Indian Geog Flashcards

Question 1

Q

Monsoon (from mindmap): defn?

Answer

A

<ul><li>monsoon are seasonal winds which reverse their direction of flow with the change of season</li><li>CS Ramage (1971) suggested the following four features of monsoon winds:<ul><li>prevailing wind direction should shift by at least 120^o betn Jan and July</li><li>Avg frequency of prevailing wind directions in Jan and JUly should exceed 40%</li><li>Mean resultant wind velocity in at least one of the months should exceed 3m/s</li><li>There should be fewer than one cyclone-anticyclone alternation every two yrs, in either month, over a five degree latitude/longitude grid</li></ul></li><li>On the basis of aboive criteria, he demarcated the area of monsoon region as a rectangle roughly extending from 35^o N to 25^o S and 30^o W to 173^o E</li></ul>

Question 2

Q

Monsoon (from mindmap):Mechanism: classical theory?

Answer

A

explained in 1686 by Sir Edmund Hailey

<ul><li>resulting from thermal contrasts betn continents and oceans due to their differential heating</li><li>his ideas are basically the same as those involved in land and sea breeze except being seasonal instead of being diurnal</li><li>Diagram</li><li>crticism:<ul><li>do not develop equally everywhere</li><li>fails to explain various intricacies of the monsoon</li></ul></li></ul>

Question 3

Q

Monsoon (from mindmap):Mechanism:Modern Theories: enumerate them?

Answer

A

<ol><li>Flohn's Air Mass Theory</li><li>Jet Stream Theory<ol><li>MT Yin and Pedelaborde</li><li>P Koteshwaram</li></ol></li><li>Flohn's explanation using summer and winter wind conditions over south Asia</li></ol>

Question 4

Q

Monsoon (from mindmap):Mechanism:Modern Theories: Flohn's Air Mass theory?

Answer

A

<ol><li>ITCZ is created near the equator where SE and NE trade winds meet. This area is the region of ascending air, maximum clouds and heavy rainfall</li><li>shifting N and S in Summer and winter (NITCZ and SITCZ)</li><li>trade winds cross the equator and are deflected due to coriolis force</li><li>Front where SW monsoon meet the NE trade winds is known as monsoon front</li><li>In July, ITCZ shifts over to Indi-Gangetic plain. ITCZ in this position is called the Monsoon trough</li><li>Diagram</li></ol>

Question 5

Q

Monsoon (from mindmap):Mechanism:Modern Theories: Jet STream Theory: westerly jet stream?

Answer

A

Jet stream is a band of fast moving air frm west to east, usually found in middle latitudes, in the upper troposphere at a height of abt 12 km

Wind speeds in a westerly jet stream are commonly 150-300 kmph.

Main contributors:

<ol><li>MT Yin and Pedelaborde</li><li>Flohn</li><li>Stephenson</li></ol>

Explanation

WESTERLY JET STREAM

Winter.

<ul><li>This is the season of outblowing surface winds but aloft the westerly airflow dominates.</li><li>The upper westerlies are split into two distinct currents by the topographical obstacle of the Tibet Plateau, one flowing to the north and the other to the south of the plateau. The two branches reunite off the east coast of China (Fig. 5.7).</li><li>The southern branch over northern India corresponds with a strong latitudinal thermal gradient which, along with other factors, is responsible for the development of southerly jet. The southern branch is stronger.</li><li>Air subsiding beneath this upper westerly current gives dry outblowing northerly winds from the subtropical anticyclone over northwestern India and Pakistan.</li><li>Winter rainfall or western disturbances: The upper jet is responsible for steering of the western depressions from the Mediterranean Sea. Some of the depressions continue eastwards. redeveloping in the zone of jet stream confluence about 30 N, 105 E beyond the area of subsidence in the immediate lee of Tibet.</li><li>Diag5.7</li></ul>

Summer.

<ul><li>With the beginning of summer in the month of March, the upper westerlies start their northward march, but whereas the northerly jet strengthens and begins to extend across central China and into Japan, the southerly branch remains positioned south of Tibet, although weakening in intensity. The weather over northern India becomes hot, dry and squally due to larger incoming solar radiation.</li><li>By the end of May the southern jet begins to break and later it is diverted to the north of Tibet Plateau.</li><li>Over India, the Equatorial Trough pushes northwards with the weakening of the upper westerlies south of Tibet, but the burst of the monsoon does not take place until the upper-air circulation has switched to its summer pattern (Fig. 5.8). The low level changes are related to the high level easterly jet stream over southern Asia about 15⁰ N</li><li>Diag 5.8</li></ul>

Question 6

Q

Monsoon (from mindmap):Mechanism:Modern Theories: Jet STream Theory: easterly jet stream?

