At the close of the twentieth century, natural hazards and disasters are one of the most common forms of disasters around the world. Natural disasters cause in significant loss of life and serious economic, environmental and social impacts that greatly retard the development process. Careful hazard assessment and planning, and a range of social, economic and political measures, can significantly contain these threats.
Most commonly, there are three components in a natural disaster plan: monitoring and early warning; risk assessment and mitigation and response. Given the improved tools and technologies available today, it is possible to provide disaster information and minimize the potential damage of disasters.
So, the national early warning systems would be discussed, as one of the important component of natural disaster risk management.
Different types of natural disasters occur, such as drought, flood, earthquake, sea-level rise, dust storm, and etc, but Flood hazard and disaster is one of the most frequent and damaging types of natural disasters. They have been the most common type of geophysical disaster in the latter half of the twentieth century in India, generating an estimated more than 20 percent of all disasters from 1950 to 2003.
A flood is an overflow or accumulation of an expanse of water that submerges land. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its normal boundaries. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area.
Floods can also occur in rivers, when the strength of the river is so high it flows out of the river channel, particularly at bends or meanders and causes damage to homes and businesses along such rivers. While flood damage can be virtually eliminated by moving away from rivers and other bodies of water, since time out of mind, people have lived and worked by the water to seek sustenance and capitalize on the gains of cheap and easy travel and commerce by being near water. That humans continue to inhabit areas threatened by flood damage is evidence that the perceived value of living near the water exceeds the cost of repeated periodic flooding.
Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding the capacity of a river's channel. Causes include heavy rains from monsoons, hurricanes and tropical depressions, foreign winds and warm rain affecting snow pack. Unexpected drainage obstructions such as landslides, ice, or debris can cause slow flooding upstream of the obstruction.
Fast kinds: include flash floods resulting from convective precipitation or sudden release from an upstream impoundment created behind a dam, landslide, or glacier.
Commonly caused by a combination of sea tidal surges caused by storm-force winds. A storm surge, from either a tropical cyclone or an extra tropical cyclone, falls within this category.
Caused by severe sea storms, or as a result of another hazard (e.g. tsunami or hurricane). A storm surge, from either a tropical cyclone or an extra tropical cyclone, falls within this category.
Caused by a significant and unexpected event e.g. dam breakage, or as a result of another hazard (e.g. earthquake or volcanic eruption).
A muddy flood is generated by run off on crop land.
A muddy flood is produced by an accumulation of runoff generated on cropland. Sediments are then detached by runoff and carried as suspended matter or bed load. Muddy runoff is more likely detected when it reaches inhabited areas.
Muddy floods are therefore a hill slope process, and confusion with mudflows produced by mass movements should be avoided.
Physical damage - Can range anywhere from bridges, cars, buildings, sewer systems, roadways, canals and any other type of structure.
Casualties - People and livestock die due to drowning. It can also lead to epidemics and waterborne diseases.
Water supplies - Contamination of water. Clean drinking water becomes scarce.
Diseases - Unhygienic conditions. Spread of water-borne diseases.
Crops and food supplies - Shortage of food crops can be caused due to loss of entire harvest.However, lowlands near rivers depend upon river silt deposited by floods in order to add nutrients to the local soil.
Trees - Non-tolerant species can die from suffocation.
Economic - Economic hardship, due to: temporary decline in tourism, rebuilding costs, food shortage leading to price increase etc.
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale .
In its most generic sense, the word earthquake is used to describe any seismic event — whether a natural phenomenon or an event caused by humans — that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and nuclear experiments. An earthquake's point of initial rupture is called its focus or hypocenter. The term epicenter refers to the point at ground level directly above the hypocenter
There are three main types of fault that may cause an earthquake: normal, reverse (thrust) and strike-slip. Normal and reverse faulting are examples of dip-slip, where the displacement along the fault is in the direction of dip and movement on them involves a vertical component. Normal faults occur mainly in areas where the crust is being extended such as a divergent boundary.
Reverse faults occur in areas where the crust is being shortened such as at a convergent boundary. Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other ; transform boundaries are a particular type of strike-slip fault. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip.
Where plate boundaries occur within continental lithosphere, deformation is spread out a over a much larger area than the plate boundary itself. In the case of the San Andreas fault continental transform, many earthquakes occur away from the plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace (e.g. the “Big bend” region). The Northridge earthquake was associated with movement on a blind thrust within such a zone. Another example is the strongly oblique convergent plate boundary between the Arabian and Eurasian plates where it runs through the northwestern part of the Zagros mountains.
The deformation associated with this plate boundary is partitioned into nearly pure thrust sense movements perpendicular to the boundary over a wide zone to the southwest and nearly pure strike-slip motion along the Main Recent Fault close to the actual plate boundary itself. This is demonstrated by earthquake focal mechanisms. All tectonic plates have internal stress fields caused by their interactions with neighbouring plates and sedimentary loading or unloading (e.g. deglaciation). These stresses may be sufficient to cause failure along existing fault planes, giving rise to intraplate earthquakes.
