1.
Operation Winter Storm
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In late November 1942, the Red Army completed Operation Uranus, encircling some 300,000 Axis personnel in and around the city of Stalingrad. German forces within the Stalingrad pocket and directly outside were reorganized under Army Group Don, to remedy the situation, the Luftwaffe attempted to supply German forces in Stalingrad through an air bridge. Originally, Manstein was promised four panzer divisions, due to German reluctance to weaken certain sectors by redeploying German units, the task of opening a corridor to the German 6th Army fell to the 4th Panzer Army. The German force was pitted against several Soviet armies tasked with the destruction of the encircled German forces, the German offensive caught the Red Army by surprise and made large gains on the first day. The spearhead forces enjoyed air support and were able to defeat counterattacks by Soviet troops, by 13 December, Soviet resistance slowed the German advance considerably. Although German forces took the area surrounding Verkhne-Kumskiy, the Red Army launched Operation Little Saturn on 16 December, Operation Little Saturn crushed the Italian 8th Army on Army Group Dons left flank, threatening the survival of Mansteins entire group of forces. The 4th Panzer Army continued its attempt to open a corridor to the 6th Army on 18–19 December, Manstein was forced to call off the assault on 23 December and by Christmas Eve the 4th Panzer Army began to withdraw to its starting position. Due to the failure of the 6th Army to breakout and the attempt to break the Soviet encirclement, on 23 November 1942, the Red Army closed its encirclement of Axis forces in Stalingrad. Nearly 300,000 German and Romanian soldiers, as well as Russian volunteers for the Wehrmacht, were trapped in, amidst the impending disaster, German chancellor Adolf Hitler appointed Field Marshal Erich von Manstein as commander of the newly created Army Group Don. Composed of the German 4th Panzer and 6th Armies, as well as the Third and Fourth Romanian Armies, instead of attempting an immediate breakout, German high command decided that the trapped forces would remain in Stalingrad in a bid to hold out. The encircled German forces were to be resupplied by air, requiring roughly 680 t of supplies per day, however, the assembled fleet of 500 transport aircraft were insufficient for the task. Many of the aircraft were serviceable in the rough Soviet winter, in early December. The German 6th Army, for example, was getting less than 20% of its daily needs, furthermore, the Germans were still threatened by Soviet forces which still held portions of the Volga Rivers west bank in Stalingrad. Given the unexpected size of German forces closed off in Stalingrad, on 23 November Stavka decided to strengthen the outer encirclement preparing to destroy Axis forces in, on 24 November, several Soviet formations began to entrench themselves to defend against possible German incursions originating from the West. The Soviets also reinforced the forces in order to prevent a successful breakout operation by the German 6th Army. However, this tied down over ½ of the Red Armys strength in the area, meanwhile, planning also began for Operation Koltso, which aimed at reducing German forces in the Stalingrad pocket. As Operation Uranus concluded, German forces inside the encirclement were too weak to attempt a breakout on their own, Manstein proposed a counterstrike to break the Soviet encirclement of Stalingrad, codenamed Operation Winter Storm. Manstein believed that—due to the inability of the Luftwaffe to supply the Stalingrad pocket—it was becoming important to relieve them at the earliest possible date
2.
Nature
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Nature, in the broadest sense, is the natural, physical, or material world or universe. Nature can refer to the phenomena of the world. The study of nature is a part of science. Although humans are part of nature, human activity is understood as a separate category from other natural phenomena. The word nature is derived from the Latin word natura, or essential qualities, innate disposition, and in ancient times, literally meant birth. Natura is a Latin translation of the Greek word physis, which related to the intrinsic characteristics that plants, animals. This usage continued during the advent of scientific method in the last several centuries. Within the various uses of the word today, nature often refers to geology, for example, manufactured objects and human interaction generally are not considered part of nature, unless qualified as, for example, human nature or the whole of nature. Depending on the context, the term natural might also be distinguished from the unnatural or the supernatural. Earth is the planet known to support life, and its natural features are the subject of many fields of scientific research. Within the solar system, it is third closest to the sun, it is the largest terrestrial planet and its most prominent climatic features are its two large polar regions, two relatively narrow temperate zones, and a wide equatorial tropical to subtropical region. Precipitation varies widely with location, from several metres of water per year to less than a millimetre,71 percent of the Earths surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the land in the Northern Hemisphere. Earth has evolved through geological and biological processes that have left traces of the original conditions, the outer surface is divided into several gradually migrating tectonic plates. The interior remains active, with a layer of plastic mantle. This iron core is composed of a solid phase. Convective motion in the core generates electric currents through dynamo action, the atmospheric conditions have been significantly altered from the original conditions by the presence of life-forms, which create an ecological balance that stabilizes the surface conditions. Geology is the science and study of the solid and liquid matter that constitutes the Earth, the geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations
3.
