What are the reasons for the formation of the desert in Northwest India?
Most of the subtropical hot deserts in the world are located on the western part of the continents and Thar is not an exception.The reason for the formation of these deserts areTrade winds ;by the time they reach the western side, they carry very less moisture as they shed all the moisture in the eastern side before reaching to the distant West.These winds are finally obstructed by the Aravali range of mountains in India (and other mountains in other continents such as Andes in South America ) and cause orogenic rain on the windward side while the leeward side ramain dry.One more major factor responsible for the formation of deserts on the western side of the continent is the presence of cold currents on West coasts of all the continents in the subtropical region.Famous examples being Namib , Sahara , kalahari deserts in Africa , Atacama in South America , Mojave , Thar in India etc.,
Why are most of the world’s deserts located on the Western margins of continents in the subtropics?
Have already answered this question. That question although was specific to hot deserts and specified latitudinal extent too, but answer will remain same for your question too. Here it is:-Hot Deserts of the WorldArabian Desert in Arabian peninsulaGreat Sandy, Victoria, Simpson, Gibson and Sturt deserts in AustraliaChihuahuan Desert in north central MexicoKalahari Desert in south-western AfricaMojave Desert in USAMonte Desert in ArgentinaSahara Desert in North AfricaSonoran Desert in North and Central AmericaThar Desert in India and PakistanThere are four major reasons responsible for why the major hot deserts of the world are located between 20°-30° N on the west of the continents:-Offshore trade winds in the region and location in rain shadow zone:- Trade winds that blow in the region, shed their moisture on the eastern part and by the time they reach the western margin, they become dry.Anticyclonic conditions:- Areas between 20–30 degree latitudes on western margins of continents are the regions of descending air. It means the air gets compressed and warm as it descends and thus the moisture keeps decreasing.Leeward sides of mountains/parallel mountain ranges:- In the case of few deserts, mountains are situated as a barrier which prevents orographic rainfall. For example:- presence of Rockies on the western coast of North America does not let moisture bearing winds do rainfall in leeward sides. In the case of Thar desert in India, Aravallis are situated parallel to the region. Therefore the moisture holding winds pass away from the region because there is absence of mountain barriers.Presence of cold ocean currents along the western coast of continents tend to stabilise the air over the coast. This prevents cloud formation and rainfall.You can see it here in the map that major deserts are located on the western parts of continents between 30 degrees North and South latitudes.
What causes Loo winds in northwestern parts of India? Which physical phenomenon works behind Loo winds?
Loo winds are strong, hot and dry summer afternoon wind from the west which blows over the western Indo-Gangetic Plain region of North India and Pakistan. It is especially strong in the months of May and June.During summer,desert regions of South Balochistan and That desert in India gets heated up to a greater extent. This creates a vast low pressure area over North Indian plains during afternoon. This low pressure area pulls in moist air from North Arabian sea. When this air mass blows over Gujarat region it loses its moisture to the parched land and becomes dry.When this air mass blows over the desert regions it becomes completely dry with high temperature and less humidity. Moreover as it passes over sandy regions of the desert, it picks up the desert and turns into a duststorm or Loo winds.During late summer months of May and June these Loo winds can reach upto the plains of Bihar often lessening the visibility of the region. Loo winds ends on the arrival of the South West monsoon!
What are the main wind belts on Earth?
The globe is encircled by six major wind belts, three in each hemisphere. From pole to equator, they are the polar easterlies, the westerlies, and the trade winds. All six belts move north in the northern summer and south in the northern winter.Global wind patterns: Winds are named by the direction from which they blow. The globe is encircled by six major wind belts, three in each hemisphere. From pole to equator, they are the polar easterlies, the westerlies, and the trade winds. All six belts move north in the northern summer and south in the northern winter.Polar Easterlies: At about the latitude of Norway and northward (60-90 degrees), the Polar easterlies blow irregularly from the east and north.Prevailing Westerlies: At about the latitude of Western Europe and the United States (30-60 degrees), the Westerlies blow from the west, tending somewhat toward the north. This causes most weather in the United States to move from west to east.Trade Winds: South of about 30 degrees the northern or northeast trade winds blow mostly from the northeast toward the equator. These were the sailor's favorite winds, since the weather was warm, and the winds usually blew steadily in an advantageous direction. Columbus used these to sail to the Caribbean.
What are trade winds?
