Monday, April 25, 2016
High temperatures and more heat waves this week
Many areas will witness high temperatures. Will the heat action plans work?
India's "killer" heat waves are back and have already claimed 130 lives this season, according to news reports. At least 30 have perished in Odisha and more than 100 have died in other states. With the onset of summer, maximum temperatures have started increasing. Unlike March-April 2015, people aren't getting much relief from high temperatures due to the absence of thunderstorms and rain. Temperatures in some areas have crossed 45°C. They have been consistently above normal in many areas of West Bengal, Odisha, Bihar, Jharkhand, Uttar Pradesh, Maharashtra, Telangana and Andhra Pradesh. Between mid-March and mid-April 2016, maximum temperatures (excluding northeastern states and Jammu and Kashmir) have been above normal by 2-4°C. The greatest impact of this has been in north-central and eastern India.
We often think that high temperatures and hot winds mean heat waves but that's not so. Countries like the United States, the Netherlands, Denmark and England have their own definitions of a heat wave. India Meteorological Department (IMD) has also created proper definitions for heat waves in plains, hilly and coastal areas. For heat waves to be declared, the maximum temperature at a place in the plains or in the hilly regions must reach at least 40°C or 30°C respectively. If this happens and deviation of maximum temperature of that place from normal maximum temperature becomes 4.5°C to 6.4°C, then a heat wave is declared. If this departure becomes 6.5°C or above, then a severe heat wave is declared. Alternatively, a heat wave is declared if the maximum temperature equals 45°C or above and a severe heat wave is declared if the maximum temperature equals 47°C or above. For coastal areas, maximum temperatures need to be at least 37°C or above and their departure from normal must be above 4.5°C.
Heat waves are India's regular "visitors" but they have caught everyone's attention in recent years due to their links with climate change.
For heat waves to form, the weather in a region needs to be mostly clear. All you need is an inflow of dry and hot near surface winds for temperatures to rise. Often there is a stagnant high pressure in the atmosphere which causes such heat waves. Cloud cover (mainly dense cloud cover), thunderstorms/rain reduce the heating of the surface due to which temperatures don't soar too high and heat waves don't form. Such dry winds bring heat waves in coastal areas when the land-sea breeze weakens.
At present, dry and hot near surface winds are blowing over the northern half of India (areas above the Tropic of Cancer) from west/northwest direction. As a result of this, many areas are witnessing dry and hot weather.
Over the years, there has been a lot of research on heat waves and their connections with El Niño Southern Oscillation and global warming. Recently, J Ratnam and other scientists from JAMSTEC Japan, and M Rajeevan, secretary of Ministry of Earth Sciences, investigated the causes of Indian heat waves and published a paper titled "Anatomy of Indian heat waves".
Using observational data for the period from March-June from 1982-2013 and statistical methods, they identified two types of heat waves in India—one over north-central India and second over coastal eastern India. They stated that heat waves in north and central India are associated with atmospheric blocking over the Atlantic Ocean. Heat waves in coastal eastern India are associated with the reduction of moisture (thunderstorms) in these areas. Winds from the west/northwest drive the moisture away and this also reduces the land-sea breeze, thereby increasing the temperature.
Hot weather this week
There won't be any significant respite this week from the ongoing heat in many areas of India. Maximum temperatures are expected to increase by a couple of degrees in the eastern and central parts of India (yellow dotted circle areas in image 1). As a result, significantly high temperatures (mostly in the 41-46°C range) are anticipated in many areas of West Bengal, Odisha, Bihar, Jharkhand, Vidarbha (of Maharashtra) and Uttar Pradesh. It appears that the effect of these rising temperatures will be the highest in West Bengal as compared to the other states of India. Once again, heat waves to severe heat waves will be witnessed in the aforementioned states. The plains of North India too will witness hot weather this week.
Following maximum temperatures are expected by Thursday, April 21, 2016:
Bankura (West Bengal): 45°C
Gaya (Bihar): 44°C
Daltonganj (Jharkhand): 44°C
Akola, Chandrapur, Wardha and Nagpur (Vidarbha): 45-46°C
Allahabad and Varanasi: 45°C
Bhubaneswar: 42°C (possibly increasing after April 21)
Balasore: 43°C (maximum temperatures are already above normal by 8°C)
Need for indigenous heat action plans
In India, more than 3,000 people were killed during the heat wave of 2003, whereas more than 2,000 people lost their lives during the 1998 heat wave. At least 1,300 deaths were reported during the heat wave of 1988, whereas more than 2,000 people were killed during the heat wave in 2015. All these years were either El Niño years or the years following an El Niño event.