Weather
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Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the lowest level of the atmosphere, Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, weather is understood to mean the weather of Earth. Weather is driven by air pressure, temperature and moisture differences between one place and another and these differences can occur due to the suns angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the largest scale atmospheric circulations, the Hadley Cell, the Ferrel Cell, the Polar Cell, Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earths axis is tilted relative to its orbital plane, on Earths surface, temperatures usually range ±40 °C annually. Over thousands of years, changes in Earths orbit can affect the amount and distribution of energy received by the Earth, thus influencing long-term climate. Surface temperature differences in turn cause pressure differences, higher altitudes are cooler than lower altitudes as most atmospheric heating is due to contact with the Earths surface while radiative losses to space are mostly constant. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The Earths weather system is a system, as a result. Human attempts to control the weather have occurred throughout history, and there is evidence that human activities such as agriculture, studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the Solar System, Jupiters Great Red Spot, is a storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies, a stars corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind, on Earth, the common weather phenomena include wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes, typhoons, almost all familiar weather phenomena occur in the troposphere. Weather does occur in the stratosphere and can affect weather lower down in the troposphere, Weather occurs primarily due to air pressure, temperature and moisture differences between one place to another. These differences can occur due to the sun angle at any particular spot, in other words, the farther from the tropics one lies, the lower the sun angle is, which causes those locations to be cooler due the spread of the sunlight over a greater surface. The strong temperature contrast between polar and tropical air gives rise to the large scale atmospheric circulation cells and the jet stream, Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow
4.
Season
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A season is a division of the year marked by changes in weather, ecology and hours of daylight. Seasons result from the orbit of the Earth around the Sun. During May, June, and July, the northern hemisphere is exposed to direct sunlight because the hemisphere faces the sun. The same is true of the hemisphere in November, December. It is the tilt of the Earth that causes the Sun to be higher in the sky during the months which increases the solar flux. However, due to lag, June, July, and August are the hottest months in the northern hemisphere and December, January. In temperate and subpolar regions, four calendar-based seasons are recognized, spring, summer, autumn or fall. Ecologists often use a model for temperate climate regions, prevernal, vernal, estival, serotinal, autumnal. Many tropical regions have two seasons, the rainy, wet, or monsoon season and the dry season, some have a third cool, mild, or harmattan season. Seasons often held special significance for agrarian societies, whose lives revolved around planting and harvest times, in some parts of the world, some other seasons capture the timing of important ecological events such as hurricane season, tornado season, and wildfire season. The most historically important of these are the three seasons—flood, growth, and low water—which were previously defined by the annual flooding of the Nile in Egypt. The seasons result from the Earths axis of rotation being tilted with respect to its orbital plane by an angle of approximately 23.5 degrees, regardless of the time of year, the northern and southern hemispheres always experience opposite seasons. This is because during summer or winter, one part of the planet is directly exposed to the rays of the Sun than the other. For approximately half of the year, the northern hemisphere tips toward the Sun, for the other half of the year, the same happens, but in the southern hemisphere instead of the northern, with the maximum around December 21. The two instants when the Sun is directly overhead at the Equator are the equinoxes. Also at that moment, both the North Pole and the South Pole of the Earth are just on the terminator, and hence day and night are equally divided between the northern and southern hemispheres. Around the March equinox, the northern hemisphere will be experiencing spring as the hours of daylight increase, the effect of axial tilt is observable as the change in day length and altitude of the Sun at noon during a year. Between this effect and the daylight hours, the axial tilt of the Earth accounts for most of the seasonal variation in climate in both hemispheres
5.
