অধ্যায় ৪: বায়ুমণ্ডল ও বায়ু দূষণ ১

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Planetary Winds: Their Types and Definition

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Planetary winds : These winds being controlled by the pressure belts, blow towards the same direction throughout the whole year. The planetary wind is of three types such as : the trade wind, the westerlies and the polar wind. So, in short, the characteristics of planetary winds are as follows: These winds being controlled by the pressure belts blow towards the same direction throughout the whole year.  Planetary winds are also known as permanent or prevailing winds  Blow from high to low pressure, over the earth surface & oceans throughout the year & in a particular direction  These winds are divided into 3 categories viz. Trade Winds (Tropical Easterlies) Westerlies Polar winds (Polar Easterlies) https://www.affairscloud.com/assets/uploads/2016/04/wind.png 1. Trade Winds (Tropical Easterlies) The sun’s rays fall vertically over the equatorial region, so the air becomes hot and goes upwards. Since the pressure is less upward, the rising air gets r
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The Vance Model of Transport Development

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Based on his work on the eastern seaboard of America, Vance (1970) developed a five-stage ‘mercantile’ model to illustrate the development of transport links and the growth of the urban hierarchy in North America (Figure 3.6). Although primarily concerned with trade, his model is important in that it stresses the impact of exogenous forces on the evolution of transport networks and their associated spatial patterns. The Vance Model of Transport Development In the initial stage, an accumulating of wealth in Europe prompted overseas expansion of an exploratory nature. Stage 2 sees the beginnings of the transatlantic trade routes based on the one-way trade in staple products such a fish, furs and timber. From 1620, permanent settlement occurs in North America; this results in Atlantic trade in both directions as settlers begin to produce commodities for export and consume manufactured products from a rapidly industrialising Europe (stage 3). Internal transport links are limited
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