A meridian is the half of an imaginary great circle on the Earth's surface, terminated by the North Pole and the South Pole, connecting points of equal longitude, as measured in angular degrees east or west of the Prime Meridian. The position of a point along the meridian is given by that longitude and its latitude, measured in angular degrees north or south of the Equator; each meridian is perpendicular to all circles of latitude. Each is the same length, being half of a great circle on the Earth's surface and therefore measuring 20,003.93 km. The first prime meridian was set by Eratosthenes in 200 BCE; this prime meridian was used to provide measurement of the earth, but had many problems because of the lack of latitude measurement. Many years around the 19th century there was still concerns of the prime meridian; the idea of having one prime meridian came from William Parker Snow, because he realized the confusion of having multiple prime meridian locations. Many of theses geographical locations were traced back to the ancient Greeks, others were created by several nations.
Multiple locations for the geographical meridian meant that there was inconsistency, because each country had their own guidelines for where the prime meridian was located. The term meridian comes from the spanish meridies, meaning "midday"; the Sun crosses the celestial meridian at the same time. The same Latin stem gives rise to the terms a.m. and p.m. used to disambiguate hours of the day when utilizing the 12-hour clock. Toward the ending of the 12th century there were two main locations that were acknowledged as the geographic location of the meridian and Britain; these two locations conflicted and a settlement was reached only after there was an International Meridian Conference held, in which Greenwich was recognized as the 0° location. The meridian through Greenwich, called the Prime Meridian, was set at zero degrees of longitude, while other meridians were defined by the angle at the center of the earth between where it and the prime meridian cross the equator; as there are 360 degrees in a circle, the meridian on the opposite side of the earth from Greenwich, the antimeridian, forms the other half of a circle with the one through Greenwich, is at 180° longitude near the International Date Line.
The meridians from West of Greenwich to the antimeridian define the Western Hemisphere and the meridians from East of Greenwich to the antimeridian define the Eastern Hemisphere. Most maps show the lines of longitude; the position of the prime meridian has changed a few times throughout history due to the transit observatory being built next door to the previous one. Such changes had no significant practical effect; the average error in the determination of longitude was much larger than the change in position. The adoption of WGS84 as the positioning system has moved the geodetic prime meridian 102.478 metres east of its last astronomic position. The position of the current geodetic prime meridian is not identified at all by any kind of sign or marking in Greenwich, but can be located using a GPS receiver, it was in the best interests of the nations to agree to one standard meridian to benefit their fast growing economy and production. The disorganized system they had before was not sufficient for their increasing mobility.
The coach services in England had erratic timing before the GWT. U. S. and Canada were improving their railroad system and needed a standard time as well. With a standard meridian, stage coach and trains were able to be more efficient; the argument of which meridian is more scientific was set aside in order to find the most convenient for practical reasons. They were able to agree that the universal day was going to be the mean solar day, they agreed that the days would begin at midnight and the universal day would not impact the use of local time. In the "Transactions of the Royal Society of Canada a report was submitted, dated 10 May 1894. Therefore, a compass needle will be parallel to the magnetic meridian. However, a compass needle will not be steady in the magnetic meridian, because of the longitude from east to west being complete geodesic; the angle between the magnetic and the true meridian is the magnetic declination, relevant for navigating with a compass. Navigators were able to use the azimuth of the rising and setting Sun to measure the magnetic variation.
The true meridian is the plane that passes through true north poles and true south poles at the spot of the observer. The difference between true meridian and magnetic meridian is that the true meridian is fixed while the magnetic meridian is formed through the movement of the needle. True bearing is the horizontal angle between a line. Henry D. Thoreau classified this true meridian
An equator of a rotating spheroid is its zeroth circle of latitude. It is the imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles. On Earth, the Equator is 21.3 % over land. Indonesia is the country straddling the greatest length of the equatorial line across both land and sea; the name is derived from medieval Latin word aequator, in the phrase circulus aequator diei et noctis, meaning ‘circle equalizing day and night’, from the Latin word aequare meaning ‘make equal’. The latitude of the Earth's equator is, by definition, 0° of arc; the Equator is one of the five notable circles of latitude on Earth. The Equator is the only line of latitude, a great circle — that is, one whose plane passes through the center of the globe; the plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator.