Winter
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Winter is the coldest season of the year in polar and temperate climates, between autumn and spring. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun, different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, in many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the elevation with respect to the North or South Pole is at its most negative value, meaning this day will have the shortest day. The English word winter comes from the Proto-Indo-European root wend, relating to water, the tilt of the Earths axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23. 44° to the plane of its orbit, when it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun, from the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun. During winter in either hemisphere, the altitude of the Sun causes the sunlight to hit that hemisphere at an oblique angle. In regions experiencing winter, the amount of solar radiation is spread out over a larger area. This effect is compounded by the distance that the light must travel through the atmosphere. Compared with these effects, the changes in the distance of the earth from the sun are negligible, the manifestation of the meteorological winter in the northerly snow–prone parallels is highly variable depending on elevation, position versus marine winds and the amount of precipitation. A case in point is Canada, a country associated with tough winters. Winnipeg on the Great Plains at a distance from large bodies of water has a January high of −11.3 °C. In comparison, Vancouver on the coast with an influence from moderating Pacific winds has a January low of 1.4 °C with days well above freezing at 6.9 °C. Both areas are on the 49th parallel north and in the western half of the continent. Winter is often defined by meteorologists to be the three months with the lowest average temperatures. This corresponds to the months of December, January and February in the Northern Hemisphere, the coldest average temperatures of the season are typically experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Blizzards often develop and cause many transportation delays, diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °F due to air with slightly higher moisture from aloft mixing with colder, surface based air
6.
Spring (season)
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Spring is one of the four conventional temperate seasons, following winter and preceding summer. There are various definitions of spring, but local usage of the term varies according to local climate, cultures. When it is spring in the Northern Hemisphere, it will be autumn in the Southern Hemisphere, at the spring equinox, days are approximately 12 hours long with day length increasing as the season progresses. Spring and springtime refer to the season, and also to ideas of rebirth, rejuvenation, renewal, resurrection, subtropical and tropical areas have climates better described in terms of other seasons, e. g. dry or wet, monsoonal or cyclonic. Often, cultures have locally defined names for seasons which have little equivalence to the terms originating in Europe, Spring is the time when many plants begin to grow and flower. Meteorologists generally define four seasons in many areas, spring, summer, autumn. These are demarcated by the values of their average temperatures on a monthly basis, the three warmest months are by definition summer, the three coldest months are winter and the intervening gaps are spring and autumn. Spring, when defined in this manner, can start on different dates in different regions, in most Northern Hemisphere, temperate locations, spring months are March, April and May, although differences exist from country to country. Most Southern Hemisphere, temperate locations have opposing seasons with spring in September, October and November, in Australia and New Zealand, spring conventionally begins on 1 September and ends 30 November. In some cultures in the Northern Hemisphere, the astronomical Vernal equinox is taken to mark the first day of spring, in Persian culture the first day of spring is the first day of the first month which begins on 20 or 21 March. In other traditions, the equinox is taken as mid-spring, similarly, according to the Celtic tradition, which is based solely on daylight and the strength of the noon sun, spring begins in early February and continues until early May. In Ireland, spring traditionally starts on February 1, St Brigids Day, the beginning of spring is not always determined by fixed calendar dates. These indicators, along with the beginning of spring, vary according to the local climate, most ecologists divide the year into six seasons that have no fixed dates. In addition to spring, ecological reckoning identifies an earlier separate prevernal season between the hibernal and vernal seasons and this is a time when only the hardiest flowers like the crocus are in bloom, sometimes while there is still some snowcover on the ground. During early spring, the axis of the Earth is increasing its tilt relative to the Sun, the hemisphere begins to warm significantly, causing new plant growth to spring forth, giving the season its name. Any snow begins to melt, swelling streams with runoff and any frosts become less severe, in climates that have no snow, and rare frosts, air and ground temperatures increase more rapidly. Many flowering plants bloom at this time of year, in a succession, sometimes beginning when snow is still on the ground. In normally snowless areas, spring may begin as early as February, heralded by the blooming of deciduous magnolias, cherries, and quince, or August in the same way
7.