The majority of tectonic earthquakes originate at the ring of fire in depths not exceeding tens of kilometers. Earthquakes occurring at a depth of less than 70 km are classified as 'shallow-focus' earthquakes, while those with a focal-depth between 70 and 300 km are commonly termed 'mid-focus' or 'intermediate-depth' earthquakes. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at much greater depths (ranging from 300 up to 700 kilometers).These seismically active areas of subduction are known as Wadati-Benioff zones. Deep-focus earthquakes occur at a depth at which the sub ducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep-focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.
Earthquakes often occur in volcanic regions and are caused there, both by tectonic faults and the movement of magma in volcanoes. Such earthquakes can serve as an early warning of volcanic eruptions, like during the Mount St. Helens eruption of 1980. Earthquake swarms serve as markers for the location of the flowing magma throughout the volcanoes. In the United States, these are then recorded by seismometers and tilt meters (a device which measures the ground slope) and used as sensors to predict imminent or upcoming eruptions.
Most earthquakes form part of a sequence, related to each other in terms of location and time. Most earthquake clusters consist of small tremors which cause little to no damage, but there is a theory that earthquakes can recur in a regular pattern.
Landslides are a major geologic hazard because they can happen at any place in the world, much like earthquakes. Severe storms, earthquakes, volcanic activity, coastal wave attack, and wildfires can all produce slope instability. Landslide danger may be possible even though emergency personnel are attempting rescue.
Following an earthquake, fires can be generated by break of the electrical power or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started. For example, the deaths in the 1906 San Francisco earthquake were caused more by the fires than by the earthquake itself.
Soil liquefaction occurs when, because of the shaking, water-saturated granular material (such as sand) temporarily loses its strength and transforms from a solid to a liquid. Soil liquefaction may cause rigid structures, as buildings or bridges, to tilt or sink into the liquefied deposits. This can be a devastating effect of earthquakes. For example, in the 1964 Alaska earthquake, many buildings were sunk into the ground by soil liquefaction, eventually collapsing upon themselves
Tsunamis are long-wavelength, long-period sea waves produced by an sudden or abrupt movement of large volumes of water. In the open ocean, the distance between wave crests can surpass 100 kilometers, and the wave periods can vary from five minutes to one hour. Such tsunamis travel 600-800 kilometers per hour, depending on water depth. Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them.
Ordinarily, subduction earthquakes under magnitude 7.5 on the Richter scale do not cause tsunamis, although some instances of this have been recorded. Most destructive tsunamis are caused by earthquakes of magnitude 7.5 or more.
Drought in India has resulted in tens of millions of deaths over the course of the 18th, 19th, and 20th centuries. Indian agriculture is heavily dependent on the climate of India: a favorable southwest summer monsoon is critical in securing water for irrigating Indian crops. In some parts of India, the failure of the monsoons result in water shortages, resulting in below-average crop yields. This is particularly true of major drought-prone regions such as southern and eastern Maharashtra, northern Karnataka, Andhra Pradesh, Orissa, Gujarat, and Rajasthan.
A cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth.
Large-scale cyclonic circulations are almost always centered on areas of low atmospheric pressure. The largest low-pressure systems are cold-core polar cyclones and extra tropical cyclones which lie on the synoptic scale. Warm-core cyclones such as tropical cyclones, mesocyclones, and polar lows lie within the smaller mesoscale. Subtropical cyclones are of intermediate size. Cyclones have also been seen on other planets outside of the Earth, such as Mars and Neptune.
Cyclogenesis describes the process of cyclone formation and intensification .Extra tropical cyclones form as waves in large regions of enhanced midlatitude temperature contrasts called baroclinic zones. These zones contract to form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, cyclones occlude as cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the polar or subtropical jet stream.
Weather fronts separate two masses of air of different densities and are associated with the most prominent meteorological phenomena. Air masses separated by a front may differ in temperature or humidity. Strong cold fronts typically feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. They form west of the circulation center and generally move from west to east. Warm fronts form east of the cyclone center and are usually preceded by stratiform precipitation and fog. They move pole ward ahead of the cyclone path. Occluded fronts form late in the cyclone life cycle near the enter of the cyclone and often wrap around the storm center.
A tornado is a violent, dangerous, rotating column of air which is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of cumulus cloud. Tornadoes come in many sizes but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust.
Most tornadoes have wind speeds between 40 mph (64 km/h) and 110 mph (177 km/h), are approximately 250 feet (75 m) across, and travel a few miles (several kilometers) before dissipating. Some attain wind speeds of more than 300 mph (480 km/h), stretch more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 km).
Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes in the world occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America. They also occasionally occur in south-central and eastern Asia, the Philippines, east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand.
The word tornado is an altered form of the Spanish word tornado, which means "thunderstorm." This in turn was taken from the Latin ton are, meaning "to thunder". It most likely reached its present form through a combination of the Spanish tronada and tornar ("to turn"); however, this may be a folk etymology. A tornado is also commonly referred to as a twister, and is also sometimes referred to by the old-fashioned colloquial term cyclone.
The Glossary of Meteorology defines a tornado as "a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud...“ In practice, for a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. Scientists have not yet created a complete definition of the word; for example, there is disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes. "Tornado" refers to the vortex of wind, not the condensation cloud
A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (see Bernoulli's principle) and rapid rotation (due to cyclostrophic balance) usually causes water vapor in the air to become visible as a funnel cloud or condensation funnel .
There is some disagreement over the definition of "funnel cloud" and "condensation funnel". According to the Glossary of Meteorology , a funnel cloud is any rotating cloud pendant from a cumulus or cumulonimbus, and thus including most tornadoes under this definition.
Among many meteorologists, a funnel cloud is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and a "condensation funnel" is a broad term for any rotating cloud below a cumuliform cloud.
Tornadoes often begin as funnel clouds with no associated strong winds at the surface, however, not all of these evolve into a tornado. However, many tornadoes are preceded by a funnel cloud. Most tornadoes produce strong winds at the surface while the visible funnel is still above the ground, so it is difficult to discern the difference between a funnel cloud and a tornado from a distance.
Occasionally, a single storm will produce more than one tornado, either simultaneously or in succession. Multiple tornadoes produced by the same storm are referred to as a tornado family .
Occasionally, several tornadoes are spawned from the same large-scale storm system. If there is no break in activity, this is considered a tornado outbreak , although there are various definitions. A period of several successive days with tornado outbreaks in the same general area (spawned by multiple weather systems) is a tornado outbreak sequence , occasionally called an extended tornado outbreak .
A multiple vortex tornado is a type of tornado in which two or more columns of spinning air rotate around a common center. Multivortex structure can occur in almost any circulation, but is very often observed in intense tornadoes. These vortices often create small areas of heavier damage along the main tornado path.
A satellite tornado is a term for a weaker tornado which forms very near a large, strong tornado contained within the same mesocyclones. The satellite tornado may appear to "orbit" the larger tornado (hence the name), giving the appearance of one, large multi-vortex tornado. However, a satellite tornado is a distinct funnel, and is much smaller than the main funnel.
A waterspout is defined by the National Weather Service simply as a tornado over water. However, researchers typically distinguish "fair weather" waterspouts from tornadic waterspouts. Fair weather waterspouts are less severe but far more common, and are similar in dynamics to dust devils and land spouts. They form at the bases of cumulus congestus cloud towers in tropical and semitropical waters.
They have relatively weak winds, smooth laminar walls, and typically travel very slowly, if at all. They occur most commonly in the Florida Keys and in the northern Adriatic Sea. Tornadic waterspouts are more literally "tornadoes over water". They can form over water like mesocyclones tornadoes, or be a land tornado which crosses onto water. Since they form from severe thunderstorms and can be far more intense, faster, and longer-lived than fair weather waterspouts, they are considered far more dangerous
A land spout (officially known as a dust-tube tornado ) is a tornado not associated with mesocyclones. The name stems from their characterization as essentially a "fair weather waterspout on land". Waterspouts and land spouts share many defining characteristics, including relative weakness, short lifespan, and a small, smooth condensation funnel which often does not reach the ground.
Land spouts also create a distinctively laminar cloud of dust when they make contact with the ground, due to their differing mechanics from true mesoform tornadoes. Though usually weaker than classic tornadoes, they still produce strong winds and may cause serious damage.
A Gustnado (gust front tornado) is a small, vertical swirl associated with a gust front or downburst. Because they are technically not associated with the cloud base, there is some debate as to whether or not Gustnadoes are actually tornadoes. They are formed when fast moving cold, dry outflow air from a thunderstorm is blown through a mass of stationary, warm, moist air near the outflow boundary, resulting in a "rolling" effect (often exemplified through a roll cloud).
If low level wind shear is strong enough, the rotation can be turned horizontally (or diagonally) and make contact with the ground. The result is a Gustnado. They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage. It is also worth noting that since they are absent of any Coriolis influence from a mesocyclones, they seem to be alternately cyclonic and anticyclones without preference.
A dust devil resembles a tornado in that it is a vertical swirling column of air. However, they form under clear skies and are rarely as strong as even the weakest tornadoes. They form when a strong convective updraft is formed near the ground on a hot day. If there is enough low level wind shear, the column of hot, rising air can develop a small cyclonic motion that can be seen near the ground. They are not considered tornadoes because they form during fair weather and are not associated with any actual cloud. However, they can, on occasion, result in major damage, especially in arid areas.