In the cycle of Earth's seasons, the equatorial plane runs through the Sun twice per year: on the equinoxes in March and September. To a person on Earth, the Sun appears to travel above the Equator at these times. Light rays from the Sun's center are perpendicular to Earth's surface at the point of solar noon on the Equator. Locations on the Equator experience the shortest sunrises and sunsets because the Sun's daily path is nearly perpendicular to the horizon for most of the year; the length of daylight is constant throughout the year. Earth bulges at the Equator. Sites near the Equator, such as the Guiana Space Centre in Kourou, French Guiana, are good locations for spaceports as they have a faster rotational speed than other latitudes. Since Earth rotates eastward, spacecraft must be launched eastward to take advantage of this Earth-boost of speed; the precise location of the Equator is not fixed. This effect must be accounted for in detailed geophysical measurements; the International Association of Geodesy and the International Astronomical Union have chosen to use an equatorial radius of 6,378.1366 kilometres.
This equatorial radius is in the 2003 and 2010 IERS Conventions. It is the equatorial radius used for the IERS 2003 ellipsoid. If it were circular, the length of the Equator would be 2π times the radius, namely 40,075.0142 kilometres. The GRS 80 as approved and adopted by the IUGG at its Canberra, Australia meeting of 1979 has an equatorial radius of 6,378.137 kilometres. The WGS 84, a standard for use in cartography and satellite navigation including GPS has an equatorial radius of 6,378.137 kilometres. For both GRS 80 and WGS 84, this results in a length for the Equator of 40,075.0167 km. The geographical mile is defined as one arc-minute of the Equator, so it has different values depending on which radius is assumed. For example, by WSG-84, the distance is 1,855.3248 metres, while by IAU-2000, it is 1,855.3257 metres. This is a difference of less than one millimetre over the total distance; the earth is modeled as a sphere flattened 0.336% along its axis. This makes the Equator 0.16% longer than a meridian.
The IUGG standard meridian is, to the nearest millimetre, 40,007.862917 kilometres, one arc-minute of, 1,852.216 metres, explaining the SI standardization of the nautical mile as 1,852 metres, more than 3 metres less than the geographical mile. The sea-level surface of the Earth is irregular, so the actual length of the Equator is not so easy to determine. Aviation Week and Space Technology on 9 October 1961 reported that measurements using the Transit IV-A satellite had shown the equatorial "diameter" from longitude 11° West to 169° East to be 1,000 feet greater than its "diameter" ninety degrees away; the Equator passes through the land of 11 countries. Starting at the Prime Meridian and heading eastwards, the Equator passes through: Despite its name, no part of Equatorial Guinea lies on the Equator. However, its island of Annobón is 155 km south of the Equator, the rest of the country lies to the north. Seasons result from the tilt of the Earth's axis compared to the plane of its revolution around the Sun.
Throughout the year the northern and southern hemispheres are alternately turned either toward or away from the sun depending on Earth's position in its orbit. The hemisphere turned toward the sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter. At the equinoxes, the Earth's axis
A heat wave is a period of excessively hot weather, which may be accompanied by high humidity in oceanic climate countries. While definitions vary, a heat wave is measured relative to the usual weather in the area and relative to normal temperatures for the season. Temperatures that people from a hotter climate consider normal can be termed a heat wave in a cooler area if they are outside the normal climate pattern for that area; the term is applied both to hot weather variations and to extraordinary spells of hot which may occur only once a century. Severe heat waves have caused catastrophic crop failures, thousands of deaths from hyperthermia, widespread power outages due to increased use of air conditioning. A heat wave is considered extreme weather, a danger because heat and sunlight may overheat the human body. Heat waves can be detected using forecasting instruments so that a warning call can be issued. A definition based on Frich et al.'s Heat Wave Duration Index is that a heat wave occurs when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5 °C, the normal period being 1961–1990.
