What is a heat wave and its effects?

A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity, especially in oceanic climate countries. While definitions vary,a heat wave is measured relative to the usual weather in the area and relative to normal temperatures for the season. Temperatures that people from a hotter climate consider normal can be termed a heat wave in a cooler area if they are outside the normal climate pattern for that area.[2]

The term is applied both to routine weather variations and to extraordinary spells of heat which may occur only once a century. Severe heat waves have caused catastrophic crop failures, thousands of deaths from hyperthermia, and widespread power outages due to increased use of air conditioning. A heat wave is considered extreme weather, and a danger because heat and sunlight may overheat the human body.

The Odisha model of minimizing damage

After the heavy casualties in 1998, the Odisha government treats it as a disaster on the scale of cyclone or flood.By February-end, the government starts the preparation for fighting heat wave with a single objective in mind: no human casualty. Schools and colleges shift to early morning sessions. They open at 6.30am and end by 12 noon.Government offices also follow the same timings. Examinations are held by March. Public transport does not operate between 12 noon and 3.30pm. Public wage programmes like, MGNREGA is halted from 11.30am to 3.30pm.

A look at the heat wave deaths in Andhra Pradesh and Telengana would reveal that most of the people killed in the two states were labourers at construction sites who continued with their work even when the temperatures were at the peak.

There are other measures in place in Odisha to minimise heat wave impacts. Public health centres keep ice slabs ready to treat stroke patients. Panchayats across the state open water booths.
The state government also puts out continuous advertisements which guide people on how to combat heat wave. Hospitals in cities like Cuttack and Sambalpur deploy extra resources to attend to heat stroke patients. The ambulance network is activated and directed to be ready along the state and national highways. The government takes the help of the civil society in spreading awareness.

During April-June, the government’s state-level and district-level calamity centres continuously monitor the India Meteorological Department (IMD) temperature forecast and devise their strategies at local levels.

In Odisha, not all districts report high temperatures. But districts with high industrial activity report the maximum temperature rise. So, the district authorities devise their own action plans.
Heat wave is predictable and one can easily point out time band and places. We can’t stop it, but we can prepare well to reduce human casualties.

Seismic gap and decollement.

A seismic gap is a segment of an active fault known to produce significant earthquakes, that has not slipped in an unusually long time when compared with other segments along the same structure. Seismic gap hypothesis/theory states that, over long periods of time, the displacement on any segment must be equal to that experienced by all the other parts of the fault.Any large and longstanding gap is therefore considered to be the fault segment most likely to suffer future earthquakes.

One such is the central seismic gap, which runs northeast of Delhi along a region woven with unstable faults and including over 10 million people. Until April 25, observers had been concerned by the paucity of earthquakes in the gap: the longer there were no quakes, the more the pent up stresses, and the stronger a future quake will be. A research team’s conclusion describes an active thrust fault below Uttarakhand pregnant with enough tension to unleash a quake measuring at least 8 on the Richter scale. This, in a state already prone to crippling landslides and floods, and with 70% of its population (of about 10 million) residing in rural areas. They attribute the tremendous tension to a geometry of rock that has partially separated from a layer beneath and caused folds and deformations. The technical term for this geometry is a décollement:the landscape and erosion rate patterns suggest that the décollement beneath the state of Uttarakhand provides a sufficiently large and coherent fault segment capable of hosting a great earthquake.

Décollement (detachment) folds develop during folding, secondary to separation of a (more competent) layer from an underlying (less competent) layer as deformation proceeds.

Describe Indian Ocean Dipole (IOD

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. The IOD affects the climate of Australia and other countries that surround the Indian Ocean Basin, and is a significant contributor to rainfall variability in this region.

The IOD involves an aperiodic oscillation of sea-surface temperatures, between “positive”, “neutral” and “negative” phases. A positive phase sees greater-than-average sea-surface temperatures and greater precipitation in the western Indian Ocean region, with a corresponding cooling of waters in the eastern Indian Ocean—which tends to cause droughts in adjacent land areas of Indonesia and Australia. The negative phase of the IOD brings about the opposite conditions, with warmer water and greater precipitation in the eastern Indian Ocean, and cooler and drier conditions in the west.

The IOD also affects the strength of monsoons over the Indian subcontinent. ‘Positive IOD’ has been found to be beneficial for the monsoon. On the other hand, a ‘negative IOD,’ when temperatures at either end of the Indian Ocean swing in the opposite direction, hampers the monsoon.

An IOD can counter or worsen an El Nino’s impact on the monsoon, according to recent research. A positive IOD had facilitated normal or excess rainfall over India in 1983, 1994 and 1997 despite an El Nino in those years. But during years such as 1992, a negative IOD and El Nino had cooperatively produced deficit rainfall.