OR

"Monsoon as a thermal engine"

Answer

A

EASTERLY JET STREAM (P Koteswaram)

Koteswaram, supported by Flohn, feels that because the Tibet Plateau is a source of heat for the atmosphere, it generates an area of rising air. During its ascent the air spreads outwards and gradually sinks over the equatorial part of the Indian Ocean (Mascarene High). At this stage, the ascending air is deflected to the right by the earth's rotation and moves in an clockwise direction leading to anticyclonic conditions in the upper troposphere over Tibet around 300-200 mb (9 to 12 km).

It finally approaches the west coast of India as a return current from a south-westerly direction and is termed as equatorial westerlies . It picks up moisture from the Indian Ocean and causes copious rainfall in India and adjoining countries.

Raman and Ramanathan while discussing the tropical easterly jet stream suggested that the easterly winds become very active in the upper troposphere after the beginning of the rainy season. The latent heat produced due to cloud cover results into inversion of temperature and causes rainfall.

Diag 5.5

Question 7

Q

Monsoon (from mindmap):Mechanism:Teleconnections: enumerate them?

Answer

A

there seems to be a link between meterological events which are separated by long distances and large intervals of time. They are called meteorological teleconnections

<ol><li>El Nino-La Nina</li><li>Southern Oscillation</li><li>Indian Ocean Dipole</li></ol>

Question 8

Q

Monsoon (from mindmap):Mechanism:Teleconnections: El nino and La Nina?

Answer

A

El Nino and La Nina are complex weather patterns resulting from variations in ocean temperatures in the Equatorial Pacific Region. They are opposite phases of what is known as the El Nino-Southern Oscillation (ENSO) cycle.

<ul><li>Originally, the term El Niño applied to an annual weak warm ocean current that ran southwards along the coast of <a>Peru</a> and <a>Ecuador</a> at about <a>Christmas</a> time. However, over time the term has evolved and now refers to the warm and negative phase of the <a>El Niño–Southern Oscillation</a> and is the warming of the ocean surface or above-average <a>sea surface temperatures</a> in the central and eastern tropical Pacific Ocean</li><li>El Nino is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean. <ul><li>It is the “warm phase” of a larger phenomenon called the El Nino-Southern Oscillation (ENSO).</li><li>It occurs more frequently than La Nina.</li></ul></li><li>La Nina, the “cool phase” of ENSO, is a pattern that describes the unusual cooling of the tropical eastern Pacific. <ul><li>La Nina events may last between one and three years, unlike El Nino, which usually lasts no more than a year.</li><li>Both phenomena tend to peak during the Northern Hemisphere winter.</li></ul></li><li>El Nino was first recognized by Peruvian fishermen off the coast of Peru as the appearance of unusually warm water. <ul><li>The Spanish immigrants called it El Nino, meaning “the little boy” or “Child Christ” in Spanish.</li></ul></li><li>The El Nino event is not a regular cycle, they are not predictable and occur irregularly at two- to seven-year intervals.</li><li>The Oceanic Niño Index (ONI), is a measure of the departure from normal sea surface temperature in the east-central Pacific Ocean, is the standard means by which each El Nino episode is determined, gauged, and forecast.</li></ul>

Question 9

Q

Monsoon (from mindmap):Mechanism:Teleconnections: El nino: effect on major continents?