A formal, peer-reviewed definition from the Glossary of Meteorology is: A period of abnormally and uncomfortably hot and humid weather. To be a heat wave such a period should last at least one day, but conventionally it lasts from several days to several weeks. In 1900, A. T. Burrows more rigidly defined a “hot wave” as a spell of three or more days on each of which the maximum shade temperature reaches or exceeds 90 °F. More realistically, the comfort criteria for any one region are dependent upon the normal conditions of that area; the World Meteorological Organization, defines a heat wave as 5 or more consecutive days of prolonged heat in which the daily maximum temperature is higher than the average maximum temperature by 9 °F or more. However, some nations have come up with their own criteria to define a heat wave. In the Netherlands, a heat wave is defined as a period of at least 5 consecutive days in which the maximum temperature in De Bilt exceeds 25 °C, provided that on at least 3 days in this period the maximum temperature in De Bilt exceeds 30 °C.
This definition of a heat wave is used in Belgium and Luxembourg. In Denmark, a national heat wave is defined as a period of at least 3 consecutive days of which period the average maximum temperature across more than fifty percent of the country exceeds 28 °C – the Danish Meteorological Institute further defines a "warmth wave" when the same criteria are met for a 25 °C temperature, while in Sweden, a heat wave is defined as at least 5 days in a row with a daily high exceeding 25 °C. In the United States, definitions vary by region. In the Northeast, a heat wave is defined as three consecutive days where the temperature reaches or exceeds 90 °F, but not always as this ties in with humidity levels to determine a heat index threshold; the same does not apply to drier climates. A heat storm is a Californian term for an extended heat wave. Heat storms occur when the temperature reaches 100 °F for three or more consecutive days over a wide area; the National Weather Service issues heat advisories and excessive heat warnings when unusual periods of hot weather are expected.
In Adelaide, South Australia, a heat wave is defined as five consecutive days at or above 35 °C, or three consecutive days at or over 40 °C. The Australian Bureau of Meteorology defines a heat wave as "three days or more of maximum and minimum temperatures that are unusual for the location"; until the introduction of this new Pilot Heatwave Forecast there was no national definition that described heatwave or measures of heatwave severity. In the United Kingdom, the Met Office operates a Heat Health Watch system which places each Local Authority region into one of four levels. Heatwave conditions are defined by the maximum daytime temperature and minimum nighttime temperature rising above the threshold for a particular region; the length of time spent above that threshold determines the particular level. Level 1 is normal summer conditions. Level 2 is reached when there is a 60% or higher risk that the temperature will be above the threshold levels for two days and the intervening night. Level 3 is triggered when the temperature has been above the threshold for the preceding day and night, there is a 90% or higher chance that it will stay above the threshold in the following day.
Level 4 is triggered. Each of the first three levels is associated with a particular state of readiness and response by the social and health services, Level 4 is associated with more widespread response. A more general indicator that allows comparing heat waves in different regions of the World, characterized by different climates, has been developed; this was used to estimate heat waves occurrence at the global scale from 1901 to 2010, finding a substantial and sharp increase in the amount of affected areas in the last two decades. Heat waves form when high pressure aloft strengthens and remains over a region for several days up to several weeks; this is common in summer as the jet stream'follows the sun'. On the equator side of the jet stream, in the upper layers of the atmosphere, is the high pressure area. Summertime weather patterns are slower to change than in winter; as a result, this upper level high pressure moves slowly
Extreme weather includes unexpected, unpredictable, severe or unseasonal weather. Extreme events are based on a location’s recorded weather history and defined as lying in the most unusual ten percent. In recent years some extreme weather events have been attributed to human-induced global warming, with studies indicating an increasing threat from extreme weather in the future. According to IPCC estimates of annual losses have ranged since 1980 from a few billion to above US$200 billion, with the highest value for 2005; the global weather-related disaster losses, such as loss of human lives, cultural heritage, ecosystem services, are difficult to value and monetize, thus they are poorly reflected in estimates of losses. Heat waves are periods of heat index. Definitions of a heatwave vary because of the variation of temperatures in different geographic locations. Excessive heat is accompanied by high levels of humidity, but can be catastrophically dry; because heat waves are not visible as other forms of severe weather are, like hurricanes and thunderstorms, they are one of the less known forms of extreme weather.