What is ‘Kaal Baisakhi’?

During the hot weather period i.e from March to May the eastern and North-eastern states of the subcontinent like West Bengal, Bihar, Assam, Orissa (parts) and Bangladesh experience dramatic appearance of a special type of violent thunderstorm know as Nor’wester.The dramatic appearance of nor’wester in the afternoon or evening of pre-monsoon months over Bengal, Bihar, Assam and adjoining areas has been a matter of great interest not only to the meteorologists but to all sections of people and has a place in literature. Nor’wester not only gives relief after mid-day heat but helps crops.

It is known as ‘Kaal Baisakhi’ or calamity of the month of Baisakh (April,15-May,15). Apart from its destructive effects like sudden rise in wind speed, lightning, thunder and hail the rainfall associated with the storm although small in amount, is extremely helpful for the pre-Kharif crops like jute, Aus paddy, summer till and a large number of vegetables and fruits and the sudden drop in temperature gives relief after unbearable mid-day heat.

It struck Bihar yesterday and thirty-two people were killed and over 80 seriously injured as the nor’wester ravaged several districts last night, destroying thousands of huts and standing crops.

Maximum number of 25 deaths were reported from Purnia district, while six have died in Madhepura and one in Madhubani.

Indian Express today covers it so well. Here is the link

What are western disturbances and what explains their unusual behaviour lately?

Western disturbances are low-pressure areas embedded in the Westerlies, the planetary winds that flow from west to east between 30°-60° latitude. They usually bring mild rain during January-February, which is beneficial to the rabi crop. But in the past few years western disturbances have been linked to disasters.

The cloud burst in Leh in 2010, the floods and landslide in Uttarakhand in 2013 and the excessive rain in Jammu and Kashmir in 2014 were all linked to these disturbances. This year, as per the India Meteorological Department (IMD), the average rain received between March 1 and March 18 was 49.2 mm—197 per cent above normal. This caused severe damage to crops in several states of the country. -crops in over 5 million hectares have been damaged.

Scientists agree that western disturbances are formed naturally. They originate in the Mediterranean region and travel over Iran, Iraq, Afghanistan and Pakistan to enter India loaded with moisture, where the Himalayas obstruct them, causing rain and snow in western Himalayas. The snow adds to the glaciers which provide water to India’s major perennial rivers. But we need to understand why this beneficial weather phenomenon increasingly disastrous.

Following views are significant

1. According to IMD, the severe rain this year is the result of the confluence of western disturbance and easterly wave from the Bay of Bengal. Easterly wave, or Easterlies, blow throughout the year from east to west. The confluence of the two winds happens throughout the year, but the results vary. They generally bring rain only to the northern part of the country but this year states in central and south India also received rain. Western parts of Madhya Pradesh, for instance, received over 2,025 times more than usual rainfall during March 1-18, while the rainfall in central Maharashtra was 3,671 times above normal(IMD data).

2. A phenomenon called Pacific Decadal Oscillation (PDO) is said to have contributed to the severity of this year’s rainfall. PDO is the name given to long-term fluctuations in the surface temperature of the Pacific Ocean.

3. Widely used weather models, such as the Global Forecast System, are consistently showing the movement of new upper air troughs into India. Such troughs in the jet streams (narrow bands of strong winds flowing in the upper troposphere) could be affecting the western disturbances which, IMD says, are present in the lower and middle troposphere. One such trough started forming in the upper troposphere over Iran, Afghanistan and Pakistan on February 26 and intensified and moved towards north-western parts of India on February 28. This led to the formation of a low-pressure region in the lower troposphere over northwest India, causing an incursion of moisture from Arabian Sea, and produced heavy rains. This shows how problematic the combination of western disturbances and upper air troughs can be for India.

4. Climate change induced: A study by the Indian Institute of Tropical Meteorology (IITM), Pune, has directly linked western disturbances to global warming. Researchers say global warming is impacting air currents and causing freak weather events. Pronounced warming over the Tibetan plateau in recent decades has increased the instability of the Westerlies and this has increased the variability of the western disturbances. According to the study, the western Himalayan region has seen a significant rise in surface temperatures since the 1950s. Observations from the area show a significant increase in precipitation in recent decades.

Also read Western Disturbance and Western disturbance to impact many parts of India

Mrunal Geography videos for UPSC General Studies

These are videos uploaded by Mrunal bhai,these videos are recorded at Sardar Patel Institute of Public Administration (SPIPA), Ahmedabad.They cover basics of geography any further videos will  be updated. But the catch is they are in Hindi and though understandable those who don’t know Hindi might face some difficulty.

Longitudes, Latitudes, Timezones & Dateline

Earth’s Interior, S & P waves, Rock-Cycle, Geological Time-eras

Continental Drift Theory

Sea Floor Spreading Theory