Tornado-like circulations occasionally occur near large, intense wildfires and are called fire whirls . They are not considered tornadoes except in the rare case where they connect to a pyrocumulus or other cumuliform cloud above. Fire whirls usually are not as strong as tornadoes associated with thunderstorms. However, they can produce significant damage.
A steam devil is a term describing a rotating updraft that involves steam or smoke. A steam devil is very rare, but they mainly form from smoke emitting from a power plant smokestack. Ho springs and deserts may also be suitable locations for a steam devil to form. There have also been reports of cold air steam devils as well.
A whirlpool is a swirling vortex that may or may not have a downdraft that forms in liquid, mainly water. A whirlpool usually forms in drains when some kind of swirl starts in the water and some kind of opening forms and gives it a downdraft. Whirlpool may also form in tides, when two powerful waves in opposite directions run parallel to each other or directly below a waterspout but it strength depends on the waterspouts strength however it is rare for this to happen
Most tornadoes take on the appearance of a narrow funnel, a few hundred yards (a few hundred meters) across, with a small cloud of debris near the ground. However, tornadoes can appear in many shapes and sizes.
Small, relatively weak land spouts may only be visible as a small swirl of dust on the ground. Although the condensation funnel may not extend all the way to the ground, if associated surface winds are greater than 40 mph (64 km/h), the circulation is considered a tornado. A tornado with a nearly cylindrical profile and relative low height is sometimes referred to as a stovepipe tornado .
Large single-vortex tornadoes can look like large wedges stuck into the ground, and so are known as wedge tornadoes or wedges . The stovepipe classification is also used for this type of tornado, if it otherwise fits that profile. A wedge can be so wide that it appears to be a block of dark clouds, wider than the distance from the cloud base to the ground.
These tornadoes are said to be roping out , or becoming a rope tornado . Multiple-vortex tornadoes can appear as a family of swirls circling a common center, or may be completely obscured Tornadoes in the dissipating stage can resemble narrow tubes or ropes, and often curl or twist by condensation, dust, and debris, appearing to be a single funnel.
In addition to these appearances, tornadoes may be obscured completely by rain or dust. These tornadoes are especially dangerous, as even experienced meteorologists might not spot them
In the United States, on average tornadoes are around 500 feet (150 m) across, and stay on the ground for 5 miles (8 km). Yet, there is an extremely wide range of tornado sizes, even for typical tornadoes. Weak tornadoes, or strong but dissipating tornadoes, can be exceedingly narrow, sometimes only a few feet across. A tornado was once reported to have a damage path only 7 feet (2 m) long. On the other end of the spectrum, wedge tornadoes can have a damage path a mile (1.6 km) wide or more. A tornado that affected Hallam, Nebraska on May 22, 2004 was at one point 2.5 miles (4 km) wide at the ground.
In terms of path length, the Tri-State Tornado, which affected parts of Missouri, Illinois, and Indiana on March 18, 1925, was officially on the ground continuously for 219 miles (352 km). Many tornadoes which appear to have path lengths of 100 miles (160 km) or longer are actually a family of tornadoes which have formed in quick succession; however, there is no substantial evidence that this occurred in the case of the Tri-State Tornado. In fact, modern reanalysis of the path suggests that the tornado began 15 miles (24 km) further west than previously thought.
Tornadoes can have a wide range of colors, depending on the environment in which they form. Those which form in a dry environment can be nearly invisible, marked only by swirling debris at the base of the funnel. Condensation funnels which pick up little or no debris can be gray to white. While traveling over a body of water as a waterspout, they can turn very white or even blue. Funnels which move slowly, ingesting a lot of debris and dirt, are usually darker, taking on the color of debris. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and tornadoes in mountainous areas can travel over snow-covered ground, turning brilliantly white.
Tornadoes normally rotate cyclonical in direction (counterclockwise in the northern hemisphere, clockwise in the southern). While large-scale storms always rotate cyclonically due to the Coriolis effect, thunderstorms and tornadoes are so small that the direct influence of the Coriolis effect is inconsequential, as indicated by their large Ross by numbers. Super cells and tornadoes rotate cyclonically in numerical simulations even when the Coriolis effect is neglected. Low-level mesocyclones and tornadoes owe their rotation to complex processes within the super cell and ambient environment.
Approximately 1% of tornadoes rotate in an anticyclones direction. Typically, only land spouts and Gustnadoes rotate ant cyclonically, and usually only those which form on the anticyclones shear side of the descending rear flank downdraft in a cyclonic super cell. However, on rare occasions, anticyclones tornadoes form in association with the mesoanticyclone of an anticyclones super cell, in the same manner as the typical cyclonic tornado, or as a companion tornado—either as a satellite tornado or associated with anticyclones eddies within a supercell.