Severe heat weather can damage populations and crops due to potential dehydration or hyperthermia, heat cramps, heat expansion and heat stroke. Dried soils are more susceptible to erosion. Outbreaks of wildfires can increase in frequency as dry vegetation has increased likeliness of igniting; the evaporation of bodies of water can be devastating to marine populations, decreasing the size of the habitats available as well as the amount of nutrition present within the waters. Livestock and other animal populations may decline as well. During excessive heat plants shut their leaf pores, a protective mechanism to conserve water but curtails plants' absorption capabilities; this leaves more pollution and ozone in the air, which leads to a higher mortality in the population. It has been estimated that extra pollution during the hot summer 2006 in cost 460 lives; the European heat waves from summer 2003 are estimated to have caused 30,000 excess deaths, due to heat stress and air pollution. Over 200 U.
S cities have registered new record high temperatures. The worst heatwave in the USA killed more than 5000 people directly; the worst heat wave in Australia occurred in 1938-39 and killed 438. The second worst was in 1896. Power outages can occur within areas experiencing heat waves due to the increased demand for electricity; the urban heat island effect can increase temperatures overnight. A cold wave is a weather phenomenon, distinguished by a cooling of the air; as used by the U. S. National Weather Service, a cold wave is a rapid fall in temperature within a 24-hour period requiring increased protection to agriculture, industry and social activities; the precise criterion for a cold wave is determined by the rate at which the temperature falls, the minimum to which it falls. This minimum temperature is dependent on the geographical time of year. Cold waves 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.
A cold wave can cause injury to livestock and wildlife. Exposure to cold mandates greater caloric intake for all animals, including humans, if a cold wave is accompanied by heavy and persistent snow, grazing animals may be unable to reach necessary food and water, die of hypothermia or starvation. Cold waves necessitate the purchase of fodder for livestock at considerable cost to farmers. Human populations can be inflicted with frostbites when exposed for extended periods of time to cold and may result in the loss of limbs or damage to internal organs. Extreme winter cold causes poorly insulated water pipes to freeze; some poorly protected indoor plumbing may rupture as frozen water expands within them, causing property damage. Fires, become more hazardous during extreme cold. Water mains may break and water supplies may become unreliable, making firefighting more difficult. Cold waves that bring unexpected freezes and frosts during the growing season in mid-latitude zones can kill plants during the early and most vulnerable stages of growth.
This results in crop failure as plants are killed. Such cold waves have caused famines. Cold waves can cause soil particles to harden and freeze, making it harder for plants and vegetation to grow within these areas. One extreme was the so-called Year Without a Summer of 1816, one of several years during the 1810s in which numerous crops failed during freakish summer cold snaps after volcanic eruptions reduced incoming sunlight. In general climate models show that with climate change, the planet will experience more extreme weather. In particular temperature record highs outpace record lows and some types of extreme weather such as extreme heat, intense precipitation, drought have become more frequent and severe in recent decades; some studies assert a connection between warming arctic temperatures and thus a vanishing cryosphere to extreme weather in mid-latitudes. In the PNAS, Steven C. Sherwood and Matthew Huber state that humans and other mammals cannot tolerate a wet-bulb temperature of over 35 °C for extended periods, that this "would begin to occur with global-mean warming of about 7 °C...