Until 2015, techniques of forecasting and detecting heat waves weren't up to the mark. Also, there wasn't any proper coordination between the weather department, state governments, municipal corporations and hospitals. As a result, proper plans for dealing with heat waves weren't devised. Having recognised this gap, IMD issued the first-of-its-kind seasonal outlook for the summer. They have also started issuing extended range forecast of heat waves using advanced climate prediction system developed at Indian Institute of Tropical Meteorology, Pune. Heat action plans have been implemented in Ahmedabad, Nagpur and Bhubaneswar. But will these measures succeed in keeping the mortality rate low?
The good thing about such heat action plans is that they increase the coordination between government agencies and the weather department which leaves the hospitals and administration better prepared to handle heat-related illness. But the measures suggested by these plans aren't that viable (in the context of India) and they don't address other local issues which are very important.
The best way of avoiding heat strokes is to stay indoors (properly ventilated and cooled spaces), wear light clothes and keep oneself hydrated. But can the working class and poor people manage to follow this advisory? A large percentage of India's population still survives on daily wages. In drought-hit areas such as Vidarbha and Marathwada, MGNREGA is the main source of income. If these people don't go out to work, their survival will become difficult. Even the odd-even scheme in Delhi requires a large number of volunteers to stand in the sun for long hours.
Heat-related illness can also occur by staying indoors. Every city has houses and slums which have poor or no ventilation, causing death due to high temperatures and suffocation. Young children and senior citizens are especially vulnerable. These action plans don't emphasise developing paramedical services but only promote some dos and don'ts.
Thus, the western world model, though good, can't work as efficiently in India. There is a strong need to develop indigenous heat action plans to address the problem.
Thursday, April 14, 2016
From the blog edition: http://www.downtoearth.org.in/blog/the-little-known-aspects-of-above-normal-monsoon-forecast-53552
A look at the changing methodology of long-term monsoon forecasting and what it means for drought in reality
Sunday, March 13, 2016
Wet and stormy weather is in store for many states
A change of weather in northern, central and eastern India is expected as winter ends and pre-monsoon season commences, with the start of March. An upper air trough (also known as western disturbance) will reach India by Friday, March 11 and destabilise weather till Monday, March 14.
Unlike last year, the start of pre-monsoon season in 2016 has been sluggish. In the first nine days of March, only parts of Maharashtra, Rajasthan and eastern Madhya Pradesh have received excess rainfall. The rainfall in other areas has been below normal.
Lack of strong western disturbances and a strong El Niño have kept India's winter warm and dry this season. As per India Meteorological Department (IMD), January to February is classified as winter season whereas March to May is pre-monsoon period. In January and February 2016, Jammu and Kashmir received just 78.8mm rainfall as against the normal of 212.9mm (strong departure of -63 per cent). India as a whole has received 17.9mm rainfall as against the normal 41.4mm (departure of -57 per cent). Region wise, rainfall departures in northwest India is -68 per cent whereas that in central India is -49 per cent. All subdivisions in north India have received scanty rainfall.
Lack of clouds and rain have kept temperatures high in otherwise cold states like Jammu and Kashmir and Himachal Pradesh. Between December 2015 and early March 2016, these states have witnessed maximum temperatures that were 2-4°C above normal.
As the western disturbance hits India, here's what can be expected.
Friday, March 11
Effect of western disturbance will commence in India. Moderate to heavy rainfall is expected in western parts of Jammu and Kashmir (including Kashmir valley). As a result, Srinagar will receive rainfall too. Rain, coupled with cloudy weather will keep daytime temperatures low. Srinagar's maximum temperature on March 9 was 7°C above normal. Hence, some respite from the heat is anticipated. Higher reaches of the state (such as Gulmarg, Pahalgam where temperatures are still below freezing at night time) will get snowfall.
Risks of water logging and flooding remain in Kashmir valley due to the rainfall forecast. Last year also, series of active western disturbances coupled with warmer weather caused a lot of rain and flooding in the state. People in low-lying areas of the state need to stay alert.
Thunderstorms along with rainfall are expected in western parts of Punjab and Rajasthan. There is also a possibility of hailstorm in the region bordering Pakistan. Over the night, light rain can be expected in north-western parts of Madhya Pradesh and western Maharashtra.
Saturday, March 12
Effect of the western disturbance will be the highest on this day. Heavy rainfall is expected in western Jammu and Kashmir. On this day as well, the risk of water logging/flooding continues. Considering the rainfall forecast, rivers like Jhelum can swell-up and hence people living nearby must take precautions, in addition other residents of low-lying areas. Snowfall will continue in the higher regions. Areas in Himachal Pradesh (tourist places like Manali, Shimla, Kullu) will get rain and have an higher risk of landslides.
Thunderstorms (some severe) are possible in north Indian plains including Punjab, Haryana, Chandigarh, New Delhi, adjoining parts of Rajasthan, western Uttar Pradesh and northern parts of Madhya Pradesh. Hailstorms may also be witnessed in these areas due to atmospheric instability (particularly in western UP and adjoining parts of Rajasthan).