Answer

A

<ul><li>Impact on Ocean: warmer than usual</li><li>Africa: In Africa, <a>East Africa</a>—including <a>Kenya</a>, <a>Tanzania</a>, and the <a>White Nile</a> basin—experiences, in the long rains from March to May, wetter-than-normal conditions. Conditions are also drier than normal from December to February in south-central Africa, mainly in <a>Zambia</a>, <a>Zimbabwe</a>, <a>Mozambique</a>, and <a>Botswana</a>.</li><li>Antarctica: El Niño conditions result in <a>high-pressure</a> anomalies over the <a>Amundsen</a> and <a>Bellingshausen</a> Seas, causing reduced <a>sea ice</a> and increased poleward heat fluxes in these sectors, as well as the <a>Ross Sea</a>. The <a>Weddell Sea</a>, conversely, tends to become colder with more sea ice during El Niño. The exact opposite heating and atmospheric pressure anomalies occur during La Niña.<a>^[92]</a> This pattern of variability is known as the Antarctic dipole mode</li><li>Australia and the Southern Pacific: During El Niño events, the shift in rainfall away from the Western Pacific may mean that rainfall across Australia is reduced<ul><li>Over the southern part of the continent, warmer than average temperatures can be recorded</li><li>onset of the <a>Indo-Australian Monsoon</a> in tropical Australia is delayed by two to six weeks, which as a consequence means that rainfall is reduced over the northern tropics</li><li>The risk of a significant bushfire season in south-eastern Australia is higher following an El Niño event, especially when it is combined with a positive IOD event</li><li>Fiji generally experiences drier than normal conditions during an El Niño, which can lead to drought becoming established over the Islands</li><li>Other impacts include a decrease in the sea level, possibility of coral bleaching in the marine environment and an increased risk of a tropical cyclone affecting islands</li></ul></li><li>North America:<ul><li>In particular the majority of Canada generally has milder than normal winters and springs</li><li>it has been historically associated with high rainfall in California, the effects of El Niño depend more strongly on the "flavor" of El Niño than its presence or absence, as only "persistent El Niño" events lead to consistently high rainfall</li><li>El Nino reduces the instances of hurricanes in the Atlantic.</li></ul></li><li>South America<ul><li>Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean, including several portions of the South American west coast.</li><li>An El Niño is associated with warm and very wet weather months in April–October along the coasts of northern <a>Peru</a> and <a>Ecuador</a>, causing major flooding whenever the event is strong or extreme</li><li>Along the west coast, El Niño reduces the upwelling of cold, nutrient-rich water that sustains large <a>fish</a> populations, which in turn sustain abundant sea birds, whose droppings support the <a>fertilizer</a> industry. The reduction in upwelling leads to <a>fish kills</a> off the shore of Peru. The world's largest fishery collapsed due to overfishing during the 1972 El Niño <a>Peruvian anchoveta</a> reduction.</li></ul></li><li>Asia<ul><li>As warm water spreads from the west Pacific and the <a>Indian Ocean</a> to the east Pacific, it takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific.</li></ul></li></ul>

Question 10

Q

Monsoon (from mindmap):Mechanism:Teleconnections: El nino: effect on Indian Monsoon?

Answer

A

<ul><li>El Nino and Indian monsoon are inversely related.</li><li>The most prominent droughts in India – six of them – since 1871 have been El Nino droughts, including the recent ones in 2002 and 2009</li><li>However, not all El Nino years led to a drought in India. For instance, 1997/98 was a strong El Nino year but there was no drought (Because of IOD).</li><li>On the other hand, a moderate El Nino in 2002 resulted in one of the worst droughts.</li><li>El Nino directly impacts India’s agrarian economy as it tends to lower the production of summer crops such as rice, sugarcane, cotton and oilseeds.</li></ul>

Question 11

Q

Monsoon (from mindmap):Mechanism:Teleconnections: El nino: how does it work?

Answer

A

Normal conditions

<ul><li>In a normal year, a surface low pressure develops in the region of northern Australia and Indonesia and a high pressure system over the coast of Peru. As a result, the trade winds over the Pacific Ocean move strongly from east to west. It is a part of Pacific Walker Circulation.</li><li>The easterly flow of the trade winds carries warm surface waters westward, bringing convective storms (thunderstorms) to Indonesia and coastal Australia. Along the coast of Peru, cold bottom cold nutrient rich water wells up to the surface to replace the warm water that is pulled to the west.</li><li>Normal conditions: <a>https://1drv.ms/u/s!AvN_8sA-Zf0djUyl04UJ7WofMpqg?e=pbsGR1</a> </li><li>Walker Cell: <a>https://1drv.ms/u/s!AvN_8sA-Zf0djU0B_7eq2TFjCBXR?e=CKnkbr</a></li></ul>

<ul><li><a>https://1drv.ms/u/s!AvN_8sA-Zf0djU4O4D0j-wOInuGn?e=ChTZ34</a></li></ul>

<ul><li>The Walker circulation (walker cell) is caused by the pressure gradient force that results from a high pressure system over the eastern Pacific ocean, and a low pressure system over Indonesia.</li></ul>

