Monsoon of South Asia

The Indian monsoon represents the main regional monsoon and will therefore often simply shortened the monsoon called, but this is not unique due to the variety of different monsoons. He extends substantially across the Indian subcontinent, but also part of a larger composite system of monsoon phenomena in space of the Indian Ocean. Meanwhile foothills extend into the south, southeast Asian, northern Australia, but also the East African region.

  • 5.1 Indus Valley Civilization
  • 8.1 Literature
  • 8.2 External links

Special features of the Indian monsoon

Because of the large continental surface, especially the Tibetan plateau, the monsoon phenomenon in India appears very clearly with an ITC - shift to 30 ° north latitude. The Indian monsoon is the only monsoon, which has an effect to the upper layers of the troposphere. This shows on the Tibetan plateau, a high -reaching reversal of the meridional temperature gradient and thus the tendency to pronounced Advektionserscheinungen. In addition, a seasonal reversal of wind directions up on the 700 -hPa isobar, it becomes clear at the level of weather maps. Neither North American, nor the West African monsoon show such a level effect, although they heat the air layers very strong near the ground. The development of a comparatively high -reaching moist deep layer of air in conjunction with the advective ascent and adiabatic cooling of the air, resulting in the monsoon rains, therefore, are typical phenomena of the Indian monsoon, as it comes in other monsoon regions only much weaker monsoon rains.

Particularly important for the people living there is the change of the seasonal rainfall, which is caused by the dry winter monsoon or wet summer monsoon. Since it is still primarily an agricultural country is in India, this rainfall is of vital importance. This refers Although primarily on the rural population, but also the Indian cities are food supply dependent on their water and to the monsoon or threatened by its extreme precipitation.

From this extreme dependence, in conjunction with the rapid growth of the Indian population and an increasingly unstable climate in the wake of global warming, resulting in a dramatic crisis potential. Particularly dramatic, this is shown in the large-scale deforestation and the resulting vulnerability to soil erosion and flooding. For this dualism between the dependence on and the dangers of the monsoon, and the characteristic attitude of the Indian people on this, which is closely linked to many aspects of Indian culture and way of life evolved into the sequence. The role of the monsoon in the context of Indian culture or cultural history, especially in relation to the Indus Valley Civilization, is explained in the section on the importance of the monsoons in more detail.

Development and annual variation

Basis Article: Emergence of a monsoon

For the regional weather pattern the large-scale thermal control with Zellularstrukturen as the monsoon depression must be combined. Even terrestrial conditions, such as the accumulation of winds at the Lee of mountains, play a strong role. Thus, the Jetstream branches in the winter monsoon season on Pamirknoten in a north and a south-east stream which fixed rests on the Himalayan waste and plays an essential role in the formation of a stable high -pressure system over north-central India. The Lee - convergence of the two jet streams has a tendency zyklogenetische what climatic impact on southern Japan and China.

In summer, the southern branch of the jet stream is initially blocked by a high level of air over Tibet, whereupon it skips to the northern jet stream at the Kunlun Shan. The person responsible for the high altitude of Tibet Tibetan plateau is ideal due to their size, altitude, seclusion and dryness for the heat on him contained air layers. It is, therefore, as explained in the section on surface heating, a thermal surface low from. This stable surface low now affects the Indian subcontinent very strong and enhances the appearance of convergence towards the continent. Thus the air is at the foot of the Himalayas less stable and the wintry Subtropenhoch disappears over India. The summer monsoon can now freely penetrate ( burst of monsoon ) to the decay of the winter monsoon. By the Tibet high and the resulting temperature discrepancies creates a strong pressure gradient, which an eastern Jetstream ( Tropical Easterly Jet) is formed, which is to the Sahara weather effect. So the Indian monsoon has global climatic effects.

Seasons

The summer monsoon sets in June / July by the already explained above ITC relocation and trade diversion ( NO Passat SW monsoon ) from the southwest and lasts until September / October. It provides moist oceanic air masses to the Western Ghats and thus causes an unstable atmosphere stratification ( see explanation in the article hairdryer), resulting in the monsoon rain and often attracts months of rainfall by itself. One speaks therefore in line with the tropical rain forest climate of a rainy season. Especially on morphological obstacles the monsoon rain as the slope of this rain can reach very high rainfall, which even in places the limit of 10,000 millimeters exceed annual rainfall. An example of this is the region around Cherrapunji, in which a annual rainfall of about 9000 mm per year usually occurs and also the global single-season record was registered by 26461 mm. In Mawsynram the monsoon rains caused the world's highest average annual rainfall of 11872 mm. This precipitation flows to a large extent from the surface runoff and regularly lead to floods in Bangladesh.