With 11–12 °C warming, such regions would spread to encompass the majority of the human population
Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not occur until the 18th century; the 19th century saw modest progress in the field after weather observation networks were formed across broad regions. Prior attempts at prediction of weather depended on historical data, it was not until after the elucidation of the laws of physics and more the development of the computer, allowing for the automated solution of a great many equations that model the weather, in the latter half of the 20th century that significant breakthroughs in weather forecasting were achieved. An important domain of weather forecasting is marine weather forecasting as it relates to maritime and coastal safety, in which weather effects include atmospheric interactions with large bodies of water. Meteorological phenomena are observable weather events that are explained by the science of meteorology.
Meteorological phenomena are described and quantified by the variables of Earth's atmosphere: temperature, air pressure, water vapour, mass flow, the variations and interactions of those variables, how they change over time. Different spatial scales are used to describe and predict weather on local and global levels. Meteorology, atmospheric physics, atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology; the interactions between Earth's atmosphere and its oceans are part of a coupled ocean-atmosphere system. Meteorology has application in many diverse fields such as the military, energy production, transport and construction; the word meteorology is from the Ancient Greek μετέωρος metéōros and -λογία -logia, meaning "the study of things high in the air". The ability to predict rains and floods based on annual cycles was evidently used by humans at least from the time of agricultural settlement if not earlier.
Early approaches to predicting weather were practiced by priests. Cuneiform inscriptions on Babylonian tablets included associations between rain; the Chaldeans differentiated 46 ° halos. Ancient Indian Upanishads contain mentions of seasons; the Samaveda mentions sacrifices to be performed. Varāhamihira's classical work Brihatsamhita, written about 500 AD, provides evidence of weather observation. In 350 BC, Aristotle wrote Meteorology. Aristotle is considered the founder of meteorology. One of the most impressive achievements described in the Meteorology is the description of what is now known as the hydrologic cycle; the book De Mundo noted If the flashing body is set on fire and rushes violently to the Earth it is called a thunderbolt. They are all called ` swooping bolts'. Lightning is sometimes smoky, is called'smoldering lightning". At other times, it travels in crooked lines, is called forked lightning; when it swoops down upon some object it is called'swooping lightning'. The Greek scientist Theophrastus compiled a book on weather forecasting, called the Book of Signs.
The work of Theophrastus remained a dominant influence in the study of weather and in weather forecasting for nearly 2,000 years. In 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system. According to Toufic Fahd, around the 9th century, Al-Dinawari wrote the Kitab al-Nabat, in which he deals with the application of meteorology to agriculture during the Muslim Agricultural Revolution, he describes the meteorological character of the sky, the planets and constellations, the sun and moon, the lunar phases indicating seasons and rain, the anwa, atmospheric phenomena such as winds, lightning, floods, rivers, lakes. Early attempts at predicting weather were related to prophecy and divining, were sometimes based on astrological ideas. Admiral FitzRoy tried to separate scientific approaches from prophetic ones. Ptolemy wrote on the atmospheric refraction of light in the context of astronomical observations. In 1021, Alhazen showed that atmospheric refraction is responsible for twilight.
St. Albert the Great was the first to propose that each drop of falling rain had the form of a small sphere, that this form meant that the rainbow was produced by light interacting with each raindrop. Roger Bacon was the first to calculate the angular size of the rainbow, he stated. In the late 13th century and early 14th century, Kamāl al-Dīn al-Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the primary rainbow phenomenon. Theoderic went further and explained the secondary rainbow. In 1716, Edmund Halley suggested that aurorae are caused by "magnetic effluvia" moving along the Earth's magnetic field lines. In 1441, King Sejong's son, Prince Munjong of Korea, invented the first standardized rain gauge; these were sent throughout the Joseon dynasty of Korea as an official tool to assess land taxes based
Atmospheric circulation is the large-scale movement of air, together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earth's atmospheric circulation varies from year to year, but the large-scale structure of its circulation remains constant; the smaller scale weather systems – mid-latitude depressions, or tropical convective cells – occur "randomly", long-range weather predictions of those cannot be made beyond ten days in practice, or a month in theory. The Earth's weather is a consequence of its illumination by the Sun, the laws of thermodynamics; the atmospheric circulation can be viewed as a heat engine driven by the Sun's energy, whose energy sink is the blackness of space. The work produced by that engine causes the motion of the masses of air and in that process, it redistributes the energy absorbed by the Earth's surface near the tropics to the latitudes nearer the poles, to space; the large-scale atmospheric circulation "cells" shift polewards in warmer periods, but remain constant as they are, fundamentally, a property of the Earth's size, rotation rate and atmospheric depth, all of which change little.