Rain/thunderstorms are expected in parts of Uttarakhand, Chhattisgarh and Maharashtra (Marathwada and Vidarbha).
Over the night, rainfall can be expected to spread in parts of Jharkhand and Bihar.
Sunday, March 13
The effect of western disturbance in Jammu and Kashmir and Himachal Pradesh will start retreating. Chances of thunderstorms in north Indian plains continue because of atmospheric instability. Some thunderstorms will be severe and are expected to bring hail (especially in parts of Uttar Pradesh, Punjab and Haryana). Jharkhand, Bihar and Chhattisgarh will also receive some showers. There is chance of rain in Vidarbha.
Monday, March 14
Thunderstorm/rain activity will move towards east India and weather will normalise in northern and central parts of the country. If present weather models are to be believed, rainfall accompanied with thunderstorms (some severe) will be seen in Bihar, Jharkhand and eastern Uttar Pradesh, northern Chhattisgarh and eastern Madhya Pradesh.
Apart from potential flooding in Jammu and Kashmir, this round of rainfall/thunderstorm will impact horticulture and crops in Punjab, Haryana, Uttar Pradesh, Rajasthan, Madhya Pradesh, Maharashtra (Vidarbha and Marathwada) and eastern states of Chhattisgarh, Jharkhand and Bihar. Most Rabi crops are in their maturity phase and some have been harvested. Hence, rains can damage the harvested produce if not stored in dry places. Hailstorms will also have the potential of damaging the crops/orchards if hail nets are not used.
As some thunderstorms will be severe, the associated threat from strong winds and lightning strikes would also be there in this period.
Thursday, January 28, 2016
Western disturbance to bring rainfall, snow in north India
Barring north India, other parts of the country will witness warm weather
A western disturbance approaching India will bring fresh bout of rainfall and snowfall in the northern part of the country.
This is good news for tourists visiting Jammu and Kashmir and Himachal Pradesh where a thick blanket of snow will greet them.
However, due to possibility of landslides the Jammu-Srinagar highway can witness disruptions from January 28 to 30. Besides, some high-altitude villages in Jammu and Kashmir and Himachal Pradesh may be cut-off due to heavy snowfall.
The interesting thing this year is that parts of central and eastern India (where rainfall chances are generally slim during winter) have received normal to excess rainfall.
This was the result of an upper air trough around mid January which brought rainfall in these parts. Jharkhand and the eastern region of Madhya Pradesh have already received heavy rainfall.
Snowfall, rains in north
The effect of the western disturbance will be felt in northern India from Thursday onwards. Cloud cover is expected in western Jammu and Kashmir, the western part of Punjab and Chandigarh. Light rainfall is expected in parts of Jammu and Kashmir.
The minimum temperature is likely to rise by a couple of degrees in these areas due to cloud cover.
On Friday, the impact of the western disturbance will be the maximum. Rainfall is expected in Jammu. Moderate to heavy snowfall is expected in the Kashmir Valley (Gulmarg, Sonamarg and other hill stations). Srinagar is likely to receive both rainfall and snowfall. Snowfall is also expected in Kargil and Ladakh.
The higher reaches of Himachal Pradesh will also get moderate to heavy snowfall on Friday. This includes places like Manali, Keylong and areas in Lahaul and Spiti valley.
Coming to the plains, rainfall is expected in Amritsar, Ludhiana, Chandigarh and other adjacent areas.
As a result of cloud cover, rainfall and snowfall, maximum temperatures will plunge in parts of Jammu and Kashmir, Himachal Pradesh and Punjab and remain below normal.
Rainfall and snow will continue on Saturday in the early hours, but from the afternoon, the effect of the western disturbance will wane.
As per current weather models, it looks like the western disturbance will fail to bring any rainfall in Delhi and adjacent areas. But with increase in the moisture level, foggy conditions may be expected between January 29 and January 31.
Barring north India, other parts of the country will witness warm weather. During the weekend, an anti-cyclone (a high pressure region) in the lower levels of the troposphere will move over western India.
This will cause warm conditions in Maharashtra, Goa and Karnataka (coastal areas), particularly between January 28 and February 1.
The wait for widespread rainfall and snowfall in north India is on as dry weather continues to affect agriculture and tourism.
In the National Capital Region, proper "natural cleansing" of air could not take place due to poor rainfall.
Haryana, Chandigarh and New Delhi have not received any rainfall this year. Rajasthan, Punjab, Himachal Pradesh, Jammu and Kashmir and Uttarakhand have received scanty rainfall (60 to 99 per cent below normal) till now.
Going by data, the rainfall scenario is poor in certain places after the withdrawal of last year's summer monsoon.
Between October 1, 2015 and January 27, 2016, New Delhi has received just 1.6 mm rainfall. This is just 5 per cent of normal rainfall when considered over a three-month period.