Summer
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Summer is the hottest of the four temperate seasons, falling between spring and autumn. At the summer solstice, the days are longest and the nights are shortest, the date of the beginning of summer varies according to climate, tradition and culture. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, a variable seasonal lag means that the meteorological center of the season, which is based on average temperature patterns, occurs several weeks after the time of maximal insolation. Under meteorological definitions, all seasons are set to start at the beginning of a calendar month. This meteorological definition of summer also aligns with the commonly viewed notion of summer as the season with the longest days of the year, the meteorological reckoning of seasons is used in Australia, Austria, Denmark, the former Soviet Union and Japan. It is also used by many in the United Kingdom, in Ireland, the summer months according to the national meteorological service, Met Éireann, are June, July and August. However, according to the Irish Calendar, summer begins on 1 May, school textbooks in Ireland follow the cultural norm of summer commencing on 1 May rather than the meteorological definition of 1 June. Reckoning by hours of daylight alone, summer solstice marks the midpoint, not the beginning, midsummer takes place over the shortest night of the year, which is the summer solstice, or on a nearby date that varies with tradition. Where a seasonal lag of half a season or more is common, by this method, in North America, summer is the period from the summer solstice to the autumn equinox. The similar Canadian tradition starts summer on Victoria Day one week prior and ends, as in the United States, on Labour Day. In Chinese astronomy, summer starts on or around 5 May, with the known as lìxià, i. e. establishment of summer. In Australia and New Zealand, summer begins on 1 December. Summer is traditionally associated with hot or warm weather, in the Mediterranean regions, it is also associated with dry weather, while in other places it is associated with rainy weather. The wet season is the period of vegetation growth within the savanna climate regime. Where the wet season is associated with a shift in the prevailing winds. In the northern Atlantic Ocean, a tropical cyclone season occurs from 1 June to 30 November. The statistical peak of the Atlantic hurricane season is 10 September, the Northeast Pacific Ocean has a broader period of activity, but in a similar time frame to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and March, in the North Indian basin, storms are most common from April to December, with peaks in May and November
8.
Autumn
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Autumn, also known as fall in North American English, is one of the four temperate seasons. One of its features is the shedding of leaves from deciduous trees. Some cultures regard the autumnal equinox as mid-autumn, while others with a longer temperature lag treat it as the start of autumn. Meteorologists use a definition based on months, with autumn being September, October and November in the northern hemisphere, in North America, autumn is usually considered to start with the September equinox and end with the winter solstice. As daytime and nighttime temperatures decrease, trees shed their leaves, in traditional East Asian solar term, autumn starts on or around 8 August and ends on or about 7 November. In Ireland, the autumn months according to the meteorological service. In Australia and New Zealand, autumn officially begins on 1 March, the word autumn comes from the ancient Etruscan root autu- and has within it connotations of the passing of the year. It was borrowed by the neighbouring Romans, and became the Latin word autumnus, after the Roman era, the word continued to be used as the Old French word autompne or autumpne in Middle English, and was later normalized to the original Latin. In the Medieval period, there are examples of its use as early as the 12th century. Before the 16th century, harvest was the usually used to refer to the season. The alternative word fall for the season traces its origins to old Germanic languages, the exact derivation is unclear, with the Old English fiæll or feallan and the Old Norse fall all being possible candidates. However, these all have the meaning to fall from a height and are clearly derived either from a common root or from each other. The term came to denote the season in 16th century England, during the 17th century, English emigration to the British colonies in North America was at its peak, and the new settlers took the English language with them. While the term gradually became obsolete in Britain, it became the more common term in North America. The name backend, a common name for the season in Northern England, has today been largely replaced by the name autumn. Association with the transition from warm to cold weather, and its status as the season of the primary harvest, has dominated its themes. In Western cultures, personifications of autumn are usually pretty, well-fed females adorned with fruits, vegetables, many cultures feature autumnal harvest festivals, often the most important on their calendars. There are also the many North American Indian festivals tied to harvest of ripe foods gathered in the wild, the Chinese Mid-Autumn or Moon festival, and many others
9.
Tropics
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The tropics are a region of the Earth surrounding the equator. The tropics are also referred to as the zone and the torrid zone. The tropics include all the areas on the Earth where the Sun is at a point directly overhead at least once during the solar year. The tropics are distinguished from the climatic and biomatic regions of Earth, which are the middle latitudes. Tropical is sometimes used in a sense for a tropical climate to mean warm to hot and moist year-round. Many tropical areas have a dry and wet season, the wet season, rainy season or green season, is the time of year, ranging from one or more months, when most of the average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics, under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is distributed through the year. When the wet season occurs during the season, or summer, precipitation falls mainly during the late afternoon. The wet season is a time when air quality improves, freshwater quality improves and vegetation grows significantly, floods cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients diminish and erosion increases, the incidence of malaria increases in areas where the rainy season coincides with high temperatures. 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. Regions within the tropics may well not have a tropical climate, there are alpine tundra and snow-capped peaks, including Mauna Kea, Mount Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina. Under the Köppen climate classification, much of the area within the tropics is classed not as tropical but as dry including the Sahara Desert. Tropical plants and animals are those native to the tropics. Tropical ecosystems may consist of rainforests, dry forests, spiny forests, desert. There are often significant areas of biodiversity, and species present, particularly in rainforests. In biogeography, the tropics are divided into Paleotropics and Neotropics, together, they are sometimes referred to as the Pantropic