During El nino year

<ul><li>In an El Niño year, air pressure drops over large areas of the central Pacific and along the coast of South America.</li><li>The normal low pressure system is replaced by a weak high in the western Pacific (the southern oscillation). This change in pressure pattern causes the trade winds to be reduced == Weak Walker Cell. Sometimes Walker Cell might even get reversed.</li><li>This reduction allows the equatorial counter current (current along doldrums) to accumulate warm ocean water along the coastlines of Peru and Ecuador.</li><li>This accumulation of warm water causes the thermocline to drop in the eastern part of Pacific Ocean which cuts off the upwelling of cold deep ocean water along the coast of Peru.</li><li>Climatically, the development of an El Niño brings drought to the western Pacific, rains to the equatorial coast of South America, and convective storms and hurricanes to the central Pacific.</li><li><a>https://1drv.ms/u/s!AvN_8sA-Zf0djU_OcnLQ7NJAph0r?e=Ld1hzv</a></li><li><a>https://1drv.ms/u/s!AvN_8sA-Zf0djVBwIq8qdFkYsEQx?e=7hYRry</a></li></ul>

Question 12

Q

Monsoon (from mindmap):Mechanism:Teleconnections:Southern Oscillation?

Answer

A

<ul><li>Southern Oscillation (S.O.) is the name ascribed to the curious phenomenon of sea-saw pattern of meteorological changes observed between the Pacific and Indian oceans.</li><li>This great discovery was made by Sir Gilbert Walker in 1920. While working as the head of the India Meteorological Service, he noticed that when the pressure was high over equatorial south Pacific, it was low over the equatorial south Indian Ocean and vice versa.</li><li>The pattern of low and high pressures over the Indian and Pacific Oceans (S.O.) gives rise to vertical circulation along the equator with its rising limb over low pressure area and descending limb over high pressure area. This is known as Walker Circulation.</li><li>The location of low pressure and hence the rising limb over Indian Ocean is considered to be conducive to good monsoon rainfall in India. In other words when there is low pressure over the Indian Ocean in winter months, the chances are that the coming monsoon will be good and will bring sufficient rainfall.</li><li>Its shifting eastward from its normal position, such as in El Nino years, reduces monsoon rainfall in India.</li><li>Due to the close association between an El Nino (E.N.) and the Southern Oscillation (S.O.), the two are jointly referred to as an ENSO event.</li><li>The main difficulty with the Southern Oscillation is that its priodicity is not fixed and its period varies from two to five years.</li><li>Different indices have been used to measure the intensity of the Southern Oscillation, but the most frequently used is the Southern Oscillation Index (SOI). This is the difference in pressure between Tahiti (17°45'S. 149°30 W) in French Polynesia, representing the Pacific Ocean and Port Darwin (12 30'S, 131°E), in northern Australia representing the Indian Ocean The positive and negative values of the SOI e. Tahiti minus the Port Darwin pressure are pointers towards good or bad rainfall in India</li><li>Walker Cell in nonrmal yrs: <a>https://1drv.ms/u/s!AvN_8sA-Zf0djU0B_7eq2TFjCBXR?e=CKnkbr</a> and <a>https://1drv.ms/u/s!AvN_8sA-Zf0djU4O4D0j-wOInuGn?e=ChTZ34</a></li><li>During El nino yrs; <a>https://1drv.ms/u/s!AvN_8sA-Zf0djVBwIq8qdFkYsEQx?e=7hYRry</a></li></ul>

Question 13

Q

Monsoon (from mindmap):Mechanism:Teleconnections:Indian ocean Dipole?

Answer

A

<ul><li>Although ENSO was statistically effective in explaining several past droughts in India, in the recent decades the ENSO-Monsoon relationship seemed to weaken in the Indian subcontinent. For e.g. the 1997, strong ENSO failed to cause drought in India.</li><li>However, it was later discovered that just like ENSO was an event in the Pacific Ocean, a similar seesaw ocean-atmosphere system in the Indian Ocean was also at play. It was discovered in 1999 and named the Indian Ocean Dipole (IOD).</li><li>The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperature between two areas (or poles, hence a dipole) – a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia.</li><li>IOD develops in the equatorial region of Indian Ocean from April to May peaking in October.</li><li>With a positive IOD winds over the Indian Ocean blow from east to west (from Bay of Bengal towards Arabian Sea). This results in the Arabian Sea (western Indian Ocean near African Coast) being much warmer and eastern Indian Ocean around Indonesia becoming colder and dry.</li><li>In the negative dipole year (negative IOD), reverse happens making Indonesia much warmer and rainier.</li><li>It was demonstrated that a positive IOD index often negated the effect of ENSO, resulting in increased Monsoon rains in several ENSO years like the 1983, 1994 and 1997. records of India Meteorological Department (IMD) show that IOD was positive in four of the 16 El Nino years during 1951-2017 (Table 5.1) and the rainfall was normal i.e. 96-104% of the Long Period Average (LPA) in three of these four years.</li><li>Further, it was shown that the two poles of the IOD – the eastern pole (around Indonesia) and the western pole (off the African coast) were independently and cumulatively affecting the quantity of rains for the Monsoon in the Indian subcontinent.</li><li>Similar to ENSO, the atmospheric component of the IOD was later discovered and named as Equatorial Indian Ocean Oscillation [EQUINOO][Oscillation of warm water and atmospheric pressure between Bay of Bengal and Arabian Sea].</li><li>Effect on Cyclonogenesis<ul><li>PositiveIOD (Arabian Sea warmer than Bay of Bengal) results in more cyclones than usual in Arabian Sea.</li><li>NegativeIOD results in stronger than usual cyclonogenesis (Formation of Tropical Cyclones) in Bay of Bengal. Cyclonogenesis in Arabian Sea is suppressed.</li></ul></li></ul>