Tornadoes emit widely on the acoustics spectrum and the sounds are caused by multiple mechanisms. Various sounds of tornadoes have been reported throughout time, mostly related to familiar sounds for the witness and generally some variation of a whooshing roar. Popularly reported sounds include a freight train, rushing rapids or waterfall, a jet engine from close proximity, or combinations of these. Many tornadoes are not audible from much distance; the nature and propagation distance of the audible sound depends on atmospheric conditions and topography.
The winds of the tornado vortex and of constituent turbulent eddies, as well as airflow interaction with the surface and debris, contribute to the sounds. Funnel clouds also produce sounds. Funnel clouds and small tornadoes are reported as whistling, whining, humming, or the buzzing of innumerable bees or electricity, or more or less harmonic, whereas many tornadoes are reported as a continuous, deep rumbling, or an irregular sound of “noise”.
First, the rotating cloud base lowers. This lowering becomes a funnel, which continues descending while winds build near the surface, kicking up dust and other debris. Finally, the visible funnel extends to the ground, and the tornado begins causing major damage. This tornado, near Dimmitt, Texas, was one of the best-observed violent tornadoes in history
As the mesocyclones approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause damage a good distance from the tornado. Usually, the funnel cloud becomes a tornado within minutes of the RFD reaching the ground.
Though tornadoes can strike in an instant, there are precautions and preventative measures that people can take to increase the chances of surviving a tornado. Authorities such as the Storm Prediction Center advise having a tornado plan. When a tornado warning is issued, going to a basement or an interior first-floor room of a sturdy building greatly increases chances of survival. In tornado-prone areas, many buildings have storm cellars on the property. These underground refuges have saved thousands of lives.
Some countries have meteorological agencies which distribute tornado forecasts and increase levels of alert of a possible tornado (such a stornado watches and warnings in the United States and Canada). Weather radios provide an alarm when a severe weather advisory is issued for the local area, though these are mainly available only in the United States.
Unless the tornado is far away and highly visible, meteorologists advise that drivers park their vehicles far to the side of the road (so as not to block emergency traffic), and find a sturdy shelter. If no sturdy shelter is nearby, getting low in a ditch is the next best option. Highway overpasses are extremely bad shelter during tornadoes (see next section). 
Climate change and agriculture are interrelated processes, both of which take place on a global scale. Global warming is projected to have significant impacts on conditions affecting agriculture, including temperature, carbon dioxide, glacial run-off, precipitation and the interaction of these elements. These conditions determine the carrying capacity of the biosphere to produce enough food for the human population and domesticated animals. The overall effect of climate change on agriculture will depend on the balance of these effects. Assessment of the effects of global climate changes on agriculture might help to properly anticipate and adapt farming to maximize agricultural production.
At the same time, agriculture has been shown to produce significant effects on climate change, primarily through the production and release of greenhouse gases such as carbon dioxide, methane, and nitrous oxide, but also by altering the Earth's land cover, which can change its ability to absorb or reflect heat and light, thus contributing to radioactive forcing. Land use change such as deforestation and desertification, together with use of fossil fuels, are the major anthropogenic sources of carbon dioxide; agriculture itself is the major contributor to increasing methane and nitrous oxide concentrations in earth's atmosphere.
Despite technological advances, such as improved varieties, genetically modified organisms, and irrigation systems, weather is still a key factor in agricultural productivity, as well as soil properties and natural communities. The effect of climate on agriculture is related to variability's in local climates rather than in global climate patterns. The Earth's average surface temperature has increased by 1 degree F in just over the last century. Consequently, agronomists consider any assessment has to be individually consider each local area.
On the other hand, agricultural trade has grown in recent years, and now provides significant amounts of food, on a national level to major importing countries, as well as comfortable income to exporting ones. The international aspect of trade and security in terms of food implies the need to also consider the effects of climate change on a global scale.
A study published in Science suggest that, due to climate change, "southern Africa could lose more than 30% of its main crop, maize, by 2030. In South Asia losses of many regional staples, such as rice, millet and maize could top 10%".
The 2001 IPCC Third Assessment Report concluded that the poorest countries would be hardest hit, with reductions in crop yields in most tropical and sub-tropical regions due to decreased water availability, and new or changed insect pest incidence. In Africa and Latin America many rained crops are near their maximum temperature tolerance, so that yields are likely to fall sharply for even small climate changes; falls in agricultural productivity of up to 30% over the 21st century are projected. Marine life and the fishing industry will also be severely affected in some places.
Climate change induced by increasing greenhouse gases is likely to affect crops differently from region to region. For example, average crop yield is expected to drop down to 50% in Pakistan according to the UKMO scenario whereas corn production in Europe is expected to grow up to 25% in optimum hydrologic conditions.
