for humans include crop failure , food crisis , famine, malnutrition, and poverty , which lead to loss of life and mass migration of people. There are negative effects on
5610-404: The residual North Atlantic SST. The linearly detrended index suggests that the North Atlantic SST anomaly at the end of the twentieth century is equally divided between the externally forced component and internally generated variability, and that the current peak is similar to middle twentieth century; by contrast the others methodology suggest that a large portion of the North Atlantic anomaly at
5695-451: The rest of society. People have viewed drought as a natural disaster or as something influenced by human activity , or as a result of supernatural forces. The IPCC Sixth Assessment Report defines a drought simply as "drier than normal conditions". This means that a drought is "a moisture deficit relative to the average water availability at a given location and season". According to National Integrated Drought Information System ,
5780-564: The same time plant growth relies on cellular division, cell enlargement, and differentiation. Drought stress impairs mitosis and cell elongation via loss of turgor pressure which results in poor growth. Development of leaves is also dependent upon turgor pressure, concentration of nutrients, and carbon assimilates all of which are reduced by drought conditions, thus drought stress lead to a decrease in leaf size and number. Plant height, biomass, leaf size and stem girth has been shown to decrease in maize under water limiting conditions. Crop yield
5865-464: The severity of drought events" and "Increased atmospheric evaporative demand increases plant water stress, leading to agricultural and ecological drought". There is a rise of compound warm-season droughts in Europe that are concurrent with an increase in potential evapotranspiration . Higher temperatures increase evaporation. This dries the soil and increases plant stress . Agriculture suffers as
5950-466: The short rains from October to December. The frequent occurrence of hydrological extremes, like droughts and floods , harms the already vulnerable population suffering from severe poverty and economic turmoil. Droughts prompted food shortages for example in 1984–85 , 2006 and 2011 . The Eastern African region experiences the impacts of climate change in different forms. For instance, below-average rainfall occurred for six consecutive rainy seasons in
6035-450: The spatial and temporal changes and variability in drought duration, severity, and magnitude at a much finer scale. This supports the development of site-specific adaptation measures. The application of multiple indices using different datasets helps to better manage and monitor droughts than using a single dataset, This is particularly the case in regions of the world where not enough data is available such as Africa and South America. Using
6120-465: The subpolar to subtropical meridional gradient in SSTs, which are not represented by the AMO index value, but which may lead to increased atmospheric baroclinicity and storminess." In a 2021 study by Michael Mann and others, it was shown that the periodicity of the AMO in the last millennium was driven by volcanic eruptions and other external forcings, and therefore that there is no compelling evidence for
6205-539: The tropical portion of the AMO. The Atlantic Multidecadal Oscillation (AMO) is important for how external forcings are linked with North Atlantic SSTs. The AMO is correlated to air temperatures and rainfall over much of the Northern Hemisphere, in particular in the summer climate in North America and Europe. Through changes in atmospheric circulation, the AMO can also modulate spring snowfall over
6290-584: The tropics, distinct, wet and dry seasons emerge due to the movement of the Intertropical Convergence Zone or Monsoon trough . The dry season greatly increases drought occurrence, and is characterized by its low humidity, with watering holes and rivers drying up. Because of the lack of these watering holes, many grazing animals are forced to migrate due to the lack of water in search of more fertile lands. Examples of such animals are zebras , elephants , and wildebeest . Because of
6375-407: The typical duration of negative and positive phases of the AMO, the current warm regime is expected to persist at least until 2015 and possibly as late as 2035. Enfield et al. assume a peak around 2020. However, Mann and Emanuel had found in 2006 that "anthropogenic factors are responsible for long-term trends in tropic Atlantic warmth and tropical cyclone activity" and "There is no apparent role of
6460-414: The uptake of nutrients from the soil, and for the transport of nutrients throughout the plant: drought conditions limit these functions leading to stunted growth. Drought stress also causes a decrease in photosynthetic activity in plants due to the reduction of photosynthetic tissues, stomatal closure, and reduced performance of photosynthetic machinery. This reduction in photosynthetic activity contributes to
6545-572: The usual solution to this ambiguity is to measure the amplitude from a defined reference potential (such as ground or 0 V). Strictly speaking, this is no longer amplitude since there is the possibility that a constant ( DC component ) is included in the measurement. Peak-to-peak amplitude (abbreviated p–p or PtP or PtoP ) is the change between peak (highest amplitude value) and trough (lowest amplitude value, which can be negative). With appropriate circuitry, peak-to-peak amplitudes of electric oscillations can be measured by meters or by viewing
6630-441: The waveform has made true RMS measurement commonplace. In telecommunications, pulse amplitude is the magnitude of a pulse parameter, such as the voltage level, current level, field intensity , or power level. Pulse amplitude is measured with respect to a specified reference and therefore should be modified by qualifiers, such as average , instantaneous , peak , or root-mean-square . Pulse amplitude also applies to
6715-410: The waveform on an oscilloscope . Peak-to-peak is a straightforward measurement on an oscilloscope, the peaks of the waveform being easily identified and measured against the graticule . This remains a common way of specifying amplitude, but sometimes other measures of amplitude are more appropriate. Root mean square (RMS) amplitude is used especially in electrical engineering : the RMS is defined as
6800-465: The west Pacific and the Indian Ocean to the east Pacific, it causes extensive drought in the western Pacific. Singapore experienced the driest February in 2014 since records began in 1869, with only 6.3 mm of rain falling in the month and temperatures hitting as high as 35 °C on 26 February. The years 1968 and 2005 had the next driest Februaries, when 8.4 mm of rain fell. Globally,
6885-725: The whole Murray-Darling basin if it did not receive sufficient water by October 2008. Australia could experience more severe droughts and they could become more frequent in the future, a government-commissioned report said on July 6, 2008. Australian environmentalist Tim Flannery , predicted that unless it made drastic changes, Perth in Western Australia could become the world's first ghost metropolis , an abandoned city with no more water to sustain its population. The long Australian Millennial drought broke in 2010. East Africa , including for example Ethiopia, Eritrea, Kenya, Somalia, South Sudan, Sudan, Tanzania, and Uganda, has
6970-513: The wind erosion of loess. In 2005, parts of the Amazon basin experienced the worst drought in 100 years. A 2006 article reported results showing that the forest in its present form could survive only three years of drought. Scientists at the Brazilian National Institute of Amazonian Research argue in the article that this drought response, coupled with the effects of deforestation on regional climate, are pushing
7055-634: Was around 10–20 year. The cumulative probability for all intervals 20 years or less was about 70%. There is no demonstrated predictability for when the AMO will switch, in any deterministic sense. Computer models, such as those that predict El Niño , are far from being able to do this. Enfield and colleagues have calculated the probability that a change in the AMO will occur within a given future time frame, assuming that historical variability persists. Probabilistic projections of this kind may prove to be useful for long-term planning in climate sensitive applications, such as water management. A 2017 study predicts
7140-633: Was coined by Michael Mann in a 2000 telephone interview with Richard Kerr, as recounted by Mann, p. 30 in The Hockey Stick and the Climate Wars: Dispatches from the Front Lines (2012). The AMO signal is usually defined from the patterns of SST variability in the North Atlantic once any linear trend has been removed. This detrending is intended to remove the influence of greenhouse gas -induced global warming from
7225-416: Was used by Enfield and Cid–Serrano as an illustration of an approach as described in their paper called "The Probabilistic Projection of Climate Risk". Their histogram of zero crossing intervals from a set of five re-sampled and smoothed version of Gray et al. (2004) index together with the maximum likelihood estimate gamma distribution fit to the histogram, showed that the largest frequency of regime interval
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