Question 14

Q

Monsoon: El nino Modoki?

Answer

A

<ul><li>El Niño Modoki is a coupled ocean-atmosphere phenomenon in the tropical Pacific.</li><li>It is different from another coupled phenomenon in the tropical Pacific namely, El Niño.</li><li>Conventional El Niño is characterized by strong anomalous warming in the eastern equatorial Pacific. Whereas, El Niño Modoki is associated with strong anomalous warming in the central tropical Pacific and cooling in the eastern and western tropical Pacific (see figure below).</li><li>El nino Modoki: <a>https://1drv.ms/u/s!AvN_8sA-Zf0djVFtN32VllHv_vm8?e=nKZdh0</a></li><li>Walker Cell for El Nino Modoki: <a>https://1drv.ms/u/s!AvN_8sA-Zf0djVJI_ADR6Z3cPdye?e=6n1eJg</a></li><li>impact<ul><li>The El Niño Modoki phenomenon is characterized by the anomalously warm central equatorial Pacific flanked by anomalously cool regions in both west and east.</li><li>Such zonal gradients result in anomalous two-cell Walker Circulation over the tropical Pacific, with a wet region in the central Pacific.</li></ul></li></ul>

Question 15

Q

Monsoon (from mindmap):IMD'16 parameters for Monsoon forecast?

Answer

A

<ul><li>temperature related parameters<ol><li>El nino in curent yr</li><li>El nino in previous yr</li><li>Northern India (March)</li><li>East Coast of INdia (March)</li><li>Central India (May)</li><li>Northern hemisphere (Jan and Feb)</li></ol></li><li>Wind related parameters<ol><li>500 hPa ridge in April</li><li>50 hPa ridge trough extent (Jan and Feb)</li><li>10 hPa westerly wind</li></ol></li><li>Pressure anomaly<ol><li>Tahiti-Darwin (Spring)</li><li>Darwin (spring)</li><li>South America- Argentina (April)</li><li>Indian Ocean Equatorial (Jan-May)</li><li>surface pressure annomaly of NE hemisphere</li></ol></li><li>Snoe cover related<ol><li>Himalayan (Jan-March)</li><li>Eurasian (Previous Dec)</li></ol></li></ul>

It was observed in late eighties that whenever more than 50% parameters showed favourable signals, the monsoon rainfall in India was normal and when 70% or more parameters were favourable, the monsoon rainfall was above normal.

Question 16

Q

CC and monsoon variations in NE: overall NE?