Over long time periods, a tectonic uplift can alter their major elements, such as the jet stream, plate tectonics may shift ocean currents. During the hot climates of the Mesozoic, a third desert belt may have existed at the Equator; the wind belts girdling the planet are organised into three cells in each hemisphere—the Hadley cell, the Ferrel cell, the polar cell. Those cells exist in both the southern hemispheres; the vast bulk of the atmospheric motion occurs in the Hadley cell. The high pressure systems acting on the Earth's surface are balanced by the low pressure systems elsewhere; as a result, there is a balance of forces acting on the Earth's surface. The atmospheric circulation pattern that George Hadley described was an attempt to explain the trade winds; the Hadley cell is a closed circulation loop. There, moist air is warmed by the Earth's surface, rises. A similar air mass rising on the other side of the equator forces those rising air masses to move poleward; the rising air creates a low pressure zone near the equator.
As the air moves poleward, it cools, becomes denser, descends at about the 30th parallel, creating a high-pressure area. The descended air travels toward the equator along the surface, replacing the air that rose from the equatorial zone, closing the loop of the Hadley cell; the poleward movement of the air in the upper part of the troposphere deviates toward the east, caused by the coriolis acceleration. At the ground level, the movement of the air toward the equator in the lower troposphere deviates toward the west, producing a wind from the east; the winds that flow to the west at the ground level in the Hadley cell are called the Trade Winds. Though the Hadley cell is described as located at the equator, in the northern hemisphere it shifts to higher latitudes in June and July and toward lower latitudes in December and January, the result of the Sun's heating of the surface; the zone where the greatest heating takes place is called the "thermal equator". As the southern hemisphere summer is December to March, the movement of the thermal equator to higher southern latitudes takes place then.
The Hadley system provides an example of a thermally direct circulation. The power of the Hadley system, considered as a heat engine, is estimated at 200 terawatts. Part of the air rising at 60° latitude diverges at high altitude toward the poles and creates the polar cell; the rest moves toward the equator where it collides at 30° latitude with the high-level air of the Hadley cell. There it strengthens the high pressure ridges beneath. A large part of the energy that drives the Ferrel cell is provided by the polar and Hadley cells circulating on either side and that drag the Ferrel cell with it; the Ferrel cell, theorized by William Ferrel, is, therefore, a secondary circulation feature, whose existence depends upon the Hadley and polar cells on either side of it. It might be thought of as an eddy created by polar cells; the air of the Ferrel cell that descends at 30° latitude returns poleward at the ground level, as it does so it deviates toward the east. In the upper atmosphere of the Ferrel cell, the air moving toward the equator deviates toward the west.
Both of those deviations, as in the case of the Hadley and polar cells, are driven by conservation of angular momentum. As a result, just as the easterly Trade Winds are found below the Hadley cell, the Westerlies are found beneath the Ferrel cell; the Ferrel cell is weak, because It has neither a strong source of heat nor a strong sink, so the airflow and temperatures within it are variable. For this reason, the mid-latitudes are sometimes known as the "zone of mixing." The Hadley and polar cells are closed loops, the Ferrel cell is not, the telling point is in the Westerlies, which are more formally known as "the Prevailing Westerlies." The easterly Trade Winds and the polar easterlies have nothing over which to prevail, as their parent circulation cells are strong enough and face few obstacles either in the form of massive terrain features or high pressure zones. The weaker Westerlies of the Ferrel cell, can be disrupted; the local passage of a cold front may change that in a matter of minutes, does.