Background InformationWind is the flow of air from High Pressure to Low Pressure region.Atmospheric air circulation on earth is depicted as follows:-Image source: Atmospheric circulation30º N and 30º S latitudes (see image) are known as sub-tropical high.Winds are named based on their origin (from where do they start) - for e.g., easterly wind originates from east.Coriolis effect - In terms of physics, Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame.Coriolis Effect and circulation of air -- In the northern hemisphere, this effect deflects the air towards right and in the southern hemisphere, deflection is towards the left. (see white arrow marks in above image)What are trade winds (or trades or easterlies) ?In simple words, these are winds blowing towards equator.At the equator, air rises up creating a low pressure, and cold air from higher latitudes rushes to fill up this space. Air rising at the equator sinks at sub-tropical region (30º N&S in both hemispheres) thereby creating a circulation of surface air towards the equator. (observe the arrow marks in the above image). This circulation encounters the coriolis force caused by the rotation of the Earth. The result is that between 20° North latitude and 20° South latitude winds usually blow from the east towards the west. This wind is called trade winds or easterlies or trades. In northern hemisphere, it is called northeasterly trades (blows from Northeast) and in southern hemisphere, it is called southeasterly (blows from Southeast) trades.Source: Geography & Geology For KidsTrades are prevailing winds, i.e., they blow predominantly from a single general direction over a particular point on the Earth's surface. These winds blow in the lower atmosphereHistorical ImportanceTrade winds have been used by captains of sailing ships to cross the oceans. The term trade winds originally derives from the early fourteenth century late Middle English word 'trade' meaning "path" or "track."It helped in the European expansion into the Americas and trade routes to become established across the Atlantic and Pacific oceans.
How are deserts formed?
Desert is an arid ( dry, hot,sandy) region , which receives less than 250 mm ( 10 inches) of annual rainfall1. Oceanic currentsCold currents from the Polar Regions flow towards the equator and, in places, come up against the edges of continents. Additional masses of cold water are added to them by upwelling from the frigid ocean depths.Winds blowing landwards over this cold water become cold and can carry little moisture forming deserts ( Atacama desert-Peru current, Namib desert-benguela current ,sonaran desert-california current,western Sahara desert- canary )2.Rainshadow regionsHot rising air cools as it approaches a mountain. Less water can be held and that side of the mountain gets rain. The cooler air that crosses over mountains is dry, so deserts form on the other side of the mountain range.The Gobi Desert in Mongolia and China is in a rain shadow due to the towering Himalaya mountain range . The Thar desert in India is the rain shadow due to Aravalli moumtain Range.3.Atomspheric pressureDue to the high temperature at the equator air becomes warm and lighter, observes moisture and raises upwards. As the air moves upwards because of normal lapse rate ( For every 1 km 6.5 degrees of temperature decreases ) air becomes dense and condense at the equator .The leftover dry and cold air moves towards sub tropical regions and desends there without giving any rainfall which results into deserts. That is the reason why many deserts are located between 30 degree North and 30 degree south latitudesThe Sahara Desert and the Kalahari Desert, both in Africa are subtropical deserts4.Distance from the seaWinds reaching the interior of the Sahara have travelled over vast area of land, and most of their water has been squeezed out of them along the way.5. Man made desertsDue to extensive use of ground water , deforestation , soil degradation , poor irrigation techniques , overgrazing , diverting rivers , Global warming leading to Desertification of landIt can take 500 years for 2.5 cm of soil to form , but it's only few years to destory it .“ Sadly , it's much easier to create a desert than a forest”
Why is the climate of the Western part of North America drier than the eastern part?
The rain shadow of several mountain ranges, chiefly the Sierra Nevada Mountains and the Rocky Mountains, keeps Western North America much drier than the humid locations of Eastern North America, which are more often affected by moist air from the Gulf of Mexico and the Atlantic Ocean.Moisture condenses at high altitude, leaving air masses arid or semi-arid after passing over mountain ranges. You will see this in regional climate patterns in the U.S. The Central Valley of California and the Mojave Desert are both relatively dry as they are in the rain shadow of the Coast Ranges. The Great Basin is extremely dry, too, as it sits in the rain shadow of the Sierra Nevada Mountains. Even the Great Plains see higher aridity due to the Rocky Mountains to the west, resulting in long dry stretches throughout the year.The Northern United States and Canada have the significant addition of dry Arctic air masses that frequently descend in winter as the jet stream drops further south later in the year. While they are very cold, they often contain little moisture. They are responsible for creating the icy dry landscape in the tundras and taigas of Canada’s northern expanses as well as the frigid winter chill of Canada’s Prairie Provinces and the American Midwest. In Canada, conditions become gradually wetter west of the Rocky Mountains (in cities like Vancouver, British Columbia) and in proximity to any of the Great Lakes (which add moisture to the air) as well as the Atlantic Ocean, which contributes to the dampness of the country’s Maritime Provinces in the east. By comparison, prairie cities like Regina and Calgary tend to be surprisingly dry. Their American counterparts in the Upper Great Plains are likewise frequently parched, even in spite of chilly winters.