Answer

A

<ol>
<li>This year, while most of India is enjoying a normal monsoon, the Northeast is once again grappling with a deficit. Excwpt Sikkim all the states were facing a deficit of ~30% till Aug 5th 2021</li>
<li>unlike India's other mountain states such as Uttarakhand,j&K and HP, NE states depend only on monsoon rf rather than glaciers</li>
<li>gravity of the problem can be gauged from the fact that the Northeast, which receives the heaviest monsoon rains in the country, now has a higher chance of experiencing a meteorological drought than western India, which receives the lowest amount of the monsoon showers.
<ul>
<li>A meteorological drought arises when the actualrainfall over an area is significantly less than its climatological mean, defines IMD.</li>
<li>probability of a meteorological drought in the Northeast was 54 per cent between 2000 and 2014 as opposed to 27 per cent in western India</li>
</ul>
</li>
<li>variations as well:While six of the eight northeastern states have recorded an overall decreasing trend in monsoon showers during 1989-2018, some of the districts, particularly in Assam, have seen an increase in floods, which is not expected in an area that is receiving less rainfall than before.</li>
<li>The other challenge is that monsoon showers in almost all the states remain extremely unreliable, particularly in July and August, the two months when most of the states receive bulk of the rains</li>
<li>An increase in rf as well as its intensity has led to changes in many rivers' flow: eg. two major tributaries of Brahmputra- Subansiri and Dibang,These tributaries have drastically altered their course in recent years, uprooting several villages along the way</li>
<li>On the other hand, a decrease in the annual rainfall dries up mountain springs. Around 200 mountain springs have already dried up in the region, suggests a 2018 report by NITI Aayog.Over 94 per cent villages in Sikkim and >50% villages in Meghalaya, Mizoram and Manipur rely on mountain springs for water</li>
<li>Declining vegetation cover due to drought stress also enhances soil erosion and can lead to desertification.As per the Land Degradation Map of India, prepared by ISRO,four of the six states with the most degraded land are in NE- Nagaland (47%) only behind UP (53%) and RJ (52%)</li>
<li>degradation of land has a direct impact on this region's rich biodiversity. Of the total 17,000 flowering plants in the country, about 5,000 species are found in the northeast, and many of them are already under stress</li>
<li>The Union Ministry of Environment, Forest and Climate Change expects the region to be 1.8-2.1^oC warmer by the end of 2030. This would increase the annual mean rainfall by 0.3 to 3 per cent, it says.The climate action plans of most of the northeastern states predict a wetter monsoon in the future along with warmer temperatures.</li>
</ol>

Question 17

Q

CC and monsoon variations in NE: Arunachal Pradesh?

Answer

A

<ul>
<li>overall trend of decreasing monsoon rains</li>
<li>While eight districts have reported a decrease in the monsoon rains—which explains the overall deficit in the state—only two, Upper Siang and Upper Subansiri, have reported an increase in rainfall.
<ul>
<li>Upper Siang district is the starting point of the Siang river, Brahmaputra’s largest tributary, and Upper Subansiri district is home to the Subansiri river, another major tributary of Brahmaputra.</li>
</ul>
</li>
<li>Simultaneous with the increase in rainfall, more than 95 per cent of the monitoring stations in Upper Siang have reported a reduction in the number of rainy days. This translates into floods both in the district and downstream in Assam.</li>
<li>most other districts of the state, particularly West and East Kemang on the western part, are reporting widespread drying up of mountain springs, which are often the primary water source for the families living in the villages nestled in them.</li>
<li>21 per cent variation or fluctuation in the amount of rainfall the state received during the monsoon season every year.</li>
<li>case study: In upper siang district, due to increase in rf,The moist conditions are favourable for pests, and their population has drasticallyincreased, this leads to crop failure especially in cases where organic farming is practised.</li>
</ul>

Question 18

Q

CC and monsoon variations in NE: Assam?

Answer

A

<ul>
<li>overall decrease in the monsoon rains in the past decades, though the drop is not as significant as in Arunachal Pradesh.</li>
<li>Assam is divided into three distinct geographical regions. To the north is the Brahmaputra river valley in the foothills of the Himalayas and to the south is the Barak river valley. In between the two valleys are the Karbi Anglong and Cachar hills.</li>
<li>Most districts north of Brahmputrashow a trend of increase in rainfall, though the increase is not significant. But theyhave seen a significant decrease in the number of rainy days. This means that the rainfall in these districts takes place in fewer days, increasing the intensity of the rains.This causes havoc in the districts south of the river even though they have registered a decrease in the monsoon rainfall.</li>
<li>The impact of this can be seen clearly in Golaghat district, which houses the Kaziranga National Park. This area gets flooded due to the swelling of the Doyang river, which flows in from Wokha district of Nagaland.</li>
<li>the riverine islands of the Brahmaputra have been identified as being the most vulnerable to diseases due to frequent floods that appear to be on the rise</li>
<li>Food security:In 2005-06, Assam experienced a drought and it had an immediate impact on the rice production in the worst-affected areas of Dhubri, Nalbari</li>
<li>The increase in floods in Assam's Golaghat district is destroying forestland inside the Kaziranga national park.This is impacting the nearby villages and hampering the natural migration routes of animals. Claims of officials annexing farmlands to compensate for NP loss are also seen from the region</li>
<li>case study:
<ul>
<li>Residents of Mas Dihiri village in Assam have shifted their homes every year since 2012 due to the Kumutiya river that constantly changes its course in response to the erratic monsoons</li>
<li>, heavy rainfall has pushed more coarse sand fragments of mountain rocks and construction debris from upstream areas into floodwaters, as against the fertile alluvial soil they usually carry. This debris impacts soil fertility when deposited along fields, hindering production of rice varieties such as Sali, Bao and Ahu downstream like Karpunpuli village along river Jiadhal, a sub-tributary of Brahmputra</li>
</ul>
</li>
</ul>

Question 19

Q

CC and monsoon variations in NE: Nagaland?