The winter monsoon is identical to the northeast trade winds and provides cold, dry air masses from the cold high over Siberia (Lit.: Goudie 2002). He begins in September / October and lasts until June / July, which is referred to this period because of the comparatively very low rainfall as the dry season. This can escalate in years with a weak monsoon to a drought and resulted often in the past to great famine.

In the picture the temporal propagation of the Indian monsoon is illustrated by a number markings. The dark blue lines represent the spread of the summer monsoon ( monsoon front ), or withdrawal of the winter monsoon in June / July and the light blue lines for the spread of the winter monsoon, or withdrawal of the summer monsoon in September / October, with one each in sufficiently good but not reliable accuracy line can assign a specific time during the year. The rule here is therefore important to note that the spread of the Monsoon influences can not be reliably and the daily accurate information represents only a rough guide, as the advance of the monsoon is a dynamic process, which is characterized by oscillations of the monsoon front. As a feature of the times this is always the appearance or disappearance of the monsoon was used.

Variability and change

The Indian monsoon as a whole provides a reliable climate phenomenon with only relatively minor differences in the course of several years dar. way reflects the mean annual rainfall of 852 mm with a standard deviation of 84 mm with a moist, but also fluctuation poor air resist. Weather observations, but also climatic evaluated trend analyzes of the same, point to an increase in monsoon rainfall in the Indian region. These are associated with increased risk of flooding, which already detectable increase in frequency and strength. It traces the causes of this development on a coupling with the global average temperature, so even with global warming.

Interaction with ENSO

The occurrence of El Niño in the Eastern Pacific area acts themselves out into the Indian Ocean and thus also on the Indian monsoon. Could quite early the Southern Oscillation Index, a parameter for the probability of occurrence of El Niño phenomenon, based on the measurements of the Observatory of the British colonial administration in India through its director, Gilbert Walker, even with the absence or the weakening of the Indian summer monsoon and the consequent precipitation are associated. It was here, then, that both phenomena are closely interwoven and mutually influence each other, which says nothing more than that the global atmospheric circulation contains no standing for themselves elements and therefore their global character in the foreground. So it is not enough to consider only the monsoon itself, if one wants to understand its dynamics and its occurrence. But also a direct connection between the two phenomena is not sufficient as it during a strong El Niño, gave normal monsoon rains for example, 1997. Very important, for example, the variability of the heating of air over the Tibetan plateau and thus in particular the local albedo, which is crucially influenced by the presence of snow-covered surfaces and the snow level. In general it can, however, in recent decades, a decreasing influence of the El Niño find on the Indian monsoon, which is still largely unclear why there is this, and especially how sustainable is this change.

Importance for the history of culture

The cultural significance of the monsoons is particularly in the case of the Indian monsoon is very strong. In addition to the role of the monsoon winds as a mediator of cultural exchange in the space of Indiks (see also monsoon ), this shows in particular the example of the Indus Valley Civilization.

Indus Valley Civilization

The Indus Valley Civilization is characterized by the fact that they very early developed an advanced hydraulic engineering and was also due to fluctuating monsoon rains rely thereon. The infrastructural developments in terms of water storage, transport and distribution achieved in the period 3500-1500 BC levels similar to those millennia later in the Roman civilization. In some areas it exceeded even this and has not been achieved in many regions of India until today again. The issue of water and water supply had reached a high priority here and the many innovations already included things like bathrooms, flush toilets, a well -supported by channel and pipe system up to the houses and a sophisticated sewage system. Although the recent archaeological finds are only of limited power, but also suggest plenty of clues to a strong economy towards reservoir, which could have helped to secure the water supply in the dry winter months. This in turn is a prerequisite for the establishment of a stable high culture and at the same time requires a large number of hydraulic engineering knowledge, and a with their use and preservation entrusted "Water elite". The need, with very different rainfall over the year could realize a highly productive agriculture therefore gave the decisive impulse to the development of such a hydraulic engineering and the associated " water culture". The same is true for other regions and not just for India, which has changed in the fundamental questions of correlation between monsoon, agriculture and man up to the present time very little.

Effects

The monsoon calls in India every year large numbers of victims. So about 1300 people died in the 2005 season due to flood and storm. In 2006, 480 victims were already complaining to the state July 31. Would the monsoon but not once occur, that would have enormous consequences for agriculture. Since the fields have to be watered, there would be droughts and up to 95 percent crop failure.

Exceptional violent impacts the monsoon of 2007. Approximately 20 million people had lost in India, Nepal and Bangladesh their homes. Alone in the Indian states of Bihar, Uttar Pradesh and Assam died to early August, more than 120 people.

After weeks of monsoon rains occur in August 2008 in Indian state of Bihar to over 1.2 million homeless and several hundred dead.

Monsoon over the Vindhyagebirge in central India

Temperature zones

Height zones

Natural disasters

For more information

For general literature sources and links, see the article monsoon.

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