More favorable effects on yield tend to depend to a large extent on realization of the potentially beneficial effects of carbon dioxide on crop growth and increase of efficiency in water use. Decrease in potential yields is likely to be caused by shortening of the growing period, decrease in water availability and poor vernalization.
Most agronomists believe that agricultural production will be mostly affected by the severity and pace of climate change, not so much by gradual trends in climate. If change is gradual, there may be enough time for biota adjustment. Rapid climate change, however, could harm agriculture in many countries, especially those that are already suffering from rather poor soil and climate conditions, because there is less time for optimum natural selection and adaption
Potential effect of atmospheric carbon dioxide on yield
Carbon dioxide is essential to plant growth. Rising CO2 concentration in the atmosphere can have both positive and negative consequences.
Increased CO2 is expected to have positive physiological effects by increasing the rate of photosynthesis. Currently, the amount of carbon dioxide in the atmosphere is 380 parts per million. In comparison, the amount of oxygen is 210,000 ppm. This means that often plants may be starved of carbon dioxide, being outnumbered by the photosynthetic pollutant oxygen. The effects of an increase in carbon dioxide would be higher on C3 crops (such as wheat) than on C4 crops (such as maize), because the former is more susceptible to carbon dioxide shortage. Under optimum conditions of temperature and humidity, the yield increase could reach 36%, if the levels of carbon dioxide are doubled. citation needed ]
The agricultural sector is a driving force in the gas emissions and land use effects thought to cause climate change. In addition to being a significant user of land and consumer of fossil fuel, agriculture contributes directly to greenhouse gas emissions through practices such as rice production and the raising of livestock; according to the Intergovernmental Panel on Climate Change, the three main causes of the increase in greenhouse gases observed over the past 250 years have been fossil fuels, land use, and agriculture.
While there is no universal definition of what the term "severe weather" means or refers to, this term can be defined as any form of weather that can pose a risk to life or property or has the capability of altering the construction of a landscape, and thus require the attention of authorities. Severe weather can vary greatly based upon a location's topography, latitude, altitude, and atmospheric conditions of the region. For example, types of severe weather in Australia include intense low pressure systems, thunderstorms, hailstorms, tropical cyclones, and strong gusts of wind. However, in Canada, severe weather are usually defined as any type of winter storms and thunderstorms.
Severe weather phenomena can be categorized into two groups based on the geographic locations they are capable of developing upon. Thunderstorms are capable of forming at any geographic location, along with their accompanied phenomena of tornadoes, lightning, and hailstorms. These weather occurrences can be categorized as general severe weather. Blizzards, snowstorms, and other forms of winter storms, as well as dust storms, have more limited distribution and can only develop within certain regions. These events are classified as localized severe weather.
The term severe weather is frequently and inaccurately used interchangeably with the term extreme weather . Extreme weather describes weather events that infrequently form or are uncommon except within a certain region. In other words, it refers to weather occurrences that do not correspond with the climatology of the area.
Once the thunderclouds have been formed, the downdrafts present in the Cumulonimbus cloud causes the remaining water molecules to freeze into solid states of ice and hail. The ice particles, containing a positive charge is separated by the updrafts, while the hail particles that contain a negative charge is moved by the downdrafts. This basically separates the differently charged particles. During the thunderstorm, the Earth's surface is composed of a positive charged. Because opposites attract, the negative charged particles on the lower cloud (caused by the downdraft) tries to contact the positive particles upon land.
The negative charges, once strong enough to resist against air resistance flows downwards towards the Earth. This is called a stepped leader. The positive particles, being attracted to the stepped leader climbs up elevated objects of trees and other objects and contacts the negative particles. Once this happens, a strong electrical current inputs the positive charges into the cloud. This creates a return stroke of lightning. The high voltage of electricity comprised within lightning is capable of releasing enough heat energy to ignite of a fire.
High winds are known to cause damage, depending upon their strength. Infrequent wind gusts can cause poorly-designed suspension bridges to sway. When wind gusts are at a similar frequency to the swaying of the bridge, the bridge can be destroyed easier, such as what occurred with the Tacoma Narrows Bridge in 1940. Wind speeds as low as 23 knots (43 km/h) can lead to power outages due to tree branches disrupting the flow of energy through power lines. While no species of tree is guaranteed to stand up to hurricane-force winds, those with shallow roots are more prone to uproot, and brittle trees such as eucalyptus, sea hibiscus, and avocado are more prone to damage
Hurricane-force winds cause substantial damage to mobile homes, and begin to structurally damage homes with foundations. Winds of this strength due to down sloped winds off terrain have been known to shatter windows and sandblast paint from cars. Once winds exceed 135 knots (250 km/h), homes completely collapse, and significant damage is done to larger buildings. Total destruction to man-made structures occurs when winds reach 175 knots (324 km/h). The Saffir -Simpson scale and Enhanced Fujita scale (TORRO scale in Europe) were designed to help estimate wind speed from the damage caused by high winds related to tropical cyclones and tornadoes, and vice versa
Dry lightning is a term in the United States for lightning that occurs with no precipitation at the surface. This type of lightning is the most common natural cause of wild fires. clouds produce lightning for the same reason that it is produced by cumulonimbus clouds. When the higher levels of the atmosphere are cooler, and the surface is warmed to extreme temperatures due to a wildfire, volcano, etc, convection will occur, and the convection produces lightning. Therefore, fire can beget dry lightning through the development of more dry thunderstorms which cause more fires.