Answer

A

overall drying trend butis witnessing an abnormal shift:monsoon rainfall is going down in the traditionally wetter districts in the north, central and the southwest parts of the state, while it is going up in the drier districts in the southern parts.

Even though the state is drained by four major rivers and a dozen minor rivers, unlike Arunachal Pradesh, it is not traditionally flood-prone, because of its mild gradient

Monsoons, which account for 68 per cent of the annual rainfall in the state, remain highly unpredictable with an almost 25 per cent variability in the past three decades.

In 2020, Nagaland was one of the few northeastern states to experience an overall deficit rainfall (29 per cent lower than normal).

The changing climate of Nagaland has also meant that only half of the 400-odd indigenous rice varieties are conducive to the region now.Rice productivity has decreased by around 50 per cent, while betel nut productivity has crashed by 40 per cent in the last four to five years

The same decreasing trend can be seen in the population of birds and butterflies in the region. Butterflies are extremely sensitive to temperature and rainfall changes, and serve as a reliable bio-indicator of the change in climate

Question 20

Q

CC and monsoon variations in NE: Sikkim?

Answer

A

Whileoverall monsoon rainfall has only marginally increased in the past three decades, three-fourths of the state is growing drier.

This has been possible because the climate in the second smallest state of India varies from place to place due to the significant variation in elevation and topography. the northern regions arecovered with high mountains while the southern region is primarily made up of plains that blend into WB.

The upward trend of the monsoons is most prominent in North Sikkim, which may be causing an increase in the flooding of the Teesta river. This in turn is leading to an increase in the landslide incidents downstream in South Sikkim, especially around Gangtok city and since 1997.

Question 21

Q

CC and monsoon variations in NE: Mizoram?

Answer

A

the only other northeastern state where the overall monsoon rainfall has seen a minor increase

The eight districts are equally split with four each showing minor increase and minor decrease

The three wettest districts—Lunglei in the centre, Kolasib in the north and Saiha in south— have seen an increase in the overall rainfall along with a substantial drop in the number of rainy days

Question 22

Q

CC and monsoon variations in NE: Meghalaya?

Answer

A

downward trend in the overall monsoon rainfall.imd data shows that deficit rainfall became a chronic problem after 2005.

While the three districts that are at the centre have seen minor changes in rainfall, the four districts on the outside have seen significant changes

The East Khasi Hill district, which receives the most rainfall, has recorded a minor increase in the monsoon rains but a significant decrease in rainy days

The state has one of the highest variations in the monsoon rainfall at almost 25 per cent.

Drought a persistent problem in Cherapunji

Question 23

Q

CC and monsoon variations in NE: Tripura?

Answer

A

perhaps the only northeastern state where all the districts have seen an overall reduction in the monsoon rains,though the change has not been significant.

This is likely to have an impact on the 10 major rivers in the state that are all rain-fed and ephemeral in nature.

Question 24

Q

CC and monsoon variations in NE: Manipur?

Answer

A

Various studies and Down to Earth's earlier reportage suggest that the statehas seen a downward trend in monsoon rainfall though IMD has not released the composite data for the 1989-2018

This is a cause for concern as Manipur is highly food insecure because of the paucity of farmland and the traditional practice of jhum

The state saw a significant increase in its annual rainfall between 1975 and 1989, followed by a phase of significant decrease in the rains between 1990 and 2007, says a study by the Central Agricultural University, Imphal, in 2016.

In 2019, Manipur received 56 per cent lesser rains during the monsoon season, as per imd. Chandel district, located in the southeast part of the state, reported an 82 per cent deficit that year. The trend continued in 2020, when the state received a deficit rainfall of 46 per cent.

Question 25

Q

CC and monsoon variations in NE: lack of appropriate data?

Answer

A

One logistical difficulty is that the monitoring stations often are not available in the places that are suffering from the maximum unpredictability. One such example is Pakke Kessang district in Arunachal Pradesh. The district’s lone rainfall monitoring station was washed away during a flood in 2004 and imd is yet to set it up again

Question 26

Q

CC and monsson variations in NE:case study of flooding due to hydro project upstream?