As a result, at the surface, winds can vary abruptly in direction
Southern Italy or Mezzogiorno is a macroregion of Italy traditionally encompassing the territories of the former Kingdom of the two Sicilies, with the frequent addition of the island of Sardinia and some parts of Lazio as well. The Italian National Institute of Statistics employs the term "South Italy" to identify one of the five statistical regions in its reportings without Sicily and Sardinia, which form a distinct statistical region denominated "Insular Italy"; these same subdivisions are at the bottom of the Italian First level NUTS of the European Union and the Italian constituencies for the European Parliament. The term Mezzogiorno first came into use in the 18th century and is an Italian rendition of meridies; the term was popularised by Giuseppe Garibaldi and it came into vogue after the Italian unification. In a similar manner, Southern France is colloquially known as le Midi. Southern Italy is thought to comprise the administrative regions that correspond to the geopolitical extent of the former Kingdom of the Two Sicilies, starting from Abruzzo, Basilicata, Calabria and Sicily.
The island of Sardinia, although being culturally and less related to the aforementioned regions than any of them is to each other, is included as part of the Mezzogiorno for statistical and economical purposes. Southern Italy forms the lower part of the Italian "boot", containing the ankle, the toe, the arch, the heel and Abruzzo along with Sicily, removed from Calabria by the narrow Strait of Messina. Separating the "heel" and the "boot" is the Gulf of Taranto, named after the city of Taranto, at an angle between the heel and the boot itself, it is an arm of the Ionian Sea. The island of Sardinia, to the west of the Italian peninsula and right below the French island of Corsica, might be included. On the eastern coast is the Adriatic Sea, leading into the rest of the Mediterranean through the Strait of Otranto. On the Adriatic, south of the "spur" of the boot, the peninsula of Monte Gargano. Along the northern coast of the Salernitan Gulf and on the south of the Sorrentine Peninsula runs the Amalfi Coast.
Off the tip of the peninsula is the isle of Capri. The climate is Mediterranean, except at the highest elevations and the semi-arid eastern stretches in Apulia, along the Ionian Sea in Calabria and the southern stretches of Sicily; the largest city of Southern Italy is Naples, a name from the Greek that it has maintained for millennia. Bari, Reggio Calabria and Salerno are the next largest cities in the area; the region is geologically active and seismic: the 1980 Irpinia earthquake killed 2,914 people, injured more than 10,000 and left 300,000 homeless.. In the 8th and 7th centuries BCE, for various reasons, including demographic crisis, the search for new commercial outlets and ports, expulsion from their homeland, Greeks began to settle in Southern Italy. During this period, Greek colonies were established in places as separated as the eastern coast of the Black Sea, Eastern Libya and Massalia, they included the southern part of the Italian Peninsula. The Romans called the area of Sicily and the foot of Italy, Magna Graecia, since it was so densely inhabited by the Greeks.
The ancient geographers differed on whether the term included Sicily or Apulia and Calabria—Strabo being the most prominent advocate of the wider definitions. With this colonisation, Greek culture was exported to Italy, in its dialects of the Ancient Greek language, its religious rites and its traditions of the independent polis. An original Hellenic civilization soon developed interacting with the native Italic and Latin civilisations; the most important cultural transplant was the Chalcidean/Cumaean variety of the Greek alphabet, adopted by the Etruscans. Many of the new Hellenic cities became rich and powerful, like Neapolis, Syrakousai and Sybaris. Other cities in Magna Graecia included Tarentum, Epizephyrian Locri, Croton, Elea, Syessa and others. After Pyrrhus of Epirus failed in his attempt to stop the spread of Roman hegemony in 282 BCE, the south fell under Roman domination and remained in such a position well into the barbarian invasions, it was held by the Byzantine Empire after the fall of Rome in the West and the Lombards failed to consolidate it, though the centr