Heat waves, droughts, cyclical climate changes such as El Niño, and other weather patterns can also increase the risk and alter the behavior of wildfires dramatically. Years of precipitation followed by warm periods have encouraged more widespread fires and longer fire seasons. Since the mid 1980s, earlier snowmelt and associated warming has also been associated with an increase in length and severity of the wildfire season in the Western United States.
Heat waves, droughts, cyclical climate changes such as El Niño, and other weather patterns can also increase the risk and alter the behavior of wildfires dramatically. Years of precipitation followed by warm periods have encouraged more widespread fires and longer fire seasons. Since the mid 1980s, earlier snowmelt and associated warming has also been associated with an increase in length and severity of the wildfire season in the Western United States.
Fire intensity also increases during daytime hours. Burn rates of smoldering logs are up to five times greater during the day due to lower humidity, increased temperatures, and increased wind speeds. Sunlight warms the ground during the day and causes air currents to travel uphill, and downhill during the night as the land cools. Wildfires are fanned by these winds and often follow the air currents over hills and through valleys. Fires in Europe occur frequently during the hours of 12:00 p.m. and 2:00 p.m. U.S. wildfire operations revolve around a 24-hour fire day that begins at 1000 hours due to the predictable increase in intensity resulting from the daytime warmth.
In mid-latitudes, convective precipitation is intermittent and often associated with baroclinic boundaries such as cold fronts, squall lines, and warm fronts. Elsewhere, the wet season is the time of year, covering one or more months, when most of the average annual rainfall in a region falls. Areas with wet seasons are dispersed across portions of the tropics and subtropics.
Savanna climates and areas with monsoon regimes have wet summers and dry winters. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is equally distributed through the year. Some areas with pronounced rainy seasons will see a break in rainfall mid-season when the intertropical convergence zone or monsoon trough move pole ward of their location during the middle of the warm season. When the wet season occurs during the warm season, or summer, rain falls mainly during the late afternoon and early evening hours.
The wet season is a time when air quality improves, freshwater quality improves, and vegetation grows significantly. Soil nutrients diminish and erosion increases. Animals have adaptation and survival strategies for the wetter regime. Unfortunately, the previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Developing countries have noted that their populations show seasonal weight fluctuations due to food shortages seen before the first harvest, which occurs late in the wet season.
Tropical cyclones, a source of very heavy rainfall, consist of large air masses several hundred miles across with low pressure at the centre and with winds blowing inward towards the centre in either a clockwise direction (southern hemisphere) or counterclockwise (northern hemisphere) .Although cyclones can take an enormous toll in lives and personal property, they may be important factors in the precipitation regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions. Areas in their path can receive a year's worth of rainfall from a tropical cyclone passage.
Acid Rain is any form of precipitation, where the water molecules presented have a unusual decrease in pH levels. Acid rain can often occur during the weather phenomenon of a thunderstorm. The voltage of electricity release by lightning is powerful enough to split nitrogen molecules in the atmosphere into separate atoms. These nitrogen atoms are reactive enough to form compounds with the water molecules presented in rain, forming nitric acid, a form of acid rain. The properties of acid rain are able to dissolve structure created out of minerals containing calcite (otherwise known as calcium carbonate). The acid rain reacts with the carbon molecules compost within the calcite, while also releasing calcium atoms.
This process then wears and dissolves away structures made of limestone and other minerals containing calcite. Other that the damage it does to infrastructures and buildings of limestone, acid rain can also produce risk and harm towards marine wildlife through increases in acidity. Tissues of vegetations are also presented with the risk of being damaged. Acid rain can also increase acidity in soil particles, which decrease the nutrients presented in harmed soil as well as encourage the presence of certain disease-agent microorganisms. Besides occurring within the presence of thunderstorms, acid rain can also occur in dense populated areas.
Dense populated areas often have high usage of energy source, which releases greenhouse gas. This can mixed with water molecules presented in the atmosphere, creating acid rain. The gas particles released by volcanic eruptions can also allow acid rain to form.