Answer

A

Runchan village on Nagaland's NW border with Assam,gets flooded because of a hydropower project built a few kilometres upstream on the Doyang river.Although Nagaland is no stranger to floods and landslides owing to heavy rain, the northwestern part of the state has never been affected by such disasters. But the 2018 floods have displaced over 3,000 families in 400 villages downstream of the Doyang river

Question 27

Q

CC and monsoon variations in NE: impact on biodiversity: examples?

Answer

A

THE BLYTH’S Kingfisher is found only at 15 places Arunachal Pradesh, 13 of which are in Pakke-Kessang district, home of the scenic Pakke Tiger Reserve. The bird is rarely seen these days due to the decline in the population of the fish on which it feeds.

significant behavioural shift in the animals and birds due to the changing temperatures, rainfall patterns and deforestation. For example, there has been “a change in the migratory route of the elephants which earlier used to stop near Saibun, the natural saltwater lake

Question 28

Q

2020 was a La Nina year but states like Kerala, GJ, J&K, NE and Odisha saw rf deficit upto 30%.factors?

Answer

A

<ul>
<li>It is El Niño’s little cousin in the Atlantic, known as the Atlantic Niño, or the Atlantic Zonal Mode.In 2021, Atlantic Niño has made an appearance. Sea surface temperatures in the eastern Atlantic have remained more than a degree higher than normal this summer.</li>
<li>Every few years, from June to August, there is a warming in the eastern equatorial Atlantic</li>
<li>Its impact on the monsoon has been known since 2014 when a study led by INCOIS showed that the number of low-pressure systems is greatly reduced by the Atlantic Niño, leading to deficit monsoons.This year has seen a sharply lower number of low-pressure systems, which contribute up to 60 per cent of the seasonal total rainfall over the core monsoon zone.</li>
<li>The Atlantic Niño affects the monsoon by producing atmospheric waves, which propagate into the Indian Ocean. These waves affect air temperatures over the Indian Ocean and influence the land-ocean thermal contrast as well as LPSs.</li>
<li>The biggest rainfall deficits from the Atlantic Niño tend to occur over the Western Ghats and the core monsoon zone. The deficit patterns are a tell-tale sign of the Atlantic Niño influence.</li>
</ul>

Question 29

Q

Delay in arrival and withdrawal of monsoon?

Answer

A

Normal date of the monsoon onset in India is June 1; and the normal date for withdrawal of monsoon is October 15

monsoon season has made a delayed entry into India in seven years since 2011, its has reported a delayed exit in all the years since 2011.

in a press release in April 2020, imd acknowledged that the monsoon now withdraws from northwest India almost 7-14 dayslater from the existing dates.

causes:

<ul>
<li>overall CC but attribution studies are needed</li>
<li>temperature on the periphery of monsoon wind system in Pakistan and Afghanistan now remains higher than normal in September, so it takes longer for the subcontinent to cool down as needed for withdrawal.</li>
</ul>

Question 30

Q

“Double Dip” phenomenon wrt Indian Monsoons?

Answer

A

<ul><li>Consecutive La Ninas following a transition through ENSO neutral conditions are not uncommon and can be referred to as a “Double-Dip.”</li><li>In 2020, La Nina developed during the month of August and then dissipated in April 2021 as ENSO-neutral conditions returned.</li><li>For the upcoming winter season, which extends from December 2021 through February 2022, there is an 87% chance of La Nina.</li></ul>

Question 31

Q

Weather changes because of La Nina?

Answer

A

<ol><li>The Horn of Africa and central Asia will see below average rainfall due to La Niña.</li><li>East Africa is forecast to see drier-than-usual conditions, which together with the existing impacts of the desert locust invasion, may add to regional food insecurity.</li><li>It could also lead to increased rainfall in southern Africa.</li><li>It could also affect the South West Indian Ocean Tropical Cyclone season, reducing the intensity.</li><li>Southeast Asia, some Pacific Islands and the northern region of South America are expected to receive above-average rainfall.</li><li>In India, La Niña means the country will receive more rainfall than normal, leading to floods.</li></ol>

Question 32

Q

How is La Niña linked with the Northeast monsoon?

Answer

A

While La Niña conditions enhance the rainfall associated with the Southwest monsoon, it has a negative impact on rainfall associated with the Northeast monsoon.

During La Niña years, the synoptic systems — low pressure or cyclones — formed in the Bay of Bengal remain significantly to the north of their normal position.

<ul><li>Besides, instead of moving westwards, these systems recurve. As they lie to the north of their normal position, not much rainfall occurs over southern regions like Tamil Nadu.</li></ul>

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