A dust storm is an unusual form of windstorm that is characterized by the existence of large quantities of sand and dust particles in which are carried by moving air. Dust storms frequently develop during periods of droughts and over arid and semi-arid regions, when less moisture is being presented within soil particles, which reduces their density and cause it to be easier to lift by moving air. Dust storms generally occur for only a few minutes before subsiding
Have numerous hazards and are capable of creating deaths when actions are not taken carefully. During the occurrence of a dust storm, visibility can be reduced at dramatically, making it harder to see. This can cause exposure to these weather phenomena for extended periods of time. Reduction in visibility causes the most damage within traffic areas. Risks of collisions with other automobiles can occur within areas of dust storm occurrences.
Aircrafts in flight during the occurrence of dust storms can be also expose to risks of crashing when flying in busy airlines or landing, due to the fast winds and reduction of visibility. The amount of oxygen intake by respiratory organs can decrease as well, resulting in possibilities of suffication. Damage can also be inflicted upon external optical organs of the eyes. Dust storms can produce many issues for agricultural industries as well. Soil erosion is one of the most common hazards within dust storm phenomena, decreasing lands available for producing crops.
Dust and sand particles associated in dust storms can cause severe processes of weathering to occur upon infrastructures and rock formation. Nearby bodies of water can be polluted by the settling of dust and sand, causing deaths along aquatic organisms. Decrease in exposure to radiation can affect plant growth, as well as provide insulation to the heat from infrared radiation, causing increases in temperature.
A hailstorm is any forms of storm that produce precipitating hailstones. Hailstorms are generally capable of developing at any geographic location that is presented with the existence of thunderclouds; occurring mostly within dry conditions. Most hailstorms are developed during presence of Cumulonimbus clouds and any other severe weather phenomenon in relation. The updrafts and downdrafts presented within Cumulonimbus causes water molecules to freeze and solidify, creating hailstones and other forms of solid precipitation.
Due to their larger density, these hailstones become heavy enough to withstand the density of the cloud, and thus fall towards the ground. The downdrafts present in Cumulonimbus clouds can also cause increases to the speed of the falling hailstones. The term hailstorm is usually used to describe the existence of significant quantities or size of the hailstones presented in such event
A downburst is created by an area of significantly rain-cooled air that, after hitting ground level, spreads out in all directions producing strong winds. Unlike winds in a tornado, winds in a downburst are directed outwards from the point where it hits land or water. Dry downbursts are associated with thunderstorms with very little rain, while wet downbursts are created by thunderstorms with high amounts of rainfall. Microburst and macro burs are downbursts at very small and larger scales respectively
Another variety, the heat burst , is created by vertical currents on the backside of old outflow boundaries and squall lines where rainfall is lacking. Heat bursts generate significantly higher temperatures due to the lack of rain-cooled air in their formation. Downbursts create vertical wind shear or microburst which is dangerous to aviation. Derecho are longer, usually more stronger, forms of downburst winds characterized by straight-lined windstorms.
An ice storm is a windstorm developed by the presence of freezing liquid precipitation and the gradual increase in damaging ice.
Trees destroyed and fallen by the freezing precipitation of an ice storm.
The accumulations of ice during the occurrence of an ice storm can be extremely destructive. Trees and vegetations can be destroyed within areas of ice storms, which in turn can bring down nearby power lines, causing the lost of heat and the access of Ice storms are occasionally replaced with the usage of the term Silver storm , referring to the color of the freezing precipitation. Ice storms occur throughout the winter season, at areas located on or above mid-latitude.
Roofs of buildings and automobiles may be severely damaged. Gas pipes can become frozen or even damaged, causing possible gas leaks. High winds occurring within areas can influence direction of waves, which may cause tidal waves to occur and increase possibility of beach erosion. Possible avalanches may develop as well, due to the extra amount of ice being presented. Visibility can be reduce dramatically that can result in extended periods of time within experiencing areas.
This is often then associated with the possibility of being presented with hypothermia and frostbites, resulting in the lose of limbs and damages inflicted on organs. The aftermath of such destructive ice storm can result in possibility of severe flooding. Sudden thawing in the ice upon surfaces can cause the high quantities of water to be displaced, especially when close towards lakes, rivers, and bodies of water
Heat waves are long periods of abnormal heatings that produce temperatures that are higher than usual. There is generally no universal definition of a heat wave because of the variation within temperatures are different upon geographic locations. Along with the excessive amount of heat, heat wave are often also accompanied with high amount of humidity. These two characteristics of a heat wave are often associated with each other, increasing the apparent temperature, in this case the heat index, to dangerous levels.
A cold wave is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24 hour period requiring substantially increased protection to agriculture, industry, commerce, and social activities. The precise criterion for a cold wave is determined by the rate at which the temperature falls, and the minimum to which it falls. This minimum temperature is dependent on the geographical region and time of year. Cold waves generally are capable of occurring any geological location and are formed by large cool air masses that accumulate over certain regions, caused by movements of air streams.